Servo - September 2015

SERVO 09.2015 35

allowed the screw to be screwed tight to the nutstrip (thus removing the need for threadlock). The screws had about one inch of threads; I cut the extra length of the screws off with a Dremel tool.

Final Touches

The motor shafts are about an inch longer than they need to be for this application; that extra length could make the shaft more vulnerable to a spinning weapon, so I trimmed the shafts with my Dremel tool to be flush with the wheel hub.

The base plate still had open holes where the spinner weapon kit power key would go, and a few gaps in the wheel well. After a few fights, the arena can become littered with dust and debris which I would rather not have inside my robot. So, I covered the holes and gaps with Gorilla tape (similar to duck tape but stronger and hairier).

With all modifications done and the robot completely assembled, it weighed in at 15. 50 oz. I tested the robot on a concrete floor and found it to be quick and responsive. It drove very straight for a two-wheeled robot (which tend to pull to one side), and the flipper arm had enough power to pick up a 1 lb object. However, the shape of the steel "scoop" that came with the lifter kit made it hard to get under my test dummy to get a good flip in. The robot was able to self-right very easily from any orientation.

Combat Report

Viper Fighter MK-2a's first trial by fire was at Clash of the Bots 2015. The first fight was against Super Orange Glow by Team Browns Mountain Lab from Greeneville, TN. This robot featured a small vertical spinning disk and a four-wheel drive system. Viper dominated this match, consistently out-running and out-maneuvering the much slower Super Orange Glow. Viper was able to get in several lifts and a few flips, plus also push the other bot to the wall a few times. In contrast, Super Orange Glow's disk did only superficial damage.

Viper Fighter's second opponent was Klazo by Near Chaos Robotics from Norcross, GA. Klazo featured a powerful spinning drum weapon and a two-wheel drive system. At the start of the match, Viper charged Klazo, met her head on, and tried to get a flip in, but did not get the scoop far enough under Klazo for an effective lift. Klazo quickly came back and clipped Viper's left side with her drum and easily took off a wheel. Viper tried to stay in the fight by "crab-walking" across the arena and got in one partial lift before Klazo took off the other wheel and ended the match in one minute.

Total damage to Viper: two broken motor shafts; one lifter arm was bent and cracked at the cross bar joint; the right front corner of the chassis was bent upward; and there were several deep gouges in the front polycarbonate plate.

Klazo went on to take 2nd place, losing only to teammate, Algos. I chose to forfeit Viper's next match so I could focus on repairing my other robot.

Conclusions

Upgrading the drive to 11.1V dramatically improves driving performance and helps get the flipper in position. The XQP-4220 servo at 11.1V performs very close to the HXT 12 kg at 9V. However, it should be noted the HXT 12 kg is only rated for 7.4V, whereas the XQP-4220 is rated for 11.1V (which should make the XQP-4220 more reliable).

Viper took several major hits from Klazo's drum but suffered no internal damage. The servo was very well protected. Over all, Viper MK-2a preformed much better than Viper MK-1. For the next version (MK-2b), I would like to protect the motor shafts from side hits and modify the lifter scoop and arm in order to get under the opponent better. SV