Author Topic: PMR #1 Drilling Engine - Mike's 4th Engine  (Read 9779 times)

Online mikehinz

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Re: PMR #1 Drilling Engine - Mike's 4th Engine
« Reply #30 on: February 26, 2021, 07:22:55 PM »
I think it adds a lot to the look of an engine to keep as much of the "as cast" surface as possible.  Good job, in my book.

Thanks!  I agree with trying to keep as much as the 'as cast' look as possible.  I'm trying to go for the most realistic look possible on this engine.

Mike
MIke
Wichita, KS, USA

Online mikehinz

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Re: PMR #1 Drilling Engine - Mike's 4th Engine
« Reply #31 on: February 26, 2021, 07:24:18 PM »
:ThumbsUp:
 Great set up's & fixturing Mike!

 John

Thanks!  It turns out i've been spending a LOT more time thinking about how to hold the parts and creating the fixtures necessary vs cutting metal directly.  I'm sure that's a common finding for most!

Mike
MIke
Wichita, KS, USA

Offline crueby

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Re: PMR #1 Drilling Engine - Mike's 4th Engine
« Reply #32 on: February 26, 2021, 07:26:30 PM »
:ThumbsUp:
 Great set up's & fixturing Mike!

 John

Thanks!  It turns out i've been spending a LOT more time thinking about how to hold the parts and creating the fixtures necessary vs cutting metal directly.  I'm sure that's a common finding for most!

Mike
Yup! Very important thing to work out ahead of cutting.     :popcorn: :popcorn: :popcorn:

Online mikehinz

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Re: PMR #1 Drilling Engine - Mike's 4th Engine
« Reply #33 on: February 27, 2021, 01:32:35 PM »
Now on to a few smaller parts.

First up is the slide caps.  These were actually quite good as received.  I just touched the bottom to the belt sander very briefly to knock the worst roughness down a bit and did the same to the sides just to remove the bit of flashing left on.  Then just a few strokes against some 400 grint sandpaper laid on top of a flat.  I also spent some time with a file on the round end to clean them up the best I could while still keeping the draft angle intact.  I didn't show any pix of those ops, but here's a a few pix with the caps clamped in the mill vise.  I've already drilled thru the ends as per the print and about to drill thru the center oil hole with a #60 bit. 



Then tapping the top of the hole 2-56 with a spring loaded tap follower and a very small tap handle. 



And the last pix of the caps on the print as finished.  Note that I drilled thru with a #60 bit as I didn't have a 1/32" bit on hand and felt like it wasn't worth making a run to my local supplier just for that small bit.



Next is the .25" brass spacers for spacing the slide caps from the frame.  This was pretty simple as a small piece of brass rod was supplied that just needed to be squared up and drilled thru.  Shown is parting off one of the spacers to length.



Then I made the valve rod and the piston rod.  Shown is the valve rod laid on top of my home-made tailstock die holder.  This device works very well.  It can hold 13/16" and 1" diameter dies and that's more than enough for 99% of the work I do.  Bigger than that, I use a standard die stock.   In any case, here it is:



The piston rod finished and laying on top of the print:



And finally the finished parts shown assembled onto the frame and the slide movement checked.  I did end up filing down the cross slide width just a bit to make sure it slid absolutely freely along its entire travel.



And one last piece for today, the cross nut.  Again, not a terribly complex part.  I didn't take a pix of the op, but I drilled the required hole thru the supplied stock on the mill and tapped it 5-40 as per the print.  Then I installed the stock in the lathe using a square collet  and parted it off to the specified length.



And the last pix shows the cross nut assembled on to the valve rod both parts laid on top of the print.



So far so good.  That's it for today.  I'm off to the top to try to solve the mysteries of model pipe threads and threading.  I have taps and dies and need to figure out what works somehow.  Questions maybe forthcoming!

Enjoy!

Mike
MIke
Wichita, KS, USA

Offline propforward

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Re: PMR #1 Drilling Engine - Mike's 4th Engine
« Reply #34 on: February 27, 2021, 01:51:59 PM »
I am mightily impressed. You are making a really top job of this, far beyond my own bungling and lame attempts on this same engine. Hats off to you.
Stuart

Forging ahead regardless.

Online mikehinz

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Re: PMR #1 Drilling Engine - Mike's 4th Engine
« Reply #35 on: February 28, 2021, 02:44:18 PM »
And now on to some really small fiddly bits, the linkage hinge pieces!

I used a square collet in the lathe, drilled and tapped a hole in each end of 2 piece, beveled it slightly and cut the 2 bits to length.  I didn't take any pix but here's the results so far.



