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So... I am doing a golf ball challenge for an engineering class and I would like a little inside info on air cannons from the pros I am a complete noobie to this material, so please feel free to give me the dumbed down version at first.

Here are the rules of the competition.
• Max distance is 50 yards
• Min distance is 20 yards
• Budget is $160 if all new parts however you are free to use any parts that you wish
• No chemical reactions (this means rocket engines, combustion, hair spray, starter fluid)
• EVERY DESIGN MUST BE SAFE OR YOU WILL NOT BE ALLOWED TO COMPETE!
• The base must be less than or equal to 4 ft by 8 feet, but other parts may extend beyond but not over 2 ft overall outside the 4 x 8 ft footprint .
• No part can extend beyond the start line during launch.
• Device must be free standing and sit on the ground.
• Device cannot be moved back or forth between to adjust for distance.
• Cost of air compressor not counted if using compressed air.
• Two practice shots at first distance, no practice shots are on second and third distances.
• Anything attached the golf ball must “fall off” before the ball hits the target.
• Someone not in the class will fire the device.
• Three scoring shots per distance.
• Making minimum distance 1 points
• 7.5 ft ring is worth 3 points
• 5.0 ft ring is worth 4 points
• 2.5 ft ring is worth 5 points
• We will have competition no matter the weather conditions.
• Tie breaker will be a fourth distance.


There will be 3 targets laying flat on the ground at anywhere between 20 and 50 meters away. The class will be separated into groups and the team with the most accurate setup, most points, wins. The winning team gets a score of 100 with each proceeding team losing 5 pts per rank.


Anyways thanks for any help in advance.

Well I suggest a sprinkler valve with a 2 inch pvc tank a a sdr 21 barrel

^^^ that'd do it
Is the shot measured from resting or from place of impact?

• Max distance is 50 yards
• Min distance is 20 yards

Not a very difficult goal. A pneumatic launcher would be best to do this. Even a 1" sprinkler valve could achieve this easily, just use the pressure, angle etc. to vary the length of the shot.

Does it have to be made by you? (stupid question i'm sure). You could buy a pneumatic golf ball cannon from one of several online spud stores that have them and then tweak the pressure and DONE!

First off that really lame bogster. I say sprinkler valve and just vary the pressure to get the distance, figure out the exact PSI for each 10 meter increment before hand.

Edit, moved this post from the other thread. This info belongs here.

mysticjbyrd wrote:There will be 3 targets laying flat on the ground at anywhere between 20 and 50 meters away. The class will be separated into groups and the team with the most accurate setup, most points, wins.

0 - 2.5 ft is the inner radius of the target (Bullseye) = 5 pts
2.5 - 5 ft is the middle radius of the target = 2 pts
5 -7.5 ft is the outer radius of the target = 1 pt


thx for link and info

He needs very consistent power between shots so it can be setup and reliably lob projectiles onto the bullseye. The bullseye is flat on the ground, not a standing target. Excessive power is not an advantage in this contest. A good tripod mount with an accurate inclinometer to assist with setting the launch angle is critical. Testing someplace to chart distance vs pressure is important. You will want to already know the angle, pressure, etc to hit the required range to drop it on the bullseye.

I would recommend a low pressure cannon with a fast valve so the variables in the valve opening is very consistent shot to shot. Use a low pressure gauge to very accurately repeat the pressure for each shot. Maybe a quality welding gas regulator or just gauge for 0-30 PSI is in order. 30 PSI is plenty of pressure to reach the farthest target with a golfball in a proper launcher.

A hand operated ball valve won't provide the consistency you require. Sprinkler valves are a little twitchy in the lower pressure range. A quality piston valve that moves very smooth without binding is key. A very small EQ port and reasonable trigger valve is required. Avoid a blow gun due to flow level on low pressure cannons. Use a brass smooth operating ball valve. A "Full Flow" ball valve works well. Many ball valves have a small orifice. Avoid those for the same reason to avoid a blow gun. High flow rate reduces the pressure lost through the piston EQ port for more consistent shots. A hand pulled QDV may be OK but their disadvantage is the possibility of messing up your aim when firing it, so I don't recommend one unless you modify one to use a spring trigger.

We graphed our launches with our competition t shirt launchers. There were lots of field tests, so when it came to the actual game, we could pick a retired number or the back row of the 300 section and put one right where we wanted it. We knew the distance, the elevation, etc. Dialing in the shots didn't take much.

Know your cannon, know the range, take lots of test shots and measure each one. Graph them.

In a piston it is important to have a SMALL leak between the chamber and the pilot area.. This is the equalization port or EQ port for short. If it is too big, then the cannon tends to not fire and the chamber pressure bleeds down a lot before it goes off so consistency is poor.

The QDV is the Quick Dump Valve cannon which uses a spool valve piston so it is mechanically opened by pulling a rod instead of triggered by opening a valve. This tends to shake the cannon some which may diminish the accuracy of the shots. Other than shaking the cannon, the QDV is a very consistent valve.

Moonbogg wrote:Does it have to be made by you? (stupid question i'm sure). You could buy a pneumatic golf ball cannon from one of several online spud stores that have them and then tweak the pressure and DONE!

Build a stable stand for it.

From the rules;
• Device must be free standing and sit on the ground.

