Model Engine Maker
Engines => From Plans => Topic started by: kvom on January 23, 2017, 04:28:31 PM
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I have ordered both of Anthony Mount's books, but they're being shipped from the UK and will likely take 2 weeks to arrive. And then I'm travelling for 2.5 weeks thereafter. In contemplation of the Benson, are there any plans available either online or from contributors here that I can get without violating any copyrights?
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Legally no.
Jo
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I'll wait then. Might decide to do one of the others in the books anyway.
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Having received the documentation, I have proceeded to model the engine in Solidworks. Fabrication looks to be a challenge because of the numerous small parts. I am thinking it may make sense to build the governor first to test my ability with finicky assemblies. In any case, the attached image is where I've gotten with the model.
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What size are you going for? and what are you using for the "red"base casting?
J
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Undecided on size. I read your 1.5x build log, and it's tempting to go that way just to be able to work with larger stock on the tricky parts. OTOH I just bought a very nice 7" flywheel at Cabin Fever that would work well with the regular size.
The base is red only because I was playing around in SW. My thinking is to mill it out of aluminum and form the edge with a router bit. I have a friend with a powder coat setup that I can use rather than paint. I'm going to experiment on some colors to see how it would look on an engine like this. It would certainly be more durable than paint.
SW gives the mass data on parts, and I priced out having the cylinder cast at Shapeways. Brass would cost over $200, but aluminum would be half that.
I'm leaving on Tuesday for a 2 week trip to Antarctica via Buenos Aires, so I won't have to make any decisions until then.
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That seems very expensive for a cylinder of that size are you thinking of cutting from the solid?
I have just done a cylinder that is 24mm bore, 36mm across the flanges and 57mm long from a mix of brass and bronze. I only had to buy the bronze for the main cylinder this was a 4" length of 1.25OD x 0.75ID hollow bronze cost £5 DBP, flanges were cut from some 1.5 x 0.25 flat bar I had laying about but likely cost less than £5GBP and same sort of cost for the bit of bronze block for the valve port block.
Dry assembled
(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Thompstone/DSC01730_zpsow8gzi42.jpg)
Soldered and finish machined
(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Thompstone/DSC01740_zpsbu9ntmdo.jpg)
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Thanks for that example. If one attaches the flanges then the decorative ribs and be turned on the cylinder without needing to bend them around the OD as with your Benson model.
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Yes and you don't need such a large bit of metal.
(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Thompstone/DSC01726_zpsg8y3z8bp.jpg)
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I discovered why I had been having some issues mating a few parts in SolidWorks. I had made an error in positioning the center point for the cylinder on the base by a couple of thou. When I redrew the base and saved it I got a lot of other errors in mating parts that seemingly had nothing to do with the correction. It's very likely a more experienced SW user could have fixed them simply, but I decided to break the engine into some smaller sub assemblies. That will isolate mating issues in one from correction to the others to some extent.
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Adventure in astragals on the menu today.
as·tra·gal
noun
ARCHITECTURE: a small semicircular molding around the top or bottom of a column.
Leave it to Jason to know the name for these decorations. Since the Benson engine has 2 of these on the column and 1 on the cylinder, I think it behooves me to know how to turn one before diving in for a fabrication (on casting set they're already on the castings).
The obvious solution is a form tool, and other than a couple of rough grinds I haven't made any. I did buy one for forming the rims on the wheels of my locomotive. So I took as my example the Clickspring youtube video where oil quenching tool steel is machined and hardened. I don't currently have any O1/O2 steel in bar form, but do have some 3/8" diameter O1 drill rod, so that was my material today.
The first order of business was to mill the rod flat to half its diameter. A shallower flat cut was also made to help alignment in the lathe tool holder.
(http://www.pbase.com/kvom/image/164907015/large.jpg)
Next, a 10-degree angle bar positioned the piece for cutting the relief angle.
(http://www.pbase.com/kvom/image/164907016/large.jpg)
Then the form for the 3/16" astragal was milled using the same size endmill. For a more complicated shape I'd use the CNC mill. I could also have drilled a 3/16" hole before milling the relief angle.
(http://www.pbase.com/kvom/image/164907017/large.jpg)
I heated it to bright red with a Mapp gas torch and quenched in lubricating oil. The result was a blackened surface, but seemed pretty hard when I attempted to file it. Then I tempered it with the torch, all rather a guessing game at the correct color, but the result was such that I could sharpen the edges with grinding wheel (oilstone would be more precise).
Testing on a piece of 3/4" brass went well. No chatter to speak of and a decent finish.
(http://www.pbase.com/kvom/image/164907019/large.jpg)
Came in to the house to find a free shipping offer from MSC, so ordered some oil hardening bar and some larger O1 drill rod.
I'll be away from home for the next two weeks as I visit Antarctica. Probably no models to visit there, but there is a steam train excursion that runs from Ushuaia and back.
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Nice tutorial on the form tool!
Say Hi to the penguins for us. Maybe you can entice some to come back and get jobs as shop elves... They smell fishy, but they dress well!
Just looked up that train at Ushuaia - cute little engine, would make a nice running model.
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So what is the temp in balmy Antarctica this time of year, it's their summer time. Send food piccys from Buenos Aires :stir:
Cletus
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BA is excellent for steaks (and leather goods made from the leftovers from steak production). I was there in 2007 for a week, but can't remember what else I are there other than beef.
I have a 3-season packing list. 4 days in BA with daytime temps in the 80s. 4 days in Ushuaia with daytime temps in the upper 40s.
The temps at the coast where I can find them on weather.com seem to be in the 30s during the day and 20s at night. We are supplied a parka and boots for going ashore in the Zodiac inflatables. I have my waterproof offshore sailing bib and long johns for lower body insulation, and a fleece jacket for upper. Likely to be too warm with the parka.
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Enjoy your trip!
Thanks for showing the form tool. Something to remember.
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Sounds like a great trip Kirk. Hope we will get to see some pictures.
Bill
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Just back from Antarctica by way of Buenos Aires and Ushuaia. The expedition photographer made a video that I have loaded to youtube:
https://www.youtube.com/watch?v=T6xGMk6WKDM
Original had a soundtrack that I had to delete to avoid copyright and blocking issues.
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Very cool, Kirk. Must have been a good trip. :ThumbsUp:
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Apropos of nothing, I have been considering purchasing a 3D printer, one that prints chopped carbon fiber as very stiff parts compared to nylon or fiberglass. Gears printed this way would be strong enough for engine models, and with a gear design tool any size gear could be produced.
For the Benson, I suspect that the cylinder, for example, could be printed in a way that with the cylinder sleeved and a port plate used. The print resolution is about .004" with a nozzle size of .0016".
The printer I'm considering is the Markforged Onyx.
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The printer I'm considering is the Markforged Onyx.
I'd be interested in why. Got a link to that?
I will be interested in a 3D printer sometime next year but not the kind I build or fuss with. I just want an out-of-the-box printer.
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Thanks for posting the video Kirk. One of those once in a lifetime opportunities and looks like you had great weather for it too!!
Bill
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To start on actually making parts for the Benson, I decide to tackle the connrod. It's a finicky part, and I will decide whether to continue with the documented 1:12 scale or do as JasonB and make it 1:8. Since JL is making the same part concurrently using manual methods, it may be interested to see of our ops match at all.
I chose brass as the material; easy on the tools and I have a good stock. Cut a 1.5" slice off a length of 4x.25" brass, squared it, and ran the facemill on one side.
(http://www.pbase.com/kvom/image/165007518/large.jpg)
Next I uses a 5/64 endmill to make the cotter holes. The drawing has the width as 1/16", but all of my 1/16 endmills have a 1/8" LOC. The width isn't really critical as long as the strap holes are the same. First set the Z0 using a 1" gauge block.
(http://www.pbase.com/kvom/image/165007519/large.jpg)
The second op is to cut the profiles using a 1/8" endmill. My CAM program is set to leave .05" high tabs at the bottom to keep everything attached to the stock.
(http://www.pbase.com/kvom/image/165007520/large.jpg)
The 3rd op cut the relief between the ends and the shaft.
(http://www.pbase.com/kvom/image/165007521/large.jpg)
Now a trick I learned over on HMEM. Fill the slots with Darvon epoxy gel and let sit an hour to cure. The epoxy will hold the pieces together even if the tabs get milled away on the reverse.
(http://www.pbase.com/kvom/image/165007523/large.jpg)
Turn over, facemill to thickness, and cut the 1/32" relief on the back.
(http://www.pbase.com/kvom/image/165007524/large.jpg)
The only remaining machining is the 7/32" round slots in the three ends of the rod. With the work held with the side vertical, a 7/32 endmill would make quick work. Given that I have a dozen 3/16 endmill but no 7/32 led me to stop work for today. I suspect a 3/16 would work just as well although the through holes in the bearings would make the walls quite thick. I'll just order a 7/32 endmill.
And in case you're wondering, 15 minutes in a 250F oven and the epoxy falls off.
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Kirk,
That looks like an interesting project, especially if you print the cylinder. Your trip to Antarctica sounded great.
Art
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Off a good start, If I remember rightly I had to mill my slots from both sides as I used 1/16" wedges even on the larger scale model as they looked too heavy scaled upto 2mm.
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Waiting for an order including the 7/32 endmill, so on to another finicky part, this time the "links" for the governor (Mount's part 46). Start with a 2" length of 1/2" square brass bar, face mill the top, and machine the profile .25" deep.
(http://www.pbase.com/kvom/image/165012724/large.jpg)
Reverse in the vise and face mill the bottom freeing the two links.
(http://www.pbase.com/kvom/image/165012725/large.jpg)
Next, mount some aluminum soft jaws and mill a pocket that matches the profile. Use this to hold each part and mill the shaft down to size.
(http://www.pbase.com/kvom/image/165012726/large.jpg.)
Still needs slots cut in the end, but time ran out for today.
(http://www.pbase.com/kvom/image/165012727/large.jpg)
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FYI, aiding and abetting the escape of an engine part may be illegal here down South. Please check with your local officials :lolb:. Nice job Amundsen 8).
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Tiny little guys they are; looks good Kirk.
Dave
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Continuing with my goal to build the governor first, I contemplated the pivot (part 44), which consists of a steel rod that's 1/8" diameter at the bottom but 3/32 over more of it's length. Mount turned down 1/8" rod using a follow rest, and this could also be done with a box tool, but I have neither. So my plan was to drill a 3/32" hole through a length of 1/8" rod and glue in the 3/32 part. I wasn't sure it could be done as is results in a 1/64" wall thickness after drilling. However, success was mine. A bit of Loctite 620 holds the two pieces together just fine.
(http://www.pbase.com/kvom/image/165015213/large.jpg)
I made two attempts at the upper pivot block and brain-farted both times, so settled for making the stop (part 49). Cross-drilled some 3/16" brass rod and tapped 2-56:
(http://www.pbase.com/kvom/image/165015214/large.jpg)
Then drilled and parted.
(http://www.pbase.com/kvom/image/165015215/large.jpg)
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Impressive Kirk, those really are some small parts too!!
Bill
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Kirk:
What is this Darvon epoxy? I looked around the 'net and didn't find anything similar. Is that the right spelling? Does it melt out, get soft, or become brittle? After poking around a little I wondered if a low meting point metal (http://www.belmontmetals.com/product/eutectic-alloys/?_vsrefdom=adwords&gclid=CjwKEAiArbrFBRDL4Oiz97GP2nISJAAmJMFa96M-16OJkhUSBL-VwjFPf9xB1VzNpsj_cCChpO-jvRoCoY3w_wcB) could also be used?
Now a trick I learned over on HMEM. Fill the slots with Darvon epoxy gel and let sit an hour to cure. The epoxy will hold the pieces together even if the tabs get milled away on the reverse.
And in case you're wondering, 15 minutes in a 250F oven and the epoxy falls off.
Thanks for sharing your process. I'd have used the two holes to try and hold the stock to a tooling plate for machining. Probably would have run into trouble, holes may be to small. Real nice to see alternatives, and the results speak for themselves.
(http://www.pbase.com/kvom/image/165012727/large.jpg)
Nice build. Thanks.
Hugh
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Sorry, it's Devcon Epoxy Gel. Brain fart. There's also a Devcon Epoxy without the gel that won't work as well. That one cures yellow. Can be bought at HD or Lowes.
