20mm Pneumatic Cannon

[HunterT]

Finished my cannon. It's been a long time coming, but that's due to the lack of parts around here. I'm planning to modify my sprinkler valve when I can find a blowgun. It has a light recoil when I fire 40 cents in pennies at 50psi out of it.

[jhalek90]

EDIT:

The one large issue that i see with this cannon is that you used a DWV (Drain Waste Vent) clean out cap for the back end of your chamber.

DWV parts are not pressure rated, and for your own safety i recommend you change it out with a proper cap.

When buying PVC always look for a pressure rating. If any part says DWV on it... it probably is not safe for use with pressure.

Other than that. the cannon looks like a good first cannon.... you will notice alot more power when you mod the sprinkler valve.

Good luck!

[MrCrowley]

Looks nice but I am worried by a few things:

1: What's with the duct tape on the joints?
2: Is that ABS pipe for the chamber? Does it say if it is pressure rated, solid core or cellular core?
3: You have a clean out cap on the chamber by the looks. You wont need access to the chamber for a pneumatic so you should use a normal end cap that isn't threaded. I believe the type of clean out cap you have used is not pressure-rated and they can be prone to blowing off due to the shallow threads.

This page will explain how to tell if your PVC is pressure rated or not:
http://www.spudfiles.com/spud_wiki/inde ... sure_rated

[HunterT]

Looks nice but I am worried by a few things:

1: What's with the duct tape on the joints?
2: Is that ABS pipe for the chamber? Does it say if it is pressure rated, solid core or cellular core?
3: You have a clean out cap on the chamber by the looks. You wont need access to the chamber for a pneumatic so you should use a normal end cap that isn't threaded. I believe the type of clean out cap you have used is not pressure-rated and they can be prone to blowing off due to the shallow threads.

1: Don't worry about the duct tape. I use proper pipe cement. The duct tape is merely holding my battery on while I look for a blow gun. It is not being used to hold the pipes together.

2: Yep that's ABS. I got a new chamber in the works. I believe it's cellular core. I could be wrong. That chamber was built before I learned about the different types of ABS pipe. I should have done more research beforehand.

3: That is a clean out cap. It will get replaced along with the new chamber.

I made sure all of my PVC was pressure rated because PVC bursts tend to fling shrapnel. I wasn't so worried about the ABS.

EDIT: Could I use a regular black 2" ABS endcap with my new PVC chamber?

[Ragnarok]

EDIT: Could I use a regular black 2" ABS endcap with my new PVC chamber?

You need to use a special cement to glue ABS to PVC, and I really don't know how strong the join is. In an ideal world, you'd use only one material.

[HunterT]

EDIT: Could I use a regular black 2" ABS endcap with my new PVC chamber?

You need to use a special cement to glue ABS to PVC, and I really don't know how strong the join is. In an ideal world, you'd use only one material.

I actually am using a PVC/ABS cement. I don't know about the availability of large PVC fittings here. I'll have to check it out.

[BFC]

You should prolly be using PVC cement on the PVC parts and the the ABS/PVC cement should be used when you are solvent welding ABS to PVC but I really really dont think that you should use PVC/ABS cement on a pneumatic cannon. On my Adv. Combustion I used PVC and ABS and where those joints came together I had to add 4 supporting bolts. But I really dont think thats a good idea on a Pneumatic, so id say definitely go for all NSF-PW pressure rated PVC pipe.

[HunterT]

You should prolly be using PVC cement on the PVC parts and the the ABS/PVC cement should be used when you are solvent welding ABS to PVC but I really really dont think that you should use PVC/ABS cement on a pneumatic cannon.

Okay, I'll stop using the multi-purpose cement. You probably know more about it than I.

so id say definitely go for all NSF-PW pressure rated PVC pipe.

I always go for pressure rated PVC. I've seen some non pressure rated PVC.