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New Guy, want ideas for a pnematic tennis ball mortar

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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New Guy, want ideas for a pnematic tennis ball mortar

Unread postAuthor: duane » Sun Aug 04, 2013 1:39 pm

Hi folks,

I'm new here, but I've looked around here a good bit.

I've seen some great stuff so far, but not exactly what I have in mind.

I'd like to build a simple, high trajectory, muzzle loaded, tennis ball mortar. I don't feel a need to bust targets, and I'm too old to search hundreds of yards looking for fired tennis balls. :lol:

This thing would be used in remote locations, so an air compressor wouldn't be handy, but I already have a 20# CO2 cylinder, with a 150 PSI regulator that I use for other things.

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(It's great for filling tires, or running pneumatic tools in remote locations) It just seems like it'd be a good compressed "air" source, since I already have it.

Having used this "air" source for several years, I know that the "air" is VERY cold. So it doesn't seem to me to be a good idea to use PVC , but I'd like to hear you guys opinions.

What I have in mind would use the CO2 cylinder to charge an about 4" x 12" chamber to about 50 PSI. From there, I'd use a 1" sprinkler valve to release this charge directly (well not exactly directly, there'd be 2 90 degree fittings) into a 2 1/2 barrel, about 24" long.

Just looking for your ideas on this.

Thanks,

Duane
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Unread postAuthor: Blitz » Sun Aug 04, 2013 4:21 pm

Cool truck, I once had a Colorado. I kinda miss it.

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Personally, I think you'd be fine so long as you regulate the pressure to that 50PSI (Sounds like you would).
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Unread postAuthor: Gun Freak » Sun Aug 04, 2013 4:32 pm

50 psi and a sprinkler valve won't be enough to fire something as large and heavy as a tennis ball. However, using a sprinkler valve to pilot a larger valve such as a 1.5" port or so piston valve would be adequate for it. This would allow you to use less pressure than a straight sprinkler valve and you'll get more shots per fill with your co2 tank.
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Unread postAuthor: Blitz » Sun Aug 04, 2013 4:40 pm

Gun Freak wrote:50 psi and a sprinkler valve won't be enough to fire something as large and heavy as a tennis ball. However, using a sprinkler valve to pilot a larger valve such as a 1.5" port or so piston valve would be adequate for it. This would allow you to use less pressure than a straight sprinkler valve and you'll get more shots per fill with your co2 tank.


It's not great, but it'd work. I've done it with a 3/4" sprinkle valve.
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Unread postAuthor: Blitz » Sun Aug 04, 2013 4:41 pm

Chamber of 2" x 24", by the way.
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Unread postAuthor: duane » Sun Aug 04, 2013 5:15 pm

Gun Freak wrote:50 psi and a sprinkler valve won't be enough to fire something as large and heavy as a tennis ball. However, using a sprinkler valve to pilot a larger valve such as a 1.5" port or so piston valve would be adequate for it. This would allow you to use less pressure than a straight sprinkler valve and you'll get more shots per fill with your co2 tank.


GF,

Thank you for the response. You said "50 psi and a sprinkler valve won't be enough to fire something as large and heavy as a tennis ball."

While I respect your opinion, I beg to differ. 50 PSI from a 1" valve will certainly fire a Tennis ball. How high, or how far? I don't know that.
No, it won't bust down a brick wall. But that's NOT my objective.

Duane
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Unread postAuthor: duane » Sun Aug 04, 2013 5:24 pm

Blitz wrote:Cool truck, I once had a Colorado. I kinda miss it.

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Personally, I think you'd be fine so long as you regulate the pressure to that 50PSI (Sounds like you would).


Blitz,

Thanks.

Duane
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Unread postAuthor: Technician1002 » Sun Aug 04, 2013 6:06 pm

To conserve fuel, I highly recommend a smaller chamber and a larger valve. A 1 iinch sprinkler valve will launch the tennis ball on 50 PSI, but you won't have to hike far to find the ball.

