Mystery steam engine

[Jasonb]

As the ports are mostlikely cored they eill not be perfectly even hence the odd numbers in my post above.

going by the image with the steel rule I would say they were aiming for 3/16 - 3/16 - 3/8 - 3/16 - 3/16 or 4.75 - 4.75 - 9.5 - 4.75 - 4.75 but ended up a bit big on the lower port.

 

[Steamchick]

This is where the talents of the engine builder came to the fore - making "special" valves based in the cored ports, not the drawing. Just by addition or subtraction of the errors on the casting c.f. drawing.
But without the drawing overlap, etc. needs to be included based on similar sized engines.
I resolved a "bad casting" valve porting by making a custom piston valve on a Stuart Sun engine. I built it with an adjustable connection to the valve to balance the timing between cylinders, but set as re-calculated was Good, so I managed to get one right. I did have the Stuart drawing though, so developing the correction of dimensions was easy.
A good game! I am fascinated following this one. Better experts than I are teaching us all. Thanks!
K2

 

[GreenTwin]

This is what I came up with.
It assumes a total D-valve travel of 0.614".
Steam port opening at full travel = 80% (typical for many old engines).

I also assumed a valve guide diameter of 0.25".
You need a little clearance to allow for heat expansion between the slot in the top of the valve and the valve rod.
There is also clearance under the valve rod.
The valve can move in and out towards the port face, so the nuts on either side cannot be tight against the valve.
Not sure how you will secure this valve to your valve rod.

This should get you into the ballpark.

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[GreenTwin]

This is what a typical D-valve looks like.
I did a flat design for you.
You really don't need a domed design like is shown in this picture.
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[GreenTwin]

It appears that on some (perhaps many) steam engines, the core for the ports were undersized, and the final port dimensions were established by precision machining.
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[GreenTwin]

These are the port face dimensions that I used.
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[chris123]

Hi jason
I get hat done as soon im back from work
Regards chris

 

[chris123]

These are the port face dimensions that I used.
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View attachment 163862

Hi green twin
It got more slots than 3
I did the paper as u mentioned
Bud i will double check
Regards chris

 

[GreenTwin]

This is what you are calling "slots", which are actually called "ports".
They should be dead ends, unless they are the input from the high pressure valve/cylinder.
Either way, the D-valve remains the same, as I show it in previous posts.
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[Jasonb]

This is what I came up with.
It assumes a total D-valve travel of 0.614".


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Chris has given the eccentric movement as12mm though if an imperial engine may well be 0.500"

 

[GreenTwin]

Chris has given the eccentric movement as12mm though if an imperial engine may well be 0.500"

If that is the case, then change this dimension.
The other dimensions above will still work.
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[Jasonb]

This is what I came up with based on the sizes I scaled off the rubbing and 12mm of valve movement. Allows a bit of internal and external overlap for the cored ports not being totally straight. Should not affect performance much, it is not as though efficiency and power are what is wanted, just a running display engine Not fully detailed the valve externals but the cavity is what matters.