Reloading Launcher

[Austin2046]

On our catapult we use a winch to pull the arm down into a gate latch held closed by a pneumatic cylinder. When we fire it first disengages the winch using a ball shifter (so the drum can spin freely) then we open the gate latch and it fires.

[zachrobo1]

We have a spring catapult that is pulled down with Andymark's Shift-to-Neutral Winch (am-2774). The winch has a ratcheting wrench inside of it to prevent it from backdriving, and a dog gear to disengage. To release the dog gear inside, we have a rotating cam on a window motor that provides all the force we would ever need. We were thinking of using the recommended pneumatics, but our robot doesn't have any pneumatics in the design so the cam made more sense.

[Ether]

Originally Posted by zachrobo1

Andymark's Shift-to-Neutral Winch (am-2774)

motor -> 50:12 speed reduction -> ratchet -> 40:28 speed reduction -> dog clutch -> winch

Disengage the dog clutch and the winch can spin freely.

[ArzaanK]

On a related note, many teams are using winch systems or a cam actuated radial release mechanism (the choo-choo) but how do you get the launcher to stay down until you want to launch (other than precariously stopping the motor at the exact moment the launcher is fully retracted)?

We have a bolt coming down from our firing mechanism that triggers a limit switch on its way down. The firing mechanism is programmed to stop at when the limit switch is pressed, and then, when a firing button is pressed, the motors engage again, running continuously until the limit switch is engaged again.

[J. Stofflett]

We use a cam cleat like you find on a sailboat.

[xXhunter47Xx]

We have a custom dog gear run by two window motors. It rolls down the catapult arm (low pivot with springs). It is actuated by a piston.
We have a button on the remote to roll the window motors, and will continue to roll them indefinitely either until the driver stops pressing it or the limit switch on the bottom is pressed.

[Tom Line]

Originally Posted by J. Stofflett

We use a cam cleat like you find on a sailboat.

You have other options as well if you are using sailing line for your winch. There are a whole host of rope clutches by different manufacturers that can be actuated pneumatically with little force. That's how we did it in 2010.

[nlj007]

900 also uses a customized Modulux Gearbox with a shift-to-nuetral. With the forces at play, we had to get creative with shifting the dog gear, but it has worked quite well.

-Team 900 Zebracorns

http://www.youtube.com/user/FIRSTRobotics900