The holes in the links are 1/16, so pretty small for screws. However, the two ends are the same diameter so they can be held in a vise. The advantage of the soft jaws is that the zero is fixed and makes it easy to swap parts without remeasuring.
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Today's jobs were to finish the two links (I had drawn them wrong in SW) and try to build the governor lower pivot block (part 48). The pivot block started with some .75" hex brass bar and ended with a lot less material. Lots of ops on this part, but I didn't stop to take pics. Here's a poser shot of the links and pivot block on the shaft.
(http://www.pbase.com/kvom/image/165024152/large.jpg)
I also got my McMaster order that included some 9/16" brass balls. I drilled and tapped two of them 1-72.
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I'm going to remake the conrod after messing up milling the half-round slots in the ends. :'(
In an effort to get something finished today I worked on the top pivot block (part 47).
The first op was drilling and profiling on the CNC mill. This part measures .5x.185x.185 inches, so quite small.
(http://www.pbase.com/kvom/image/165038337/large.jpg)
Using the machinist vise held in the Bridgeport vise I machined off the stock from the bottom. After tapping the center hole 2-56, I flipped it in the vise to drill the hole for the pivot shaft and mill the 5/64" slots.
(http://www.pbase.com/kvom/image/165038350/large.jpg)
Shown mounted on the pivot shaft:
(http://www.pbase.com/kvom/image/165038357/large.jpg)
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Spent the past few shop sessions trying to make the arms for the governor, with several failures. Today I tried a new technique, starting with some 1" round brass bar held in a 5C collet centered on the CNC mill:
(http://www.pbase.com/kvom/image/165075051/large.jpg)
Being able to first surface the end on the lathe makes this form of stock easier to prepare than brass bar. The CNC mill machines the profiles of the arms .100" deep; then drills the 1/16" center holes with a center cutting endmill.
(http://www.pbase.com/kvom/image/165075053/large.jpg.)
The collet then goes back on the lathe, and the arms are parted off leaving a very thin layer on he bottom. The two arms can then be separated with scissors.
(http://www.pbase.com/kvom/image/165075054/large.)
Then mounted on the small vise, and the bottom later is machined off. After measurements the same setup is used to bring each piece to .078" thick. This was harder than it might seem as I ruined two by taking off too much. One issue was that my parallels weren't the right height on hold them and I was relying on some shim stock.
(http://www.pbase.com/kvom/image/165075056/large.jpg)
Finally the 1/16 endmill is used to cut a cross hole in one end and a length of 1/16" drill rod is glued on. After curing, the blocked hole is redrilled.
(http://www.pbase.com/kvom/image/165075057/large.jpg)
The next step is to attach the 7/16" diameter balls to the ends with glue.
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I can't find anywhere that Mount talks about the pins that hold the governor together. Since the holes are 1/16 (.0625"), I'm thinking I need some 0-80 screws. Any other ideas?
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I just made some flat headed pins and threaded the end, for your size I would go 1/8" dia head by 1/16" long and then a plain 1/16" shank with the end threaded.
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1/16" major diameter thread is a 0-80. $12.90 from AME for a die. $8.71 for 25 steel nuts. $6.38 for 25x3/8" steel screws. $2.22 for 25 steel washers. Think I'll go with screws and nuts. Not as elegant but should work for the purpose. Interesting to see what JL decides when the time comes.
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Looking at the governor pivot bearing, Mount specifies a "3/16x40" thread, which as far as I can find does not exist in normal standards. 10-32 seems closest to the M5x.5.
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It is one of our ME or Model Engineer standard thread forms, I think it would be like a 10-40UNS but if you have the 32tpi one that should do.
Some of the model pipe threads that PMR do would also fit the bill
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Looking at the governor pivot bearing, Mount specifies a "3/16x40" thread, which as far as I can find does not exist in normal standards. 10-32 seems closest to the M5x.5.
the 3/16-40 must be standard somewhere, I have taps and dies for it. I think I got them originally for the touch hole plug on a flintlock I was building, so maybe its a gunsmith item. Did some looking, PM Research has them here:
https://www.pmmodelengines.com/shop/tools/straight-pipe-thread-taps-dies/
Dont remember where I got mine, it was about 10 years ago.
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I made the pivot threads 10-32, the die I have. Here's a family shot of the governor.
(http://www.pbase.com/kvom/image/165079678/large.jpg)
I ordered the 0-80 screws/nuts/washers to tie it all together. I still need grub screws for the stop and top pivot block plus the gear to drive it.
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Kirk-
What about using pressed pins rather than 0-80 hardware? I think pins would look cleaner.
-Bob
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I would have needed to drill the holes in the pivots smaller and arms/links larger. As it is all are 1/16. The arms and links need to pivot freely.
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Others have mentioned that PMR uses "3/16-40" for 3/16 inch model pipe fittings. I'm pretty sure I bought a 3/16-40 tap from them and the tube was marked #10-40.
The major diameter of #10 being .190, it's pretty much the same thing. McMaster-Carr sells #10-40 taps and dies.
--Tim
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As you can see in the photo I just used 10-32. It's not a critical specification.
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Hi Kirk,
I sat in awe as I read this construction log to date Kirk. I have learned much from your clear and informative text . CNC machines and a new 3D printer in the offing indicate your passion for the hobby.
All the best as you assemble the governor and create more beautiful parts. :ThumbsUp:
Cheers...John
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Thanks for looking in JL. A barstock build is a bit different than with castings, and I'm following yours as well. I did order some aluminum plate for the base yesterday, and am investigating using a router bit to shape the edges similar to the casting.
The 3D printer is still just an idea though.
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With the governor pieces waiting for attachment I made a start on the column. Stock is 1.125" aluminum round bar, just slightly smaller than the drawing's 1.188. Various lathe ops to turn a 1/2" diameter x.30" long spigot on each end, drill through 17/64, and center drill the ends to allow support by a live center. Skim turn to 1.113" diameter, with 4" other than the spigots to work with.
(http://www.pbase.com/kvom/image/165084742/large.jpg)
The spigots allow gripping with the collet chuck on either end, and will be retained for centering in the base and the column's capital.
After mounting in a V-block, the Bridgeport was used to machine the flat for mounting the bracket (part 41), as well as the 3 tapped holes for attaching it. Best to do this now before tapering the column.
(http://www.pbase.com/kvom/image/165084743/large.jpg)
The capital is a separate piece also turned from aluminum. It will be held to the column body with two countersunk 2-56 screws and aligned by the spigot. The capital can be removed to position the two astragal moldings.
(http://www.pbase.com/kvom/image/165084788/large.jpg)
Next time in the shop I'll set up the taper attachment on the lathe. The taper is an included angle of just over 4 degrees. The DROs on the lathe help a lot in adjusting the taper attachment, but it's still a touchy job.
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I had the overnight thought that I should make the bracket that attaches to the column before applying the taper, as it would be easier to adjust the fit if needed were the column still cylindrical.
I had only a short amount of shop time today so used it to prepare the stock I will use to machine the bracket. A piece of brass bar 1.125x.6x2.25" that I had left as a cutoff from a previous project. After squaring the saw cuts I drilled the 3 clearance holes where the bracket will be screwed to the column.
(http://www.pbase.com/kvom/image/165090464/large.jpg)
The plan is to mill the bracket's arm profile .25" deep on the CNC mill, and then machine away the rest from the bottom.
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With the profile cut 1/4" deep, the slots are filled with epoxy to hold the part firmly as the bottom is milled. I'll let the epoxy cure for several hours first. At the end it's heated to release.
(http://www.pbase.com/kvom/image/165096408/large.jpg)
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I have to scrap this part and start over. What I didn't realize is that to hold the piece securely in the vise the epoxy needs to be surrounded by metal. When I was close to the right hand side in removing the excess metal the part came loose from the vise. I'll need to start over with a larger piece of stock. :(
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I am playing catch-up again on your build Kirk. More teeny but beautiful parts...very inspiring!!!
Bill
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Missed the post on the governor.
Looks fantastic!
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Masterful work Kirk!
I know everyone realizes the challenge this tapered column presents.
Is it hard to program a CNC machine to cut the bracket?
John
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Rather than use the epoxy can you not solder the machined side to a piece of scrap metal, machine the other side and then melt the part off the solder.
Failing that a hacksaw and files works well ;)
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Rather than use the epoxy can you not solder the machined side to a piece of scrap metal, machine the other side and then melt the part off the solder.
Failing that a hacksaw and files works well ;)
That would be too easy. :) I've been trying to get my hands around the epoxy technique, so this is more of a learning experience than a hunt for the easiest method. That said, it's not clear how well the solder would clean off the surface.
An alternate method that would certainly work is to mill the profile into soft jaws and hold the part that way while removing the excess from the bottom. I have done that many times. I could also generate several small tabs around the perimeter that would be filed off at the end.
Hacksaw and files are so 20th century. 8)
@JL. The profile is a very easy CAM operation. One draws the profile in CAD and exports it to a DXF file, In the CAM program I just select the profile line, specify which side of the line to machine, and give parameters for tool diameter, depth to cut, depth increments, spindle speed, and feed rate. For profile that involve slots I also specify that the tool is ramped rather than plunged into the stock.
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I'm following along and enjoying it, Kirk. I sometimes get a kick out of how far the most of go, looking for 21st century technology to help recreate 19th century work. I know it sure has helped my Amex points :Jester:
Cletus
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I'm following along and enjoying it, Kirk. I sometimes get a kick out of how far the most of go, looking for 21st century technology to help recreate 19th century work. I know it sure has helped my Amex points :Jester:
Cletus
It is ironic. Unfortunately some 19th century technology, like widely available iron casting, is no longer available to us. Pattern making and iron casting would eliminate a lot of the need for assembled parts and CNC.
Chuck
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Of course I could have done as JL and ordered the casting set. I prefer working with bar stock as opposed to castings.
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Kirk, I'm not degrading in any respect, as a matter of fact, I really enjoy seeing both routes to a common destination. Chuck, I guess the "evolution of skill sets ".
Cletus
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Hi Kirk. Your description of the CNC process - :insane:
I'm sorry; I'm a luddite. But I do know where the 'ON' button is on the back of my computer...
I'm learning much from this thread nevertheless Kirk. :popcorn:
Cheers...John
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To be more explicit. The DXF file just encodes the drawing as a collection of lines and arcs as drawn in CAD. A profile is a path of the tool that follows the line but offset by the radius of the tool. If the line is closed then the profile is either outside or inside, but if not closed I have to tell the program which side of line to offset.
It appears that I don't have a "good" piece of brass stock with which to redo the bracket. Stock that I do have would mean milling away 50% to get an oblong block with which to start. I may put it aside until NAMES, where I may be able to pick up a piece of brass close to the objective.
In the meantime the aluminum I ordered for the base arrived today, so I may spend some time on it. I'll be away most of next week, so not much progress expected.
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Could you not CNC it out the shaped part from thinner plate and just solder the end of the bracket that bolts to the column onto the end. Would save a lot of swarf.
Or mill it out of a bit of angle iron if you don't want to solder.
Or saw the block that you do have and save that 50% for something else rather than just turning it into swarf.
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@JasonB: I could do any of those things in theory if I weren't stubborn. :hammerbash: The stock I want to save Is a piece of 2x2" brass bar that could be more useful in the future.
Spent an hour or two assembling the governor. A few pieces needed a bit of filing, and it's still a little stiff, but the bottom pivot moved up when the arms move out. Those 0-80 fasteners are tedious to work with. Fortunately the Wiha nut driver set I have goes down to 3/32, which is the size of these nuts.
(http://www.pbase.com/kvom/image/165107573/large.jpg)
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Wow - that looks amazing! If you didn't know, would swear it is several times as large. Nice!
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Nice looking governor Kirk!
Looks like you are doing the tedious parts first.
Dave
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Great looking governor Kirk.
They're one of the more interesting aspects of any engine.
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Being that we're heading to frigid Chicago for the girls' spring break ( :shrug: ) I decided to try to make some progress on the engine that I could finish in one day. So I chose the eccentric straps as the target.
First step is to chuck some 1" brass round rod on the lathe, face it, and drill/ream 1/2".
(http://www.pbase.com/kvom/image/165115290/large.jpg)
Then with the same collet in the square collet block, it was over to the CNC mill to cut the outer profile.
(http://www.pbase.com/kvom/image/165115300/large.jpg)
Then back to the lathe to part off. Then some sanding on the cut edge to remove burrs and bring to size. Repeat the above for the second strap.
