Servo - January 2012

BUILD REP RT:

Rollin’ With the Punches

● by Andrea Suarez

Win or lose, the best combat robots always put on a show. That means no drive system failures unless your robot is in pieces. Bigger bots can achieve this through redundancy: four motors, four speed controllers, etc. However, a single motor-controller-wheel combo can be more than 15% of your insect weight bot!

The first revision of WhipperSnapper — my one pound robot with a modular (horizontal or vertical) five inch spinning disk — had been cursed with persistent gearmotor and wheel failures. In planning for a redesign, choosing the right components became essential. I switched from the Finger Tech Gold Spark to the new Silver Spark gearmotors with larger pitch gears for vastly improved reliability (still under $25).

The Finger Tech Lite hubs are much lighter than other aluminum hubs, and they provide two set screws on each hub. Even other lowest durometer wheels transferred most of the shock to the gearbox and provided little forgiveness during impacts, so I decided to use the much softer foam Lite Flite wheels instead.

This new drive combo has survived its first two full events ( 13 matches) with no drive system failures, and saved me enough weight for a much needed weapon upgrade!

The real test to this new setup,

however, came in a Mecha-Mayhem match-up against Low Blow from Pretzel Robotics. Thirty seconds into the match, Low Blow’s giant under-cutter got a big hit to WhipperSnapper’s wheel, cracking the gray snap-on plastic and pulling off the foam. In a turn of fate, WhipperSnapper’s wheel got wedged between Low Blow’s spinning bar and the bottom of his frame, stalling the weapon and deflecting his bar far enough to raise both of his wheels off the floor!

My 22.2:1 Silver Sparks survived the hit and the Finger Tech Lite hub remained secured to the motor shaft. The damage was easy to repair — a dab of CA glue to hold the foam wheel onto the remaining Lite Flite plastic and

Lite Flite wheels after Mecha-Mayhem

2011. No Silver Spark gearbox or motor failures despite an intense event!

WhipperSnapper was back in action.

Having the Lite Flite wheel fail before the Finger Tech hub insures that your robot won’t lose its wheels unless they are destroyed, saving the embarrassment of seeing your wheel roll away as the announcer starts the countdown. These easy drive changes shot WhipperSnapper’s record from 3-2 to 14-4 in just two events, winning 2nd at GCRS 8 and 1st at Mecha-Mayhem 2011. SV