Then off to the mill vise.  I used a 3/32" carbide end mill to mill away the center or edges of the bit respectively.



I had to change orientation of one of the bits at some point in order to get the milling done.



A pix showing how small these bits really are.  I rounded the corners off with a belt sander, very carefully comparing with a radius gauge and checking the fit periodically.  That op is not shown. 



The valve rod assembly so far.  Everything fits luckily!



No pix of the operations, but here's the final pix of all the brass nuts that needed to be made.  Sizes are 5-40 and 10-32.  This just involved using a hex collet on the lathe, drilling thru and tapping, beveling the edge, parting off and then turning each nut around in the collet and finishing and beveling the backside of each piece.  The only tricky part is getting the parted off nut held in the collet.  I just threaded each nut onto a screw, then inserted it into the collet and made sure it was running straight and performed the bevel and polishing bit.



And lastly the eccentric rod.  I just cut the rod to the required length, marked the bend locations and by hand, bent the rod while held in my bench vise.  I compared it against the print during the process to make sure the bends were about correct.  I think there's some tolerance in all this so close is good enough!



All for today.  Enjoy!

Mike
MIke
Wichita, KS, USA

Online mikehinz

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Re: PMR #1 Drilling Engine - Mike's 4th Engine
« Reply #36 on: March 03, 2021, 03:01:15 PM »
And we're on to the cylinder in today's pix.  This part has some challenges due to the references required and when they become possible to measure from.  So, some of the steps and setups have to be repeated in order to get to various final dimensions, at least the way i thought about it and did it. 

First pix is the raw casting, just after I worked it over a bit on the belt sander.  This was to just take off the worse of the rough spots and get flat enough surfaces to be secured in the vise.  Notice in the print, the first tricky dimension.  Note that 2 dims are referenced from the center of the valve rod hole, that is the top of the valve chest and the bottom of the slide valve surface.  But that feature can't be done initially since the part is very difficult to hold at this point.   Also note that i used a permanent marker to note the front and rear of the cylinder as the raw casting is symmetrical but the operations make it non-symmetrical as the valve rod boss is removed from the top but left on the bottom.  This matters as the inlet port needs to end up on top and the outlet port needs to be on the bottom when finished. 



So the first thing I did was to hold the cylinder by the ends using some AL packing against the moveable vise jaw.  Then I used a 1/4" carbide end mill to just lean up the face of the valve chest and the bottom of the valve chest.  There was no attempt to get to the stated dims at this point, I just wanted to get some flat surfaces. 



Now since the valve chest face is flat, I oriented that face toward the fixed jaw and used some packing against the moveable jaw.  Then I squared it up as much as possible using a machinists square on the side and indicating across the top keeping in mind that the casting is still quite rough.



One end of the cylinder finished.  This isn't done to an exact dimension, but rather I milled it down until the surface was smooth and the valve rod boss more or less disappeared.  At least is LOOKS like the print at this point, but its not yet possible to hit an exact dimension here.



Now we have 2 flat surfaces!!  So, now the cylinder is flipped over and can sit flat on a parallel on the bottom and flat against the fixed jaw.  AL packing is still used on the moveable jaw side.  So milling can commence!  And of course now it's possible to get the cylinder OAL to spec.   That's a 1/4" carbide EM spun "pretty fast"!



Measuring the length of the cylinder using a depth gauge to get the OAL to the print spec. 



Part shown against the print just for reference:



Next is finishing up the valve rod packing gland area.  This involved drilling thru then creating a recess for the packing material and drilling and tapping 2-56 for the small fasteners used to hold the packing gland in place.  This is my typical setup for tapping small holes, a spring loaded tap follower and a very small tap wrench.



Now back to finish off the valve chest area since we have the required reference feature.  First I oriented the cylinder in the mill vise now having 3 flat surfaces!  I used a DTI get the cylinder oriented as flat as possible.



Then I used a depth mic measuring to a 1/8" rod inserted thru the valve rod hole.  That way I could figure out the required distance from the center of the rod hole to the top of the valve chest and from that feature to the bottom.



Then taking the top of the valve chest to the required dim using a 1/2" EM.



Taking the bottom of the valve chest to .438" from the top, but of course this is really referenced from the center of the valve rod hole.  I used a 1/4" carbide EM for this operation.  Also I had set the centerline using the 1/8" rod thru the valve rod hole, as this really need to be the center of the part from this point forward.



