Seems like it would be possible to code this all up in a spreadsheet, and have it take the design parameters in and do the drawing for you? That would allow for playing with the lead/lap/advance/throw/etc and see the results, to help wade through all the design possiblities.
I've seen that sort of thing done, but have never gotten that deep into line drawing/chart drawing in spreadsheets. I could dust off my C++ compilers and libraries and do it that way, but thats not very portable for sharing with others. Maybe even code it in PostScript to generate a PDF picture. HTML and have a page for a web browser? Hmmm. Must be a good tool for that - don't have MatLab any more, that would do it in about 20 characters of incomprehensible but powerful code... GCode that would print it or CNC it on a plate?! 
Uh-Oh, my past life as a software geek is leaking out!! 
Edit: What does the distance 0.281 represent again?
Hi Chris, yes if you know how to code any program to do this it would be great. Something stand alone or on the web so others could use it with the normal software on a computer would be fantastic. I think that if it was like Docksteader's Zeuner module it would be very handy. If the program could start the construction with only 3 key variables it would be even better.
It is not really hard to construct a Bilgram diagram but to do multiple constructions to see 'what if' could get a bit tedious.
A better answer to "What does the distance 0.281 represent?" is it is the linear advance. This is shown in Audels Fig. 388 Pg 213. Now to the answer to the question "What is linear advance?" see Fig.387 Pg. 206. to see that linear advance equals lap plus lead. So we can add linear advance to the things we learned from the Bilgram diagram for S/N 50.
I mentioned one fact found on the slide valve drawing I cherry picked out of the drawing drawer but there are a few more dimensions that will be useful for this slide valve design.
I mentioned that the outside width of the valve is 4 11/32", the inside exhaust cavity is 2 1/2" wide, the outside length of the valve is 7 63/64", and the inside length is 7". The card number is 7404 and the superseded card is 942-A-5048. This valve was used for 8" x 8', 9" x 8", 8" x 12" and 8" x 10", so I could have picked several Shay engines to make the Bilgram diagram for. The note "REFER BACK TO CD. #3." is what made me pick that valve on the card with 8 different slide valves on it.
So without peeking at the answer sheet card #3 what else do we know about the valve design of S/N 50? To start I have to make some assumptions:
1. Port opening equals port width and bridge width.
2. Inside lap is equal to zero.
3. The width of the port is equal to the width of the bridge.
4. At the end of the valve travel, the outer edge of the valve completely opens the valve no more no less, so we do not have over travel or under travel. Port opening is a confusing name. If we look at the angle of advance line it is clear that port opening plus lap is equal to 1/2 the valve travel. By saying port opening is equal to port width when the valve travels the port width then travels the lap distance, it should be clear that that distance traveled is equal to 1/2 the valve travel.
Wow, that was a lot of beating around the bush but I really hope that it made the difference between port opening and port width a bit more clear. This is also covered in the book on Pg. 205.
Okay, the valve inside length is 7", so Pg. 184 the length of the ports are usually 0.8 times the diameter of the cylinder. Cylinder bore 8" times 0.8 equals 6.4, so a bit shy of 7" which has to be the dimension on card #3.
Assumption #2, no inside lap makes the width of the exhaust port the same as the inside width of the valve or 2 1/2".
The distance between the valve face steam edges is the valve outside width minus twice the lap or 4 11/32 - 1/2" = 3 27/32".
Port width = port opening = bridge width = 1/2".
Now, this should all add up. to 2 x port width + 2 x lap + 2 x bridge width +exhaust width = total valve length.
1 + 0.5 + 1 + 2.5" = 4" which leaves us 11/32" short. That means that we have inside lap or the bridge width is not 1/2" or a bit of both. The port opening might not equal the port width, so it looks like assumptions 1 & 2 need to be checked for truth.
Well, that is all I can think of that we know from the Bilgram diagram and a few assumptions. Time to check the answer sheet card #3.
Cheers Dan
I think I finished the edits to this so now to pull card #3 for real.