As an engineering project, it would help to play with GGDT and model various barrel length and chamber sizes.

Does anyone have a good table of golf ball velocities and travel distance so this can be correlated to GGDT predictions? Dialing in ahead of time the expected pressure operating limits would be very helpful in selecting a gauge for it.


I know, More acronyms.. GGDT Gas Gun Design Tool. There is a link to it in the wiki.
http://www.spudfiles.com/spud_wiki/inde ... rnal_links

http://www.launchpotatoes.com/index.php ... oductId=49
I think you should build something like this but with a single sprinkler valve, but to keep the design so you can change the angle ofthe barrel with only one valve, you'll have to connect the 2 bottom ports on the barrel (that join to each of the QEV's) back up to each other in a tee fitting and then have the lead to the valve and then chamber.

This will mean you'll have a lot of dead space, but it's not like performance matters a whole lot here.

With that design it just means it's free standing and has a simple system to change the barrel angle.

The range involved means performance doesn't have to be spectacular. I would go for a sprinkler valve, electronically actucated for consistency, operating at a fixed pressure.

The work would have to go into a base which has two important features:

- Adjustable legs and and on-board spirit levels to ensure it's always tangential to gravity.

- A barrel that is incrementally adjustable for elevation, preferably with some kind of threaded mechanism with a corresponding scale.

One it's built, it's a matter of rigorous calibration. With a slow projectile of relatively poor ballistic coefficient, wind is going to be a huge factor, so any zeroing must include a detailed record of wind strngth and direction. Something like this little device is a cheap way of being professional about your approach.

For Science! Remember the difference

I'll go against the grain and advise against a sprinkler valve. Why go through all the trouble when a QEV (something DESIGNED FOR AIR RELEASE) is $23? The $10 saved by going with the sprinkler valve isn't worth the time/effort required to modify it (IMHO).

I'd also build a fixed elevation gun and vary distance strictly via pressure. You will almost certainly need a regulator anyways so it's no big deal to turn the knob one way or the other. By contrast, if you want variable elevation, you've opened up another can of worms (ie, another variable).

I would think the critical part of the design isn't the gun, or valve, or chamber or barrel...

It's the carriage. You need a stiff carriage that can be reproducibly set to the desired angle. It can't sink into the ground, or vary in the way it sits on the grass, or be driven into the ground when fired.

The second most critical design feature is probably the reproducibility and precisions (though not necessarily the accuracy) of the pressure gauge.

Personally, I would fix one of those two variables. Either always launch at the same angle or always launch at the same pressure. Use the other variable to control range. Trying to reproducibly change two variables will be much more difficult.

Getting reproducible pressures may be tricky and you should probably come up with a way to insure the pressure is consistent. The chamber temperature will tend to rise or fall a bit after the chamber is pressurized depending on how you do the pressurization. That change in temperature gives a change in pressure. So, figure out a pressurization and firing schedule that is precisely timed. Every launch must follow the same firing timing. If you don't want to time things, and if how much time you take isn't an issue, I would pressurize then let the gun sit for at least several minutes before firing. That'll let it thermally equilibrate. Of course, that means you can't have any leaks.

A typical regulator will be pretty consistent during a given firing session but may not be all that consistent from day to day.

It would be interesting to sit down with a ballistic calculator and see if it is easier to get a consistent range with a shallow launch angle or a steep one. Which is more sensitive to small changes in pressure or launch angle?

A shallow launch angle will give much more "roll out" after the GB hits the ground than will a steep launch angle.

A hop-up might be a good idea. Not to increase range but to get consistent spin on the GB. You could also just bend the barrel a bit.

During the competition have a laptop handy and use the early shots to correct the later shots.

Sounds like fun.

It would be interesting to sit down with a ballistic calculator and see if it is easier to get a consistent range with a shallow launch angle or a steep one. Which is more sensitive to small changes in pressure or launch angle?

Steeper angle means longer flight time, more time to be affected by the prevailing wind.

Might I suggest the targets be made of paper stretched over a frame, so ensure hits show irrespective of any subsequent rolling.

jackssmirkingrevenge wrote: Steeper angle means longer flight time, more time to be affected by the prevailing wind.

Might I suggest the targets be made of paper stretched over a frame, so ensure hits show irrespective of any subsequent rolling.

A shallow angle makes huge variations in distance with minor elevation or pressure changes. A repeatable lob onto the target would most likely be best, like tossing bean bags.

Most likely he has no control over the contest site construction. Nice suggestion, but simple spotters would suffice to see the landing impact.

Thought: It hasn't been clarified if first impact or final resting point of ball counts.

IF it's final resting point....

I'm wondering if the best approach wouldn't be to simply build a pendulem with a pitching wedge attached to it. The point being that the backspin induced by an actual golf club would reduce rollout.

Just a thought.


edit: And honestly, it's just a damned shame that the student doesn't get to operate the machine - that it's another person. 'Cause otherwise it would be fun to just show up with a pitching wedge and a lot of practice.

Technician1002 wrote:A shallow angle makes huge variations in distance with minor elevation or pressure changes. A repeatable lob onto the target would most likely be best, like tossing bean bags.

There's no evidence that howitzers are any more accurate than conventional artillery...

Heck, does it specify one projectile per shot? Go the whole hog, make an auto and go for MRSI

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