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Is this safe to use?

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Is this safe to use?

Unread postAuthor: BeaverRat » Thu May 06, 2010 1:56 am

First off, this is my first post!

I have done considerable searching before posting this question...

Is it safe to use Non pressure rated cellular ABS in a combustion spudgun? Through my searches I understand that most people say that it is fine and at the pressures of a combustion gun, everything will hold up. I understand there have been tons of "ABS Vs PVC" threads... But I ask this question as a comparison to this website.

http://www.burntlatke.com/safety.html

They state that it is very unsafe to use Cellular Core ABS in spud guns.

What is the verdict? I don't want plastic shards blowing up anywhere near me... I allready have a ABS gun, and would prefer not to rebuild it in pressure rated PVC, but I will if ABS is dangerous. Also, this will only be used in the "spray n pray" method.

Thanks
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Unread postAuthor: jackssmirkingrevenge » Thu May 06, 2010 2:03 am

Ram a tight fitting projectile into the barrel and trigger it from a safe distance. Chances are it will blow to smithereens. I wouldn't risk it personally, especially if it's relatively large diameter piping.
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ABS test

Unread postAuthor: Technician1002 » Thu May 06, 2010 11:49 am

I annually test an ABS Cellular Core cannon to over 90 PSI every year and have had no failures. Your results may vary. I still need to do this year's test. I'll post the results later.

My personal results are here. The pressure tests are at typical spray and pray spudguns. Do not use exotic fuel such as welding gas or add pure oxygen.

http://www.spudfiles.com/forums/abs-cellular-core-test-cannon-t17968.html

This test is for ABS only. This does not apply to cell foam PVC.

Edit, I had the time to do this year's pressure test. Results are below. Click on the photos to enlarge. The cannon pipe label is clearly shown. It is ABS Cellular Core DWV.
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Attachments
2010a.jpg
My 3 QDV cannons. Newest is on the left, oldest is on the right. One on the right is getting a 30 minute pressure test.
The metal 2 inch QDV launcher is shown with 3 ABS barrels, a 2 inch, 3 inch and 4 inch. ABS makes great barrels. They are lightweight.
2010b.jpg
Compressor cycled between 85 and 100 PSI during the test as the cannon piston still leaks a tiny bit.

This is very clearly marked ABS Cellular Core DWV
2010c.jpg
We have an old appliance to recycle. A paper shop towel on a 2 inch piece of 1 inch EMT is launched into the base. The blue fluff is a shop towel in the hole.
2010d.jpg
Damage caused by the ABS Cellular Core Test cannon, now 8 years old.
2010e.jpg
Gauge Detail
Last edited by Technician1002 on Thu May 06, 2010 5:31 pm, edited 3 times in total.
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Unread postAuthor: mark.f » Thu May 06, 2010 5:02 pm

I'd say cellular core ABS would be fine for a combustion spudgun.

However... if you can find solid core ABS, it would be about ten times better. Several members have made scores of solid-walled ABS guns using metered MAPP with little incident.

Try looking for ASTM 2661 on piping, although you may have little or no success finding solid-core ABS if you live in the U.S. All ABS fittings I have seen are solid core, so that's an easy part of the gun to obtain.

Good luck and be safe. Use eye protection (should be done with all cannons, though especially ones with shaky construction materials).

EDIT: Tech, do you completely fill your cannons with water before pressurizing? Or do you just pump in air to pressure test it?

The safest way I've seen done is to fill a device with water completely, and pump in air through a spot on the cannon least likely to fail.
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Unread postAuthor: Technician1002 » Thu May 06, 2010 5:18 pm

@mark

I used to fill the cannon with water in fear it might grenade. Now that I have seen several videos and photos of the failure mode of the stuff, i don't bother anymore. i hook up the airline and just stand back a few feet with proper eye protection, heavy pants, jacket, etc. 100 PSI can make a very loud report, but it is probably not going to expel shrapnel. I stand clear of obvious bits that can be thrown such as the fill valve, and valve core. After the pressure test, I operate below 3/4rs the test pressure for the remainder of the year. This year's pressure test is done. While I was at it, I went ahead and tested the other cannons.

This 100 PSI test is well within the maximum pressures you can expect from a spray and pray or propane cannon.

Edit; This guy from crazybuilders tested the failure mode of PVC. The reason PVC is not approved for compressed air systems is due to the failure mode. It is not safe when it fails. ABS has a ductile failure mode instead of a brittle mode. This makes it safer when it does fail. Burnt lake simply goes on the one pipe is not rated for pressure and does not address what pressure it can hold and it's failure mode. Following industry recommendations, PVC is unsuitable for compressed gas service.
http://www.crazybuilders.com/item.php?id=000010&type=project_section
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Attachments
2010f.jpg
T shirt cannon test at 100 PSI. 2 inch ABS Cellular Core barrel is attached.
2010g.jpg
Just for grins I dropped in a D cell battery, bled the pressure to 80 PSI and shot it with no wadding. Even with lots of blow-by, it almost went through the back of the appliance.
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Unread postAuthor: BeaverRat » Mon May 10, 2010 7:35 pm

Thanks...
Is there a video that shows what happens when ABS Cellular Core pipe does fail? I understand that it fails in a ductile mode, but it would be interesting to see it actually happen.
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Unread postAuthor: Technician1002 » Mon May 10, 2010 7:40 pm

BeaverRat wrote:Thanks...
Is there a video that shows what happens when ABS Cellular Core pipe does fail? I understand that it fails in a ductile mode, but it would be interesting to see it actually happen.


I have seen some, but I would have to search to find them again. It splits down the side when it fails.
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Unread postAuthor: MikeNice » Fri May 21, 2010 2:28 am

All my guns are (except for my current project) is cell core PVC. (I know you're asking about ABS but I'll get there.) I know of just 2 failures in the last 8 years with ANY of my guns (12). 1 was because the barrel was dropped on concrete and probably fractured first. 2 was because the user thought acetylene was a good idea. (I didn't see it happen but I understand it was quite spectacular. No injuries at all) If all you're using cell core for, PVC or ABS, is a spray and pray type cannon and ONLY firing wet projectiles (potatos, apples, onions, nectarines, etc) and ONLY using conventional fuels, (Static Guard, Tag body spray, etc.) then my personal experience would tell you to go for it. Make sure you know how to properly solvent weld. Have a blast. ABS is lighter weight and more chemical resistant than PVC, but other than that, for a spray and pray it just doesn't matter all that much. I've seen and used ABS and PVC cannons and like I said only personally know of just 2 failures with no injuries after hundreds of pounds of spuds, and dozens of cans of fuels.

I know some of you are going to have a problem with my saying that but that's MY experience with those materials.
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Unread postAuthor: Moonbogg » Fri May 21, 2010 8:26 am

Advanced combustion with cellcore ABS on propane. Many shots, no issues.

http://www.spudfiles.com/forums/first-s ... 16718.html
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Unread postAuthor: Technician1002 » Fri May 21, 2010 9:31 am

The ABS cannon getting the pressure test in an above photo has been dropped several times, stepped on, scratched, etc. No failures.

I've had to retire several PVC cannons that got dropped and cracked. It is why the Mouse Musket is retired. It started leaking when I started to fill it. I heard the leak and stopped before it blew up. The reducer on the muzzle end cracked along with the end of the chamber. Under full pressure this would have shattered.

I found a page with photos of an ABS spudgun that split.

http://www.spudfiles.com/forums/abs-cannon-explosion-t8573.html

Please note that this did not make shards.
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