Steam engine slide valve

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New Member
Feb 21, 2023
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Napa, CA
Working with castings from "burnzoil" foundry in No. CA. eBay seller. Great casting kits and additional cylinders for my Donkey Engine. Customer service also excellent. Several build pix. but no plans included. I need help with slide valve pocket dimensions. Some advice has been 9% width reduction of area over two adjacent ports. My cylinder ports are .280+.200+.300=.780X.09=.702. Sound reasonable ? Thanks, Thomas
Can you post a picture of your ports as the sizing is not quite clear or ideal, are these cast in ports that need further machining to clean them up?

Very common to have the central port that connects to the exhaust twice as wide as the ports either side, material between ports equal to the width of the outer ports. Cavity as said above and then little lap of running on air, a bit more if on steam.

Make the eccentric after you have designed the valve to give the required movement.


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Thanks Charles, did not spot that and he does not seem to have come back so little point in bringing the thread back to life.