Like many teams, we would like to build a t shirt cannon.
Anyone has any recommendation on what regulator to use on a scuba tank or SCBA tank to bring the pressure down to an acceptable range?
Any suggestion would be appreciated!
Why do you want to use a scuba tank over just a 120psi air tank? On our t shirt cannon we are using two 5 gallon air tanks and when we shoot t shirts we have plenty of air. We do have an onboard compressor but we would probably have enough air for shooting shirts without it.
If you want something small and durable check out the Palmer pursuit regulators. Otherwise a standard welding regulator will work fine.
With our previous version of the cannon, we used a standard scuba regulator to bring the pressure down from ~3000 psi to ~100psi, then one of our FRC-legal regulators (or very similar) to get to operating pressure of 40-60 psi. When we had the timing on the 3/4" solenoid valve set down around 40 or 50 ms, we can get several football games out of each filling of the scuba tank, and two batteries on the robot for driving, lighting, and operating the valves would last a game; we set it up with two batteries in parallel. When we had tried using a compressor on board, we went through several battery changes per game.
This summer, we are moving our air cannon to a gasoline-powered golf cart, so we’re going to go back to the onboard compressor paradigm.
Some teams are using the air tanks used in car suspensions. Similar to those found at this link:
I am all set on the tank… look like local fire department may supply us with SCBA tank…
I am looking for the regulators… very curious on brand and model your team use.
Thank you!
There are certain safety concerns with using SCUBA tanks. In particular, they should be visually inspected annually and hydro-tested every 5 years. If you’re getting a used tank, the last hydro test date should be stamped on it. 3000 psi is a lot.
Can’t recommend any brands but we used a standard SCUBA 1st stage regulator on ours. We didn’t have the money at the time, but you can buy SCUBA gauges that then attach to the high pressure side of the reg so that you know how much pressure is left inside. The low pressure output is usually adjustable to a point, we had the dive shop set it to 120psi then used another pressure regulator down stream that we could manually adjust for our shot pressure.
We recently modified our T-Shirt cannon to use a SCBA tank instead of an air compressor (the compressor had a hard time keeping up with use). I don’t know what kind of regulator we’re using off the top of my head, but I’ll definitely take a look at it tonight and post the information. I know it’s rated to like 5000psi or something like that and will adjust it down to roughly 120psi so we can connect it to a standard FRC pressure regulator to regulate it down to 60psi-90psi (the smaller regulator gives a much better fine-tuning of the pressure).
Since the tank was donated used, we had it pressure tested at a local supplier up to like 7000psi (or something ridiculous like that); that said, we only plan to run it between 2000psi-3000psi (what our local fire department can fill it to). We estimate we can get over 100 shots out of a tank.
One important thing to note; at least in the case of our tank, it’s critical to protect the tank from external impacts. Our tank is enclosed in an aluminum shroud to prevent damage that could result in a catastrophic failure. Some of our mentors also seem to think the enclosure might help contain a catastrophic tank failure should it somehow occur, though I’m far more dubious of this.
If you saw how scuba divers treated those things, you might not be quite as worried. The tanks themselves are very tough. The place to be concerned is the valve. If that snaps off, you have a torpedo.
Yeah, the enclosure does shield the valve as well, though if it were to break I don’t think anything we have holding it would be enough to prevent it from shooting out of the bot like a missile, 3000psi is no joke, the FRC tanks are dangerous enough at only 120psi. :yikes: