I biuld the chassis kit and added all my own eletronics to get it to work with one sonar ranger when it rived but there are two problems: 1. the drain on the battery with my stamp IIsx, 2 speed controlers, ultrasonic ranger, and 4! motors will only let the robot run for aproxemently five minits on one battery (racing pack: 7.2V, 1400mA). This is not ideal at all for may experiments as I need to constantly change the programming, test it and the battery just dose not last. I will instead biuld a smaller chassis with 2 mod. servos for now. 2.This is not so mutch a problem in the long run but an advantage, but for now it is a newsence. The ultrasonis rangers can only see solid object directly in front of them, so one faceing forward will not see the the robot's side is running into or scraping the wall. But when I get some more money I'll buy two more rangers for left and right and my robot will see everything.