Punch Mechanism Design Help/Review

Hey all,

My team wanted to make a high powered t-shirt cannon (original, I know) as an off-season project. I figured a punching mechanism would be most relevant to FRC, so I created a preliminary design for our launcher. The only thing I am missing is some kind of shock absorber at the end. Not sure what exactly to use there.

Feedback would be much appreciated! This design was inspired by 503, 67, and 314.

Features include:

  • Ball Shifter (via Vex Pro, 8.333:1 low gear, neutral “high gear”) with output shaft used to spool Kevlar string
  • 24in Igus KOP slide track
  • 3D printed or milled carriage
  • Up to 148.8lbs of spring force (adjustable in 49.6 lb intervals)
  • Sheet Metal Construction




I like the puncher!

For shock absorbtion, try rubber bumpers (like this) or use springs to catch the carriage at the end of the travel.

I think you can take a good deal more material out of the plates if you care about weight or finger access. I know the shifter has an encoder, but it may also be worthwhile to add a limit switch at the fully-cocked point. Rivets may not be the best choice for the side wall mounting, since if the CF spring breaks it’ll be very difficult to replace (finger access holes can solve this if you like rivets). Also, consider how you’re going to mount this - if there’s a pivot, then you need to center it around the center of mass to make it balanced. Remember to add screw access holes for the ball-shifter on the bottom plate for the sake of those building this. Also, if you can do 148 lb, consider making your travel shorter - this robot had 200 lbs and shot a much heavier element.