Elmer's Opposed Piston Engine 2x scale

[philjoe5]

I’ve decided to make Elmer Verburg’s Opposed piston steam engine, but at 2x the usual scale.  This engine has an interesting way of channeling steam (or air, in my case) through ports in the crankshaft so it’s been on my bucket list.

I checked out a few build posts for this engine, and picked up lots of good ideas.  So thanks to those who traveled on this path before me.  I shall follow in your footsteps and will occasionally wander off track just because I never did listen to mom.

I had two questions that have come up as I went through the plans.

I.   There are 2 holes 1/16” diameter in the cylinder.  They appear to be oil ports but in my drawing they don’t communicate with the bore.
II.   A 1/16” hole is drilled through the faces of both eccentrics and the central disc.  I assume this is a locating hole and it’s exact position is unimportant as long as it passes through the eccentrics when they are at opposite extremes.

Thanks for any help.  I’ll do my best to post pictures on a regular basis.

A search through my “flywheels” bin turned up this gem which will be perfect:



I don’t know how long it’s been sitting there or what I had in mind for it but obviously I found something else at the time.  It even has a 1/8” keyway broached.  I suspect I made this flywheel 4 years ago when I bought my first set of broaches and tested one of them out on this flywheel.  Waste not, want not.

Nothing is very complicated so far, and having the right tools saved the day.  I had a nicely finished piece of 303 Stainless steel that I chose for the crankshaft.  Normally I drill or ream a hole in a mating part first, then turn down the shaft to fit.  In this case though I didn’t want to try and adjust the diameter to fit a ½” (0.500”) reamed hole.  Sure enough when I reamed the hole 0.500” in the bearing and tried sliding the crankshaft through while the bearing was still held in the lathe, it wouldn’t go.  Out came the set of over/under reamers, and when I reamed the hole 0.501” the crankshaft fit perfectly.

The crankshaft flats were milled by holding the part in a 5C collet block.  There are more holes in this thing than a politician’s campaign pledge, but it came out OK:



I've also made good progress on the column and bearing.  Here's a trial assembly of parts mostly completed:



I'm planning to remove some of the excess stock on the column after I get the engine assembled

Cheers,
Phil

[zeeprogrammer]

 

Get ready. 

[Don1966]

Cool Phil, I be watching as well.......

Don

[b.lindsey]

Always good to see another Elmers thread starting up Phil. I am sure you will do  Elmer proud with this one.

Bill

[sshire]

Phil
When I did my 2X, I did some "cosmetic changes." I'll look at my drawings to try and answer your questions.

[philjoe5]

Thanks guys for your interest.  Anxiously awaiting your reply Stan. 

Someone asked me once why I always seem to scale up my engines.  When I was introduced to this hobby 9 years ago I had no idea what I was getting into (still don't).  But ally could be had on eBay for about $1.50 - $2.00 delivered to my doorstep.  So whenever I saw a good deal I bought some including this 2" x 4" x 48" (it's shorter now):



I've been chipping away at it over the years and it's perfect for my 2x scale cylinder which will be 1.5" x 1.5" x 4"

Cheers,
Phil

[sshire]

Phil
The mystery 1/16" holes in the cylinder (I just scaled everything up, so mine are ⅛") are exhaust ports. They are at the bottom of the cylinder and do go through to the bore.

The holes in the eccentric serve two functions:
1. Locating hole for aligning the eccentrics.
2. They receive a pin which is trapped between the disks to maintain the eccentric alignment when running.

Disclaimer: my observations may be totally incorrect, as I'm three engines away from that build. However, Elmer's text instructijon for the eccentrics and disks and his drawings for aligning the eccentrics seem to align with my thinking.

If it runs, I was probably correct. If it doesn't run, it's Cletus' fault.

[philjoe5]

Stan,
I was thinking the engine pushes exhaust down the column and out through the central hole in the crankshaft.  No

Thanks for the other information.  Do you have a phone # for Cletus   I usually troubleshoot my engines at 3 am EST.

Cheers,
Phil

[philjoe5]

I needed to make 3 discs that are 0.062” thick x 1.750” diameter with a 3/8” center hole.  These are used to fabricate the crankshaft.  The plans specify steel for these but I had a piece of brass in that diameter so I chose this material.  Parting was straightforward.  Someone on this site once showed the trick of placing a rod held in the tailstock drill chuck to catch the parted off pieces and I used it here. 



