Assuming you are talking about outside diameter, these numbers are very close to what Accucraft uses on their two cylinder Shays. I think it would be sufficient.
Make sure your throttle is not too restricitve as it could become a bottle neck...
Posted By Reed on 06/18/2008 5:05 PM
I’m planning to use 5/32” piping to feed each 1/2”clylinder. The pipe from the throttle will be 3/16” and split in the smoke box to 5/32” for each cylinder, will this be sufficient?
Reed SA 240
Unless you are building a racing engine, 3/32" will be quite large enough - as well as being easier to benmd to shape.
Accucraft steam pipe is 3mm OD = 0.181" (1/8" OD = 0.125") and is standard for there locos I have or know of. Cross sectional area of 3/16" OD (4.97mm) is nearly 3x Accucraft 3mm OD (19.4mm vs 7.1mm CSA). How big a steam pipe is needed for 1/2" cylinders? Maybe someone knows about the fluid mechanics and deminishing returns.
Does it depend on Dry Pipe OD as the limiting factor? Accucraft's dry pipe is 3mm, a big steam pipe doesn't have much effect beyond 1/8" from what I have read and been told.
To answer a couple of the questions asked, I’m scratch building a #1 gauge 2-4-0. The boiler is completed and tested and will coal fired. The dry pipe is 3/16” to the throttle and also 3/16” from the throttle to the smoke box. The in the passages in the cylinders are .104 (#37) drill which is the same ID as 5/32” copper pipe. The more I looked at the holes smaller they seemed to be. Then I was studying the pictures of k5pat’s pictures of the S2 he is building and steam pipes looked huge compared to mine. So I thought I would ask.
When Mike (Shaymaker) suggested 3/32” it dawned on me that the 1” engine I completed in 1979 and run the wheel off of it has 1 1/4” cylinders only has ¼” piping from the steam dome to the steam chests and it was never in need of more steam.
I’m going to use 1/8” pipe in the smoke box; it will a lot easier to install and leave more room for sweeping the flues. If it’s big enough for Accucraft it will work for me.
Thank you all for your suggestions.
Reed Kosmal" border=0>
Here are some pictures of my project; the two of the locomotive were posted a while back. Since then I was a few hours from running on air but I was unhappy with the cylinder arrange and decided to make to new ones including steam chests and rear heads. The other picture is my quarting jig.