If you are entering a competition to attack the castle in a game the 1 inch sprinkler valve is excellent as the limited range can provide for repeatable launches so you can make a chart with pressure, angle, etc so you can mortar bomb a target. High pressure high velocity launches become very difficult to predict the landing with any accuracy.

Other than toss your tennis balls into the air, and limited distance, do you have any other design goals?

Again you use less fuel per shot with higher pressure and a much smaller chamber due to the limited flow rate of your chosen valve. Fuel still pouring into the barrel long after the projectile has left is a waste of fuel. Your goal to save fuel is to empty the chamber into the barrel prior to the projectile exiting the barrel. A smaller chamber, larger valve, and higher pressure will all help conserve fuel.

Download GGDT and play with the numbers.

Filling a "spare air tank" to allow the gas to warm and expand before using it in your launcher will also save some gas usage.
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Unread postAuthor: duane » Sun Aug 04, 2013 6:26 pm

Technician1002 wrote:To conserve fuel, I highly recommend a smaller chamber and a larger valve. A 1 iinch sprinkler valve will launch the tennis ball on 50 PSI, but you won't have to hike far to find the ball.

If you are entering a competition to attack the castle in a game the 1 inch sprinkler valve is excellent as the limited range can provide for repeatable launches so you can make a chart with pressure, angle, etc so you can mortar bomb a target. High pressure high velocity launches become very difficult to predict the landing with any accuracy.

Other than toss your tennis balls into the air, and limited distance, do you have any other design goals?

Again you use less fuel per shot with higher pressure and a much smaller chamber due to the limited flow rate of your chosen valve. Fuel still pouring into the barrel long after the projectile has left is a waste of fuel. Your goal to save fuel is to empty the chamber into the barrel prior to the projectile exiting the barrel. A smaller chamber, larger valve, and higher pressure will all help conserve fuel.

Download GGDT and play with the numbers.

Filling a "spare air tank" to allow the gas to warm and expand before using it in your launcher will also save some gas usage.


That's the kind of advice that I was looking for. 8)

I'll certainly look into it.

Thanks,

Duane
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Unread postAuthor: duane » Mon Aug 05, 2013 5:21 pm

OK, I've downloaded GGDT, and am having problems installing it on my Windows 7 PC. I get the 339 error. I am administrator, so there must be somethings else wrong.

Any ideas?

I'll be searching, but in the meantime, if one of you guys has an answer...

Thanks,

Duane
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Unread postAuthor: Blitz » Mon Aug 05, 2013 5:33 pm

Make sure everything's in the same directory, best advice I can give. Also, even though you say you're an administrator on your machine (poor practice, BTW :P ), right click on the executable and select "run as administrator."
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Unread postAuthor: duane » Mon Aug 05, 2013 5:48 pm

Blitz,

That worked. :D

I'm not as computer savvy as I'd like to be, but since I'm the only one who has physical access to this machine, and I have a log-on password set up, why is having myself set up as administrator poor practice?

I'm not challenging what you said, I just want to understand.

Thanks,

Now I can start trying out GGDT.

:lol: :lol:

Duane
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Unread postAuthor: Blitz » Mon Aug 05, 2013 5:50 pm

It's all good!

Naturally, it's fine to have access to an administrator account, but using one for daily activities opens you up to security risks. Most malicious software takes advantage of that to get into your system.
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Unread postAuthor: dart guy » Mon Aug 05, 2013 7:00 pm

You should have an air chamber connected to a ball valve, then you should have the ballvalve connected to a spring loaded trigger. This will release air quicker.
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Unread postAuthor: duane » Mon Aug 05, 2013 7:06 pm

Wow.

I've been playing with GGDT for just a little while now. There are SO many variables that I don't know the correct number to use.

I'll have to do some more footwork, to figure out the correct numbers to use, but just playing around with numbers, I can see that GGDT is awesome...

You could build thousands of "virtual guns", compare them, and not spend any money. So the disclaimer says it's 5-10% accurate. So what?

That beats the heck out of wildcat experimentation, huh?

Thanks guys,

Duane
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