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Posted: Tue Oct 14, 2008 5:23 pm
by EphOph
You could go with 1" flexible PVC and it wouldn't restrict flow any more than a 1" sprinkler valve (put the valve on the barrel side).
The new design looks good except for the "U" fitting. I'm not 100% sure, but I think they only make those in DWV, which is very bad for pneumatics. Use two pressure rated 90 elbows instead (that goes for all other parts too). They will also be cheaper if you put the reducer bushing on the chamber side (thus using two 2" elbows instead of two 4" elbows).
Posted: Wed Oct 15, 2008 4:09 pm
by psycix
If you can find PRESSURE RATED flexible pvc, then use that. If not, then simply use that over-under construction.
Way more reliable and better for the flow.
Posted: Wed Oct 15, 2008 6:40 pm
by brogdenlaxmiddie
BCITRobotics- In your diagram, you had a single 180 degree elbow piece. I just wanted to make sure that you knew those are in no way safe for use in a pneumatic. They aren't pressure rated... period.
Edit- dammit, beaten again!
Posted: Wed Oct 15, 2008 8:58 pm
by cdheller
rp181 wrote:use a threaded busing and a hose barb.
+1
Fittings are made with threads
.
"""We kind of figured that by loading our ammo (in this case t-shirts) close to the end of the barrel and by packing it tightly, pressure would build up behind the shirt and then fire it out when the pressure exceeded the frictional force needed to get the shirt out of the barrel"""
You are actually planning on firing into a crowd with this device?
?
Posted: Wed Oct 15, 2008 9:15 pm
by SEAKING9006
If you want additional pressure to build up behind the shirt, use a burst disk.
Posted: Sat Oct 18, 2008 4:38 am
by psycix
The static friction is nothing compared to the forces acted out by the pressure so there wont be much pressure buildup. You could count the amount of presssure buildlup in psi on one or maybe two hands.
For a fast increase in pressure, use a burst disk or simply a good valve with alot of flow and a low opening time.
Posted: Wed Oct 22, 2008 8:19 am
by BCITRobotics
This is exactly what we wanted because it doesn't have all the adapters to go from the sprinkler valve to the muzzle and pressure chamber. Is it the size sprinkler valve you are using?
and yes, we are firing it into a crowd. we hope to get it done before basketball season. this includes switching from PVC to maybe aluminum or something. This is just our "rough draft."
oh. I found this under the lego sight topic.
I forgot. the previous diagram wasn't ours
http://blog.makezine.com/archive/2007/1 ... _proj.html
we saw it on youtube
http://www.youtube.com/watch?v=FgCz7C6jEIk