GTA

All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: RMM on January 01, 2015, 01:37:44 PM

Title: Valve question?
Post by: RMM on January 01, 2015, 01:37:44 PM
Can someone tell me what seems to be a nominal protrusion of the valve stem past the the valve backing block (the part of stem that the striker hits)??  If needed I'm working on 2 QBs and an FDPCP/stalwart 60/Bobcat.
Title: Re: Valve question?
Post by: rsterne on January 01, 2015, 02:07:23 PM
About 0.100" stock.... I took off 0.050" from the rear of the backer block to make sure that the lift at the low pressure end of the string was not limited by the striker hitting the block.... and then ended up using a bstaley O-ring stack with a 0.050" spacer anyway.... This was on a Gen1 FD-PCP, I think QBs are more, IIRC....

Bob
Title: Re: Valve question?
Post by: RMM on January 02, 2015, 10:14:58 AM
Thanks for the primer length for the 60's Bob.  The reason I asked is on my QBs one is .152 and the other is .132 but this may be my fault with adding Delrin poppets as I might have screwed (threaded stem) on one or not the other to a wrong dimension.   

Enjoying this crazy hobby but I seek knowledge, I want to fish.  There is a book, a primer for airgun theory that is out of print and hard to get but the name of author and book eludes me, so would you or anyone have the answer??   
Title: Re: Valve question?
Post by: rsterne on January 02, 2015, 01:58:47 PM
0.132" is probably enough, although may limit the lift at the low pressure end of the string, causing the velocity to drop suddenly right at the end.... If you are using CO2 it won't matter.... I usually try and make sure there is about 0.150" of lift available, up to .25 cal, although seldom do you actually run more than ~ 0.120"....

Bob
Title: Re: Valve question?
Post by: ray in wi on January 02, 2015, 02:34:30 PM
Would the book be....
The Airgun from Trigger to Target by Gerald Cardew, or ....
The Airgun from Trigger to Muzzle by Gerald Cardew ( I believe this one was the first book).
Title: Re: Valve question?
Post by: RMM on January 02, 2015, 03:11:15 PM
Quote from: rsterne on January 02, 2015, 01:58:47 PM
0.132" is probably enough, although may limit the lift at the low pressure end of the string, causing the velocity to drop suddenly right at the end.... If you are using CO2 it won't matter.... I usually try and make sure there is about 0.150" of lift available, up to .25 cal, although seldom do you actually run more than ~ 0.120"....

Thanks Bob and now I have some numbers to work with but work on the airgun terminology with one being 'lift' thus I'm looking for educational material fill my want to learn theory and not just go through the actions.  :)