ALUMINIUM PISTON

[RICHARD GREEN 2Participant @richardgreen2]

Hello

I am making an aluminium piston for a steam engine from 6082 alloy, 4 1/4" bore diameter, ( cast iron cylinder )

Does anyone know how much clearance I should allow between the piston and cylinder , taking into account the expansion of the alumunium piston with steam at 150 psi ( 185 degrees C )

Richard.

Edited By RICHARD GREEN 2 on 02/07/2014 11:49:35

[RICHARD GREEN 2Participant @richardgreen2]

[JasonBModerator @jasonb]

Most of the traction engine guys allow about 0.002" – 0.003" per inch dia.

J

[Anonymous]

Assuming that we're talking traction engines running at a few hundred rpm the forces involved in reversing the direction of the piston at the end of each stroke are not that high, even with a solid cast iron piston. I would agree with JasonB on the clearances, but personally I would not be happy with the resultant rattling fit.

So just to be different I have designed hollow cast iron pistons for my 4" scale SCC engines. As a flavour here's a screen shot of an FEA analysis of one half of the LP piston:

The hollow LP CI piston is actually slightly lighter than an equivalent solid aluminium piston.

Regards,

Andrew

[Author]

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