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DWV fittings question

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: Technician1002 » Tue Nov 09, 2010 10:29 pm

MrCrowley wrote:Were they using CO2? Looking at the video it is hard to tell if the cannon just slipped out of its sockets or if the socket exploded.

Your mouse musket was dropped right on the fitting it seems, the cannon last 5 years which is pretty impressive anyway. I myself wouldn't use a cannon after that long.

If DWV ABS has similar fittings as DWV PVC, then the failure seen in that video may not have been avoided by the use of ABS since short socket depths in the fittings could still cause a failure.


I honestly don't remember if they used CO2. The failure was from the design. The cannon has 3 arms, an over under design with the chamber in the center, a T, 2 sprinkler valves, and then two barrels on elbows. Due to the design the recoil of the launch broke the smaller elbow or pipe at the rear of the barrel, due to the support at the muzzle end and the loose barrel, this tweaked the entire launcher so all the small plumbing shattered causing the chamber to rocket off into the stands. The launcher contained no DWV and passed the safety inspection.

I don't remember the event that caused the Mouse Musket crack, but I belive it was standing on end and fell over. The crack was discovered much later after the new piston was built. It was never dropped from a high distance. It only fell it's own length.

If you look at my ABS test cannon, I have had good luck with ABS even when the DWV sockets are not fully seated, unlike PVC. That fitting has to deal with the torque of barrel whip and has survived fine.
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Last edited by Technician1002 on Wed Nov 10, 2010 12:08 am, edited 1 time in total.
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Unread postAuthor: jrrdw » Tue Nov 09, 2010 11:19 pm

mlz3000 wrote:Alright, looks like I am going to change the 4" chamber into one made of 2" PVC, as Home Depot has plenty of NSF-PW fittings at 2" and below.

I'm thinking I'll get a cross joint, and with some 90 degree turn attachments I'll make the chamber out of three parallel pieces of 2" PVC rather than one length of 4" PVC

Is there anything intrinsically wrong with this design?


This design works well for me...
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Unread postAuthor: mlz3000 » Wed Nov 10, 2010 8:33 am

jrrdw wrote:This design works well for me...


It looks like it works fine, but the over/under design I drew up looks cleaner to me. Just a matter of preference.

Plus, I'm still at the stage where primer stains are more than apparent on my guns :oops: , so the fewer joints, the better.
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Unread postAuthor: jrrdw » Wed Nov 10, 2010 9:29 am

You can get clear primer if you like that better.
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Unread postAuthor: Technician1002 » Wed Nov 10, 2010 11:03 am

With a little care and tipping all the parts so gravity runs the drip to the end instead of along the pipe, primer runs are easily controlled.

Here is an example of a 1 inch joint properly glued and no ugly drips.
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