Elmer's 36 Reversing Wobbler - 2x - Imperial - Mike's 2nd engine

[mikehinz]

I had a good amount of time in the shop today and started on the most difficult part of this engine, the crosshead guide.  I'm going to break this into 2 parts as I got thru arguably the more difficult part today and need to wait a bit until i start back on the machining ops.  You'll see why shortly!

Starting with the material.  It sure doesn't resemble a crosshead guide at this point, but you have to start somewhere!  The bar stock is .5 x 2.25" 1018 and the tubing is A513 DOM  1.125" x 0.156" x 0.813"


After cutting off a piece of the bar stock, I took it to 2 x 2 in the mill and then drilled the clearance holes for the 10-32 shcs's and a center hole.  I enlarged it with a 3/8" drill and then a 3/4" drill.


Then I bored it out to about .80 ID just so it would be smooth and true.


Then over to the lathe, mounting the part up in the 4J and getting it on center using the DTI. 


Making sure the face was running true also.


Cut off a piece of the tubing.   Showing it on the print next to the square part.  I'm guessing you can see where this is going!  I had bored a 1.259" counterbore .1875 deep on the lathe so that the tubing fit with just a little clearance in that counterbore.


Pix showing how the 2 parts go together.   This strongly hints of what's coming next!  I'll bet someone has already guessed!


The tubing has been brought to the required length and thoroughly cleaned with emery.  Nice and shiny at this point!


And finally the long-anticipated secret op is revealed.  Silver soldering.  I've never silver soldered before, but to be fair, in my far distance past I did a lot of welding and brazing so it's not entirely unfamiliar but new processes are always scary.  I went to the local welding shop and they recommended this stuff, Harris Safety-Silv 56 and Stay-Silv white flux.  The flux is in thick liquid form so it just needs to be brushed on.  I'd cleaned the parts thoroughly with acetone just prior to applying the flux and putting the parts together for brazing.


A pix of my gas (oxy-acetylene) rig, a small Victor torch body with Victor regulators and a very poor home-made cart. 


And here's the part after the brazing op was completed.  It took more heat than I had expected.  I started with a Victor #0 tip and changed it to a #2 tip when it was obvious that I wasn't getting the parts hot enough.  I had the flame set to be on the carburizing side as that's what Harris recommends for this process.  I have NO pix of the brazing process as I had my hands completely full during the brazing!


And finally a pix from the backside of the assembly.  It looks like I managed to get the silver solder to fully 'draw' thru the entire joint.  I didn't spot any gaps at all on the backside.


Soooo, I'm just letting the part cool now and will start cleaning it up tomorrow.  If I drank, i'd have a beer about now!  I must admit I was nervous, but I figured that I could remake the parts pretty quickly should something have gone terribly wrong. 

Also, during the process, i figured out that I can't built this part as I drew it.  I need to now put the item back in the lathe, square up the square mounting flange and bring it to depth, plus I need to make a pass with a boring bar on the ID to make sure it's smooth and true and is at the correct ID.  My original plan was to just put a simple .25" in the square flange put that left me now way to do the boring operation.  So what I plan to do is to make a 'plug' out of SAE 660  1.25" OD and counterbore a matching recess in the flange.  Then press the plug in place with some Loctite after I'm finished boring.  I've got it all hand-drawn but need to modify the model and prints showing this mod. 

So tomorrow is a big day!  I'll clean up the part and see if it's any good, plus start the final machining ops on this.  One tricky bit will be milling the slots in the guide as Elmer did.  I think I can do it, but need to attempt the setup to be sure.

All for today!

Enjoy!!

Mike

[Kim]

Nice work on the silver soldering!

I use Oxy-Acetylene for silver soldering.  With steel, you can be a bit more direct with the heat, but with brass, you have to be really careful or you melt the brass!  I've found that you don't get the parts hot enough, fast enough, they starts to turn all black and sooty on me. I'm no expert though.  Sounds like you've done a lot more work with the torch than I have!

Pretty nice looking joint to me though.  Should look great when its cleaned up!
Kim

[mikehinz]

Nice work on the silver soldering!

I use Oxy-Acetylene for silver soldering.  With steel, you can be a bit more direct with the heat, but with brass, you have to be really careful or you melt the brass!  I've found that you don't get the parts hot enough, fast enough, they starts to turn all black and sooty on me. I'm no expert though.  Sounds like you've done a lot more work with the torch than I have!

Pretty nice looking joint to me though.  Should look great when its cleaned up!
Kim

Kim, I entirely agree with you on the heat on the larger steel parts.  I was scared by a lot of the info I had read about keeping the heat down, but in retrospect most of that info was for brass fittings.  These parts took a lot of heat, certainly not as much as brass brazing, but still more than I had initially expected.  They did come out a bit more black and 'sooty' than I had expected, but I had to swap tips on my torch mid-way thru the process and that certainly wasn't SOP.  Oh well, next time I'll know better.  I'll clean the parts up later today and hopefully finish them off.