(http://www.pbase.com/kvom/image/165115302/large.jpg)
Next clamp the strap in the machinist vise, and use the CNC mill to drill and round the spigot for the eccentric rod.
(http://www.pbase.com/kvom/image/165115304/large.jpg)
Finally tap the spigot 3-48.
(http://www.pbase.com/kvom/image/165115305/large.jpg)
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The eccentric straps look good Kirk.
I'm assuming that for a CNC project those would of been fairly simple milling operations. Not so much if they had to be done manually. Anyway, I'm curious as to how difficult it was to write the program to make those 2 milling operations happen?
Jim
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@Jim
Nothing in CNC is difficult once you know how. But unless you're doing 3D surfaces, your basic 2.5D operations are similar to what you'd do manually. These ops are profiles, pockets, and drilling. Once you have a CAD drawing loaded in the software, it's a matter of filling in some forms to describe the operations. The first op is just an outside profile since the hole was already present. For the second, I had 4 ops. First, a spot drill; second drill 1/16 through; third drill 3-48 tap drill partial depth; 4th outside profile.
All the parts for this engine I could have drawn in Draftsight as 2D CAD. However, now I'm modeling the parts in Solidworks and generating the CAD output from the models.
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Back from 4 days in freezing Chicago, and a little bit to show from a short time in the shop.
As I had the eccentric straps, I thought I'd work on the eccentrics to go with them. Using some 3/4" mystery steel rod, I used the CNC mill to drill the off-center hole for the crankshaft and the collar around it.
(http://www.pbase.com/kvom/image/165138890/large.jpg)
Then over to the lathe to turn down the rod to fit the strap. Got a nice sliding fit.
(http://www.pbase.com/kvom/image/165138906/large.jpg)
The next operation would have been to turn the groove needed to retain the it in the strap, but it occured to me that I should have one of the rods made to ensure that it all works properly. To make the rod I need to insert a 1/16" pin into some 3/32" rod, which is then threaded 3-48. In order to accomplish all this I need a 3/32 collet. So that's another item on the MSC order list for when the next free shipping coupon arrives.
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Is it not easier to turn the 1/16" onto the end of the 3/32" rod and that can be done in a 3 jaw. Also 3-48 is going to cut quite close to teh 1/16" hole.
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I am going to try turning down the 3/32 rod, but that also requires the collet. My lathe's chuck won't close on a rod that small.
That said, I was able to do an insert op for the governor rod, and that also had a 1/64 wall thickness after drilling. So it's worth a try. Minor diameter of the thread is still .01" larger than the 1/16 hole, so I have hope that will work too. Time will tell.
I wonder if it would not have been better to use 1/8 rod instead and 5-40 threads.
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1/8" would look a bity chuncky, I only used 1/8" on my 1.5times one. I have also done a couple of other similar sized engines and use 3/32" or 2.5mm on them and its about the right proportion with the piston rod which is generally larger than the valve rod.
What about a split bush or even a drill chuck held in the lathe chuck to hold the 3/32" stock
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@Jim
Nothing in CNC is difficult once you know how. But unless you're doing 3D surfaces, your basic 2.5D operations are similar to what you'd do manually. These ops are profiles, pockets, and drilling. Once you have a CAD drawing loaded in the software, it's a matter of filling in some forms to describe the operations. The first op is just an outside profile since the hole was already present. For the second, I had 4 ops. First, a spot drill; second drill 1/16 through; third drill 3-48 tap drill partial depth; 4th outside profile.
All the parts for this engine I could have drawn in Draftsight as 2D CAD. However, now I'm modeling the parts in Solidworks and generating the CAD output from the models.
That's a great explanation Kirk, thanks. I can see where CNC would open up some fun possibilities.
Jim
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1/8" would look a bity chuncky, I only used 1/8" on my 1.5times one. I have also done a couple of other similar sized engines and use 3/32" or 2.5mm on them and its about the right proportion with the piston rod which is generally larger than the valve rod.
What about a split bush or even a drill chuck held in the lathe chuck to hold the 3/32" stock
Drill chuck won't work as the eccentric rods are ~3" long. But I do have one I can experiment with on a short length of stock pending the collet purchase. A bushing could also work, but there are plenty of other parts to work on in the meantime.
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Today's project is the forks at the end of the eccentric rods. Start with some 3/8" brass rod and, on the lathe, drill 1/2" deep with a #43 drill (3-48 tap). Then on the manual mill 2 side flats 1/4" long and 1/4" apart.
(http://www.pbase.com/kvom/image/165143597/large.jpg)
Then on the CNC mill, drill cross holes for 2-56 clearance and mill the profile.
(http://www.pbase.com/kvom/image/165143598/large.jpg)
Back to the manual mill to mill the center slot 5/32" wide and 3/16" deep.
(http://www.pbase.com/kvom/image/165143601/large.jpg)
Then to the lathe to turn down the spigot and part off.
(http://www.pbase.com/kvom/image/165143602/large.jpg)
Finally to the tap stand. Finished result:
(http://www.pbase.com/kvom/image/165143603/large.jpg)
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Some more unfocused work for today.
First I parted off 5" of 1/4" drill rod that will serve as the crankshaft. Rather than tuning down from larger stock to leave the mounting for the flywheel, my plan is to turn/drill/glue that mount to the crankshaft. The flywheels I bought at Cabin Fever have 7/16" center holes with the ability to tighten onto the shaft with clamp screws. Therefore, no key needed to retain the flywheel. I'll wait to attach the mount to the shaft at assembly time, and as well I'll wait to fit the crank at the other end once that part is made.
(http://www.pbase.com/kvom/image/165149091/large.jpg)
Next I revisited the issue of providing the end of a 3/32" eccentric rod narrowed to 1/16'. I mounted my tapping chuck on the lathe with a short length of 3/32 rod, and was successful in drilling a 1/16" hole.
(http://www.pbase.com/kvom/image/165149095/large.jpg)
I inserted a length of 1/16" drill rod in the hole and secured it with Loctite 620. I'll let it cure for a day and then see if I can thread the end 3-48 without cutting into the smaller rod.
(http://www.pbase.com/kvom/image/165149096/large.jpg)
Last part of the day is the crosshead. I decided to make it from brass rather than steel, but I doubt it matters. Starting with some 1/2" diameter brass rod, I drilled and tapped 2-56 for the set screw.
[/img]http://www.pbase.com/kvom/image/165149104/large.jpg[/img]
Then turned down the spigot.
(http://www.pbase.com/kvom/image/165149164/large.jpg)
Then over to the Bridgeport to machine the sides. I was originally going to do this part on CNC but decided this way would be faster. In reality it was about the same amount of time.
(http://www.pbase.com/kvom/image/165149201/large.jpg)
Then drill and tap the sides for 3-48 and then drill/ream the top for the 1/8" piston rod.
(http://www.pbase.com/kvom/image/165149239/large.jpg)
Then all that was left was to part off on the lathe and sand off the nib from parting.
(http://www.pbase.com/kvom/image/165149292/large.jpg)
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Interesting clamp on the flywheel, is one half of the clamp machined as part of the wheel hub?
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The clamp is one piece that's a press fit into the actual bore of the flywheel.
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The clamp is one piece that's a press fit into the actual bore of the flywheel.
So the end where the clamping jaws are, is that saw-cut to form the two halves, like a collet?
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Yes. The cuts go about halfway through the bore.
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After letting the trial eccentric rod cure overnight, I mounted it in the tapping chuck on the lathe once more and applied the 3-48 die. No cut through with the threads, and nothing loosened up, so that's good to go. Screwed into the strap for fit.
(http://www.pbase.com/kvom/image/165156612/large.jpg)
Then I went back to the half finished eccentric, drilled and tapped for a 2-56 set screw, turned the center groove, and parted off.
(http://www.pbase.com/kvom/image/165156613/large.jpg)
With the three parts assembled, the eccentric is retained by the 1/16" nib riding in the groove. Rotation is a bit stiff but should wear in.
(http://www.pbase.com/kvom/image/165156614/large.jpg)
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Aha - was wondering how you were going to retain it on the eccentric, using the end of the shaft is a neat way to do it. Could even scribe in a line where the top/bottom joint would be to get the full split follower look?
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The book recommends scribing a part line as well as dummy bolts.
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In preparing the stock for the base, I noticed that I was not getting the sides square. Checked the vise tram on the Bridgeport and the fixed jaw was off 50 thou from one end to the other. Good reminder to check tram more often.
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I decided to get to work on the base today. This is a part where having the casting is an advantage. First step was making a semi-temporary fixture on some quarter inch aluminum. Ran a face mill over it and drilled and tapped 5 mounting holes 5-40, plus 1/2 and 1/4 reamed holes for locating later.
(http://www.pbase.com/kvom/image/165162269/large.jpg)
Then machined the base itself. I used a large facemill to face as well as profile the boss for the cylinder. Then drilled all the necessary holes.
(http://www.pbase.com/kvom/image/165162271/large.jpg)
Next, screwed the base to the fixture, located the 0,0 coord from a ground pin in the 1/2" hole, and milled the outer profile.
(http://www.pbase.com/kvom/image/165162272/large.jpg)
I still need to tap the mounting holes for the riser on which the column and pump sit. As well I want to mold the outer profile with a corner rounding bit. I did not drill any holes for the cylinder mount; I'll wait to see if I make the cylinder flange as per plans, or possibly slightly larger.
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Hey Kirk
As long as you had the CNC fired up why not surface in a nice radius around that outside edge?
I have been enjoying following along with your build and it is looking great!
Dave
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Dave, I do plan to do so. Got a corner rounding bit on standby alert.
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Not sure what CAM you are using; can you do a contour or (water line) tool path with a ball end mill?
Dave
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Last couple of bases that I have done I just freehand ground the corners of a blunt milling cutter with a small concave 1/4 circle on the corner of each flute works a treat.
If you get the size right you can run your CNC at the same path, eg if the moulding is 2mm wide then profile with a 6mm cutter and modify a 10mm cutter, in both cases the path of the ctr of the tool will be 3mm from finished edge. This makes things easy when doing it manually like I have to.
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My plan is/was to use a 1/8 corner rounding bit, but positioned both lower and further in than if I were just rounding the top. This gives a molding effect. I did some experiments with it on some scrap to get the parameters. However, I needed to remove 93 thou of thickness from the .375 stock, so I'll have to see if that leaves enough material.
I am aiming for a convex form for the outline. A concave form would be easy using a ball mill.
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Yes the "quirk" is easily added by comming lower and further in with the cutter or if following the same path with a home ground one you use a larger cutter.
Does the extra thickness have to come off the top or bottom? would not hurt to have the base thicker.
These two just have a top quirk
(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Muncaster/DSC01827_zps7ihbe4ra.jpg)
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If I had wanted to machine the base as drawn by Mount then I would have needed 1/2" stock to start, and even then it would be a fraction short. Since I am making it from two pieces the lower part thickness isn't critical. In terms of the other part dimensions, only the difference between the height of the cylinder boss and the column boss matters.
I started with .375" stock and machined off .093" to create the cylinder boss, leaving .282. The trial I did on the scrap has the bit descending .225" from touching the top of the stock, so I'm good there. Laterally I'm moving in .13" from touching off the side of the tool. Assuming the barrel has a 1/2" diameter, then in CNC terms it would be specified as a tool with a .24" diameter for an outside profile.
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Before running the corner round bit on the base, I tried out my calculations on a bit of aluminum.
(http://www.pbase.com/kvom/image/165168621/large.jpg)
The calculation based on the tool's diameter was a bit off, but I just used a series of negative roughing (overcut) passes until it looked OK. So with a final decision to use a .08" overcut and using .02" of radial cutting on each pass, I ended up with this:
(http://www.pbase.com/kvom/image/165168622/large.jpg)
My F&S software doesn't handle corner rounding bits; I used 1100 RPM and 10 IPM.
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Looks to me like it came out swell. :ThumbsUp:
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Last part of the base today. After drilling all the holes in some 1/4" brass, the boss for the column in cut out. Note the use of 3 small tabs to hold the part inside its parent stock.
(http://www.pbase.com/kvom/image/165172565/large.jpg)
Then over to the Bridgeport to mill to thickness using a face mill. This op removes the tabs.
(http://www.pbase.com/kvom/image/165172574/large.jpg)
In position on the main base. I need to order some 3-48 screws to fasten them together.
