Author Topic: REVERSING VALVE FOR AIR/STEAM ENGINES  (Read 708 times)

Offline Ramon

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Re: REVERSING VALVE FOR AIR/STEAM ENGINES
« Reply #15 on: June 29, 2018, 07:42:09 AM »

If you think about it Brian this valve changes the direction of inlet of the steam/air. A slide valve engine has a constant direction of pressure and is only reversed by changing the valve position relative to the crank shaft hence the many forms of 'reversing' gear designed over the years, mainly to improve/enhance the cut off.

There was a lovely little inline piston valved twin cylinder model boat engine produced by one of the UK manufacturer at one time. A very neat version of this valve was set between, and integral with, the cylinders giving it a genuine 'forwards to go forward back to go back' capability. (I think that phrase came originally from the old East German DAF car ?) I have no idea who made it - perhaps Jason would know.

It's all been done before - you're just a little late for the party I guess but there's nothing like discovering things for the first time  :)

As they would say over here in ol Suffolk - "jest you keep ona troshin bor, yor dewin a foyne jorb" (Just keep on with the threshing boy, you're doing a fine job)  :ThumbsUp:

Regards - Tug



"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline Jasonb

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Re: REVERSING VALVE FOR AIR/STEAM ENGINES
« Reply #16 on: June 29, 2018, 08:44:41 AM »
The other issue with reversing the flow on a slide valve even if you did have the eccentric at 90deg to the crank is that the air/steam would just lift the valve off the port face.

Can't help on the boat engine I'm afraid

Online crueby

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Re: REVERSING VALVE FOR AIR/STEAM ENGINES
« Reply #17 on: June 29, 2018, 02:35:53 PM »
Actually there is at least one version of a slide valve (d valve) type engine that does do this. The slew and crowd engines on the Marion steam shovels had a central valve that reversed the flow of steam/exhaust passages, and a double layer slide valve that allowed it to work. Here is a cross section with how they did it:

In that pic, the steam is coming in the left hand hole (red in the yellow block) and being directed to the right hand end of the cylinder, pushing the piston left, and the exhaust is directed to the grey hole.

Then, in this next pic, the slide valve is moved to the right, putting the steam to the left of the piston, and the exhaust going out the right of the piston.  There is steam pressure all around the slide valve, holding it down. When the center valve is in the other direction, steam would be directed to the grey hole and exhaust to the red hole, reversing the direction the piston is pushed.


This is not a theoretical thing I thought up, this is actually how the Marion engines worked.

Offline Ramon

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Re: REVERSING VALVE FOR AIR/STEAM ENGINES
« Reply #18 on: June 29, 2018, 03:17:52 PM »
Well 'there you go' Chris - just shows that you can learn something every day no matter how old you are  :ThumbsUp: You'd have to agree though it's not a 'conventional' slide valve - in model terms that is ;) It would be an interesting challenge to make one.

I found a pic earlier of the Perseus engine by Cheddar Models (that is not the engine I was thinking about previously) that apparently has 'slide valves' and a reversing steam/air 'system' set to the side of the cylinders - wonder if that was on a similar principal?

Thanks for the enlightenment Chris

Regards - Tug
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Online crueby

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Re: REVERSING VALVE FOR AIR/STEAM ENGINES
« Reply #19 on: June 29, 2018, 03:20:34 PM »
Well 'there you go' Chris - just shows you can learn something every day no matter how old you are  :ThumbsUp: You'd have to agree though it's not a 'conventional' slide vale - in model terms that is ;) It would be an interesting challenge to make one.

I found a pic earlier of the Perseus engine by Cheddar Models (that is not the engine I was thinking about previously) that has 'slide valves' and a reversing system set to the side of the cylinders - wonder if that was on a similar principal?

Thanks for the enlightenment Chris

Regards - Tug
Later on in my Marion shovel build I'll be making 3 of this style engine, for crowd, slew, and steering. The main hoist engine has a conventional d valve. Only way I figured this one out was by studying thier patent on that valving, which fortunately had plenty of cross section views.

Offline mnay

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Re: REVERSING VALVE FOR AIR/STEAM ENGINES
« Reply #20 on: June 29, 2018, 07:08:05 PM »
Brian,
thanks for sharing the drawings on the reversing valve.  I have a couple of engines I can use it on.

the rest of the group,
I appreciate the info and discussion on valves

Mike