Thanks for commenting on this project!

Mike

[mikehinz]

Well, I spent a fair bit of time in the shop today but progress was slow and I'm left with at least one question for the forum.  I'll ask the question at the end of the post.  I'd finished the silver soldering operation on the crosshead guide yesterday so today i wanted to progress as much as possible getting the part completed. 

First, I chucked the part in the 4J by the square flange so that I could cleanup/polish the cylinder portion.  First pix is indicating in the part at some distance from the chuck.


Then centering up nearer in toward the chuck.  This gets to be a bit of an iterative process to get it running true with no wobble, particularly when you're not gripping much with the chuck.


Then I took a VERY light skim cut on the square flange and just used emery cloth on the cylinder to polish it up.  The silver soldering process turned out pretty good as it turns out.


Then I turned the part around in the chuck and again indicated it in to center.  This time was much easier as I had a much better grip on the part.


Then I took some fairly light passes as this is an interrupted cut.  I needed to get the thickness of the flange down to the spec'd thickness and this process should make sure that the flange is square with the cylinder OD at this point. 


Then I started boring the ID to the required diameter, that being .875".  Also, this should now mean that the cylinder ID is square with the mounting flange and also concentric with the OD.  At least that's my hope and fantasy!  This boring operation was slow, tedious and terrifying!  I had to hang out my boring bar almost 4".  I was turning pretty slow, 260 rpm and taking only about .010" cut on radius each pass.   That bar is the best one I have, it's an Iscar carbide bar using a CCMT insert. 


Finished part on the print.  Notice that I put in a shallow 1.25" counterbore.  Since I couldn't leave a solid end on the guide, I opened it up and then made a SAE 660 bronze plug to be Loctited into place to provide an air seal and guide for the piston rod.


This shows the bronze plug inserted into the crosshead guide.  I didn't follow Elmer's plans on this aspect of the engine.  Since I'll never run this on steam, I didn't do the packing gland that he called for, but made this more simple assembly.  The piston rod is .250 and the hole is .251 so it should run fine on air, at least that's my hope.


And the last pix of the day.  This shows the grosshead guide with the plug, the piston, the piston rod and the crosshead all assembled together.  The remaining major operation is to cut the tricky slots on the sides of the crosshead guide.  I think I have a way to do this, but we'll see.


Now my question.  The bore on the crosshead guide is about .001 over the OD of the crosshead, but the finish on the ID of the guide isn't that good.  The boring was tough.  I was turning too slow and even taking shallow passes at the end, the finish wasn't that great.  I do have a small brake cylinder hole and ran it thru several times, using WD40 as a lubricate.  This cleaned up the finish a lot but it's still rough for my taste and running the crosshead thru the guide sure doesn't feel as smooth as I'd like.  I suspect there would be an issue running the engine if I just leave it in this condition.    So, the question is, what should I do?  I can run the hone thru more but I'm not sure that's going to make things much better.  Should I consider buying or making a lap and getting some lapping compound to get this guide round and smooth?  I feel like I should do that before I mill the slots in the guide.

Any and all input on the above is very welcome!

All for today.

Enjoy!

Mike.

[AOG]

 My 2 cents is to leave it alone. If you oil it and run it in and it will seat itself.

Tony

[mikehinz]

I had a pretty good day in the shop today.  Progress was a bit slow but there was a lot of contemplation and trial on various stages of crosshead guide operations. 

First, a coda.  Tony (AOG) suggested I just leave the crosshead guide and crosshead fit as they were and it would wear in with running.  I had   contemplated lapping and all sorts of exotic processes.  Based on his suggestion, and realizing this was just a guide, not part of a system that had to hold compression, I decided to just hone the bore a bit more until I ran freely.  I did so with a small brake cylinder hone and after about 5 minutes of honing, I managed to get a pretty good sliding fit, although not quite as free as I'd like.  But now I'm pretty confident it will run it whenever I assemble the engine and apply air.  So, with that accomplished I decided to move forward with the rest of the ops on the guide.

Now a quick 'off the main subject' note and pix.  I really like using 5C collets.  I have a number of machinable 'pot' collets that are very useful for holding large, thin parts or for repeated operations.  I needed to clean up the other side of the reversing valve so I simply bored out a AL pot collet to 2" ID about .125" deep.  I was then able to easily hold the reversing valve flat and true to clean it up.  So, an aside just for general info.  This pix shows just taking a very light finishing pass and putting a small bevel on the corner.


Now on to the main action for today, completing the crosshead guide. 

