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Reversing a Piston Valve Engine

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catceefer:
Good evening.

I wonder whether anyone can help with a question about reversing a piston valve engine?

I have sketched out the attached plan, taking the dimensions and general layout from information on the internet. Whether they are good or not is another matter.

Have I understood it correctly that if I simply use a reversing valve to put steam in the pipes currently labelled "Ex", using the current "In" as the exhaust, the engine will run in reverse? The plan is to make this a twin cylinder, so it should be self-starting. I should like to avoid valve linkages to reduce complexity.

Regards,

James
piston valve engine.jpg

kvom:
That's correct.  Reverse inlet and exhaust for reverse.

catceefer:
Thank you. Does that work if it is double acting? As far as I can work it out, if both of the outer ports on the valve are used as inlets, the piston locks up as they are both trying to let in steam at the same time.

Have I misunderstood the operation of the valve timing?

Regards,

James.

crueby:
The valve should only connect the center port labeled In and just one of the outer ports labeled Ex to the cylinder at a time. The yellow squares show where the valve blocks passage, they slide side to side in the diagram together. In the diagram you posted, the valve is in the transition state from moving the piston one way or the other, so no pressure is going to the cylinder at all at that instant.

catceefer:
Thank you. So, if I understand correctly, if steam enters the centre port the steam is acting on on both sides of the piston in turn as the engine rotates making it double acting in one direction, but when the reversing valve changes to flow so that the steam goes in to one of the end ports, it'll become single acting. Have I interpreted that properly?

Regards,

James.

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