Steam valve design

[mcjustis]

I'm working on a fairly large (for me anyway) engine now and I have a question. I made the slide valve to print and also the base of the steam chest on the side of the cylinder is to print. When I put them together there is a time when both of the intake holes are exposed, as in the valve is between both intake slots covering the exhaust. I'm no steam afficionado, but I would think if both intake holes were exposed that the piston would just stop. Am I wrong? I don't like the way the valve is coupled to the eccentric rod anyway, so I'm planning on remaking the valve and the rod, but I'm curious if there's a convention on the valve design. Should the cutout in the valve be the same length as it is on the cylinder across one intake and the exhaust? Also is there a rule of thumb on the outside edge dimensions of the valve. I have a fairly crude picture attached, hopefully I am making sense.

valve.jpg (116.48 KiB) Viewed 1380 times

Thanks for any help,
Martin

[Bill Shields]

As you assume...that will not work.

You need to review some valve design literature before you go further.

Fred Colvin's treatise on it is very good and was considered an industrial standard at the time.

Fred H. Colvin from Sterling Mass (Herbert)

"Link motions, valves and valve settings" is the one you want.

You can find it on Google books

[Charles T. McCullough]

Here are the two basic designs:
Top: Outside Admission "D" (or slide) valve,
Bottom: Inside Admission piston valve.
.

Valve Gear Part 4 Fig 13 Adjust Valve.jpg (182.37 KiB) Viewed 1335 times

[VGC]

The movement and coordinates for opening and closing are the first ones to be fixed when building a fully new steam loco, but you need a basic understanding of the idealized movement for that.
Starting from an existing design, you can get along without this basic understanding itself but have to follow the movement of a valve gear which is not much more simple too
For Walschaerts valve gear, I just found a direct download link here: https://steampunksavant.com/archives/wa ... odgoog.pdf