(http://www.pbase.com/kvom/image/165172575/large.jpg)
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Well that's coming along nicely Kirk.
Eric
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Great stuff. I like how you handled the tabs from the original piece.
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No photo, but made the second eccentric, this time using some extra stressproof rod I'd bought during the Joy engine build. I believe the first one was 12L14 from the way it machined, but that steel is liable to rust. I may just remake that one from the stressproof as the whole part takes less than an hour now that I have the programming.
Next time I'll start on trial two of the conrod.
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Third try at making the conrod in brass. All is well when the shape is freed from the stock. I left the "crossbar" in between the arms to prevent distorting them when clamped in the mill vise.
(http://www.pbase.com/kvom/image/165182244/large.jpg)
All was well on the extra manual milling until it came time to remove the crossbar. As soon as it was severed, the endmill grabbed the nearer arm and bent it slightly. I was able to manually bend it back, but whether it's precise enough remains to be seen.
(http://www.pbase.com/kvom/image/165182246/large.jpg)
In any case, I turned the bearings and did a test fit.
(http://www.pbase.com/kvom/image/165182248/large.jpg)
At this point I'm thinking I should just make a 4th one from steel. I have the process down pretty good by now. >:(
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Fairly short day in the shop as I was watching the golf on TV. Rather than another try at the conrod I decided to attempt the crank. Its profile fits withing a 1" circle, so I chose to CNC it using some 1" round rod.
(http://www.pbase.com/kvom/image/165187709/large.jpg)
Cut off on the lathe with a parting tool, then taken to proper thickness on the bridgeport, then finally the smaller boss on the CNC mill.
(http://www.pbase.com/kvom/image/165187710/large.jpg)
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In today's episode I attempt to build the bearing blocks and main bearings in a manner such that the crankshaft will turn smoothly when all assembled eventually. After preparing two pieces of 1/4" brass that I cut from a larger piece of scrap, they measured.75x1.3". Both got a reamed 3/8" hole 1/2" from the bottom edge, which is the edge against the fixed jaw.
(http://www.pbase.com/kvom/image/165202738/large.jpg)
Then with both pieces aligned with some drill rod and parallels, the mounting holes (for 3-48 tap) were drilled. As long as the matching holes in the entablature are drilled correctly the bearings should align closely. I used a center-finder on the drill rod to center them.
(http://www.pbase.com/kvom/image/165202740/large.jpg)
I then used the CNC mill to profile the sides, and then various manual milling ops brought them to nearly finished status (still have to do the tapping).
(http://www.pbase.com/kvom/image/165202742/large.jpg)
I then turned the main bearings on the lathe from some bearing bronze, using the bearing blocks to ensure a fit. Family shot afterwards.
(http://www.pbase.com/kvom/image/165202743/large.jpg)
The caps will need to be done sometime soon.
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The bearing caps are quite simple in the CNC world. First op is to machine the profile in some 1/4" brass . In this case, .30" DOC for a final target of .25" width.
(http://www.pbase.com/kvom/image/165208299/large.jpg)
Over to the Bridgeport to mill to width, drill 3-48 clearance holes, and spot face to clear the screw heads.
(http://www.pbase.com/kvom/image/165208300/large.jpg)
After tapping the mounting holes in the bearing blocks, the assembly using 1/4" long screws from American Model Engineering.
(http://www.pbase.com/kvom/image/165208301/large.jpg)
The 3-48 screws seemed closest to the metric screws Mount specifies, but in this case I think in retrospect that 2-56 might have been a better proportion.
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Looking good Kirk. I've been following. :popcorn:
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Don't let Jo catch you using screws, you know what she is like wuth her studs ;)
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Jo's studs? Tell me more!
I might try making some later, but for now I'll just get screwed. 8)
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I don't talk about my studs anymore, I embarrassed some of the members with my tales of what I do with them :embarassed: and they have rarely been seen since :(
Jo
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The past two days I've started on the pieces that will eventually become the cylinder. Taking some advice from Jason and will try JB Weld to stick them all together. All the parts except the port block are made from a length of 1.5" diameter bearing bronze I had left over from the Joy build. The port block is brass, and I started with some 1" square brass bar. The profile was CNC milled; luckily I had a good endmill with a 1.5" length of cut for this part.
(http://www.pbase.com/kvom/image/165217931/large.jpg)
The concave portion matches the .75" outside diameter of the cylinder. I didn't have a 5/8" reamer but did have a 16mm. Go figure.
(http://www.pbase.com/kvom/image/165217933/large.jpg)
Ovr
Next op was to mill the spigot for the exhaust, which also brings the port face to correct width.
(http://www.pbase.com/kvom/image/165217934/large.jpg)
Next, mill the spigots on either end, bringing the port face to final length.
(http://www.pbase.com/kvom/image/165217935/large.jpg)
Over to the lathe and drill/bore to obtain a close sliding fit to the cylinder.
(http://www.pbase.com/kvom/image/165217936/large.jpg)
Now turn and part off the missing flange for the cylinder.
(http://www.pbase.com/kvom/image/165217937/large.jpg)
Final job of the day is to use the form tool I made a few weeks back to make the decorative ring (astragal).
(http://www.pbase.com/kvom/image/165217938/large.jpg)
It will need to be cut open to fit around the port block. Seems it's a lot simpler just to start with the casting.
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The cylinder parts are coming together nicely!
What was the reason for making the flange for one end of the cylinder a separate part rather than turning it in on the original bar?
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So the astragal could be slid in. If I had turned it and the flange integrally then fitting the port block would be difficult. OTOH, I could have tried to do it like Justin, who cut the astragal to make it wrap. I am thinking of leaving the engine unpainted and so wanted the astragal uncut.
The other benefit is that I can ensure a close fit between the flanges and the port block this way.
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Looking good Kvom :-)
I've learnt something new today - didn't realise those decorative rings were called Astragals
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Kirk, this is masterful work. You must have an engineering background. Your work is so clean and precise.
John
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I don't talk about my studs anymore, I embarrassed some of the members with my tales of what I do with them :embarassed: and they have rarely been seen since :(
The members or the studs? :lolb:
Sorry Kirk. I couldn't resist.
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'astragal'...I'd never heard that term before. Comes from Greek and Latin for vertebrae.
Great looking part. :ThumbsUp:
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I learned the term astragal only from Jason where he mentioned it in JL's build. Today's work was to make the steam chest, and since JL already made this it's not a mystery part. After sizing the stock (I happened to have some 3/8x3/4" brass bar, the first ops on the CNC mill were just to drill the mounting holes (2-56 clearance) and mill the interior pocket. A 1/8 endmill would have been quicker, but none of mine had flute length < 1/4". So I found a 7/64 with over 1/2" flute length, but which I could feed at only 1.5 IPM. That pocket took nearly 30 minutes to mill, but I had a book to pass the time. On a manual mill I'd have chain drilled out the center first.
(http://www.pbase.com/kvom/image/165226621/large.jpg)
Then stood it up in the vise to profile the elliptical spigot and drill the necessary hole. Mounting screws are 1-78.
(http://www.pbase.com/kvom/image/165226622/large.jpg)
This is certainly the smallest steam chest of any of my previous engines. An interesting observation is that Solidworks allows me to draw the spigot as an ellipse and when saving as DXF converts it to a polyline with 96 segments. I am wondering where in SW configuration is the setting for the tolerance that controls the segment generation.
The problem with closeup photos is that you can see all the places I need to clean up. ;D
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@JL - I graduated with a mechanical engineering degree but worked as a software developer my entire career. All the mechanics has left me other than some concepts. But I can look up things and understand them (sometimes).
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I learned the term astragal only from Jason where he mentioned it in JL's build. Today's work was to make the steam chest, and since JL already made this it's not a mystery part. After sizing the stock (I happened to have some 3/8x3/4" brass bar, the first ops on the CNC mill were just to drill the mounting holes (2-56 clearance) and mill the interior pocket. A 1/8 endmill would have been quicker, but none of mine had flute length < 1/4". So I found a 7/64 with over 1/2" flute length, but which I could feed at only 1.5 IPM. That pocket took nearly 30 minutes to mill, but I had a book to pass the time. On a manual mill I'd have chain drilled out the center first.
Then stood it up in the vise to profile the elliptical spigot and drill the necessary hole. Mounting screws are 1-78.
This is certainly the smallest steam chest of any of my previous engines. An interesting observation is that Solidworks allows me to draw the spigot as an ellipse and when saving as DXF converts it to a polyline with 96 segments. I am wondering where in SW configuration is the setting for the tolerance that controls the segment generation.
The problem with closeup photos is that you can see all the places I need to clean up. ;D
Oh sure...........just keep it up with all this CNC stuff............it's getting more interesting all the time! :atcomputer:
Jim
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@JL - I graduated with a mechanical engineering degree but worked as a software developer my entire career. All the mechanics has left me other than some concepts. But I can look up things and understand them (sometimes).
If it's any consolation, I graduated from college in 1966 with a degree in Electronics Engineering Technology. I worked in the field for 6 years before buying a Commercial Salmon Troller and heading to sea. About the only thing I remember about electronics is Ohms Law. :wallbang: For years I've always wished I would of taken Mechanical Engineering Technology. Would of been much more useful through the years.
Jim
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Today's goal is to make a simple part with few ops needed. The valve rod gland is made from some 3/4" round brass rod held in a 5C collet. First on the lathe drill the center 3/32 hole for the valve rod.
(http://www.pbase.com/kvom/image/165233659/large.jpg)
Then move the collet and work to a collet block and set vertically in the CNC mill. Drill the mounting clearance holes (.081") and mill the two profiles.
(http://www.pbase.com/kvom/image/165233661/large.jpg)
Check that the spigot fits the steam chest. If it were too large it could be turned down on the lathe before parting. As it happens I have a good fit and just needed to part it off.
(http://www.pbase.com/kvom/image/165233663/large.jpg)
(http://www.pbase.com/kvom/image/165233665/large.jpg)
A bit of sanding to remove the tit left by parting and it's done. Glands for the piston and valve rods will be done the same way.
(http://www.pbase.com/kvom/image/165233667/large.jpg)
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Kirk you plan to soft solder or silver solder the port face on. Been following you quietly by the way. Looking great but I am finding CNC uses a lot of metal just to carve out one piece. A lot of waste don't you think?
Don
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There's no doubt some pieces could be made with smaller stock. But sometimes the ability to hold the stock easily overrides that. The gland could be made with 1/2" round, but the ellipse is 1/2" long and might get shaved. I don't have any 9/16 or 5/8 rod, so 3/4 it is. Besides the part is pretty small.
The port block could have been machined from smaller square bar had I had any. But I have about 15 feet of 1" square or larger, so a bit of waste on 1.5" of length isn't that concerning.
As for the port block, I was thinking to follow Jason's lead and use JB Weld to assemble the cylinder parts. Soldering would be more secure, but I don't have much confidence in my soldering ability. I'm going to solder the entablature before hand; it's likely more forgiving, so we'll see how that goes first.
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Kirk here's a write up and photos of how I did mine.....http://www.modelenginemaker.com/index.php/topic,3702.msg72293.html#msg72293
Don
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I had already gone through your build thread, Don. Very impressive.
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Cocked up a part today but learned something. I attempted the bracket for a second time by attaching two pieces of brass at right angles with silver solder. After a pickle and squaring the result in 3 dimensions, I ended up with this:
(http://www.pbase.com/kvom/image/165238898/large.jpg)
The smaller piece is 1/8" thick, and the larger 1/4". But when I attempted to machine the profile on this large piece while clamping the smaller in the vise, the endmill lifted the piece bending at the joint. Where I want wrong was butting the smaller piece against the larger so that the width of the solder joint was 1/8". Had I done it the opposite, the joint would be twice as wide and twice as strong.
Attempt number 3 pending. ::)
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The woodworker in me says that you should dovetail the joint!
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So now I have a possible problem in completing this build. I can't find an online supplier for the helical gear in the size needed. Plans say 15 teeth, 48 DP, .442 PCD. Anyone have an idea?
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HPC Gears have those listed
http://hpcgears.com/pdf_c33/25.42-25.45.pdf
Phil
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Cut 'em :naughty:
Eric
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So now I have a possible problem in completing this build. I can't find an online supplier for the helical gear in the size needed. Plans say 15 teeth, 48 DP, .442 PCD. Anyone have an idea?
Yeah Kirk make them I did with the help of Chuck Fellowers fixture. They were my first Helical gears. You can do it to, look at my thread and see the gears I made and fixture and cutter to make them with.
