HAS ANYONE EVER...

[T.L.A.R. eng]

Has anyone ever made a swage clamp to reduce the size of a 2-cycle model nitro engine cylinder liner to 're-size' the liner and restore compression?

I have heard others throwing around phrases like 'pinch' etc. I think there are guys doing this in the r/c car industry but it seems to be a hidden black art.

Anyone tried this? What was the results?

[Kipper]

Could you "roll" it?

[T.L.A.R. eng]

I am not sure, never thought of rolling.

From what I have gathered, they use a disc with a slot and bore the hole to the o.d. of the sleeve, then clamp the sleeve using a screw through the slot to 'resize' the sleeve using 1/8 turn incriments of the clamping screw.

However, no one really seems to sure if it works or not. I was wondering if someone here could enlighten me with their experience?

I know in the 'old days' we used to knurl the piston skirts to expand them to fit the egg shaped funnel....I mean bore...but I haven't seen the results of trying to squeeze or roll the sleeve tighter.

[HuFlungDung]

I suspect that rolling will only make it larger and never smaller.

If you did succeed at reducing the diameter of the ID, the OD is going to be less, so how will the liner then fit the block? Or what am I missing?

I am not sure what diameter your liner would be, but one notion that comes to mind is using something like an ER collet as a swager. This would be 'cruel and unusual use' of a collet, and you'd likely need to turn up a heavy female taper to support the collet, because you'd be actuating the thing with a hydraulic press.

Most likely you would also want to turn out a male plug to put inside the liner before you swage it in a press, because you need a positive stop so that you don't go too far. I suspect the liner would deform more readily if you can do this at an elevated temperature, I'm not sure how practical that is.

[T.L.A.R. eng]

I agree that rolling might be uncontrollable and could probably expand the sleeve the wrong way. I really don't have the equipment capability.
From what I understand, the loss of 'pinch' and compression is wear of .001 or less causing a loss of the oil seal. I am not sure what the effect of loosing .001 o.d. of the sleeve will have overall on the engine. The area to be swaged if I understand correctly, is the just the area above the exhaust opening in the sleeve that gets the swage treatment.
The engine in question is a .015 non ringed r/c truck engine. Why don't I just go out and buy a new sleeve/piston assembly? Naw, too easy. I have a lathe, not enough new projects, and some free time on my hands this winter and I am very curious as how well or not so well this would work. At this point, the only thing I stand to loose is some free time and a worn out piston/sleeve.

[Kipper]

Originally Posted by HuFlungDung I suspect that rolling will only make it larger and never smaller. If you did succeed at reducing the diameter of the ID, the OD is going to be less, so how will the liner then fit the block? Or what am I missing?

Usually these liners are "tophat" shaped...I was thinking along the lines of a 3 wheel knurler with ball races instead of knurls? (if you hit the top of the piston with a hammer..... )

[RICHARD ZASTROW]

You might consider plating the bore.

Dick Z

[dynosor]

Originally Posted by RICHARD ZASTROW You might consider plating the bore. Dick Z

Plating the piston might be easier.

How about swaging or upsetting the piston to a larger diameter? You could overdo it and turn it back down on your lathe. Just measure the profile before you start and try to recreate that at a larger diameter.

[T.L.A.R. eng]

Originally Posted by Kipper Usually these liners are "tophat" shaped...I was thinking along the lines of a 3 wheel knurler with ball races instead of knurls? (if you hit the top of the piston with a hammer..... )

The liner does have a .097 thick flange at the top to locate in the block.
The difference between compression and no compression seems to be very slim. I think the 'pinch' is actually a mechanical wedging at TDC. Then the mechanical wedge goes away after the engine stars and the liner expands to a running fit. Seems the differences in sizes are .0005 and under. Piston being the same size as the taper at the top of the bore being best.
Finiky these little 2-cycles!

I don't think it's possible to expand the light weight piston without breaking it.
Early in my auto repair career some years ago I witnessed a fellow using two large ball pein hammers one on top of the other, to expand the pistons of a 39 Chevy straight six! Lay one ball side down on the center of the piston and strike the face of it with the other hammer repeatedly untill the piston stopped rocking in the bore! Really!

I started to make a swage tool this afternoon, but won't be able to finish it untill next week. My curiosity is really getting the best of me.

[T.L.A.R. eng]

I can't beleive I fell for this waste of time!
I made the tool and found that it is possible to swage a brass sleeve to a smaller i.d.
However.....it is hard to tell when enough swage has been applied. To little and the sleeve springs back, to much and the piston no longer fits.
Went too far and the piston no longer fits. No problem, just lap the sleeve....wait......chrome plated i.d. Well that shines real nice now! Still .0009 too small but shines real nice!
I ended up resizing the piston smaller to fit the bore again. Now it has pinch again and seems to have better compression.
The engine is back in the truck and after running it, it really doesn't run any better than it did worn out.
I guess this method isn't exactly tried and true.
Long story short, I should have spent the time doing a customer job instead to pay for a new engine to replace the worn out one. Was really a waste of time in my opinion.

[HuFlungDung]

Originally Posted by T.L.A.R. eng I can't beleive I fell for this waste of time! I made the tool and found that it is possible to swage a brass sleeve to a smaller i.d. However.....it is hard to tell when enough swage has been applied. To little and the sleeve springs back, to much and the piston no longer fits. Went too far and the piston no longer fits. No problem, just lap the sleeve....wait......chrome plated i.d. Well that shines real nice now! Still .0009 too small but shines real nice! I ended up resizing the piston smaller to fit the bore again. Now it has pinch again and seems to have better compression. The engine is back in the truck and after running it, it really doesn't run any better than it did worn out. I guess this method isn't exactly tried and true. Long story short, I should have spent the time doing a customer job instead to pay for a new engine to replace the worn out one. Was really a waste of time in my opinion.

Don't feel bad! Sometimes you've just got to try stuff and find out how it works out. Wisdom of the present moment arises from experience from the past.