Of course, this postponed my favorite past time of rummaging through the swarf under the lathe bench looking for the pieces and discovering all the tools lost since the last epiosode.

The cylinder is made from some 1.5” x 1.5” x 4” aluminum barstock.  I like Stan Shire’s version using round stock and milling a flat to mate against the column but I had the aforementioned slab of rectangular ally that was convenient to use.  I bored this on the lathe, and as is my usual practice, I took 2 spring cut passes at the end.  The chip from the first one isn’t hard to see.  It’s lying across the lathe ways here:



I found mention of the 2 extra exhaust holes in Stan’s post.  I think I may drill/tap them 5-40 and experiment with putting bleed screws in those holes, just for fun.

I checked the cylinder for taper.  I made a dowel of 0.997” diameter that fit in one end, but not the other.  I made another dowel 0.996” diameter and it fits in the small end, so I have about 0.001” of taper over a length of 4 inches.  Not enough to worry about.  I’ll make both pistons 0.996”.

Here’s a family portrait:



And a trial assembly:



I'll be starting the connecting rods next. 

Cheers,
Phil

[sshire]

I love the bleedscrew concept. Looks great so far.
The swarf-searching exercise certainly is fun. I was cleaning around the buffer (which grabs parts and flings them to some secret part of the shop) and found a conrod for an engine that I made 2 years ago.

[zeeprogrammer]

Nice progress Phil.

 

[Don1966]

You don't mess around Phil, hell you been busy bud and I'm enjoy the ride.........

 

Don

[b.lindsey]

Looking good so far Phil. Tuning in daily to check your progress.

Bill

[philjoe5]

I started work on the “middle” con rods today.  I have some #7000 series aluminum purchased on eBay as “Fortal”.  It machines beautifully and I’ve used it for several engine parts over the years, cylinders, connecting rods, pistons. 

I began by milling these to oversized blanks.  I decided I would approach this machining task by treating the “blanks” as castings.  I identified center lines on both x and y axes and scribed my layout lines accordingly.  Each piece was drilled/reamed for link pins on the small end and bored on the crankshaft (big) end and the 3/8” limit holes for the big end were drilled.   


The final setting on the boring head was noted for the first piece and the second piece was bored to the same setting.  I took 3 spring passes with the boring bar which I find necessary when boring on my mill.  The swarf on the vise is from the first spring pass. 



Next I milled the ¼” slot on the small end.



Now milling the thin end of the connecting rod.



Milling the central shank of the con rod here.  The steel rod is acting as a very low profile parallel, just to keep the bottom milled side flat


These parts are now ready for the rotary table.  I have a clamping fixture for the small end but  will need to make one for the big end.

Cheers,
Phil

[Don1966]

Nice connecting rods, are you going to round the ends?

Don

[b.lindsey]

Looking good Phil...still following along here 

Bill

[philjoe5]

Don - yes, I'm off building a clamping fixture for the big end, I think I have one for the small end.  I usually wait until I finish a part before posting but I haven't added anything for a while and I may be another week before I get those ends rounded.

Bill - thanks for dropping by; I knew you looked in because there's some popcorn on the floor under my computer desk

Cheers,
Phil

[Art K]

Phil,
I think I was out on the garage making chips and missed this. The build is looking good.
Art

[philjoe5]

Thanks Art.

After boring the con rod blanks I realized my limit holes for the big end had been placed too close to the bore.  Thinking I might be able to blend in my mistake I continued on.

I made a fixture for holding the connecting rod on the rotary table.  I use an MT2 collet to hold the fixture.


The milling of the big end had no surprises.



After blending as much as possible, this is the end result



They are functional but too ugly for my taste .  So, time to get back on old hoss and try again.


Cheers,
Phil

[Don1966]

Well Phil I think you have it down pat for the next time around bud. Looks like a new RT there buddy.....


 
Don

[philjoe5]

Thanks Don.  That 6" rotary table is only a few years old.  It's a Phase II, I'm satisfied with their tools.

A second attempt at these con rods is underway.  I discovered where I made my mistake with No. 1 and unless the shop demons  show up I should have a good progress report next time

Cheers,
Phil

[philjoe5]

Well the shop demon did show up again.  But before we get into that I couldn't help but admire the lightness of the (slightly funky) con rods made last week.  So starting with trial #2, I weighed the blank



and the con rod



Wow, 85% of the blank ends up here



Anyway, on to trial #2.  I set up this milling step with a piece of drill rod sitting on the base of the vise so that the part could span the gap in the center of the vise base.



