Cylinder material choice for an IC engine

[rhitee93]

I'm going to expose my ignorance about IC engines here, but why do most people go to cast iron for the cylinder material? Does it have a performance advantage over steel?

I am planing an Upshur farm engine build next, and was thinking about using a steel cylinder and aluminum piston because I have the material handy. I'll most likely go the viton o-ring approach for the piston rings since this is my first IC engine.

 

[sssfox]

Cast iron is porous and holds oil better, so the rings last longer.
If you are using O-rings, it doesn't matter.

 

[Jadecy]

What kind of steel were you planning to use? I have seen several kits that provide a piece of 4130 Chromoly DOM (drawn over mandrel) tubing as the cylinder liner.

For an o-ring ring you'll want a very smooth surface finish.

I like dur-a-bar cast iron because of the consistency and surface finish but a nice piece of stress proof might work well for a model engine with rubber o-ring for a ring. I wouldn't try 1018. It can be a bit gummy and more difficult to get a good surface finish.

Leaded steel (I think 24L14) should work fine as well.

 

[rhitee93]

What kind of steel were you planning to use?

I usually have some 4140 and 12L14 lying around. With an o-ring, I would expect to lap/polish the bore to a pretty fine finish.

 

[django]

Fine grain cast iron is generally used for cylinder liners because of its resistance to deformation at high tempratures and its natural self lubricating properties of the graphite within its grain structure, contrary to popular myth (as quoted in a previous post) cast is definitely NOT Porous. I don't think that an O ring (even Viton) would ever be suitable for an IC engine.

 

[Brian Rupnow]

Django---I have two i.c. engines which I have built that are both running viton o-rings, and running very well.--That being said, these are display models that run for maybe 15 to 20 minutes at a time. If they were engines running in a service , as in a lawnmower or some other type of work, they probably wouldn't do terribly well. Gail from New Mexico did some "destructive testing" of small i.c. engines running Viton o-rings, and I think he logged upwards of 100 hours and they were still working fine. If Rhitee is going to use an o-ring, then there isn't really any sliding contact between the cylinder wall and piston, so he could use pretty well any material. My hit and miss engine has a 316 stainless cylinder with an aluminum piston and Viton o-ring. My Webster has a 1018 mild steel cylinder, aluminum piston, and a Viton o-ring. You are correct about the self lubricating properties of grey cast iron.

 

[Mcgyver]

-I have two i.c. engines which I have built that are both running viton
o-rings, and running very well

Viton and IC is a scary proposition and imo should never be done. Read up on what the hydrofluoric acid does to flesh - it is produced if a fluoroelastomer, ie viton O ring is heated past 300C. Get a bit of hydrofluoric acid on you and amputation is how they stop it from burning.

Maybe you or your buddy just haven't taken them apart yet, or may they didn't get hot enough to be a problem.... but it should clear Viton are NOT for high temperture applications. There are other O ring materials to use.

To the OP's Q, whether you machine or lap it for the finish, you can't go wrong with good quality cast iron. Machine's beautifuly, is a good bearing surface, is stable and will lap to a mirror finish.

 

[Omnimill]

Even in spite of this:

http://www.hse.gov.uk/mvr/priorities/fluoroelastomers.htm

I'd still be a bit wary of using Viton rings in a IC.

Vic.

 

[Mcgyver]

Omnimill, you are right, it's goodto strike the right balance on the subject

I've read those moderating docs and I think what their intent is is to bring some calm to the notion of handling and using them for intended applications; ie: that there's danger over 300C notwithstanding, they are otherwise benign......but the MSDS is quite clear on the decomposition results over 300 and what happens with hydrofluoric acid exposure is real. It's not overreacting to say they should not be promoted for IC or any high heat use...imo its a safety matter just like wearing safety glasses and no one wants to see the uninitiated get hurt.

hey.......what happened to my likes?...had a dozen before ....I must have really said something wrong

 

[Tin Falcon]

I would think part of the design question here is what are you doing with the engine. If it is just something to build and run once in a blue moon for fun' then viton and steel should be fine .
If you are goining to run it with a load and or run it a lot IMHO the ci and metal rings wuold be better. as far as the hat concern is it is a strictly run once in a whil demo I do not see a problem. Cheapo45 sets his up next to me it runs about 15 20 minutes on the little tank of fuel and it get warm . that is it warm . our car engines do a lot of work and get hot. but an idling IC especialy hit and miss really needs little cooling.

 

[seagar]

I use mild steel cylinder and cast iron pistons in model aero engines.

Ian (saegar)