stainless cylinder question

[chrispare]

so I have made some stainless cylinders for an ic engine, now what piston material should I use? I would like to go without rings if possible.

Any opinions?

Chris

 

[Brian Rupnow]

I used 6061 aluminum for the piston in my Kerzel hit and miss engine with a 316 stainless cylinder. It has worked great since I built it. I did use one Viton o-ring on the piston.----Brian

 

[enfieldbullet]

you're better of with rings, whats the bore size?

i'd go cast iron for the lubricity, stainless galls fairly easily(why rings are a good idea, a tight piston fit might be a problem)

stainless again is a no-no. galls very easily.

 

[chrispare]

The bore is 5/8
Was thinking of alum or brass.
I would had used different material but this is what I got so trying to work with it.

Chris

 

[Lawijt]

Stainless steel have a very bad heat dissipation. I build once a exhaust for a 2-stroke engine , worked very good & going good in resonance , but when it going too high temperature , it was the most bad exhaust in the world.But is was not for a small engine.

 

[enfieldbullet]

we're probably overthinking this and you won't have problems either way.

consider making a brass jacket on the cylinders, but maybe that's too much trouble.

i'd go with brass if you're worried, it would keep the revs slower(weight) thus minimizing relative speed of the parts. and it has better wearing properties than alum.

 

[chrispare]

So would a steel or stainless piston be a nono?

 

[Woodster]

The general rule of thumb is to use Dissimilar materials so a stainless piston in a stainless cylinder is a no-no. You can however use pretty much anything else.

 

[enfieldbullet]

woodster is right.

if you're up to it though go ahead and try it, if it seizes you will just loose your work (stainless on stainless).

steel on stainless not so bad, no so good either. it could still gall.

i remember once hearing about a story in the aeronautical industry that they were having a problem assembling a stainless steel bolt on a stainless steel part, it would get stuck after just a couple turns even with grease. stainless galls THAT bad.

as the piston/cylinder fit will be rather tight as you chose no rings i'd keep it 'safe' and choose a softer material.

 

[Brian Rupnow]

Aluminum expands a great deal more than stainless steel when heated. If you make the piston a tight enough fit to run with no rings and give good compression when its at room temperature, it may expand and seize in the cylinder very quickly when the engine heats up. The hit and miss engine I built with a stainless cylinder and an aluminum piston has a water jacket all around the cylinder, and since it is a hit an miss, it runs very cool anyways. I get away with it because my piston is a "loose" fit in the cylinder, but the viton o-ring maintains the seal to hold good compression. If the piston does expand a bit from the heat of the burning fuel acting on it, there is enough room that it doesn't seize. The piston may "grow" a bit, but the viton ring just compresses a bit more. I have ran this engine 4 hours non stop and had no problems. I do run a bit of 2 stroke oil mixed with the gasoline.

 

[Hopper]

Dont use a stainless piston in a stainless bore. It will most surely burr up and gall. Stainless nuts on stainless bolts are quite famous for doing this. Funny stuff stainless is. I would use brass or cast iron.