Don
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Small 1mm or less cutter and you should be able to CNC them ;)
As you have not made the entablature yet you could adjust the PCD to suit what is available locally and just move the vertical post that the governor sits on.
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I inquired at Polly Models and can get the gear from them.
Boston gear doesn't supply anything small enough. I see lots of gears on eBay that are used in model helicopters, but there doesn't appear to be any specs on them.
The CNC option would likely work using the 4th axis.
I'll likely just buy the gears. Maybe Don would make it for me. :noidea:
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Today I made a start on the entablature, since the gear issue was on my mind. Cut out the side plates from some 3/16" brass bar since I don't have appropriate 1/8. After face milling on each side the thickness of each is .167.
(http://www.pbase.com/kvom/image/165245198/large.jpg)
Now the goal of assembling it is to retain the spacing between the centerline and the center of the side bar that will mount the governor. Since the plans have a total width of 1" and 1/8" thick sides, that dimension is just 7/16" or .4375 (close enough to the .442 PD of the gear). So using the sides I have, the outside width of the entablature will be (.4375 + .0834) * 2 or 1.043". And thus the spacers between the sides will be 1.043 -.334 = .709. That is the size I will need to make.
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One sure way to get Don to do them is bet him a shrimp po'boy that he can't do them. I do know how dem coonasses is :lolb: :lolb:.
Eric
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@Don - you listening? :help:
Got the sides soldered together, although I'm still getting varied result with SS. Of the 4 joints here only 2 of them had a decent flow. Since I cleaned and fluxed them at the same time I'm not too sure why. Possibly my solder is too thick (1/6" wire, 45%). I might try hammering into a thinner sheet next time out.
Poser shot below. I need to trim to length, drill the mounting holes for the bearings, and add the governor mount. I think I'm going to powder coat this part, then epoxy a brass base.
(http://www.pbase.com/kvom/image/165245793/large.jpg)
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I would not qualify as an expert at silver solder, or even very good, but the times I've had the most trouble getting the solder to flow right was usually a result of not getting the parts hot enough to flow the solder before the flux burned off, switching to a larger tip on the torch helped in those cases. Other times I got one side hot, but the mating part was still too cool, and the solder flowed out onto the hot side and not into the joint.
My 2 cents worth, probably worth about 10% of that, still learning that art....
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Yes usually lackl of heat which does not get the part hot enough for the solder to wick into the joint or takes too long to get things upto heat by which time the solder is exhausted.
Also you need a small gap for the solder to wick into, don't clamp flat surfaces together, put a couple of light punch marks on one of teh surfaces so the burr around the punch mark acts as a tiny spacer.
1/16th wire will be fine its what I use 99% of the time
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I had a similar problem a few days ago with solder not flowing properly whilst trying to join a 3" dia brass tube to a square brass sheet base, initially I had used a substantial piece of steel on the top as a weight to stop things moving while soldering but found the solder just formed globules and didn't flow.
Once I removed the steel weight and replaced it with something smaller as less of a heat sink and placed the job further into the corner of my I hearth I found the extra heat made all the difference and had no problem second time around.
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I had parts clamped (lightly) so that possibly explains the problem.
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Yes usually lackl of heat which does not get the part hot enough for the solder to wick into the joint or takes too long to get things upto heat by which time the solder is exhausted.
Also you need a small gap for the solder to wick into, don't clamp flat surfaces together, put a couple of light punch marks on one of teh surfaces so the burr around the punch mark acts as a tiny spacer.
1/16th wire will be fine its what I use 99% of the time
YEAH YEAH,I'm listening. Follow Jason's suggestion for proper flow. I use Easyflo solder 56% silver. On the gears i can make them, but it will be a while before i get to them. Are you using Anthony's dimensions?
you really need to learn how to make them and it is really easy to do with the help of Chucks fixture. I am attaching the PDF of Chuck's fixture and my spreadsheet on gears if you don't already have it. The Helix calculation will give you the cutter to use and all dimensions. Just enter the DP and number of teeth.
For some reason the forum wouldn't let me attach the Gear Calculation sheet so go to plans and drawings and download it.
Don
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I am using Anthony's dimensions. I'm not against making a gear per se but generally I'm not enthusiastic about making a 1-off something that's commercially available relatively cheaply. I do admire those who spend the time as you did but for me it would a chore, not a pleasure.
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Despite spending most of the afternoon watching the Masters golf tournament, I managed to get a little done. Brought the entablature to length and drilled the mounting holes for the bearing blocks. Mount shows these holes to be countersunk from the bottom, so I suppose he used socket screws there where they wouldn't be seen. I have no 3-48 sockets at present so left the holes as drilled and used hex head screws.
Then mounted the cylinder port block in the machinist's vise in order to drill the holes in the face. Since I couldn't use parallels here, I ensured that it was mounted flat by turning the vise and part upside down on the surface plate before tightening.
(http://www.pbase.com/kvom/image/165250755/large.jpg)
After tapping the mounting holes it was nice to see that they matched up with the steam chest.
(http://www.pbase.com/kvom/image/165250757/large.jpg)
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On the original the beraing supports were part of the cast entablature so that is why he hid the bolt/screw heads, holes were then filled and painted.
You could just counterbore large enough to fit the across corners of your hex fixings and saw a small slot in the head so they can be tightened with a screwdriver. Does not matter what they look like as the holes can be filled before painting or if you are leaving bare then counterbore deeper and loctite in brass plugs and file flush.
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Given that Mount designed the model based on an engraving, I don't feel particularly constrained by every part of the plans. Even with countersunk socket screws it would be pretty hard for anyone to imagine their presence. I did check that there's enough room to countersink #3 socket heads.
Today I continued on with the steam chest by attacking the valve nut. Having some 3/8" square brass bar, that was one dimension I didn't have to mill. Drilled and tapped the 3-48 hole for the valve rod and reduced the thickness to 1/8".
(http://www.pbase.com/kvom/image/165271426/large.jpg)
After sawing off the nut, some filing and sanding brought the 1/4" width.
(http://www.pbase.com/kvom/image/165271428/large.jpg)
The first op on the valve was to mill the bottom cavity and the outer profile on the CNC mill. Stock is some 3/4" bronze rod. Before removing from the mill the fit to the steam chest is checked.
(http://www.pbase.com/kvom/image/165271441/large.jpg)
The rest of the machining of the valve was done manually. I saw no reason for the 3/32" dimension on the slot for the valve rod since both the valve and nut are centered by the steam chest cavity. And not having an endmill to cut it I just used the same 1/8" endmill as for the lateral slot for the nut.
(http://www.pbase.com/kvom/image/165271443/large.jpg)
I do notice that when the valve is as far to one end as is possible the port is only partially exposed. I need to compare the maximum travel here with the throw of the eccentric. Might need to file the corners of the steam chest a bit (or chamfer the corners of the valve).
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I've done a couple of similar valves using the holes rather than slots in teh port face and file the corners off the valve to fit the radius on the inside of the chest as its easier.
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Yes, you have to give some space to allow adjustement of the valve travel.
removing metal on the valve would change lap for the steam distribution, rounding off the corner may be enough, but the valve looks cramped...
I like the way you build parts all along the thread, very nice, thanks to share.
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Wonderful work Kirk.
John
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Back in the shop today I sanded a bit off the bottom corners of the valve, and now have enough travel to fully open both ports. I can take off a little more if needed.
Two main tasks of the day. First was to fit the astragal to the port block. Mic shows width of the block as .628, so I whittled away opening a gap until I got a tight sliding fit. Perfect for one side, but the exhaust spigot is in the way on the other. I have an endmill close to the diameter of the spigot, so milled a curve into one end of the astragal. pretty close fit (closer than it looks in the pic).
(http://www.pbase.com/kvom/image/165275339/large.jpg)
(http://www.pbase.com/kvom/image/165275341/large.jpg)
Second goal was trial 3 on the bracket. The soldered part was glued to an aluminum fixture block with Devcon epoxy get and allowed to cure over the weekend. Then the profile was milled through the brass. I drilled the hole for the regulator rod, but taking a clue from Jason I decided to wait until both the column and cylinder are on the base, and the exact position of the piston rod can be found.
(http://www.pbase.com/kvom/image/165275342/large.jpg)
After a 350F oven bake for 40 minutes, the epoxy releases with just a little effort. Mounted to the column to check fit.
(http://www.pbase.com/kvom/image/165275636/large.jpg)
Time to taper the column it seems.
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I hadn't used the my lathe's taper attachment for several years so it took a while to get it set up. Setting the taper itself is helped by having DROs. Zero both X and Y at the start, move the carriage to the end, divide the two resulting readings and apply the inverse tangent on a calculator to get the angle. With some tweaking I was able to get the angle to 2.01 degrees.
Since I started with a smaller diameter than Mount specified (1.125 vs. 1.188), I found that the taper started to cut into the threaded holes at the top. So I've decided to leave the bottom 1" untapered.
(http://www.pbase.com/kvom/image/165279042/large.jpg)
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For the central decorative ring (astragal) on the column, I chucked a length of 1.125" brass rod in the lathe and drilled through a 3/4" hole to accommodate the boring bar. Then using the taper attachment I tapered the hole until the column could go it half way.
(http://www.pbase.com/kvom/image/165290810/large.jpg)
Then used the form tool before parting off. The astragal fits tightly without any solder or epoxy.
(http://www.pbase.com/kvom/image/165290814/large.jpg)
Other than that, the only job of the day was to drill and tap the crank for a 2-56 set screw and turn down the end of the crankshaft to fit.
(http://www.pbase.com/kvom/image/165290815/large.jpg)
With the casting, the center of the governor mount lines up with the outer edge of the entablature. Since I used thicker material in the fabrication, I wanted to see where that point would be, since I need to come up with a boss to accommodate it.
(http://www.pbase.com/kvom/image/165290816/large.jpg)
It appears that a quarter inch boss would just fit within the material of the sides. I need to think about how to do the fabrication some more.
It was hot yesterday. Time to turn on the shop AC.
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This afternoon I made a start on a non-operative version of the pump. Since it doesn't need to pump water, I was a little free with some dimensions, mainly the top of the pump and its gland. By making them .5" diameter, I could use 1-72 screws instead of 0-80.
First op is turning the pump body from some 3/4" brass rod. 5/8 would have worked had I had any.
(http://www.pbase.com/kvom/image/165294697/large.jpg)
Then on the mill to drill the hole for the output pipe. I used a 1/4" endmill for this, and checked fit with some brass rod.
(http://www.pbase.com/kvom/image/165294699/large.jpg)
Then mounting holes for the gland, to be tapped 1-72.
(http://www.pbase.com/kvom/image/165294700/large.jpg)
Very similar turning and drilling for the output pipe-flange and gland.
(http://www.pbase.com/kvom/image/165294701/large.jpg)
Poser shot of the three on the base. I still need to drill the flange for bolting to the base, and to decide how to attach the output. I think epoxy will be neater than solder, esp. as the output is a tight fit to the body.
(http://www.pbase.com/kvom/image/165294702/large.jpg)
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I like how you added the ring to the middle of the column - another one to file away....
:popcorn:
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Hi Kirk,
Oh, it's nice to see you making this part. I can learn so much from watching. :praise2:
John
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JL: if you want to pump water with yours you'll have to work a lot harder than I did on the pump. That said, other than soldering the output pipe to the body, it's mainly following the plan and being careful.
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Some finishing on parts already mostly done.
First job was drilling side exhaust passage in the port block, plus drilling and tapping the flange for 1-72 screws.
(http://www.pbase.com/kvom/image/165299615/large.jpg)
Then I epoxied the pump output to the body and let it cure during lunch. Then setup to drill the mounting holes in the flange for 0-80 screws.
(http://www.pbase.com/kvom/image/165299617/large.jpg)
Now I could bolt the pump to the base from below. Tweezers required when working with 0-80 nuts and washers.
(http://www.pbase.com/kvom/image/165299621/large.jpg)
Since the screw heads are proud of the base bottom, I used a 1/8" endmill to counterbore the main base so that the upper base would set flat.
(http://www.pbase.com/kvom/image/165299624/large.jpg)
(http://www.pbase.com/kvom/image/165299627/large.jpg)
Other than that, I also drilled and tapped the steam chest input as 10-32, not having a 3/16-40 tape or die. In any case, that size pipe allows a 1/8" bore, which is slightly larger then the output pipe.
