# My Elbow Engine - Confessions of How I Fixed My Errors



## rake60 (Aug 15, 2007)

_With John's original thread on this engine filling up, I thought I'd we should
split it up a bit._

As soon as saw this engine I had to attempt it.
John's beautiful build was even more of an inspiration to give it my best 
shot.  My best shot just didn't get it. :-[ So I went into the damage
control mode. I found that the base and upright support were out of 
square .005" To fix that I clamped the base to the mill table and dusted 
the lower cylinder base to clean-up. Then in the same set up I skinned 
across the upright support in the area where the upper cylinder mounts.





The second deviation was on the pivot bolts. I used standard 10-32 
socket head bolt and fitted the cylinders with thin wall bushing that I cut
.005" longer then the cylinders to allow free rolling clearance.




Third deviation was the pistons. I made mine of plain 1018 cold roll steel.
Cut them for a snug fit, smeared them with toothpaste and turned the 
engine over my hand until they'd lapped themselves in for a free turning 
fit. Put the air to it the first time and it binds up tight. Out of shear 
frustration I grabbed a can of wheel bearing grease that was near by and
smeared it on the pistons. Hooked the air to it again and it took off.

[ame]http://www.youtube.com/watch?v=cpP-PT_fC7o[/ame]

I'm not real happy with the final results. Might just have to give this one 
another go from the beginning someday, but not soon. It has been the
most frustrating project I've ever done. :-\

Rick


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## Bogstandard (Aug 19, 2007)

Well done Rick.
What are you worried about, if it runs it is a success.
Now you know the pitfalls you will be able to knock another one up and get it running in a couple of days. :lol: 

John


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## gilessim (Aug 19, 2007)

I've also had headaches making mine!, it isn't running yet but the pistons I've found to be a pain ,it's bad enough getting them all the same length, but how do you get them all to bend exactly in the same place?, mine all came out slightly different, or "L" shaped, either we have to make the turned down section shorter or maybe make a little nick, dead in the middle of the rod to make the start of the bend easier, I've had my hair cut really short today ,so I can't get hold of enough to pull anymore out!...Giles


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## rake60 (Aug 19, 2007)

My softer 1018 steel bent a little easier than drill rod would.
In fact I bent mine without heat, chucking the full length on of end in the 
lathe and using a close fitting piece of tubing over the opposite end.
I made 6 pistons and used the three that were closest to being identical. 
To get them perfectly square I grabbed one end in the center 
groove of the mill vise and ran the table in and out with an indicator on
the center of the flat piston to tweak it to dead nuts flat.

Yet another cheat...   

Rick


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## Bogstandard (Aug 19, 2007)

Giles,
If you read my post about making this engine you will notice my comments on bending these little buggers. I would use bending bars about 12" long, and get the centre section red hot. If you put the torch in say your vice and hold the centre section in the flame, once it gets reddish you can put pressure on the bend and I found with mine it bent in the middle no problem. Don't put a nick in them, it is liable to fracture at that point as you are bending.
If you can't get pieces to the same length I would suggest making a back stop for your lathe mandrel, using one of these you should be able to make 50 pieces all within 0.001". If you don't know how to make one let me know and I will raise a post in the tools section to show you how to do it.

John


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