suggestions needed on making piston rings

B

Buzzer John

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Anyone have any thoughts on how to go about making a couple of piston rings? I acquired an old moped bike with a locked up motor, and in getting it freed up the rings broke into many parts. The piston is 40.2 mm dia and the groves are 1.5 mm wide by 1.8 mm deep. I don't have a surface grinder, but am thinking if I could find some the correct dia I could sand them thinner if needed. An online search has so far not turned up anything other than some China mfgr wanting to sell me several thousand. Material is another question. The original ones were cast iron, I think, would steel work? Perhaps a piece of cast iron pipe could furnish the stock, if I can find the right dia. Pipe with 1.5 ID and .125 wall should do fine. What actual dia should they be turned to? Will they spring open when the gap is cut? Any thoughts are most welcome, Thanks, John
 
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I would make a visit to a couple of auto machine shops, lawn equip shops,etc, before I would begin the adventure of making rings.
 
You could probably learn a bit from browsing the smokstak forum:

http://www.smokstak.com/search.htm?...RID:11&ie=ISO-8859-1&q=piston+rings&sa=Search

Those guys know where to buy custom rings, and I know I have read a couple of how-to's on there. In general, steel on cast iron isn't the normal choice, in my understanding. And normal cast iron pipe isn't the best, but a malleable iron fitting can be machined into usable rings.
 
I've made a few and as Tony stated, they need to be made of malleable iron so they wear into the cylinder wall, not the other way around. They should also be made over sized, split, compressed and clamped on a mandrel before machining them to the final (bore) diameter. If that isn't done, they won't be round when compressed and consequently they won't seal.

Tom
 
why not match your piston up to a new one, it can be done and bore your block to the piston:biggrin:mac, i put a briggs piston in a honda 3 wheeler and its still going lol
 
Sounds like alot of work to me.
I think I would try to find some thing available, Or atleast something very close, and re cut the ring lands if need be.
Man, gotta be someone out there that could supply them to you. Tony has allready mentioned the guys that build those little engines, could be a good lead for you. Good Luck
 
I've made several over the years,don't remember source of this info, but it works: Mtl., ductile iron.
Ring dia. before splitting should be 1.02-1.027 times cyl. dia.
I.D. to O.D. thickness should be 1/32 of cyl. dia.
Amount cut out of ring split = cyl. dia. x .09
Ring side clearance .002-.0035, max .004
 
piston ring help thanks

Thanks for all the suggestions. The Otto site looks promising. I'll give them a call Monday. Also, that antique machine forum looks interesting. I think the suggestion of altering the grove has merit. That's one of those" now why didn't I think of that" moments. John
 
update on suggestions needed on making piston rings

Today I called that Otto Gas Engine Works, and talked to Dave. He was very helpful and thought he could help. He called back in a short while with the good news that he had a source for exactly what I needed. They aren't cheep, but it will be worth it to get the right parts. He said it would be about 10 days before I get them. When they come I'll post how they work. I was surprised to find Dave was familiar with the little town near where I live. He knew the fellow that was known as the magneto man who had his shop in town. That follow died 10 or more years ago. John
 
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