Author Topic: Piston- clearance  (Read 344 times)

Offline crankshafter

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  • Molde, Norway
Piston- clearance
« on: September 30, 2017, 07:43:10 PM »
Evening all.
I'm in the progress of  building a 1 cylinder IC engine of my own design, 35mm bore , cast iron rings, aluminum piston.
And here's a question: what clearance for piston/cylinder should aim for.

CS

 
 
"I cut it twice, and it's still to short"!!??">#%

Offline 10KPete

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Re: Piston- clearance
« Reply #1 on: September 30, 2017, 07:55:04 PM »
A couple of thou will do it...

Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Offline Roger B

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Re: Piston- clearance
« Reply #2 on: September 30, 2017, 08:00:36 PM »
What is the cylinder made from, you made need more clearance with an aluminium piston.
Best regards

Roger

Offline crankshafter

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Re: Piston- clearance
« Reply #3 on: September 30, 2017, 08:11:33 PM »
Roger.
Sorry :embarassed:but the cylinder is cast-iron

CS
"I cut it twice, and it's still to short"!!??">#%

Offline Brian Rupnow

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Re: Piston- clearance
« Reply #4 on: September 30, 2017, 08:22:47 PM »
No, even with an aluminum piston, 0.002" clearance will be enough. Sometimes people deliberately make the piston about 0.001" oversize, then "wring it" into the cylinder using diamond lapping paste. If you do that, you can get away with no piston rings at all. That is effectively zero clearance, and is often used on two cycle engines where a piston ring would get caught and break on the cylinder ports. You wouldn't do that with an aluminum piston, because it expands more quickly than cast iron and could seize in the bore.