pic: Team 48 Something or Other

[Travis Hoffman]

Originally Posted by Chris is me

I'm quite excited to see this. We have a lot of similarities in our robot design. I only wish we had thought to use a clever mechanism like this instead of a winch and shifter. Did you find OTS rack gears that didn't weigh a ton or did you make your own?

All gears are steel and were purchased from AndyMark, including the 56-T pinion. We bought the 20 DP, 14.5* PA rack gear from McMaster (http://www.mcmaster.com/#6295K113). The total stroke of the unit is 6" (incl. 4" of ball contact), so the rack isn't that heavy.

Here is a test fire of the prototype at about 100 lbs. of tension. We are expecting to add some more tension for the final iteration:

http://www.youtube.com/watch?v=5r2GO3_s-9s

igus' Y.E.S. program (http://www.igus.com/wpck/4856) graciously supplied the 1" aluminum shaft we're using as the punch rod, as well as the open-top linear bearing pillow blocks (which conveniently let the 3/8" wide rack gear slide right through them, contributing to the compactness of the launcher design).

One of the benefits of this linear punch design over others is that there is zero drag on the action from the unwinding of a winch spool.