The problem is I picked up a piece of 1/4" drill rod instead of the 3/16" I intended.  So as I started to mill the part, I was rewarded with this:



At first I thought my trusty vise had failed me (Rule 1,  blame the tool first ).  Then I realized my mistake.  The big end is 0.250" thick so I had no gripping power on the part.  So, for one of the con rods, I'm into trial #3.  Happily for trials #2, #3, I didn't disassemble my boring bar so I could take it to the same setting and get a bore that was consistent and fit my fixture for the rotary table work.

Cheers,
Phil

[zeeprogrammer]

 

You're an engineer aren't you? If not, you certainly have the makings for it.
Measured the waste. That's pretty cool.

[b.lindsey]

That is a shame Phil, but having had a couple of brain lapses today I feel your pain. Hey, it all a learning experience, and however long you do it, the gremlins seem to be one step ahead.. Always!

Bill

[Don1966]

Phil I can relate buddy, on my Benson I remade the governor swivel 5 times. The dam part was trying to intimidate me but I showed it..........
Well buddy I hate to see you doing it again but it's part of the fun........

Don

[fumopuc]

Hi Phil you are not alone with this kind of mishap. Shortly I have started some milling without checking the dimenson of the already clamped cutter. I have been sure that it was a 10 mm cutter, I have touched the edge, started milling and the part was scrap. I have tried to blame the DRO, the mill, the vice, the drawing, the designer but without success. The real reason was the cutter with 12 mm diameter, which was clamped from an earlier job and the operater of the mill who did not recognize this, so me.

[sshire]

On a shelf over the bench, I have incorrectly made parts from various engines. The intent was to not repeat those mistakes. Didn't help. I keep discovering new methods of screwing up parts.

[philjoe5]

You're an engineer aren't you?

Zee, I'm really not but I play at being one in my shop.

Thanks Bill for reminding me that “I suffer not alone”

I remade the governor swivel 5 times

Don, that’s a lot of trials, but I made 5 con rods for my recently completed sun and planet engine so we both know that all that practice paid off, right?

Achim, thanks for the encouragement

Stan – you’re lucky you have a shelf that all your bad parts will fit on.  I had to go to a recycle bin.

OK, but in the end, there’s this:


 

Cheers,
Phil

[philjoe5]

I started with some 1144 alloy free machining steel and turned a length to the diameter of the big ends of the con rods.  Having made a clamping fixture for the big end I had a good idea of how far to turn down the stock for a sliding fit for the con rods.  Here I tested the diameter using both con rods.  The fit is close enough to support the con rod without flopping down but it's not too tight either


Next, I drilled and reamed the crankshaft hole with a ¼” offset.  The first few times I drilled off center holes on the lathe I was convinced that when the drill bit contacted the work it would promptly snap off.  Then I learned to focus on the end of the drill bit instead of the workpiece flopping around.

The eccentrics were parted off and the assembly of eccentrics and con rods was tested for clearance by clamping it in the vise.  The con rods move easily with eccentrics clamped so clearance is OK.

I now have all parts for the crankshaft completed. 

So after a trial assembly, the quality control manager allowed me to proceed making the next parts.  The crankshaft assembly is shown here inserted into its brass sleeve bearing.


Cheers,
Phil

[zeeprogrammer]

Very successful! 
And thanks for the scale. Reminds me that I keep forgetting to do the same.

What kind of quick-change tool post is that?

[b.lindsey]

Nicely done Phil, you got those gremlins cowering in the corner now

Bill

[Don1966]

Looks good to me Phil and like Bill said, keep those Gremlins away........ 

Don

[philjoe5]

Thanks guys.  And Zee, that's an AXA 100 QCTP.  The photo perspective is outrageous, it appears in the photo to be about the size of a small import automobile

Cheers,
Phil

[sshire]

You've got the most "challenging" part finished. 
It's looking great, Phil.

[philjoe5]

Thanks Stan, I was hoping 

I began making the arms of this engine from ¼” aluminum stock.

I wanted to use this nicely finished aluminum plate I picked some time ago, Alcoa machined plate.  I cut and milled the arms to their blank dimensions. 



After a bit of study I realized I could cut the end of the arm using a reverse curve of two different diameters, ½” and 5/8”.  I constructed this diagram using Corel Draw to get some critical dimensions.



