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Mini golf ball cannon

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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Mini golf ball cannon

Unread postAuthor: pvcmaster » Wed Feb 06, 2008 4:33 pm

As part of a tech project, I need to launch a golf ball over a 6 ft. wall 10 ft. away and onto a bullseye 30 ft. away. The bullseye is laying flat on the ground. This cannon will be mounted on a small vehicle so it must be very small, about 14 in. long without the barrel.

My question is, is it really possible to shoot a 45gram golfball 30 ft. with a 15 cubic inch chamber at 8 psi, or is something wrong. It goes against all of my experience to believe it. The chamber will be a 2" endcap, a 2" coupler, and a 2"x1" reducer. The valve is a 1" sprinkler, and the barrel is 4-5in of SDR21.
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Unread postAuthor: psycix » Wed Feb 06, 2008 4:46 pm

9 psi is a VERY LOW pressure
GGDT may not be completely correct since this is such a low pressure and also the ballistics calculator doesnt give 100% exact values.

You should just build this gun and set it at an angle and then try different pressures until you find the right pressure.
Consistancy is the most important factor of your gun.
Then regulate less and more pressure and experiment alot until you find out the right setting.
Get a large accurate gauge.

Note that temperature changes may affect your pressure needed.


btw, does a sprinkler seal off well enough when on such a low psi?
Most piston valves also leak when there is not enough pressure to create sealing force. (although a sprinkler is a diaphragm)
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Unread postAuthor: pvcmaster » Wed Feb 06, 2008 4:53 pm

But is it at least possible with a relatively low pressure (under 50 psi)? I just dont want to have to rebuild it.

Im pretty sure the valve seals around 8-10 psi
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Unread postAuthor: psycix » Thu Feb 07, 2008 9:07 am

Then you should reach your goal, just epxperimenting with pressures from 5-20 psi and finding out wich pressure works best.

Build the cannon, test it, check out what the right pressure is and let me hear how you progress :)
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Unread postAuthor: MaxuS the 2nd » Thu Feb 07, 2008 9:10 am

I don't think 9 psi would do much at all. It may be enough to pop it out of the barrel, but that would be about it.

What a strange project. :D
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Unread postAuthor: psycix » Thu Feb 07, 2008 9:14 am

MaxuS the 2nd wrote:I don't think 9 psi would do much at all. It may be enough to pop it out of the barrel, but that would be about it.

What a strange project. :D


Yup GGDT is wrong I think.
But it is very easy to up the pressure a bit until it does work good.
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Unread postAuthor: jr » Thu Feb 07, 2008 6:38 pm

I built a small g-ball cannon with a 1:1 ratio and it barely went 50 ft.

it was 3" end cap, 3" coupler, 1" sprinkler and sdr26 barrel!!very disappointed :cry:
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Unread postAuthor: pvcmaster » Thu Feb 07, 2008 9:41 pm

It went 50 ft. at what pressure?
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Unread postAuthor: psycix » Fri Feb 08, 2008 7:25 am

jr wrote:I built a small g-ball cannon with a 1:1 ratio and it barely went 50 ft.

it was 3" end cap, 3" coupler, 1" sprinkler and sdr26 barrel!!very disappointed :cry:


pvcmaster wrote:It went 50 ft. at what pressure?


Used SDR21 as a barrel?
Thats not pressure rated pipe and thus he should have kept the pressure LOW
Unless he sleeved it.
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Unread postAuthor: Ragnarok » Fri Feb 08, 2008 8:00 am

psycix wrote:Used SDR21 as a barrel?
Thats not pressure rated pipe and thus he should have kept the pressure LOW unless he sleeved it.

I had heard that 1.5" SDR 21 was rated to 200 psi - but it was quite flexible, so sleeving it was advised to stop it bending.

EDIT: 30 ft is an incredibly low distance.

It should be no trouble to go that far, but you've got the wrong kind of numbers for modelling that valve.

Looking at my range calculator, you don't need much power at all to fire just 30 feet - just 35 fps would be enough. That's under 2 ft-lbs of muzzle energy, and you don't need much of a launcher to put that energy into a golfball.
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Unread postAuthor: pvcmaster » Fri Feb 08, 2008 2:56 pm

What specs should I use for my valve, it would help a lot in the future.
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Unread postAuthor: clide » Fri Feb 08, 2008 4:22 pm

These numbers probably aren't perfect, but they should give a decent model.

Type:Barrel Seal
Seat Diam: 1"
piston diam: 2"
vent diam: 0.15"
Pilot volume: 1 in3
Flow Coef.: 30%
Piston mass: 1 oz
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Unread postAuthor: frankrede » Fri Feb 08, 2008 5:45 pm

psycix wrote:
jr wrote:I built a small g-ball cannon with a 1:1 ratio and it barely went 50 ft.

it was 3" end cap, 3" coupler, 1" sprinkler and sdr26 barrel!!very disappointed :cry:


pvcmaster wrote:It went 50 ft. at what pressure?


Used SDR21 as a barrel?
Thats not pressure rated pipe and thus he should have kept the pressure LOW
Unless he sleeved it.

Sdr-21 is pressure rated...
like ragnarok said, too 200 psi.
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Unread postAuthor: psycix » Sun Feb 10, 2008 2:55 pm

Ragnarok wrote:
psycix wrote:Used SDR21 as a barrel?
Thats not pressure rated pipe and thus he should have kept the pressure LOW unless he sleeved it.

I had heard that 1.5" SDR 21 was rated to 200 psi - but it was quite flexible, so sleeving it was advised to stop it bending.


Ooooo
didnt know...
Another thing learned :)
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