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Seeing JL's latest update reminded me I'd not done anything about the linkage between the governor and the steam chest. I'd not even modeled the brackets. Not having a lot of shop time today, I settled for notching the entablature and drilling/tapping the mounting holes for the bracket. I then decided to make the pivot in two pieces as machining 1/8" square from 1/4" round is not appealing. In fact, I used 3/16" square as I have both the material and a square collet to turn it. I milled the slot 5/64 as per plan, but with extra material I may enlarge it to 7/64 to make fabricating the rocker arm a bit easier.
(http://www.pbase.com/kvom/image/165308289/large.jpg)
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Looking good Kirk :ThumbsUp:
I see that you got your old Avatar back - great, I missed it :)
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Still following along and enjoying :ThumbsUp: :ThumbsUp: :wine1:
"astragal" that's not a word I have come across before :headscratch:
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Today I made the bracket that supports the governor pivot Stock is nominal .375x.188" brass bar. Drilling and profile ops done on the CNC mill.
(http://www.pbase.com/kvom/image/165312397/large.jpg)
After cutting off on the bandsaw, the part is reversed to mill off the bottom, bringing thickness to .125".
(http://www.pbase.com/kvom/image/165312398/large.jpg)
Assembled, awaiting delivery of some 1-72 screws for attachment to the entablature.
(http://www.pbase.com/kvom/image/165312400/large.jpg)
I epoxied the cylinder parts together; after curing I'll finish it by drilling the mounting holes in the flanges and then the "nervous" steam ports.
This morning I called Polly Models in the UK to order the skew gear. Who knows how long that will take to arrive?
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I received my McMaster order after the last post. One item is a box of 2-56 x 1/8" set screws, of which I need 5 thus far (2 governor, 1 crank, 2 eccentrics). I discovered that these need a .035" (.9mm) hex driver, while my smallest in a set is .049". So I'll need to order a WiHa driver unless I find someone selling them at NAMES this weekend.
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With cylinder glued together, it was time to drill and tap the mounting holes. I had purposely made the flanges a bit larger than to plan, and now made the bold circle larger as well, leaving room for a 2-56 model scale nut to fit. First order of business was to find the center of the bore.
(http://www.pbase.com/kvom/image/165315806/large.jpg)
Then drill the and tape the holes. Same process with the cylinder reversed.
(http://www.pbase.com/kvom/image/165315809/large.jpg)
Ready for steam ports to be drilled next time out.
(http://www.pbase.com/kvom/image/165315811/large.jpg)
Although the holes are tapped and the nuts are not needed, I will screw them onto the ends of the mounting and cover screws for appearance sake.
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Still here Kirk. It's an interesting thread and the parts are looking good.
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After a great weekend at NAMES and a Monday occupied with kitchen upgrades, I got back in the shop for a couple of hours. The project for today was to start on the cylinder cover. Stock was a length of brass hex 1.5" across the sides. After facing both ends, I reduced one end to the target diameter of 1.2" for a length of .40". Then it was off to the CNC mill to drill the mounting holes for the cylinder and gland.
(http://www.pbase.com/kvom/image/165348975/large.jpg)
Then the gland spigot was milled.
(http://www.pbase.com/kvom/image/165348976/large.jpg)
After tapping the gland hold 1-72, it was back to the lathe to part off the cover, which was then reversed to bring it to the desired dimensions. This chuck is quite useful for holding thin parts as parallels can be placed between the jaws to space the work evenly.
(http://www.pbase.com/kvom/image/165348977/large.jpg)
Assembled on the cylinder to check the mounting hole fits.
(http://www.pbase.com/kvom/image/165348978/large.jpg)
The holes for the gland and piston rod will be drilled with the cover mounted on the cylinder, ensuring that they're centered on the bore.
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Lovely work and work holding examples.
I'm going to have to look for an affordable source of brass , it is such a colourful material. Somehow I suspect I will instead end up learning how to plate :-)
Gerrit
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Lovely work and work holding examples.
I'm going to have to look for an affordable source of brass , it is such a colourful material. Somehow I suspect I will instead end up learning how to plate :-)
Gerrit
Look for commercial suppliers in your area, many will sell you offcuts and leftovers (drops) at a good price, though selection is limited. I've gotten great deals that way.
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To fit the piston to the cylinder we need a gland for the cylinder cover and then a piston and piston rod, and all the pieces have to line up. Having already a piston and its cover, the gland is next. Took a piece of 3/4" brass rod (5/8 would have done), faced on the lathe, and then moved to the mill where the mounting holes were drilled.
(http://www.pbase.com/kvom/image/165353838/large.jpg)
Then a 3/16 endmill finishes the shape.
(http://www.pbase.com/kvom/image/165353839/large.jpg)
Then back to the lathe to part off and bring to correct dimensions.
(http://www.pbase.com/kvom/image/165353840/large.jpg)
Next the cylinder is chucked on the CNC mill and the center of the bore is determined as accurately as possible. Then the cylinder cover is attached with screws and the center 1/4" hole is machined .187" deep. I used a spiral mill with a 3/16" endmill so that I'd have a flat bottom and also be able to enlarge it slightly if needed. In fact the gland was a very tight fit, so I made a second pass that increased the radius of the hold be .001".
(http://www.pbase.com/kvom/image/165353841/large.jpg)
Then with the gland attached to the cover I drilled and reamed a .126" through hole.
(http://www.pbase.com/kvom/image/165353842/large.jpg)
Now we need a piston. I started with a piece of .875" stressproof steel rod on the lathe that I faced and reduced in diameter to .650" (Bore is .630"). Then drilled for a 5-50 tap and parted off a bit more than .280". Re-chucked this piece to face the opposite end and tapped the through hole.
For the piston rod I parted off ~4.5" of 1/8" drill rod and threaded one end for about 3/8". I screwed the rod into the piston and chucked the combination on the lathe using a 1/8" 5C collet. Now I could turn the piston to the final diameter using the cylinder as the test. Finally faced the piston to .25" and cut a .62" groove in the center.
(http://www.pbase.com/kvom/image/165353843/large.jpg)
With everything assembled the piston travels fairly smoothly the length of the cylinder.
(http://www.pbase.com/kvom/image/165353844/large.jpg)
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Looking very nice Kirk.
Are the bolts in the cylinder cover temporary or are you going to place studs in the threaded holes and use nuts to draw down the cover?
I marvel at the skill in making and applying that astragal.
John
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I made the bolt circle for the flange large enough for the model screw heads to turn, so one option is to screw them in underneath and put a nut on top, emulating a stud and nut. For the bottom flange long screws will come up from the bottom through the base securing the cylinder with nuts.
Finishing that part of the base will be one of the next things to do.
I need to order some 1-72 screws from AME for the glands.
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When I originally machined the base I didn't drill the mounting holes for the cylinder and as well left the spigot at .75". Now that the cylinder dimensions are known today's task is to fit it to the base by drilling the 2-56 clearance holes and fitting the spigot.
(http://www.pbase.com/kvom/image/165359143/large.jpg)
After ensuring a good fit, I reversed the base to countersink the holes and attached the cylinder. One of the screws got a nut, something that simulates a stud-nut combination. The holes under the port block may be a challenge to get a nut there.
(http://www.pbase.com/kvom/image/165359147/large.jpg)
And the obligatory family shot.
(http://www.pbase.com/kvom/image/165359149/large.jpg)
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Make sure you flute the column so all the motion is directed in the proper direction!
:lolb: :lolb:
Looks great!!
Pete
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Drilled the steam channels today, an operation that went without drama.
(http://www.pbase.com/kvom/image/165363580/large.jpg)
I marked the side of the port block with the target point in order to confirm the angle and depth, then milled a flat with a 1/8" endmill, spot drilled, and then finished with a 3/32" drill. I used a spindle stop but felt the breakthrough just before the stop point. Note the use of the 3" long parallels I picked up at NAMES. Much preferable to the 6" ones I'd used before with the small vise.
The cylinder is now complete.
My other job for the day (no pics) was to counter bore the base for the column attachment, which consists of a thin brass disk into which 1/4" drill rod is pressed. The upper end is to be threaded 1/4-20. A nut on top will secure the column and entablature in position.
At this point I need only make the conrod (3rd try), steam chest cover, and the eccentric rod for the valve before being able to try it on air.
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The entablature casting has a circular boss in the center on one side for mounting the governor. The center of this boss needs to be at half the pitch diameter of the skew gears from the centerline of the crankshaft. With the entablature clamped in the vise and the crankshaft mounted, I used a center finder to locate both the centerline of the crankshaft and the center of the entablature. Then with the spindle offset .455" from the crank centerline, I used a 5/16 endmill to plunge .75" deep into the entablature wall.
(http://www.pbase.com/kvom/image/165367606/large.jpg)
The boss itself is a piece of 5/16 brass rod drilled and tapped to fit the governor. In this case 3/32 through and .25" deep 10-32 tap. I was anticipating needing to solder the boss, but it turned out to be a tight fit and I
pressed it in.
(http://www.pbase.com/kvom/image/165367607/large.jpg)
With the governor mounted:
(http://www.pbase.com/kvom/image/165367608/large.jpg)
Quite by chance, the skew gear from Polly Models arrived in the mail today.
(http://www.pbase.com/kvom/image/165367609/large.jpg)
Chucked in the lathe and parted off the center of the teeth with a 1/16" groover.
(http://www.pbase.com/kvom/image/165367610/large.jpg)
The part with the boss was drilled out to 1/4" (for the crankshaft), and then drilled for a 2-56 grub screw.
(http://www.pbase.com/kvom/image/165367611/large.jpg)
The parted end is already drilled 3/16, so a length of 3/16 brass rod was loctited and left to cure several hours, then drilled 3/32 to fit the governor. Next time in the shop I'll fit this part with a grub screw, mount it on the governor, and see if the two mesh.
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That picture with the governor mounted is NICE! Bet that plunge cut was a little nerve wracking.
:popcorn:
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Actually it went very smoothly. The sides are thicker than the 1/8" found in the casting. 4-flute carbide endmill.
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Mounted both gears for a trial fit. I was happy to see that rotating the crankshaft rotates the governor. Fit is slightly stiff and I think gears will need working in.
(http://www.pbase.com/kvom/image/165373259/large.jpg)
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I gave the entablature to my friend to powder coat. While waiting for it to be done I made a see-through steam chest cover from 1/8" acrylic and started to fit the bracket to the piston rod.
After finding the center of the cylinder, I mounted a spot drill and rotated the cylinder until the bracket was under it. Seems it doesn't stick out far enough for the hole to be centered in the end of the bracket.
(http://www.pbase.com/kvom/image/165385441/large.jpg)
Moving the X axis until it looks centered shows as 14 thousands on the DRO. So my plan now is to drill the hole in the bracket center and then insert shims between the bracket and column.
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Only progress today worth a photo is an adapter I made for eventually supply air to the engine. Some 3/8" brass rod drilled and tapped 1/16-27 NPT on one end, then turned and threaded 10-32 on the other. Drilled .102" through.
(http://www.pbase.com/kvom/image/165390085/large.jpg)
(http://www.pbase.com/kvom/image/165390086/large.jpg)
Also made the ram for the pump.
I need to shorten some 1" 2-56 screws to about 5/8" in order to fasten the steam chest and its cover to the cylinder, but ran out of energy.
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Got back to the engine this afternoon, the first task being shortening screws so as to fasten the cylinder, steam chest, and cover together. I realized I had made a slight error in mating the port block to the cylinder in the opposite direction that I'd originally intended. That meant that the flange integral to the cylinder (and hence most guaranteed to be orthogonal to the bore) will be on the bottom, while the attached flange will have the cover attached. Since I had drilled the cover and gland while attached to the integral flange, I feared that the bore for the piston rod might not be as dead on as intended.
So with the pieces assembled, I applied air to the steam chest and manually operated the valve rod. It seems that with the bottom port open the piston rises to the top, but not vise-versa. So either the piston jams a little at the top or is blocking the port. Next time I'll undo the cover and see what's happening. The good news is that there's very little air leakage with no gasketing or packing.
(http://www.pbase.com/kvom/image/165413673/large.jpg)
The second job was to make the astragal for the bottom of the column. For this I made a second form tool with a 3/16" diameter arc, but this time I used a slice 3/8" of O1 tool steel rather than O1 drill rod. This went quite well, and testing the tool on a 1" brass drop was successful. So mounted some 1.5" hex bar on the lathe and turned the end down to 1.375" diameter before using the form tool. Then I bored the center out testing the fit with the cylinder end itself (remember that the bottom end wasn't tapered.
