Sunday, February 21, 2010

Exhibition at Wicked Faire

Yesterday I took the walking robot to the Wicked Winter Renaissance Faire to show off and entertain with. The trip was quite successful, with many fairgoers entertained. Unfortunately the problems I've been having with the HS5645MG gearboxes resurfaced. In this version I was running with hybrid servos containing the electronics, motors, and gears from HS5645MG servos installed in HX12K servo cases. HX12K cases were used simply because the ones I had were already fitted to the robot frame, and because I didn't have enough intact HS5645MG servo cases. HS5645MG servo innards were use because the HX12K servos had terrible position control and easily burned out motors.

Over the course of the day I had two gear failures. Both of them were identical to the failure I've seen before, with the second-to-last (counting from the motor) gear in the gear train losing teeth. This gear is surprisingly thin for the torque it's carrying. The same gear in the HX12K servo is significantly thicker, and in my robot has never failed.

I had spare gear sets on hand and was able to repair the damage and keep the robot going, but this is an unacceptable and expensive failure rate. I believe it may be possible to construct a hybrid servo using the gears from the HX12K and the motor and control board from the HS5645MG, which if it worked would give me the solid position control of the HS5645MG and the durability of the HX12K. Once the weather improves I will start working on that.

The other failure, which stopped my showing off the robot for the night, was when the antenna broke off the transmitter. The wire antenna that can come attached to the XBee radio module is made out of some very cheap and brittle coarse-stranded wire. I had long ago replaced the wire antenna on the receiver with a length of ultra-flexible wet noodle wire. Now I'll be doing the same with the transmitter.

I sold a few of the Uranium Ring Oscillator Pendants I've made at the faire, and had enough interest from people in them that I've set up an Etsy account. There's nothing much there now, but when I have some more jewelry made I'll be posting it there.