Simple tshirt cannons

Our team just had its FIRST meeting of the year, and we are happy to have a ton of new people. With that in mind, we would like to start off the year by making a tshirt cannon. We don't need anything as complex as 254's Shockwave (My favorite robot of all time. ALL TIME.), but we would like a simple 2 or 3 barreled pneumatic cannon on a drivable chassis.

So my questions are:

1. What kind of materials should we get for the cannon? (PVC or no?)
2. About how much time would building it take? (just building, not bugging/programming)
3. About how much money would the cannon itself take? We have the rest of the parts.

Thanks!

[NickE]

1) PVC is not pressure rated for compressed gases. If holding compressed gasses, a PVC failure will be violent and explosive. For this reason among others, Team 254 chose metal barrels and pressure rated air tanks for Shockwave and was very happy with this choice. If you're looking for something simpler than the welded construction we used, others have had success in the past with steel pipe. If you're just looking to do 2 barrels, it probably makes sense to skip the revolving mechanism and simply have one valve for each barrel. Keep in mind that high performing and safe valves are expensive. We went with a 1" NPT MAC Valve.

2) If you already have a mobile drivebase, you could probably build a very simple cannon in ~3 weeks if you work hard depending on how much custom construction is done.

3) For all of the piping, tanks, valves, etc, you're probably looking at slightly under $1000 to build a good, safe, cannon but you'd have to price it out depending on what parts you decide to use and which you already have. If you don't already have a set of electronics and a drivebase, the price would jump significantly.

Good luck and feel free to contact our team if you have any questions. Contact info is at team254.com. Just be sure that whatever you build is completely safe so you won't put yourself or others at risk.

Thanks! We have all of the electronics and drive base materials, we just need a cannon. We appreciate your help, and will contact you if need be.

[davidthefat]

From what I can see from the Shockwave, the barrels do not use an encoder, but rather a photo sensor to orient itself. Have you guys ever thought of improving on the design to truly be a gatling t shirt launcher? Incorporate some reloading mechanism and up the RPM. But it does give me an idea of making a gatling paintball or airsoft tank...

[NickE]

Originally Posted by davidthefat

From what I can see from the Shockwave, the barrels do not use an encoder, but rather a photo sensor to orient itself. Have you guys ever thought of improving on the design to truly be a gatling t shirt launcher? Incorporate some reloading mechanism and up the RPM. But it does give me an idea of making a gatling paintball or airsoft tank...

The barrel rotation is sensorless and uses a unique locking mechanism to ensure that each barrel is securely locked into place before shooting. This design eliminates the possibility of the barrels rotating as the cannon shoots. As seen in the picture below, a bearing on a piston-actuated lever fits into slots on the barrel backing plate. We are very happy with this mechanism and it has shown to be extremely reliable with no failures. We have discussed the possibility of an auto-reloading mechanism but have not done any serious work on one.

[Doug G]

We use two metal tanks tied together with 1" braided hose to a Metal ball valve that is manually operated (it is the safety valve). Out of the ball valve we use a 1" sprinkler valve actuated with a spike relay and then to some braided hose to a 4" PVC barrel. We operate the whole system at 60 psi and have to repressurize the tanks after 4-6 shots.

Yes, the plastic sprinkler valve is not rated for air, but it was simple and with the safety valve, it isn't held under pressure for that long. We've used the system since 2004 on 4 different drive bases. Our current drive base has articulated mecanum front and back.

Here's a quick video we did for the local tv station website...
www.vandenrobotics.com/Videos/RobotSpirit2.wmv

We can launch up to 4 cheeseburgers to the top of our stands at games.

[Walter Deitzler]

Originally Posted by SuperNerd256

254's Shockwave (My favorite robot of all time. ALL TIME.)

I don't know, 1986's TITAN is pretty darn cool...

Originally Posted by LedLover96

I don't know, 1986's TITAN is pretty darn cool...

But can it shoot tshirts?

[Tommy F.]

Originally Posted by SuperNerd256

But can it shoot tshirts?

Nope, but it plays Guitar Hero.

Originally Posted by 7h0m54

Nope, but it plays Guitar Hero.

Just the guitar, or th entire band?

[Walter Deitzler]

Originally Posted by SuperNerd256

Just the guitar, or th entire band?

Just the guitar.

http://www.youtube.com/watch?v=mNrtTx3ReDk

[Tommy F.]

Originally Posted by SuperNerd256

Just the guitar, or th entire band?

Just the guitar, but it's still awesome.

http://www.youtube.com/watch?v=VLQhX0nZV6I

Someone should make an entire band of robots!

[Walter Deitzler]

Originally Posted by SuperNerd256

Someone should make an entire band of robots!

That would make my day.