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O-Rings in Cast iron cylinders

Posted: Tue Apr 15, 2008 8:35 pm
by Wayne Davis
I would like to ask the list if it is OK to put O-Rings in the pistions for an engine with cast iron cylinders. I have used them in an engine with a bronze liner and like the way they worked.

It is time to do an overhaul on my 1" 040 and I was thinking about switching it to O-rings rather than the cast iron rings in it that are surely worn. Is cast iron cylinders to rough for them? The engine engine is 19 years old so thought the walls should be smooth from all the use.

Wayne Davis
Creston, Iowa
somewhere in the middle
Iowa Model Steam Engineers

Posted: Tue Apr 15, 2008 9:10 pm
by Mike Walsh
Umm.... IIRC 0-4-0's have cast iron cylinders, but they have steel sleeves. These sleeves allow the use of piston rings.

If yours doesn't have sleeves, how has it held up? I only ask because I thought the norm was steel sleves in cast iron castings.


Posted: Tue Apr 15, 2008 9:37 pm
by Wayne Davis
I have not pulled the heads or taken the pistons out yet. I don't think this is a problem except I think I have a ring that is stuck in the piston. I had some water left in the cylinder and got a small spot of rust on the bottom of cylinder a couple years ago. When I pulled the head to remove this spot they looked OK, but I should have pulled the piston out.

The main reason I want to do an overhaul is for valve linkage ware and to surface grind the valve seats. I did not have access to a grinder back when I built it and want to redo the valves and valve face.

Wayne Davis


Posted: Wed Apr 16, 2008 5:25 am
by Bill Shields
work just fine, as long as you keep the bore smooth (lapped is good) and rust / pit free.

You cannot leave such an engine with water in the cylinders and allow any sort of corrosion.

Otherwise, o-ring life can be measured in hours.

Posted: Wed Apr 16, 2008 8:37 am
by appalachian american
I would stick with the rings. They really do a better job in a reciprocating cylinder.

Are you having some bypass now? I finished my 1 1/2" 0-6-0 in 1980, and she is still tight. If you will keep the crossheads worked so she stays in line properly, those iron rings should last a long time.

I am a hydraulic cylinder guy in real life, and in a reciprocating application rings will go way past a million cycles. That's a lot of trips around the track!

Good luck!


Posted: Wed Apr 16, 2008 10:49 am
by Ben_Smith
Hey Wayne,

I've got Viton O rings running in CI cylinders in my Shay. You've seen it run a few times. Works just fine so long as your lubricator is working well. I usually replace them every winter as part of my "before spring running" maintenance. You may want to polish up your cylinder bores a bit before makiing the switch, though. You will probably also need to re-machine your pistons to fit the O rings. The groove should be 1.5 times the thickness of the O ring. You'll also want to make the groove shallower than the thickness of your O rings by about .010" or so (I think that is what I put mine at... but really can't remember)

O Rings

Posted: Thu Apr 17, 2008 7:17 am
by John Rukgaber

I have used viton O rings in my mogul and they have been in for some time. It has bronze liners in it. I have been hesitant to use them in my locomotive with cast iron cylinders so this is a good post. I am looking forward to the input from others that you get.


Posted: Thu Apr 17, 2008 8:01 pm
by Wayne Davis
Hi Ben

Below is a web page that I have on our Iowa Model Steam Engineers link page. It give the recommended tolerances for different sized O-rings. I used this on my 1" 280 to get the right size grove for the piston. It has bronze liners and works great.

Wayne Davis
Creston, Iowa
Somewhere in the middle ... cating.htm