Servo - November 2012

RADIO UPGRADE.

Rock and Rover

READY FOR ROVERING.

particularly well-suited to such a design; the multiple mounting holes on each frame piece make basic adjustments of the link dimensions quick and easy. Leftovers from the 3-in-1 Rover kit and the bag of extra parts had far more than enough frame pieces to build our arm and claw mechanism, and soon we were ready for some testing.

Red Planet Rover, Come On Over

Before we attached our four bar linkage to the gear mechanism, we wanted to confirm that our trusty old Futaba radio and receiver would play nicely with the VEX motor and the rest of the moving parts on the Rover itself. We wired up the mechanism – motor to receiver and battery to receiver — and fired up the Futaba. The mechanism sprang to life and the large gear began to turn ponderously, much like the relaxed pace of an ancient water wheel on a lazy stream. The slow speed was expected given the gear ratio, and we hoped that would also translate to big enough torque to raise a long arm and a rock sample at the end of it.

Now, we had a working gear train and a claw assembly. Fastening the components together was made delightfully easy by the serendipitous alignment of the Minds-i and VEX mounting holes. Before mounting the whole thing to the robot, we wanted to ensure that the claw operated the way we intended. Performing any redesigns would be much easier before attaching the arm to the bot.

When we fired up the arm, we were pleased to see that once the claw opened or closed the entire arm would raise or lower. Unfortunately, the claw opened before raising the arm, and closed before lowering it. This was the opposite of what we wanted to do, and it pretty much looked like the claw was flipping off its careless creators. When we took a second look at our mechanism, it was obvious why it was happening.