Search found 8 matches

by Backyard Pneumatic
Sun Aug 18, 2013 5:52 pm
Forum: Pneumatic Cannons
Topic: Secondary QEV for Breech Action
Replies: 6
Views: 2278

Ok, yeah, I had considered a mechanism similar to the one you described, and I even bought a flow control. the issue with that though is that the longer the bolt mechanism, the shorter the barrel length I have available, because the 9/16 brass I have is only in 1' lengths. I figure I could build som...
by Backyard Pneumatic
Sun Aug 18, 2013 4:02 pm
Forum: Pneumatic Cannons
Topic: Secondary QEV for Breech Action
Replies: 6
Views: 2278

Secondary QEV for Breech Action

Hi All, I've been working on a semi-auto airgun and I have a few design questions. It works on many of the same principles as the gun in wyz's semi auto tutorial video (thanks, by the way), however there are several modifications. I would like to use it to shoot nerf darts, but this makes the build ...
by Backyard Pneumatic
Thu Jul 18, 2013 7:56 am
Forum: Pneumatic Cannons
Topic: Barrel Alignment and Piston Travel Distance
Replies: 16
Views: 4821

well, these explanations seem to make sense to me. Hopefully the GGDT results will prove accurate (although I'll need to find a chrony somewhere). My plan is to pilot the piston valve with a 1" sprinkler valve, although I could use a 3/4 qev that I'm working on Thanks for the help. My cannon should ...
by Backyard Pneumatic
Wed Jul 17, 2013 2:18 pm
Forum: Pneumatic Cannons
Topic: Barrel Alignment and Piston Travel Distance
Replies: 16
Views: 4821

Well, I got GGDT, and have been fiddling with it for a while. It seems like with the piston I have now, opening time will be about 5 ms. I was also experimenting with other aspects of the cannon, and the strange thing is that when I increase the dead volume (the space after the valve and before the ...
by Backyard Pneumatic
Wed Jul 17, 2013 8:21 am
Forum: Pneumatic Cannons
Topic: Barrel Alignment and Piston Travel Distance
Replies: 16
Views: 4821

Sounds like it would be a good Idea for me to get GGDT and mess around with it some. Unfortunately I'll have to wait until my dad gets home from work because my computer user has no Administrative Privileges to download things :roll: For now, I'll make it my goal to leave flow unrestricted and take ...
by Backyard Pneumatic
Tue Jul 16, 2013 8:34 pm
Forum: Pneumatic Cannons
Topic: Barrel Alignment and Piston Travel Distance
Replies: 16
Views: 4821

Thanks technician. I'd thought that 1" piston travel seemed a bit restrictive. I just had seen a post where Jackssmirkingrevenge advised someone to reduce travel to d/2 to reduce pilot volume. I want to find a good balance between air flow and pilot volume. My current plan is to put the barrel about...
by Backyard Pneumatic
Tue Jul 16, 2013 4:09 pm
Forum: Pneumatic Cannons
Topic: Barrel Alignment and Piston Travel Distance
Replies: 16
Views: 4821

Barrel Alignment and Piston Travel Distance

Hi All, my first Pneumatic launcher is well under way (a 3" Piston cannon :D ) but after browsing the forums for a while I discovered a few design concepts that I wonder if anyone has tested the first of which is how far the barrel should be extended into the piston housing. I drew a simple diagram ...
by Backyard Pneumatic
Sun Jun 23, 2013 11:24 am
Forum: Ammo & Parts
Topic: Pressure Rated DWV?
Replies: 4
Views: 4367

Pressure Rated DWV?

Hey Guys, new member here with a materials question. I'm finally getting started on my first serious pneumatic, a 3" piston valve launcher, and was picking up some PVC when I found this stuff: [img] its labeled as both dwv and pressure rated, which doesn't make sense to me, but I assume that it'll b...