Next was milling the rather deep exhaust and intake ports into the bottom of the valve chest.  This is the start of the exhaust port using a 3/16" EM.  The tricky thing is that it's hard to see what's going on down deep in the valve chest plus I frequently used a vacuum and/or air blast to clear the chips quite often.



Then doing the inlet port using a 3/32" carbide EM.  Note that I wrote the movement of X on the vise as I really, really didn't want to screw things up at this point!



Last operation at this orientation of the part was to drill and tap the holes for the cover plate.  Pretty straightforward, just moves using the DRO in x,y.  Centerline was still established from the previous operation. 



The cylinder against the print trying to show the operations completed so far.



Next comes the cylinder boring operation.  The tricky part is to figure out where the cylinder center should be, as the rough cored hole isn't at center nor is it round or smooth.  So what I did was to indicate the valve rod packing area hole to make sure the spindle was exactly on the Y axis centerline as I'm taking that feature as the center of the cylinder's world.  X should also be fixed at this point. 




Then I used a DTI ball point just for a reference, and swept the OD of the cylinder to get cylinder as close as possible in Y. 



Then I moved the DTI ball point to close to the existing cast center hole and swept that area to see how close to center is actually is/was.  It turned out to be not good, but not terrible either and it's oblong with a one very rough side.  But there's plenty of material so it should clean up just fine. 



Then I started to bore using my Criterion boring head and as short a bar as I could use to get thru the entire depth.  You can see that start of the cut cleans up the bore pretty well, the difference between sides turned out to be about .020"



Then boring and measuring until the 1.000" target is achieved.



I also gauged the hole with a 1" plug that I had on hand from a previous project.



Next was drilling and tapping the cylinder cover holes 5-40.  I did this with x,y moves on the DRO after centering up the cylinder.  I drew up the pattern with the required PD and hole placement using CAD as I don't have a hole pattern function on my rather old DRO.  Same operation on each end of the cylinder.



The cylinder shown against the print.  More ops still to come!



I lapped the cylinder to get it as round as smooth as possible.  I used Timesavers abrasive material and a 1" brass lap progressing from course to medium to fine. 



I turned the lap as slow as possible in my lathe while hand holding the cylinder.  It always amazes me how much difference lapping makes.  You THINK you have a smooth, round hole, but lapping improves it greatly.  I went thru this process as I intend to use an o'ring for the piston seal.



Next comes the scariest part, at least to me!  One of my fears, is that by this point in the process, I've put some much time into the part that screwing it up during the final ops would be very painful!!  This is drilling the inlet and exhaust ports between the cylinder and the valve chest.  The print calls for these holes to be drilled at 20 degrees so a bit of a tricky setup is needed.  I don't have any sort of any compound sine vise but I do have a Kurt vise mounted on my mill and I have a small toolmaker's vise.  So the first thing was to get the toolmaker's vise mounted in the Kurt at 20 degrees.  I used a 20 degree angle block, inverted it in the toolmaker's vise and indicated it flat.



Then after setting up the toolmaker's vise at the correct angle, I used a tooling ball inserted in an adapter that fit the cylinder.



Then indicating the ball in order to find the 'center' of the cylinder, which of course is really the center in Y but in X is center as included, but not when flat.  Soooo, recalling high school level geometry and trigonometry, it is possible to find the required dimension of the print, which is specified when the part is flat. 



I didn't show how the operations started, but once I found the required dimensions, I used a 1/8" end mill to create a flat spot at each location in order to start the drilling operation.  This is necessary so that the drill starts straight.  The drilling operation is shown.  The drill need to end up in each of the inlet ports.  The same operations need to performed on each end of the cylinder, but I don't show the operations on the other end.



Just to prove that the holes are correct, I shined a light from each end and it can be seen in the ports within the valve chest.

First end:



Second end:



I didn't the operation but the prints call for the inlet ports to be enlarged fully to 1/8" width and 1/8" deep.  I didn't show the operation, but this just involves placing the cylinder in the vise in the flat position, find center, establishing the cutter depth and making the cuts.  Shown is the finished cylinder end, same on both ends.



At last, we're at the very last operations on the cylinder!!  This is drilling/tapping the inlet and exhaust ports.  The prints call for 1/4-40 and I'd never run into this particular thread before.  Some searching revealed many standards for model pressure piping and I became ever more confused the more I read.  It turns out that I very possible got some bad taps from a vendor (I'll document more issues separately in the appropriate forum) but I DID end up with taps that worked that are the METP (Model Engineering Taper Pipe) also known as MTP (Model Taper Pipe) in 1/4-40 size.  These are of course taper type taps so tapping depth is critical.  So after I sorted this all out, here are the pix.

I placed the cylinder as required in the mill vise and then inserted a 1" rod thru the cylinder and indicated it to make sure the bore of the cylinder was horizontal.  I did this to assure that the to be drilled ports landed in the correct locations.



Since there's no real reference to these port locations, other than 'center of boss', I inserted a 1/2" rod in the mill spindle and visually centered the rod over the port boss. 



Then I skimmed the boss with an 1/2" EM taking about .005" off just so as to clean up the surface.



Then drilling thru with a #5 drill.



Then tapping with the 1/4-40 METP tap.  I checked the depth frequently to assure the taper was not too deep nor too shallow.



Each port completed and shown with some brass fitting from PM Research.  Going forward I'll probably make my pipe fittings as I did also purchase the require dies.



Using a light to make sure the exhaust port is drilled properly.



And finally, smoothing the valve chest bottom face using some fine emery cloth and using the slide valve for pressure.



Whew!  I got thru the entire part with no major mistakes!  This took several days as I spent a LOT of time thinking about the order of operations and how to do certain things.  Choosing the inlet/outlet threading method also took some time as there seem to be sooo many standards and approaches plus getting some bad taps initially also slowed me know.

In any case, took a look and enjoy!

Mike






MIke
Wichita, KS, USA

Offline tvoght

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Re: PMR #1 Drilling Engine - Mike's 4th Engine
« Reply #37 on: March 03, 2021, 03:38:49 PM »
Mike, I enjoy your setups and logical approach. The photos are good and descriptive.   --Tim

Offline Johnmcc69

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Re: PMR #1 Drilling Engine - Mike's 4th Engine
« Reply #38 on: March 04, 2021, 12:34:14 AM »
 :ThumbsUp:
 Great work on the cylinder!
  :popcorn:
 John

Online mikehinz

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Re: PMR #1 Drilling Engine - Mike's 4th Engine
« Reply #39 on: March 04, 2021, 04:14:18 PM »
John, Tim, thanks for taking a look and thanks for your complements!

Mike
MIke
Wichita, KS, USA

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Re: PMR #1 Drilling Engine - Mike's 4th Engine
« Reply #40 on: March 04, 2021, 04:33:05 PM »
Now that I have the cylinder finished, I wanted to make the associated parts so that I can check fitment of each as I go along. 

So first up is the valve chest cover.  The raw casting was pretty smooth and flat, so I just worked the topside against some sandpaper to reveal the screw boss locations.  Then I put it on some parallels in the mill vise and very lightly skimmed the bottom side with my almost antique Valenite insert end mill.  I only took off about .010" and it cleaned up pretty well.



Bottom view as finished.



Top view showing the screw bosses after just a few strokes against sandpaper on a surface plate.  I didn't mill the boss locations at all.



Tested the fitment against the cover on the valve chest.  I wanted to see how it looked with brass washers under the bolts, but that doesn't look right to me, so I'll end up with just plain scale bolts when it's finally assenmbled.



Next on to the slide valve.

First is just cleaning up the bottom with a 3/8" EM.  I took a minimal amount off, something like .015"



Then I inverted the slide valve and milled the required slots as per the print using an 1/8" HSS EM.  I didn't show it, but I did test the fit of the valve rod and the valve nut against the slots, both separately and when assembled.  I went for a bit of a loose fit slide nut to slot fitment.



I didn't show the operations, but here's the slide valve inserted showing the milled recess as per the prints.  Fairly straightforward using a 1/8" carbide EM.  The trick being carefully watching the DRO so as NOT to overshoot any of the moves.  General laziness prevented me from doing the obvious and setting stops!



And finally for this part, the slide valve assembly shown in the cylinder valve chest in order to test the fitment.  All good!



This is probably enough for this post.  I'll post another short series of pix showing the top and bottom cylinder heads here shortly.

All for now.   Enjoy!

Mike
MIke
Wichita, KS, USA

Online mikehinz

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Re: PMR #1 Drilling Engine - Mike's 4th Engine
« Reply #41 on: March 04, 2021, 05:03:44 PM »
I wanted to post on how I did the cylinder heads yet today. 

First up is the bottom cylinder head, the one that's cast bronze.  To start the part, i used my 3 jaw chuck and gripped it as well as possible on the extra-long spigot and then turned the larger OD, but I left it a bit oversize at this point.  The pix shows the ops after I turned the part around and started turning the spigot down to its final OD. 