(http://www.pbase.com/kvom/image/165413674/large.jpg)
Once a tight fit was attained, the ring was parted off.
(http://www.pbase.com/kvom/image/165413675/large.jpg)
The fit is tight enough not to need any adhesive.
(http://www.pbase.com/kvom/image/165413676/large.jpg)
I have jury duty next week, so I don't know when I'll get into the shop next.
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Looking fine! That astragal looks great. The valve issue should be sorted easily, sure you will get it going.
:popcorn:
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Making the connecting rod the 3rd time, this time from O1 tool steel yielded a better result. Then only had to make the straps twice. :hammerbash: Because the holes for the cotters and wedges aren't square, I'll need to do some filing on the cotters to get a fit, but here's where I am with the roughed out wedges holding things together.
(http://www.pbase.com/kvom/image/165476028/large.jpg)
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That looks great! A little bit of time with the needle files and ghe slots will be done. Excellent!
:popcorn:
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Been with you Kurt just been quiet but enjoying your build. Getting close are you making the flywheel or purchasing one?
Don
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Don, I bought a pair of finished flywheels of the correct size off the consignment table at Cabin Fever. There's a pic on replay #77 from March 19.
I started to do some filing on the various cotter/wedge/holes for the conrod, but it was slow going. The cotters and wedges are very hard to hold onto. I also managed to knock one of the strap-bearing combos off the bench and onto the floor, where the shop elves confiscated it. They're not too hard to remake, but I decided to give the filing a rest in hopes that they show up. For the remaining two straps, i redid the holes by making an additional pass around the edge and employing corner relief with a 3/64" endmill. Here's one of the results:
(http://www.pbase.com/kvom/image/165480651/large.jpg)
So I won't need to file these anyway.
Couple of smaller tasks got done. I drilled and reamed the hole in the bracket through which the piston rod passes, I could have done so when the rest of the part was made originally. Here's the setup I came up with:
(http://www.pbase.com/kvom/image/165480649/large.jpg)
And the trial fit:
(http://www.pbase.com/kvom/image/165480650/large.jpg)
I can move the piston rod, but the tightness of the bracket's mounting screws can cause binding. The hole is .126", but I may use a #30 reamer to give it more space.
Last job of the afternoon was turning the "big end bolt" that connects the conrod to the crank. Turned from 1/4" drill rod and threaded 3-48 on the end.
(http://www.pbase.com/kvom/image/165480652/large.jpg)
Still waiting for my buddy to powder coat the entablature.
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Finally got the entablature powder coated. I don't think it looks too bad. Test fit on the column:
(http://www.pbase.com/kvom/image/165520872/large.jpg)
With the crank at its bottommost position I can tell how much to take off the piston rod next time in the shop.
(http://www.pbase.com/kvom/image/165520873/large.jpg)
Rest of today's shop time was filing and fitting the cotters and wedges to the conrod.
(http://www.pbase.com/kvom/image/165520874/large.jpg)
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Looks great with the wedges in place!
:popcorn:
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Did a bit of adjustment to be able to mount the conrod to the piston rod and free up the motion, including reaming the bracket hole with a #30 reamer. Also made the 2 crosshead pivots (part 24). Then with the conrod and flywheel connected to the crankshaft, I found that the rotary motion is quite smooth. Of course this flywheel is oversize (7") and quite heavy, so the rotational mass overcomes any sticky spots.
(http://www.pbase.com/kvom/image/165526696/large.jpg)
The next steps will be to mount the eccentrics on the crankshaft and to then figure the lengths of the two eccentric rods.
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Kurt,
Good to see the progress. I must admit the flywheel looks oversized and undoubtedly will overtake any rough spots.
Art
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Today's goal was to assemble the crankshaft with the eccentrics and skew gear, then fit the eccentric rods. This was fairly straightforward as pertains to the eccentric rod for the pump, and the length is not super critical as long as the dummy ram stays inside the pump body.
Ran into a glitch on the valve eccentric when I discovered that I had neglected to through drill the head of the valve rod. So I had to unscrew the valve rod in order to do so. Then I had a problem re-installing it since apparently the valve nut must have moved. I removed the column and everything on it in order to get access to the steam chest, but was able to nudge the nut back into place and screw in the rod without removing the steam check cover.
Reassembly and finishing the valve eccentric rod will wait for another day. I want to do a little better fitting on some pieces first. Also, the length of the eccentric rod needs to be more precise in order that the valve travel is centered. There's about .2" of adjustment possible from the fork end.
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I attempted to attach the governor pivot to the entablature today and discovered that it interfered with the crankshaft. Turns out I had made it from 3/16 stock instead of 1/8. I'd also modeled it incorrectly in SW (as 1/8 round instead of 1/8 square). When I modeled the assembly in SW I see that the clearance is still very small. We'll see how close it is once I machine off the extra material and reassemble. Looking at JLs engine photos, I can't tell what the clearance is but it's not large.
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You will probably only have 1/32" between shaft & pivot, my larger one looks about 3/64"
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I've decided to remake the bracket so that there's a bit more more space. Even after reducing the diameter of the pivot it's too close for comfort.
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Finished remaking the valve eccentric rod. This time I just turned the tip of the eccentric end down to 1/16 from 3/32 rather than drilling and gluing in some 1/16 in the end. For some reason I had originally thought that op would be difficult. :shrug:
I was able to do an initial assembly of the the eccentrics and adjust the position of the fork on the valve eccentric so that the valve does move through a 360 turn of the crankshaft. Any further need to center the valve in its travels will be done by turning the valve rod itself.
I did find a problem brought on by not following Mount's dimensions exactly. I made the entablature cross piece wider than the bearing carriers, and as a result they interfere with the jam nuts on the eccentrics. With the eccentrics moved inboard to clear, the eccentric rods aren't vertical as can be seen here:
(http://www.pbase.com/kvom/image/165558282/large.jpg)
So next time in the shop I need to disassemble to remove the entablature and machine vertical grooves in the ends to clear the nuts and rods.
I ordered a dental mirror on eBay to be able to look at the valve position through the acrylic steam chest cover. Once I have that and the above fix I should be ready to attempt a run on air.
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Looking great! I'll go make some more popcorn for the first run video.... :popcorn:
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I had an interesting thought last night. Normally to time a slide valve engine you adjust the eccentric and fix it with a grub screw. On this engine the tapped hole for the screw is only .045" long meaning a 2-56 screw has only 2.5 threads engaged. OTOH, the grub screw holding the crank has 8.5 threads of engagement possible. So would it make sense to secure the eccentric to the crankshaft with loctite. and then set the timing using the crank?
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Once you have got the timing right, loosen off the grub screw and slide the eccentric to one side, file a flat where the screw bears and then put it back together. That way you don't need to apply any large forces to the grun screw to hold the eccentric in place as it is unlikely to slip against the flat. I have two grub screws at 90deg on my eccentrics
Crank would not likely have had a grub screw originally eiother forged /shrunck onto teh shaft or pressed on with a key. Eccentric would have been adjustable to allow the desired running direction to be set when on site.
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Makes sense, Jason.
This morning after milling the relief groove in the entablature, I assembled the engine to discover that something isn't aligned properly. At TDC the column gets pulled towards the cylinder. The column and entablature are able to wobble despite being held together with the base by a length of 1/4" threaded rod cinched down quite tightly. If I squeeze the cylinder and column together manually the crank turns fairly smoothly.
As a start of diagnosis, I'll disassemble again and check how the column mounts to the base and also how parallel the entablature and crankshaft are to horizontal via surface plate.
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Sounds like one of the mating surfaces may be slightly convex
Or is there an uneven build up of that powder coat on one surface
External corners not eased enough to clear small radius on mating internal corners left by the tip of insert tooling
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If its just a TDC, is it possible that the piston is hitting the top cap, stopping it from moving just that last little bit?
Not that I've done that. Nope. Not today, anyway! :zap:
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I discovered that the first problem (column tilting) was caused because I didn't have a flat washer under the bottom nut, so that the nut was bearing on the tapered surface of the column bore. Once I added a washer I could tighten it securely.
Moving on to problem two, I have the piston sticking about a third of the way from the top. I am seeing this with the piston rod inside the bracket, and as well when I tighten the cylinder cover snugly. It appears from inspection that the piston rod itself is not as straight as it needs to be, so I plan to remake this before proceeding further.
Another problem that's apparent is that the flywheel I have is much too heavy for this engine. The weight on the end of the crankshaft puts significant leverage on the entablature, especially as the bearing carriers are held on with 2-56 screws.
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More exploration. I remade the piston and rod, this time using loctite. The prior one I did a press fit that might have caused some bending of the rod. Drill rod isn't perfectly straight either, esp. small diameters.
I removed the bracket and cylinder head, and was then able to show a quite smooth operation of the crank and piston. Then with the head replaced, I find that tightening the mounting screws unevenly can jam the rod, but that's fixed without any problem. Next I found that the gland was causing some friction, and the direction the gland is mounted to the head has a big effect. By opening up the hole in the gland by the next size # drill allows quite free motion of the crank and piston by hand.
At this point adding the bracket without its mounting screws shows a gap with the cylinder of approximately 15-20 thou. Next time in the shop I'll cut some shim stock to try to get it to align for free motion.
My dental mirror showed up in the mail. Still not much room to deploy it but it's better than nothing.
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:pics: Kurt I just bent the bracket on mine to aligh it but carefully. Been follow you and sorry to see the problems your having bud keep at it, it's a great engine.
:cheers:
Don
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Bending the bracket doesn't look like a solution as it's too short. Got some feeler gauges and determined that the needed space seems to be .033". I have some .031" shim stock that I will drill and mill if I can get my a$$ in gear. I determined the needed spacer by holding the bracket against the feelers and rotating the crankshaft.
Not sure how it got that far off.
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I made the shim for the bracket from some .031" stock, and with it between the bracket and column I am able to turn the crank with my fingers. With that problem solved, I mounted the governor and flywheel for a family shot. Although it turns reasonably smoothly, I have an annoying squeak in one part of the rotation. Oiling the usual suspects didn't help, and I can't determine by ear where it's coming from.
One other issue appeared, in that the governor balls will hit the top of the pivot. Looking at the drawing it appears that I made the arms too long so that the balls sit too low. Shouldn't be hard to rectify.
(http://www.pbase.com/kvom/image/165598048/large.jpg)
Time to attach the eccentric rods and try to time it, next time out.
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I had a squeak on mine, it was the piston rod pulling the guide up slightly as it was not quite sitting tight against the column.
You should be able to hear it on the upstroke above the compressor noise
[youtube1]https://www.youtube.com/watch?v=jNeaWlhRw7E[/youtube1]
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First run on air:
https://www.youtube.com/watch?v=eO9fZU4dGbc
Squeak is on the downstroke starting with the crank horizontal. Approximately 20 psi to run.
One problem that became evident is that the pin connecting the conrod and crank must have too much friction, as the securing nut comes off after a short run. I am not feeling any obvious air leaks around either of the glands, even with no packing installed.
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Hi Kirk, congratulations for the first run.
This motion with the low revs is a pleasure to watch.
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I discovered that squeal was coming from the bracket, and if I applied a bit of upward pressure with my finger the noise went away. So by adjusting the torque on the three screws that attach it to the column, I was able to eliminate the noise to a major extent.
The other main issue was the nut coming loose from the crank pin. This was caused by the rotation of the pin and the nut touching the crank causing the nut to unscrew. I reversed the timing (flywheel clockwise as seen from flywheel side), so now the rotation would tend to tighten the nut. Jason's turns that way, but JL's turns the other way, but doesn't seem to have had that problem.
With the transparent steam chest cover, the engine is very easy to time. I just set the crank at TDC and adjust the eccentric so that the valve nut is centered between the two nuts centered on the side. I didn't really need the dental mirror for this.
One concern I have it the eccentric rod or fork turning during operation. The jam nuts on either side are 2-56 and 1/8" across the flats. My smallest open wrench is 3/32, and a nut driver won't work, so I'll want to make a 1/8" wrench; I don't like trying to tighten nuts like this with pliers.
I think it's time to disassemble and do some finishing work I put off before. Oil cups are one thing, and a flat on the crank end of the crankshaft to make the crank more secure;y attached. I also want to get some Eastwood Diamond Clear spray to prevent tarnish or corrosion, as I don't intent to paint any of the metal.
http://www.eastwood.com/eastwood-diamond-clear-dtm-and-painted-surfaces-aerosol.html
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Beautiful engine.
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Kirk, you might consider a set of these. They go down to 5/64ths.
https://www.amazon.com/gp/aw/d/B003HGHU8E/ref=mp_s_a_1_13?ie=UTF8&qid=1497052260&sr=8-13&pi=AC_SX236_SY340_FMwebp_QL65&keywords=moody+tools
Good quality tools, I have a set and use them often.
Bill
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Kirk, you might consider a set of these. They go down to 5/64ths.
https://www.amazon.com/gp/aw/d/B003HGHU8E/ref=mp_s_a_1_13?ie=UTF8&qid=1497052260&sr=8-13&pi=AC_SX236_SY340_FMwebp_QL65&keywords=moody+tools
Good quality tools, I have a set and use them often.
Bill
I'll second Bill's recommendation. I have a set and they're quite handy.
Jim
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You will probably get a smoother running engine if you time it to have about 7degrees lead rather than zero that your setting method is giving at the moment. It lets a tiny bit of air/steam into the cylinder just before the piston reaches the end which has a cushioning effect but that is something that can be played with on final assembly.
That was what I found with the bracket it was just moving slightly and tightening the screws and making sure it was seated solidly cured the squeak.
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Thanks for the tip on the wrenches. I will be ordering a set once Amazon gets the Prime issue fixed (trying to charge shipping currently).
When I retimed the engine for a second run in the opposite direction, it ran much better than the first run. Whether the lead changed or not is hard to tell given that I'm eyeballing the valve nut. Since I'm going to take it apart now I'll see how it goes after the reassembly.
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Once you know the valve nut is exposing equal amounts of port either side the actual "timing" can be done just by looking at the high point of the eccentric. As you have it now it is 90degrees ahead of teh crank so you just need to slacken teh grub screw and move it a little more in teh direction of rotation. If your grub screw is placed inline with the max throw of the excentric at the time it is made it is quite easy to see where things are just by looking at the angle of the hex key.
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That's what I figured. I'll give it a try. That said, my view of the valve nut and centering it is hardly exact; whether it's dead on or 7 degrees +/- might be hard to tell.
I probably should replace the screws holding the steam chest together with studs (2-56 all thread) once it's apart. Then I could remove the cover when timing and have a better view of the ports.
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I received the set of Moody small open end wrenches today. Excellent quality as it appears.
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I think you will find them most useful Kirk!!
Bill
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After 6 days out of the country followed by 4 days fighting a cold I imported, I decided it was time to do something in the shop.
Normally I've been buying oil cups from various model supply vendors as they're cheap and look good, but this time I decided to make 4 for the Benson. After all, I've had my little CNCed LMS lathe for over a year and thus far have only made the frame spreaders for the Coventry. These are made of 5/16" brass rod.
After firing up Mach4 and determining the X0 and Z0 for the turning tool, the tool is set at Z0 and the stock is tightened in the chuck while in contact with the tool.
(http://www.pbase.com/kvom/image/165729971/large.jpg)
Then it's a matter of running the program to turn the profile.
https://www.youtube.com/watch?v=qoJ56B6OmbA
I then reverse the stock and cut a second profile on the other end. With two pieces of stock I get 4 cups ready for finishing on the manual lathe.
(http://www.pbase.com/kvom/image/165729972/large.jpg)
After some drilling and parting, I ended up with these.
(http://www.pbase.com/kvom/image/165729974/large.jpg)
I had intended to thread the ends, but since the eccentric straps are so thin I think loctite is a better solution.
For anyone interested, I am using eCAM to generate the G-Code.
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Interesting to see the cnc lathe in action, thanks for the video of that!
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Unlike the busy beavers on the forum, I've been lax on making progress towards finishing the engine. With Cabin Fever 6 months away and no new project begging to be started, it seems like there's no rush to completion.
In any case, today I spent a bit of time in the shop. First off, I milled a flat .01" deep on the end of the crankshaft. Te idea is to be able to remove the crank and replace it without changing the configuration of the eccentrics. I'd previousy turned a groove to prevent a burr from the set screw making it difficult to remove the crank.
(http://www.pbase.com/kvom/image/165760495/large.jpg)
Since I've decided to leave the engine unpainted except for the flywheel, I'd like to keep the brass parts from tarnishing. Terry Mayhew on the other forum pointed me to Eastman Diamond Clear coatings. I ordered a can each of the glass and satin versions, but tests on the some brass didn't show a great deal of difference. So with the engine completely disassembled, I'll start to polish with Brasso to remove the existing tarnish and spray a couple of thin coats on the brass parts.
(http://www.pbase.com/kvom/image/165760496/large.jpg)
Started on that effort and got a few parts done before my energy gave out. I still need to drill the eccentric straps and bearing covers to attach the oil cups. Plus remake one of the governor arms that came unglued.
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Hope you are feeling better Kirk. Summer colds are the pits!!! The oil cups look as good or better than store-bought ones :)
Bill
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I did get the brass parts cleaned and sprayed, then did a partial assembly before other tasks got in the way.
I decided I needed to remake the arms on the governor after one came apart. Originally I drilled a 1/16" hole in the lower end and glued the rod into both the arm and the ball. Aside from one glue joint failing, I made the rod too long so that the balls were too low with the engine stopped. The new design of the arm is to have an extension drilled and tapped 0-80. Likewise, the brass balls are also drilled and tapped, and the rods are threaded on each end.
Here's the arm with a screw attached.
(http://www.pbase.com/kvom/image/165945413/large.jpg)
For scale, the separation of the two holes is .5". With the governor assembled:
(http://www.pbase.com/kvom/image/165945414/medium.jpg)
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I now have the engine re-assembled, and next job is to time it and get it to run. I have also designed an aluminum base for display that will be a future shop task.
For the governor to connect to the input, a "rocker" is needed. This is a finicky part to make, so I drew it up in Solidworks, exported as STL, and sent it to Shapeways to be made in brass. Hopefully this will work better for me than George's auto parts in stainless.
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Started on the sub-base and initial did timing. Timing is probably off a bit, but I'm doing some run-in before any tweaking.
https://www.youtube.com/watch?v=cGuvS2COk5c
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Just viewed it on Youtube and gave you a thumbs up.
Thomas
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For the base of the engine, I decided to make an elliptical sub base that will in turn rest on a wooden plaque. The sub base was machined from some 1/2" aluminum tooling plate I got on eBay. It seems to have been Blanchard ground based on the finish.
The plaque in the pic is a bit large, so I intend to order a smaller one that hasn't been used for mounting anything. Initially I'll attach the engine to the plaque with 2-sided tape until I decide if I want inlet piping to connect through the floor.
For anyone interested, I machined the ellipse from a piece of rectangular stock .3" deep. Then machined soft jaws to hold the ellipse and milled the rest of the stock from the "bottom".
(http://www.pbase.com/kvom/image/166020035/medium.jpg)
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I spent most of the day making the forks that go on the ends of the operating rod, which connects the governor to the inlet valve. Basuically the same part as the eccentric forks and made the same way, although at half the size. All went well until after the final op. which was tapping them 0-80, at which point I find that my 0-80 screws are too loose to hold. I'm not sure what went awry as I drilled the holes with a #55 as before. In reality I'll probably just glue them on when it comes time. Possibly some JB weld and redrill could work.
(http://www.pbase.com/kvom/image/166026674/large.jpg)
Still need a bit of polish.
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I received my printed rocker arms from Shapeways this weekend. I ordered a version in polished brass for use on the engine, but since versions in plastic were quite cheap and didn't add extra shipping, I ordered one (yellow) in "strong flexible" plastic and another (black) in "hi def acrylate" to get a example of these materials.
Cost for the brass version was $14.00, black $5.57, yellow $2.73. Shipping $4.99. Order accepted on Aug. 7, shipped on the 17th.
(http://www.pbase.com/kvom/image/166056590/medium.jpg)
All three versions seem quite accurate, although the holes vary a bit. They are drawn as 1/16" diameter. A 0-80 screw passes cleanly on the brass version, but are tight on the plastic and need to be screwed through to widen the holes.
A test fit shows that I made the diameter on the mating collar of the bottom pivot block a bit too large, so I'll need to reduce it to fit.
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I received my printed rocker arms from Shapeways this weekend. I ordered a version in polished brass for use on the engine, but since versions in plastic were quite cheap and didn't add extra shipping, I ordered one (yellow) in "strong flexible" plastic and another (black) in "hi def acrylate" to get a example of these materials.
That is very interesting: are there any printing marks on the brass rod?
Jo
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As the brass is investment cast from printed wax and then polished I would hope most of the layering will have been lost, they do say fine surface detail can be lost when it is polished so that should take care of layering.
how do the parts measure up for length? Did you have to send then with a shrinkage allowance for casting or do shapeways take care of that?
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The easiest dimension to measure was the outside of the 'C' feature, which I mic'd as .380", where the drawing was .375".
The separation of the holes in the brass part match up with those in the black plastic part to within the tolerance of a 0-80 screw passing through both together. Seems evident that Shapeways accounts for shrinkage, if any.
I machined the lower pivot block diameter down so that the arm fits well. Shop time has been curtailed by eclipse watching and other things.
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Added the rocker assembly to the entablature, and it fits well. I ran out of 0-80 washers and nuts and ordered some yesterday, so I'll need to get the delivery to finish that part.
(http://www.pbase.com/kvom/image/166078727/large.jpg)
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One issue I'm struggling with mentally is the throttle valve (part 42). How do I get the cross hole to end up horizontal when the valve is screwed into the steam chest? One idea is to thread the end of the bar stock, screw it in tight, and then try to scribe a guide line for the rest of the machining. Alternatively, just machine according to the drawing and use some shim stock between the valve and the steam chest to allow proper orientation (perhaps a thin layer of epoxy would work too).
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Turn it from round stock and leave the square part just over size. Screw the valve chest onto the throttle valve and use a square against the valve chest while you grip the round stock in an ER block or indexer, remove valve chest square up the 4 sides, drill and tap for the spindle gland and round off around the thread.
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I was hoping to find a way that didn't involve disassembling the engine. I should have done this work beforehand. :Doh:
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Another tiny part needed to finish the engine: throttle lever
(http://www.pbase.com/kvom/image/166105613/large.jpg)
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Sounds like this small change will do you some good! :)
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Yikes. Best let the junior shop elf make that one - teensy!
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I remade the forks for the operating rod today, since the previous ones had been drilled with the wrong size tap drill for 0-80.
Getting close to being done with this engine.
(http://www.pbase.com/kvom/image/166114692/large.jpg)
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Hi Kirk,
How goes the engine?
John
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After spending 3 weeks in Japan, I've had 2 weeks of jet lag. I don't remember having this much trouble getting sleep cycles back in step from previous trips to Asia. Must be age-related.
Finally decided to get back in the shop yesterday and today to get back to the engine. I won't go into the multiple times taking things apart and reassembling, but I came to the conclusion that my "system" of clamping the column and entablature to the base with a threaded rod needed some improvement, mainly to keep things from rotating while tightening. I also saw that when running the force of the piston rod caused some visible rocking of the column.
With the bracket on the column, I verified that the piston rod would pass freely as long as the column was in the right position. So I put a thin layer of epoxy between the column and base, oriented so that the bracket wasn't binding, and clamped the column until the epoxy cured. Now I could mount the entablature and use the threaded clamp rod to lock it without the column possible turning.
After assembly (no governor), everything turns much more smoothly. I'll do the timing next time in the shop and shoot for a run.
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Kirk,
It's a good thing you locked the shop elves out cause they'd have a field day with those small parts. Looks great, runs great.
Art
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All put back together. I tested that it ran before adding the governor stuff, so once I get around to shortening a bunch of 0-80 screws I should be able to call this one done.
Not in a diorama, nor do the governor or pump actually work, but the end result is the "look" I was after.
This will be delicate to take to CF.
(http://www.pbase.com/kvom/image/166583481/large.jpg)
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Looks great!
For travelling, can the flywheel be removed to take off the weight of it from the rest?
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I can remove the flywheel and governor. Probably need a box with foam padding for the rest.
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That is a very nice looking engine. I like the balance of brass to other materials. :ThumbsUp:
Jim