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4 Shot Repeater Marble Rifle

Unread postPosted: Tue Jun 29, 2010 4:35 pm
Author: Immur4323
Hey everyone, this is my second cannon and it is awesome. It uses a modified sprinkler valve as the main valve and is a repeater. I can get about 3 powerful shots every time I pump it up. I messed up my first barrel and couldn't go to home depot to get another, so I put a 3/4" cpvc pipe in a 1" pvc pipe and put the 1" in a 1 1/4 pipe that had the right adapter.

The air reservoir is 2" ABS about 2 feet long and the barrel is 40 inches of 3/4" cpvc. The reservoir is connected to the firing chamber by a 1/2 inch valve that is opened a small amount so it lets in air slow enough that it doesn't all fire in one pull of the trigger. Here is a video of me firing it, with damage!!! Yay!

[youtube]http://www.youtube.com/watch?v=I8IGaQm-ppY[/youtube]

Unread postPosted: Tue Jun 29, 2010 4:39 pm
Author: clemsonguy1125
Good for you second gun, just a couple things you may want to change
-ABS Chamber, never use ABS plastic for a pneumatic
-Duct Tape Handel, Looks bad
-Barrel Support, looks like it could use a barrel support
Other than that good gun

Unread postPosted: Tue Jun 29, 2010 4:41 pm
Author: Gun Freak
Me and my friend made one almost identical to that but with a 1/2 ball valve instead of the SV and a tank twice as long, 1/2" barrel and a break barrel breech load for nerf darts. We got about 6 shots off one fill so it was pretty good for only 30 bucks. Nice job, makes me want to build one similar again, you should paint it. 4/5!

Oh and things to improve,
the chamber
support
add a breech loader
and I would also change the duct tape or at least cover it with some felt or something.

Unread postPosted: Tue Jun 29, 2010 4:43 pm
Author: Immur4323
Why not ABS? I've gone up to 160 psi on that pipe. Also the duck tape is the stock with padding, but yeah i could use a barrel support.

Unread postPosted: Tue Jun 29, 2010 4:45 pm
Author: Gun Freak
I don't think ABS is rated high but it does have good fail characteristics.

Unread postPosted: Tue Jun 29, 2010 4:46 pm
Author: clemsonguy1125
ABS isnt made for pressure, just cause you took it that high doesnt mean it wont blow up next time, also never mix ABS pipe and PVC fittings If you want stock padding Id use pipe insulation, It looks better

Unread postPosted: Tue Jun 29, 2010 4:51 pm
Author: woodscout
pretty good looking gun, you should clean it little bit and get rid of the ABS chamber :wink: . and the pipe insulation for the stock is a good idea

Unread postPosted: Tue Jun 29, 2010 4:53 pm
Author: ramses
ABS is generally considered fine, as long as it is not cellular core. Even that is used occasionally.

Unread postPosted: Tue Jun 29, 2010 4:57 pm
Author: clemsonguy1125
Tech ran some tests(over 10 years) and was fine, but Its not pressure rated, plus at 160 psi its more dangerous, its considered dangerous to even use pressure rated pipe at that pressure

Unread postPosted: Tue Jun 29, 2010 5:37 pm
Author: jor2daje
They also make solvent specifically for connecting abs and pvc, aslong as you use that, and dont use foam core, I think abs is as safe if not more safe than pvc. Especially at high pressures where abs is more prone to rupturing that exploding. I think its stupid when people immediately shoot down using abs whenever they see it if they have no experience with it, they are simply passing on this ignorance to a new comer.

Unread postPosted: Tue Jun 29, 2010 6:27 pm
Author: Technician1002
I have tested 4 inch ABS to 100 PSI. I would hydrostatic test any non pressure rated pipe. A recently posted video shows how this is done.

See my sig for my first QDV. It is all ABS foam core except the valve core.
[youtube]http://www.youtube.com/watch?v=wyNvE3wxZJM[/youtube]

Unread postPosted: Tue Jun 29, 2010 6:42 pm
Author: clemsonguy1125
jor2daje wrote: see it if they have no experience with it, they are simply passing on this ignorance to a new comer.
IF he uses proper solvent and stays below 100 psi, he may be fine, Im not passing on ignorance, Im passing on saftey, theres a reason ABS is not pressure rated. PVC is the same price as ABS so in the future I suggest using PVC.

