Check out our cannon bot!

[greencactus3]

never really seen one in real life so i dunno so, wahts that clanking noise as it fires? valve? oh btw what kind of tanks are you guys using?

[ZZII 527]

As a general warning, be EXTREMELY careful if you are using PVC for pressurized air storage. Even if it is rated to pressure much higher than what you will be using, it can be dangerous. It is designed for incompressible liquids that don't store much elastic energy. Compressible gases, on the other hand, store tremendous amounts of energy and can cause violent explosions. It is for this reason that PVC manufacturers explicitly state that it is not to be used with compressed air.

If you are going to use PVC for an air cannon, make sure it is pressure rated (it will say so right on the pipe) and make sure you properly cement all connections. Also, DO NOT use it outdoors in cold weather - the plastic becomes very brittle and is more likely to fail.

[sanddrag]

I can confirm that sprinlker valves will work off of 24VDC. For PVC, don't put any more than maybe 25 psi in it without gluing all the pieces, and when you glue them, let it dry for a long time to make sure it is fully cured.

But air cannons are very fun projects. You can easily make a quite nice fog horn too.

One thing I did while messing around with this stuff was to drill out a PVC end cap and thread in a quick release fitting for the air hose. It worked fine, and was very easy to do. Just to let you know in case you were wondering how to hook up the air, that is one way.

[billbo911]

As promised, here is the video from Sunday night at the Sacramento Kings game.
Please forgive the quality, I have not yet had a chance to clean it up. I will once I get the correct software running.
Team 1147 at Arco In the background you will hear the team being announced just after the shirts land in the upper deck!

[greencactus3]

Originally Posted by sanddrag

I can confirm that sprinlker valves will work off of 24VDC.

can anyone confirm for 12 or 14V DC? why tho? i dont understand why.... kinda like how a light bulb works i guess? and anyone explain the sound i asked about 4 posts down?

[Dick Linn]

Good place to start is wikipedia - search for potato cannon. In there, there is a link to here: http://www1.iwvisp.com/thehalls/ggdt/ where you can get software to calculate theoretical velocities and stuff. He also has a page showing how to modify a sprinkler valve for rapid discharge (for manual firing), and pages discussing different designs of spud guns and paintball guns.

Make sure you read various safety warnings about PVC guns! Use only pressure-rated pipe, prep the pipe and use primer, allow the cement to cure for at least 24 hours and don't use them in hot or cold weather.

You could probably modify a sprinkler for pneumatic opening, then use a 12 volt air valve from one of the old pneumatics kits as the trigger instead of the solenoid.

Our latest toy is a 20 lb. propane tank connected to a 1 inch pipe. Overkill, yes, but shooting a carrot at something solid makes instant carrot juice. More like orange fog.

[billbo911]

Originally Posted by D. Linn

Our latest toy is a 20 lb. propane tank connected to a 1 inch pipe. Overkill, yes, but shooting a carrot at something solid makes instant carrot juice. More like orange fog.

And here I though I was the only mentor that had more fun with these "toys" than our students do! Silly me!

[Dick Linn]

My 16 year old does the building, I just buy the goodies.

My favorite is a 2 liter soda bottle with a 1/4 to 5/16 inch (or so) hole in the cap. About a 6 to 7 second spritz of propane from a torch, put the cap back on, put it on some sort of guide rail and light it. WHOOSH. It ignites and the exhaust goes sonic, so watch your ears and don't get burned by the hot exhaust. It'll send a bottle quite aways. You have to squeeze the bottle a few times to purge between firings. The bottles start to deform after several launches.

[Rickertsen2]

I always hear people talking about using sprinkler system valves for homemade pneumatic projectile launchers. The valves on my sprinkler system are motor actuated ball valves. They take about 4 seconds to open fully. This seems rather slow. Is this what people are talking about or is there some other tyoe of sprinkler valve? I have built several devices using quick release valves from semi-truck air brake systems and they have worked well.

[ZZII 527]

Some pics and video of one of the meanest Vex bots known to exist:

http://web.mit.edu/scolton/www/tankbot1.jpg
http://web.mit.edu/scolton/www/tankbot2.jpg
http://web.mit.edu/scolton/www/tankbot3.jpg
http://web.mit.edu/scolton/www/tankbot4.jpg
http://web.mit.edu/scolton/www/tankbot_clips_web.wmv
http://web.mit.edu/scolton/www/tank_slow_web.wmv

[greencactus3]

Originally Posted by Rickertsen2

I always hear people talking about using sprinkler system valves for homemade pneumatic projectile launchers. The valves on my sprinkler system are motor actuated ball valves. They take about 4 seconds to open fully. This seems rather slow. Is this what people are talking about or is there some other tyoe of sprinkler valve? I have built several devices using quick release valves from semi-truck air brake systems and they have worked well.

there are solenoid ones. which would mean they are fast.... but apperently according to a link someone else posted before, those solenoids still arent fast enough. im planning to get a standard solenoid one soon. see what i can make outta it. i have some big plans for next spring.

[Dick Linn]

Check here: http://www1.iwvisp.com/thehalls/ggdt/

For a sprinkler system, I'd imagine a motor-actuated ball valve is better. You don't want to open or shut a sprinkler (hydraulic) system quickly. But a cheap valve may be better suited to pneumatic operation, especially as modified. I think these valves are about $16., last I remember.

[Doug G]

Originally Posted by greencactus3

there are solenoid ones. which would mean they are fast.... but apperently according to a link someone else posted before, those solenoids still arent fast enough. im planning to get a standard solenoid one soon. see what i can make outta it. i have some big plans for next spring.

We just used a standard off the shelf sprinkler valve that has a diaghram and is actuated by a knob manually or by a solenoid. The solenoids are supposed to operate at 24 VAC. But after some experimentation we found a single spike relay connected to just 12-13 VDC on the robot works fine. At first we thought we were going to have to configure an additional power supply, but in the end we didn't Now to rig up a motor to a compresser to charge our two large tanks - hmmm, might need a deep cycle marine battery as well.

I heard about Elk Grove's (1147) T-Shirt Launching robot at the Kings game - if you do it again let us know (not ride your coat-tails, but to promote robotics of course) we'd be happy to join you out there.

[billbo911]

Originally Posted by Doug G

I heard about Elk Grove's (1147) T-Shirt Launching robot at the Kings game - if you do it again let us know (not ride your coat-tails, but to promote robotics of course) we'd be happy to join you out there.

The request for future performances has already been placed! We now wait with baited breath. If we do get an invitation to do it again, we will most certainly request that you join us. Promoting FIRST Robotics is way more important than promoting just our team! Besides, a little competition on the court is way more fun, and better exposure, than performing solo.

BTW, did you follow the link and see the short video I posted a few frames back? You should have seen the smiles on these kids faces after they came off the court! <--- That's what they all looked like.
In fact, here is a link to a picture I snapped as they were exiting the court. It doesn't even do justice to what we saw once they got off the court and thought about what they had just done.