Am unclear about steam valve dimensions and setting up
Model Engineer Centennial Collection Issue 7 - Stationary Engines
|mike robinson 2||29/11/2009 13:54:55|
|18 forum posts|
The Stuart drawing item 31 shows a milled pocket in the gun metal valve that is 1/2 wide and 5/8 tall * 1/8 deep. The dimension fixing a start position for the 1/2 inch wide pocket is not shown so it could be milled out anywhere - clearly not correct.
I have read Tubal Cains book on building a No.9 and he refers to the valve having a line and line exhaust lap and a 3/32 steam lap. According to TC the start of the steam transfer pocket is 7/32 from the "toe" of the slide valve The eccentric has a 5/16 throw.
Having modelled in CAD the cylinder ports at the as cast dimensions and the valve and I am still uncertain of dimensions for the pocket such that the ports are "fully" open at each end or have the correct "lap". If one end is set up to be fully open then a the other end of the 5/16 stroke the port is only half open,
I would like to understand steam lap can anybody describe what it is and or how to calculate this so I can be certain of the dimensions to cut the pocket.
Appreciate any help - I have illustrations from CAD but cant upload - to this site.
Thanks , Mike
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.