Unread postPosted: Tue Jun 29, 2010 7:33 pm
Author: Technician1002
clemsonguy1125 wrote:
jor2daje wrote: see it if they have no experience with it, they are simply passing on this ignorance to a new comer.
IF he uses proper solvent and stays below 100 psi, he may be fine, Im not passing on ignorance, Im passing on saftey, theres a reason ABS is not pressure rated. PVC is the same price as ABS so in the future I suggest using PVC.


Please note that PVC is NOT RATED for use in air systens at ANY pressure.

This boils down to which NOT RATED for air pipe is safer? ABS or PVC?
PVC piping is relatively inexpensive, easy to install, lightweight, and corrosion resistant. However, PVC has one major drawback. It is brittle. An inadvertent impact could cause the piping to shatter, endangering surrounding personnel. Most PVC pipe manufacturers warn against using PVC for compressed air service due to potential liability from such failures. The Plastic Piping Institute, in their Recommendation B, states that plastic piping used for compressed air transport in above-ground systems should be protected in shatter-proof encasements, unless otherwise recommended by the manufacturer. In many states, the Occupational Health and Safety Administration (OSHA) has stepped in and regulated against using brittle plastics such as PVC in these applications, and additional states are following suit.


Quote is from http://www.hydraulicspneumatics.com/Classes/Article/ArticleDraw.aspx?HBC=TechZone/FluidPowerAcces&NIL=False&CID=6547&OASKEY=TechZone-FluidPowerAcces

I tested ABS for this reason. Combustion cannons use it. I have had PVC fail several times. I looked for something safer.

Quote from the same article;
These new thermoplastics are safe because they expand at the point of failure, tearing open rather than fragmenting dangerously. They do not accumulate scale on their ID, nor does pitting or corrosion occur, and they are unaffected by synthetic and mineral oils used in compressors.


Not only is PVC unsafe for air, in many locations it is against OSHA regulations.

I do agree that the proper transition glue must be used between ABS and PVC. The wrong glue is a failure waiting to happen.

Unread postPosted: Tue Jun 29, 2010 7:46 pm
Author: clemsonguy1125
Well more PVC guns do fail but more are built to, combustions have a low pressure spike, I trust then with propane meters and spray and pray. Also PVC Is made to hold water pressure, some to 1000 psi, at least it's made to hold pressure, even if it's not air, that's why I use all my pneumatics lower than 100 psi. But in the end it's his choice of what he wants to use. If he trusts it that fine, if not that's his choice too.

Unread postPosted: Tue Jun 29, 2010 8:18 pm
Author: Technician1002
Well more PVC guns do fail but more are built


By that token there should be some but not many pictures of failed ABS cannons. I specifically looked for them. The only ones I found were using exotic gas mixes such as adding Oxygen from a welding torch.

There is the occasional blown off clean out cap, and a few unglued ABS cannons launching barrels, but there is a total lack of any ABS exploded cannons that I could find. The ratio of PVC/ABS to PVC/ABS failures is not the same ratio. In some locations unglued barrels are common as they are removable for breech loading. Sometimes the ABS barrel launches in the shot, but is unharmed and used again.

Do you have ANY links to pictures or videos of ABS spudguns failing? I looked a long time trying to find a few. The few I found were due to unusual fuel applications.

Finding photos and video of PVC blowing up is a simple youtube search. Look for Spudgun Explosion. Then narrow the results to find the ABS ones.

The total lack of ANY normal combustion ABS failures led to the building of the ABS Cellular Core test cannon listed below in my sig. I already had several PVC parts shatter. They include the piston in the Mouse Musket, the piston in The Dragon, the crack in the chamber of the Mouse Musket, and later the female adapter on the rear of the ABS test cannon. I originally used a pressure rated PVC sched 40 part for that, but it too shattered and I got the piston launched out the back into my foot. Ouch! I was wearing leather shoes, so other than a bruise, I was OK. I changed to ABS for that part too and doubled the length of my bumper and have had no further failures.

Note the bumper next to the golf ball. I doubled it's length after the PVC female adapter on the breech of the cannon shattered. Note the red paint on the plug. The original female adaptor was painted red to match the barrel.
Image

The cannon is fired this way. Step on the rope and lift the cannon. When the PVC on the end broke, the piston launched into my foot. The ABS replacement has lasted.
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