First pix shows a milling hold-down clamp, laying upside down.  Note how I ground the end of it narrower and rounded the bottom a bit.  You'll see why in the next series of pix.


This is the setup on the mill that I ended up using.  I'd thought of all kinds of ways to hold the work, but all had issues.  I ended up as you see.  I clamped the square flange end onto the milling table, thereby assuring the slots to come would be properly oriented.  Then I shimmed up the other end using a parallel and some old gage blocks suitable only for shimming, not precision ops or checking.  Since I was milling away the side, I had to somehow clamp to the bottom of the cylinder, not the top.  My breakthrough in figuring out how to do this was when i realized things like milling clamps can be modified, or even custom ones made!!  Shocking I know and I'm sure many are laughing now since this surely isn't anything new to most people, but for whatever reason, I'd not thought about it until now!  This pix shows roughly squaring the part up using a square.


Closeup of the modified milling clamp and the shim stack.


Then using a DTI to make sure the part is parallel with the table.


Then making sure the part was the same height along its length.


Milling the 'near' side.  I used a 1/4" 4 flute carbide end mill turning about as fast as an old Bridgeport can go.


Since the carbide end mill was too short to cut the entire width, I made a finishing pass with an extended reach 2 flute HSS end mill.  That cleaned up the remaining edge well.


The finished part laying on the print.


The guide, crosshead, piston rod and piston all shown assembled in the first view.


And the final pix showing the opposite side view.


Sooo, that concludes all the machining operations on all the parts.  I'm quite excited to get to this point, especially the crosshead guide as that was to me, the most difficult part with many operations that I'd not done before. 

Tomorrow I plan to start cleaning, assembling, deburring, lapping etc so that I can assemble the engine and try it out.  I'm sure somewhere I'll run into some sort of problem(s) and have to modify or remake something.  I did get some springs for the reversing valve and the cylinder pivot mechanism but I'm not at all confident that they'll work.  I may have to end up ordering some, as the only source of springs locally are the Ace Hardware stores, at least as far as I've found so far. 

So, hopefully the next pix are of a working engine!  Or maybe me with my sad face on.  We'll see!

Enjoy!

Mike

[zeeprogrammer]

That crosshead guide came out looking swell! 

[b.lindsey]

That came out terrific. It should be a runner soon!!

Bill

[Kim]

Nicely done, Mike!  Your crosshead guide looks great!
Kim

[mikehinz]

I didn't get any time in the shop yesterday and precious little today due to an out of town meeting and visiting my MIL in the nursing home.  But I did get a bit of time today to progress a bit.  So here's what transpired.

I spent a fair bit of time trying to improve the finish on some of the parts.  My main conclusion is that I don't care much for a bunch of polishing and I'm not convinced that I like the way it looks.  What I liked the look of the best way finishing with Scotch Brite pads and a powered wheel.  I did figure out that you had to be VERY careful with the powered wheel as you can easily round edges.  I also used some 400 and 600 grind sandpaper laid on top of a discarded small surface plate that I got from a local shop that was getting rid of.  It's more than adequate for lapping flat surfaces though.  i spent a considerable amount time lapping (if you can call it that) the column faces, the cylinder face and the reversing valve, just in an attempt to get the best possible contact surface to avoid air leaks.  I also cleaned up the parts, degreased them and did secured the necessary bits together.

First is a pix of the crosshead guide after I applied Loctite 603 to serve as the lower piston guide.  The round insert is made from SAE 660 bronze so hopefully it will work well against the piston rod, which is made from drill rod.  An extremely exciting shot of Loctite curing!


Here's a pix of the assembled base, column, crankshaft and crankshaft bushing housing.  it all appears to fit and the flywheel seems to run true.


A closeup pix of how I sealed up the drilled passages.  I tapped each hole and then used 10-32x1/4" brass setscrews with a drop of Loctite 545 to seal them up.  I liked the look of this vs driving in plugs in each hole and sanding them flush.  You can also see the finish I got with the Scotch Brite.  As i said above, I actually prefer this finish.


And the cylinder and cylinder pivot components all assembled.  Everything fit and rotated freely and smoothly, at least by hand.  I also made a run for different springs and found some more suitable springs, at least that's my hope.  Tomorrow I'll need to cut one of the springs and reassemble. 


So tomorrow, the crosshead guide insert should be ready to go and I should get the spring situation more or less sorted out.  I hope to be able to get the assembly work finished and to apply some air to the engine to see if it runs!  I hopeful, but I always have a fear that I've overlooked something important. 

A co-worked and I used to always be amazed when we actually got things to work.  We were always pessimistic about our chances of success.   He's Scottish and I'm an old farm-boy so pessimism seemed to be our fundamental nature.  That same thought process has carried into retirement with me evidently!

In any case, enjoy!

Mike.

[Ye-Ole Steam Dude]

Looks good Mike, I like that finish.

