Team 639 Code Red Robotics - The Red Raptor

http://www.youtube.com/watch?v=KTpc00wzTOY

For our 2013 robot, we were inspired by teams in 2012 like 548, 330, and 340 that chose to minimize exterior factors and shoot from as close up as possible. To that goal, we built an arm that raises our shooter up to shoot close range to the HIGH, MIDDLE and PYRAMID goals. Ask and I’ll try my best to answer any questions anyone may have.

Also, the video doesn’t really show it but we are running tank treads.

Rampcamp 2013! Neat linkage, what drives the “wrist” on the shooter?

Aah, thank you for asking. The wrist is by far the most obnoxious and least well working part of the robot; we’re trying to fix that before our Week 1 this Thursday.

The story of the wrist is a saga that does not yet have an end:

The original design (and one that lots of places in the video have) is a right window motor. The thought was that we wouldn’t have to run it constantly as it couldn’t be backdriven. Unfortunately, we had to remove the locking pins to get it to work - even with a Victor it locked up. After removing the pins, it had enough torque to move the shooter. However, as we should have learned years ago, window motors don’t like constant loads; they’re very low duty cycle. As such, after about 10 minutes of use (borderline acceptable for match play but not for testing and calibrating), it overheated.

Our first thought was to replace the chintzy window motor motor with something a bit more beefy; the Andymark 9015. We machined an entire system for connecting the two only to find out that when the window motor is backdriven (we should have put the locking pins back in!) the shaft in the Andymark was given an incredibly amount of lateral force, pushing it into the motor and breaking the motor.

Our second idea was to keep a refrigerator full of window motor motors in our pit and hot swap them into the gearbox every match. This is very arguably legal because theoretically, though you are running a Denso window motor with its proper motor, it is not its motor. Q&A ruled it illegal.

The latest tested idea, deployed on bag day was a AM9015 PG71 with bevel gears giving it the same driving direction the window motor. It worked for about 15 minutes and then started smoking after we accidentally blew the potentiometer in our PID loop by driving over its limit (330 degrees, the wrist can turn something like 345; we learned this the hard way). We’re not really sure if it started smoking purely because we drove it into its self at stall for 20 seconds before we realized the loop was broken or if it was purely the fault of the motor/gearbox combo and the load we are asking of it.

Our current solution to these issues is a PG188, a BAG in a VersaPlanetary 100:1, and a number of mechanical interlock solutions (solenoid shaft wrappers, passive assist, solenoid locking it into place, etc…)

In the video, the robot had a window motor on it for the first couple shots and the PG71 for pyramid shots. We actually caught the moment it started smoking on tape, perfect for the blooper reel: “Oh my god it’s smoking. SHUT IT DOWN! EMERGENCY STOP SHUT DOWN SHUT DOWN!”

Luckily, all the tested methods have worked for at least 2:15, enough to play a match and the beauty of this robot is the minimal amount of calibrating it needs: All we need is the angle for shooting position.

We were burned last year by an inconsistent shooter so our entire design philosophy this season was “minimize outside factors”.