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Piston Valve Engine - How to Reverse?

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James Alford11/04/2017 16:01:47
429 forum posts
77 photos
Mainly out of interest I have been looking at piston valve steam engines. I have found plenty of examples of single acting designs that cannot reverse. I can only find comments about reversing the steam and exhaust feeds to reverse a double acting engine, but no actual explanations.

Does anyone have any clear drawings or diagrams that show how to reverse these engines?

Thank you.

John Haine11/04/2017 18:52:55
3777 forum posts
220 photos

Look up Stephenson's link

John Olsen11/04/2017 22:26:34
1155 forum posts
92 photos
1 articles

A simple piston valve engine with no lap or lead can be reversed by swapping over the inlet and exhaust. A changeover valve can be made to do this. This doesn't need any change to the engine itself, just a valve with four ports. In one position A goes to B and C goes to D. In the other position, A goes to D and C goes to B.

You can't reverse a slide valve engine in this way because the valve would lift off the valve face when steam is applied to the inside.

Steering engines for ships used to use this idea.


JasonB12/04/2017 07:27:02
20249 forum posts
2207 photos
1 articles

If you do have some lead on the valve then the engine will run in one direction and that can be changed by the eccentric in the same way you would a normal slide valve engine be that with a simple slip eccentric or one of the other reversing gears such as the above mentioned Stephensons

James Alford13/04/2017 02:58:54
429 forum posts
77 photos
Thank you for the replies. I shall look into the types of links suggested.

John: do you know of any drawings of reversing valves on piston valve engines? I have only seen them with oscillating engines and am confused how they work on piston valves designs.


Stewart Hart13/04/2017 07:25:54
656 forum posts
354 photos

Simplest way to reverse is as Jason said is with a slip eccentric this Grasshopper Engine I built has a piston valve and slip eccentric if you send me a PM with your email address I'll send you the plans.





Edited By Stewart Hart on 13/04/2017 07:33:33

Edited By Stewart Hart on 13/04/2017 07:34:07

Henry Artist13/04/2017 09:04:18
121 forum posts
46 photos

Most Wilesco engines use a slip eccentric.

The Maxitrak Allchin uses Stephenson's linkage on a piston valve engine.

If you want a reverser valve (i.e. it swaps the inlet and exhaust) go read "Making Simple Model Steam Engines" by Stan Bray.

James Alford13/04/2017 17:05:38
429 forum posts
77 photos
Henry: Thank you for the book suggestions. I shall visit our county library reserve stock where the lesser-read, but worthwhile books are kept. They might have a copy.

Stew: that would be appreciated. I have sent a PM with my details.



Edited By James Alford on 13/04/2017 17:07:22

James Alford08/03/2021 08:30:29
429 forum posts
77 photos

Resurrecting a old thread of mine: I have been working on other things, but now am thinking about this engine again.

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.

piston valve engine.jpg



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