Safely unloading launcher after power off

So my team and I are going to build a shooter similar to team 1114 in 2008. What we were wondering is how could we safely Dis-arm the shooter once the match starts if we are using a wench to pull it back.

I think you’re talking about after it ends…

I can think of a couple of ways. The best one might be to have a “fire” signal trigger right before the end of the match, thus disarming the launcher–I’ve seen this done with pneumatics before. Another that would work would be to have a locking pin (with a “Remove Before Flight” streamer attached, in case of leaving it in robot before matches) to hold the launcher back at any time it’s armed and not to be fired, bring it back to the pit, and reverse the winch slowly with a command off the driver’s station after powering back up.

I am fairly new to lab view could we just have a 2min timer count down at the start of the teleoperated period or is there no way to “detect” the start of teleop.

In Labview, I don’t know. I believe there is a “flag” that runs a teleop program; what I would do would be to put something like the following in right at the start: “If this code is active, run counter. At computer equivalent of time 1:59.5 on counter, actuate X to disarm launcher.” You’d have to play with the time; I’d suggest also having a “demo” version of the code with that particular section commented out (past experience).

My cohorts came up with a nice way to make the winch safe for our surgical-tubing powered shooter. We use a VexPro shifting gearbox, with one speed converted to neutral by removing the three balls from inside its output gear.

We only allow the software to shift the winch to neutral right before firing it. So it will be in gear when idle, such as after the match ends. That way, when the cocked shooter’s trigger is released by hand, the winch cable will back-drive the motors through the gearbox, which absorbs a lot of energy and releases slowly and safely.

We’ve tested it and it works.

We will work on making it easy to visually determine if the gearbox is in the right gear. We may add a flag to the shifter so that it looks red when it’s not safe.