Then I installed the collet setup on my lathe, and gripped the head by the spigot.  Then I turned the OD to the final dimension.  Doing so now makes sure that the OD of the part is concentric with the spigot and the TBD drilled thru hole.  I also thinned the part as required and make the .031" boss as called out on the prints. 

Shown is the cylinder head against the print, partially completed.



To finish the part, I used a 'pot' 5C collet.  Shown is milling out a recess in the collet so that I could grip the part.  Use of this type of collet allows a reasonably good grip on very thin parts.



Then I installed the pot collet in a collet block and placed it in the mill vise, making sure that it's square with the vise. 



Then I centered the head under the spindle using a DTI against the spigot.  I then drilled the hole pattern using x,y DRO coordinates.  Then I shortened the spigot to the final dimension as shown.



Then testing the fitment against the cylinder.



And testing fitment against the frame.



Now on to the top cylinder head. 

First I used the same pot collet and inserted the raw casting and turned the exposed portion to the required OD.



I didn't show turning the other side of the top head but I did turn the .031" boss as per the print.  Shown is after moving the pot collet setup to the mills and centering the part under the spindle using a DTI.



I didn't show the drilling operation, but it's relatively easy as I could just drill thru the part and into the AL of the pot collet without any problem of damage to the drill.  Shown is the bottom side of the finished part laid on top of the print.



The final pix is the head shown on top of the cylinder to check the fitment.  A miracle occured and it fit properly!!



That's it for today.  Enjoy!

Mike
MIke
Wichita, KS, USA

Offline Admiral_dk

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Re: PMR #1 Drilling Engine - Mike's 4th Engine
« Reply #42 on: March 04, 2021, 10:43:14 PM »
You are really on a fast track forward with this build Mike and nice looking parts too  :ThumbsUp:

Still following along  :cheers:    :popcorn:

Online mikehinz

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Re: PMR #1 Drilling Engine - Mike's 4th Engine
« Reply #43 on: March 05, 2021, 07:31:40 PM »
You are really on a fast track forward with this build Mike and nice looking parts too  :ThumbsUp:

Still following along  :cheers:    :popcorn:

Thanks very much for following along!   

I'm not as fast as it appears!  I'm catching up on several previous weeks of work.  I took pix along the way, but didn't start posting them until fairly recently.  In real time, I'm just finishing the engine, painting, getting a proper base for it, final assembly etc.

Thanks!

Mike
MIke
Wichita, KS, USA

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Re: PMR #1 Drilling Engine - Mike's 4th Engine
« Reply #44 on: March 05, 2021, 08:10:49 PM »
Time for a few more small parts. 

First up are the 2 packing glands.  The first pix shows filing and fettling the parts in my bench vise in order to smooth them up a bit and to get rid of the flashing.



These packing glands about drove me crazy before I got them done.  I tried several things, but what worked, sort of, was super-gluing them to a piece of AL round stock and indicating them to run more or less on center in the lathe.

Super glued to the top of some round stock.



Then centering up the rough part in the lathe.



Then drilling thru one of the glands on the lathe:



Then I turned the part around in a lathe collet to finish the backside off. 



Centering and locating the points to drill thru for the mounting holes.



Somewhere in the process the super glue let go and I had to figure out a way to finish the parts.  Soooo, I ended up clamping the glands on my small tooling plate as shown.



Just a photo of the setup pieces.  The rough bit AL is just some waste material  placed under the part in order to avoid drilling into my tooling plate. 



And finally, the finished glands laid on top of the print.

Pix 1



Pix 2



So my lesson from all this was to not rely on super glue for holding small parts.  I guess I'll either try Loctite 638 or possibly use 60/40 solder to attach the small part to be machined on top of a small scrap of brass.  Any suggestions as to what works best?

Next up is the piston.  I decided not to use the material supplied in the kit as it's 12L14 as near as I can tell.  I had a bit of cast iron bar stock which I prefer for pistons, and started to turn it to diameter.



Trying the turned down section in the cylinder.



I greatly prefer o'rings vs the teflon rings as supplied so I modified the groove dimensions to provide about .005" compression on the oring.  And of course I used only a single o'ring.  I made the groove with a 2 mm grooving/parting tool that can be seen in the photo.



Then after drilling thru the piston, I made the counterbore by holding a 3/8" EM in the tailstock chuck.  I've always had good luck with this method.



And finally for the piston, it's shown against the print assembled with the piston rod and cross slide.



That's it for these small parts.  Next up is the crankshaft but I'll start another post as that item has a lot of steps to complete.

Enjoy!

Mike
MIke
Wichita, KS, USA

 

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