Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Builds, Repairs, Show Your Machines! => Technical Tips, Builds, and Help => Topic started by: millwright1163 on December 11, 2022, 05:50:41 am

Title: Re: piston to wall clearance
Post by: millwright1163 on December 11, 2022, 05:45:45 pm

 Vitron o-rings for piston rings. I am not marred to the aluminum pistons, I just happen to have a piece of aluminum in my scrap stock that measures just the right size. [just lucky]

Title: Re: piston to wall clearance
Post by: Stoker on December 11, 2022, 01:26:34 pm

I don't believe .002" is too much clearance, but it may well be too little clearance given that the coefficient of expansion for aluminum is significantly greater than that for cast iron. May depend on what temperature/pressure steam you intend to operate at from your steam source.

Are you intending to use any form of piston rings?

Title: piston to wall clearance
Post by: millwright1163 on December 11, 2022, 05:50:41 am

I am building a model live steam engine. The bore is 1-1/4 x about 2 inches. the cylinders are cast iron and the pistons will be aluminum or brass. Vitron O-rings. How much clearance is acceptable between the cylinder walls and the pistons? I have aluminum pistons that the diameter is .002 inch under but am unsure if that would be too much clearance. Thanks in advance, and Happy holidays to all.