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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: Fnord » Tue Aug 24, 2010 12:44 pm

I doubt he has access to the necessary metal or pvc fittings for a 4" valve, but something I've considered doing in the past is making one from fiberglass. The entire valve body could be made from a single piece if you can layer it on fast enough to outrun the resin cure-time.
A diaphragm valve would be ideal, and you could make a bolt-on service plate. No PTFE tape or pipe dope required.
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Unread postAuthor: Jimmy K » Tue Aug 24, 2010 3:04 pm

Those irrigation pumps on eBay would have a cross sectional area (total) of about 14.13 square inches, 1.57 square inches more than a 4" valve. But in the ad it says that one is broken and that "solenoids not included". Guys, I'm at a loss. I don't know what to do.
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Unread postAuthor: MrCrowley » Tue Aug 24, 2010 3:15 pm

But in the ad it says that one is broken and that "solenoids not included

You don't need the solenoids. You can modify them for pneumatic actuation. You can remove the guide rod too. I bought four 2" valves like that, 27 years old, no solenoids, one broken, one damaged diaphragm. I've got two working so far.

In the auction you get one working valve and one non-working valve, you probably can fix it unless it is a crack in the valve body or such. Even holes in the 'phragm can be fixed.
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Unread postAuthor: Jimmy K » Tue Aug 24, 2010 4:11 pm

Are those modifications pretty easy? I guess I should just read all the other threads on that stuff. Since I'm new to pneumatics (only combustion experience), would it be hard for me to screw up those valves?
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Unread postAuthor: MrCrowley » Tue Aug 24, 2010 4:23 pm

Not too difficult. Here's the topic about the valves I got:
http://www.spudfiles.com/forums/27-year ... 21488.html

Here's the cannon I used one on:
http://www.spudfiles.com/forums/basic-t ... 21527.html

All I had to do was unscrew the guide rod, drill out the guide rod hole (was slightly bigger than 3/8" NPT) to 1/2" NPT, threaded a 1/2" fitting in it and epoxied it around the edges.

I think if you took it slow and went through step-by-step with us, you should be able to modify it successfully.
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Unread postAuthor: Fnord » Tue Aug 24, 2010 4:26 pm

If you understand how a diaphragm valve and piston valve work, you won't have any problems modifing them. You'll be able to look at the valve when you get it and know what needs to be done.
Ask the guy for pictures of the broken one before you buy it though.
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Unread postAuthor: Jimmy K » Tue Aug 24, 2010 7:12 pm

So after some revisions:

10' SCH 10 aluminum barrel;
11 gallon chamber;
2 3" Irrigation valves;
1 Hydraulic cylinder;
Generator
Air compressor
Trailer
Tractor

Good / Bad?
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Unread postAuthor: Technician1002 » Tue Aug 24, 2010 8:41 pm

Good.

Careful planning on your part is needed so the recoil of the barrel doesn't rip the plumbing apart. Consider adding the mounting flange to the barrel instead of the tank to take the recoil force. The tank can just hang on it like a paintball tank.

The other performance factor is the number of turns between the tank and barrel. Keep this a small as possible. Limit the length of the small diameter plumbing to keep it as short as possible. Excess plumbing can cause flow loss.
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Unread postAuthor: Fnord » Wed Aug 25, 2010 8:19 am

Good.
If you haven't already bought a compressor you should get one that runs directly from a small engine. A generator just adds an unnecessary component to lug around and maintain.

If you're more mechanicaly inclined you can even make your own from a lawnmower engine and an existing compressor. It's fairly simple.
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Unread postAuthor: D_Hall » Wed Aug 25, 2010 8:37 am

Fnord wrote:Good.
If you haven't already bought a compressor you should get one that runs directly from a small engine. A generator just adds an unnecessary component to lug around and maintain.


On the other hand, a gas powered generator is a toy that is useful in many more situations than spudding. I mean, I've used my generator when I've gone camping, but I don't ever recall wishing I had a gas powered compressor while camping....
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Unread postAuthor: Jimmy K » Wed Aug 25, 2010 3:00 pm

Fnord wrote:Good.
If you haven't already bought a compressor you should get one that runs directly from a small engine. A generator just adds an unnecessary component to lug around and maintain.


I need power for a computer. I got a friend to program a microprocessor to control linear panning and for trajectory calculations.

And that guy with the valves on eBay posted a lot more pictures, but didn't specifically say what was wrong with the second one. Can you guys take a look at it?
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Unread postAuthor: dewey-1 » Wed Aug 25, 2010 3:27 pm

It appears the solenoid on the damaged valve is the problem.
You do not want to use solenoid activation any way.

You will being using pneumatic activation.

If you plan on parallel operation of the valves with a common pneumatic actuator you might consider a 1" sprinkler valve as an actuator.

See my example here:
http://www.spudfiles.com/forums/comfy-c ... 11219.html
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Unread postAuthor: Jimmy K » Mon Aug 30, 2010 3:37 pm

I bought those two valves. I hope I'm doing the right thing. Plus some guy gave me this large turret thing... so yeah I'm back to doing pan and tilt.
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Unread postAuthor: Jimmy K » Wed Sep 01, 2010 4:01 pm

Got the valves today. Who's up for taking me through this modification?
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Unread postAuthor: MrCrowley » Wed Sep 01, 2010 4:06 pm

Jimmy K wrote:Got the valves today. Who's up for taking me through this modification?

Could you post a few pictures of the inside and the guide rod etc?

First thing I did was removing the guide rod. Mine screwed out, so try sticking it in a vice and unscrewing it. If it does have threads and you unscrew it, test some fittings and see if the guide rod threads were NPT. Mine were pretty close to 3/8" and I would've tapped in 3/8" if I had more 3/8" fittings, which I didn't so I tapped in 1/2" (which did crack the guide rod threads a little bit but I epoxied it up).

You will also want to remove the solenoid and epoxy the hole where the solenoid was and any other hole on the valve lid (except where the guide rod was of course), I think mine had a hole for flow control which I also epoxied.
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