I often begin making a part with my best raw material, then inflict great damage upon it, and end up remaking it with lesser material.  You know what they say about doing something over and over the same way and expecting a different result.

This time I cut short piece of ¼” aluminum, milled it true and drilled the end 5/16”, milled it at a 7 degree angle, then placed it on the rotary table to form the 5/8” diameter curve.  At the same time I made a 7 degree angle block from some 1/8” brass stock.  I have a set of angle blocks but they’re ¼” thick and my stock is ¼” thick.  I already studied the effect of clamping stock and parallels of identical nominal thicknesses.  Now having blended the 2 curves, I ended up here.  This validates my calculations.



And now I only had to go after my valuable Alcoa machined plate stock.  They machined exactly like the practice piece.  They were modified from the plan in that the 5/16” hole was placed at the top as well as the bottom since I wanted the upper conrods to be a bit more robust.  I checked the parts for equality using 2 dowel pins.  Everything lines up OK.





Cheers,
Phil

[Tennessee Whiskey]

Geez,  and after all that ciphering they still came out looking great  . DOG  and I have been taking turns on the phone and so far neither have had any "help line" calls from you : I see now why 

Cletus

[b.lindsey]

Very nice Phil.  Tricky parts, but they turned out great. We need a family shot soon!!

Bill

[zeeprogrammer]

Looks great!

The drawing says 'hard aluminum'. What is that and why would it be called out that way instead of just 'aluminum'?

[Don1966]

I guess you showed them parts didn't you Phil?  That we'll teach them to try to spoil things.......
That really turned out great Phil and I am glad you didn't have to remake them.......

 
Don

[philjoe5]

Cletus - I don't think I've heard the term "ciphering" since I was a student at St. Francis Catholic School in the '50's   But hey, I've not lost it yet

Bill - family shot is coming soon, when I finish the upper con rods

Zee -  "hard aluminum"?  That's a good question.  I'm taking it to mean if I hit it with a plastic hammer it won't dent

Don - that is the question I'm asking myself...when I made the "practice" piece did I actually have to remake the parts that I made?     We need a philosopher like Marv to chime in and settle this.  Technically, if the "practice" piece ends up in the scrap bin, then I guess I had to remake the part

Cheers,
Phil

[AOG]

The drawing says 'hard aluminum'. What is that and why would it be called out that way instead of just 'aluminum'?

My understanding is that 2000 and 7000 series are considered hard aluminum. But I think what Elmer really means is don't make the part out of something like 1050 or 1100 aluminum.

Tony

[fumopuc]

In my understanding  'hard aluminium' is a everywere available stock like 7075 here in Europe.
I agree also 100% with Tony, it is only an advice, not to use the very soft grades.

[zeeprogrammer]

Thanks Tony and Achim.

Where does 6061 fall? That's all I ever get...mostly because I don't know different and it seems the most popular.

[AOG]

Where does 6061 fall? That's all I ever get...mostly because I don't know different and it seems the most popular.

6061 isn't as strong as 2024 or 7075. The reason we use it is that it's cheaper and it machines much better than the other 2 types of aluminum. Since most of our models don't do much work it's fine for most things.

Tony

[philjoe5]

Connecting rods to the piston were next on the list since the rotary table is still occupying real estate on my X3 mill table.

I started with 5/8” square aluminum, and milled two pieces to ½” x 5/8” x 2.2”  Now I’m winging it from the plans except for the dimension between the piston pin and the arm, which is 2x that indicated on the plan.  I just cut away any metal that didn’t look like my con rod, then rounded each end on the rotary table.  I kept in mind the dimensions of the inside of the piston so that the con rod would fit with necessary clearance.  This photo shows the slotted end being milled on the rotary table.  I have inserted a piece of sacrificial ¼” square aluminum into this end to prevent the ends from bending as I tighten the piece to the fixture.



And the completed the con rods



I think this may be the first model I’ve built where the exact same name is given to two parts that look totally different






Cheers,
Phil

[philjoe5]

Next, I tackled the pistons.  I had a piece of 1 1/8” brass round that was a good starting point for my 1” pistons.  I turned them to fit the cylinder; they were within 0.0005” of each other accounting for the taper I experienced when I made the cylinder.

