Frisbie

[PaulR]

Blew the lid off, and blew stew all over the ceiling.

Turned meat into dripping!
(Not sure how well that joke travels, maybe 'dripping' is a UK-only thing?)

[Casting Iron]

As they use to say in the 60's, "It was a bad scene man......".

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[Casting Iron]

This is my guess on how it is arranged.
I would think that the pivoting valve would have vertical slots on the cylinder side, with the height of the slots being the distance between the lower steam port and the port that goes into the cylinder.

The port on the top of the valve is a thru-hole, which is the exhaust, and it would also have a vertical slot facing the cylinder.
Steam ports (on the port face) are the ones at the bottom.

There would have to be some careful drilling horizontally, vertically, and at an angle, through the cylinder support member, to get the steam passage routed back to the boiler.
The ends of these drilled holes, except at the boiler, would have to be plugged.

Edit:
Looking at the port face with the pivoting valve removed, you would see two holes going into the cylinder, and two round steam ports.
Looking into the inside face of the pivoting valve, you would see two upper through-holes, with slots protruding down from these two holes, and then on the lower side of the valve, two more slots that don't connect to anything, and are on the inside face of the valve only.

Edit2:
Looks like my dad silver-soldered a plate on top the boiler, and drilled the lower horizontal steam passage in it, and then drilled/extended the passage at an angle into the boiler.
The cylinder appears to bolt on, I guess so it can be final machined prior to being installed, without having to turn it while it is attached to the boiler.
The vertical steam passage upwards from the silver-soldered plate into the cylinder wall would have to be sealed (the joint between the cylinder and the plate sealed).
Another horizontal steam passage is drilled into the wall of the cylinder, and then the two lower ports drilled into this passage at 90 degrees.
The end of this upper passage would be plugged.
Then drill holes into either end of the cylinder.

For the port face of the valve, machine four shallow slots, and then drill through on the top two slots.

Can anybody follow this explanation?
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[Casting Iron]

Looks like the holes in the cylinder don't go straight in, but rather there are passaged drilled from either end, with a cut into the end of the cylinder.

Looks like the slots on the inside of the pivoting valve were milled on the rotary table.

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[Jasonb]

Pat, where are you seeing these steam ports mentioned in your first edit?

Looking at the broken engine I can see three holes and a central pivot pin.

Assuming the two holes higher up go to each end of the cylinder then the third would have to be the steam supply

Most photos of these engines show the pivoting valve plate to be quite thick so that would allow for some slots to be cut into it's face, the exception being the second photo in the first post.

I think I have it working in a hand sketch, will check it later in CAD to be sure, easier if teh third steam supply hole was central

[Jasonb]

So here is my thinking based on the three holes that can be seen in the port face of the broken engine's cylinder.

The cylinder is grey

The three holes Red

The valve the green/blue I have shown the lower "passage slot" going all the way through for clarity, in reality it would be only half depth. needs a bit of tweaking to get the holes lined up better but shows the principal.

First image is when the valve is in the mid position, two ports to the cylinder ends closed and steam from below only going into the void of the slot.

Second photo The valve at full travel. Steam can now travel along the recess to the left end of the cylinder pushing the piston to the right where the used steam can exit through the right hand hole in the valve.

Third Photo. The valve at it's other extream of travel steam going in on the right and out on the left

[uuu]

This is my guess on how it is arranged....

Can anybody follow this explanation?
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Yes - that arrangement was my reading of the position.

[Admiral_dk]

Thank you both - very logical solution .... and as Jasons would be the cheapest to make - that one is probably the one used 

Per         

[Casting Iron]

I am throwing out guesses.
I don't have a good understanding of it.
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[Admiral_dk]

Does it help if I say that in Jasons illustrations there is only hole all the way through @ the two small holes on top - the rest is an internal passage milled / cast into the Valve.

The top Pic shows no connection from the big Inlet hole (Steam into the Valve) to any of the Ports - nor from the Ports to the Exhaust holes (the two small ones).

Second Pic shows the Steam Inlet connected to the Left Port and the Right Port to the Right Exhaust hole => Piston moving to the Right side.

Third Pic shows the Steam Inlet connected to the Right Port and the Left Port to the Left Exhaust hole => Piston moving Left.

[PaulR]

Thanks for all the replies, glad it's proving of interest - I need time to digest the answers! However, if it requires fancy drilling or slot cutting it'll probably be off the menu for my next engine.

[Jasonb]

Assuming you will not be trying to recreate an exact replica of the engine and just want to try a different valve system then it is not hard to simplify the basic geometry. That was why I just did straight slots and a hole that could be done with just a lathe and an endmill held in the chuck (yes I did that when I started out)

The passages in the cylinder would be no more than holes drilled straight into the face and joining ones drilled straight in from the end and edge. Even bring the air in from above so it is easy to connect the compressor to and leaves the bottom face for mounting to the frame.

If the third inlet hole was placed centrally then the recess on the inside face of the valve can be simplified even more.