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