Then I drilled out the inside with progressively larger center cutting end mills.  And finally I cross drilled/reamed them while holding them in a 5C collet block.  I discovered that I didn’t have sufficient clearance inside the piston and needed to take about 0.080” more in diameter to fit the con rods.  I didn’t want to hold the pistons in a three or four jaw chuck for this operation so I made use of an ER-40 collet chuck on hand.  Even though it’s not a pass through chuck I’ve found it useful at times due to it’s very low runout.



And here, assembled with con rods in place with a temporary piston pin


Cheers,
Phil

[zeeprogrammer]

Nice Phil.

On your previous post you were using the rotary table to round off the end of a part. I see the bolt holding it in place.
Was there anything else clamping the part down?

Just curious, as with my luck, my part would be spinning as soon the end mill hit. 

[philjoe5]

Zee,
In that picture I have a 5/16" screw holding the part on the flat base of the fixture.  Sometimes I will put a slot in the fixture to prevent the part from spinning but with a screw of that size holding the part I've never had a misadventure.  Also, my depth of cuts don't exceed 0.050", so I take several passes and always feed into the tool's cutting edges.

Cheers,
Phil

[philjoe5]

I have a piece of cast iron to serve as a base.  That will need some milling work.  This is pretty much a family portrait except for six shoulder bolts or pivot pins and the base.


I made four shoulder bolts but held off on the two that connect the upper con rods to the arms.  I want to cobble the assembly together to see how much clearance I had.



This is the cobble with 5/16" screws holding the upper con rods to the arms



Doesn't look like a lot of clearance when the pistons are at TDC, so I'll probably just make some pivot pins.

Getting close now.

Cheers,
Phil

[philjoe5]

Pivot pins were made for the con rods on top.  I assembled the engine and set the timing and gave it a test run.  I tried the engine without drilling the 2 vent holes in the cylinder and it runs fine without them.  On  the 1x scale it may be a problem according to Elmer.

Timing was easy to do because the crankshaft keyway was cut on crankshaft with one of the flats (valves).  It was easy to get the crankshaft assembled so that the flat was vertical, ie, no air, when the pistons were just at TDC. 

I found another flywheel I'd made years ago that was smaller in diameter that seemed a better scale for this engine.  I'd made it before I'd started cutting keyways so I ran a 1/8" broach through it and it does the job.

Then I painted her up and here's the result with a few views:




And, of course, the video.

<a href="https://www.youtube.com/watch?v=CAo_fj5iFdw" target="_blank">http://www.youtube.com/watch?v=CAo_fj5iFdw</a>

All in all, a neat little engine with interesting valving incorporated into the crankshaft.

Thanks for looking in

Cheers,
Phil

[b.lindsey]

Very nice Phil, at the beginning of your video, it was running so slow and smooth I thought it was in slow motion, but no...sure sign of a well built engine. Congrats!!

Bill

[zeeprogrammer]

Really nifty Phil.

I had the same thought as Bill. Cool.

What is that part coming off the big brass next to the flywheel?

[toolznthings]

Nice Job !! looks great !

Must be something in the water. I did a double scale of the same engine a few months back. Nice project.

Brian

[sshire]

Bravo!
A very nice runner and I love the colors.

[philjoe5]

Guys - thanks for the complements

Bill -  I was surprised how slow I can get this single acting engine to run.

Zee - that part is a push-to-connect air fitting, so that's the air/steam inlet

Brian - that makes 3 of us, Stan, you and I

Stan - my choices of color scheme are dwindling.  I've accumulated about 40 rattle cans of paint over the past 8 years.  I don't want to add to that so I pick what colors I have enough of to do the job

Cheers,
Phil

[Alan Haisley]

Really nice job, Phil

Alan

[philjoe5]

Thanks Alan.  A few warts and bruises but otherwise I'm pleased with it.

Cheers,
Phil

[Don1966]

Phil sorry I am falling behind her but she turned out great buddy and a great runner. Very nice work all around buddy.......

Don

[philjoe5]

Thanks Don.  I'm in the same boat trying to find time to keep up with all the build logs going on .  Now that I'm between projects, maybe it'll be easier

Cheers,
Phil

[Roger B]

A very nice runner and an interesting mechanism   

[tvoght]

Nice work Phil. The slow speed operation is impressive.

--Tim

[philjoe5]

Tim, Roger, thanks for looking in.  Apparently there are other Elmer designed engines that use the crankshaft as a valve, "Standby" being an example.  I think Cheepo45 built that one.

Cheers,
Phil