Have a great day,
Thomas

[toolznthings]

Following along and it's looking to be a good runner ! 

[jonesie]

hi mike also when you put the part back in the lathe after the brazing you could  help hold and center it by using your live center in the tail stock just run it in to hold it and help center,can always remove later to do work on the end. i do this at work at and also have a bullnose center for bigger stuff. parts are looking good

[mikehinz]

hi mike also when you put the part back in the lathe after the brazing you could  help hold and center it by using your live center in the tail stock just run it in to hold it and help center,can always remove later to do work on the end. i do this at work at and also have a bullnose center for bigger stuff. parts are looking good

Thanks for the great suggestion!  After I saw this, I wanted to try it out.  But I discovered that my live center and my dead center are both tool small for this guide.  I'd run into a similar problem some time back and I think I'll have to purchase a bullnose center for my lathe.  I've done some work for my brother that involved some larger tubing and so I'm sure I'll need it in the future.  Besides, 'who ever has the most tools when he dies, wins!'

Regards,

Mike

[mikehinz]

Well, after a bit of struggle at the very end, I finally got the engine to run.  I'll make a few comments in this post regarding the issue(s) and show a bit of detail of the final steps.

After I had the engine fully assembled, it would not run.  Being optimistic, I simply put air into the port and nothing happened.  After a bit of checking i found that when I tired to turn turn the engine by hand, it was incredibly stiff and tight.  I spun it over for a bit using a drill motor on the crankshaft and that didn't make anything better.  So i started tearing it back down to see if I could figure out what was going wrong. 

The first issue I found was that the piston I had made of Noryl PPO seemed to distort and had a surprising amount of friction within the cylinder.  Also, careful checking with a mic indicated that it had gone a bit out of round.  Sooo, after a bit of thinking, I decided to remake the piston using cast iron.  This proved to be a wise idea as the subsequent testing within the bore showed much less friction at the same clearance.  Plus i could see the cast iron and aluminum cylinder were wearing in to fit each other better.  Here's a pix of the final op on the cast iron piston, parting it off.


I then tried just the assembled cylinder, crosshead guide, crosshead and piston, pushing the piston assembly thru the bore by hand.  I still noted what I felt was too much friction and a bit of binding at certain areas of the stroke.  So after careful consideration, panic, desperation, etc, I took just a bit more off the OD the crosshead and brought the clearance between the crosshead and the crosshead guide to .003".  Better but there was still some binding.  So then I took a look at the .25" hole in the bronze insert at the top of the crosshead guide.  There was .001 clearance between the hole and the piston rod.  I THINK what was going on it that when assembled, there was just enough tolerance 'slop' between all the parts and consequently the assembly would not travel smoothly.  So, I opened up the hole to .257" so I had .007 clearance and finally success!! at least when running that sub-assembly together by hand.  Then back to fully assembling the engine.

I had to do a bit of experimentation with different spring configurations on the cylinder pivot assembly. 

It turns out that the springs have to be quite strong.  For the larger spring that holds the reversing valve down, I ended up with a 0.97" OD, 0.76" ID with a .105" wire diameter spring.  The spring rate is supposed to be 27#/inch.  I cut it to about 1.0" long with a cutoff blade in an angle grinder.  So I think I ended up applying about 13 or 14# to the reversing valve mating surface.  With that spring, i didn't notice any air leaks, bu that the valve still moved fairly easily but did stay in place while the engine was running.

For the pivot rod spring, I ended up using a 1" Long, 0.5" OD with a .041" wire diameter spring.  The spring rate is supposed to be 10#/inch.  I left it 1" long and after the spring was in place I'm estimating that there is about 5# being applied to the cylinder to column interface.  I THINK ideally there could be a bit more pressure, but I didn't notice any air leads while running so I'll probably leave it as is. 

Sooo, after all that, see the following!

Finished engine pix 1.


Finished engine pix 2.


Finished engine pix 3.


Finished engine pix 4.


And finally, a video of the running engine!!

<a href="https://www.youtube.com/watch?v=IvRPZeODYlU" target="_blank">http://www.youtube.com/watch?v=IvRPZeODYlU</a>

The engine is running at around 2 or 3 psi and the reversing action is shown.  I did speed it up for a bit of the video, around 20 psi, but I don't have a tach or any way to tell how fast it's running.  I was more interested in making sure it ran smoothly at slow speeds and that it actually reversed.

So, I'm quite pleased to get from a working model and drawings to an actual running model!  There were some tricky bits and it took me right at one month, but I did get it done!  I also successfully perform some machining ops that I'd never done before, silver brazing, drilling deep small holes, some more complex work holding and operations on both the mill and the lathe.  Hopefully that experience will help on future models.

All for now.

Enjoy!!!

Mike.