robots?

I believe you're talking about the Mattel "Big Trak"? My nephews had one of those many years ago. I believe it used tank-type steering; six wheels, and it could either lock one set and pivot using the others, or reverse one side. I've got some surplus gearboxes and motors from the Big Trak that I purchased several years ago. They're kind of neat; they have two motors and gear trains, linked together with a couple of big magnets. If you run both in the same direction, the magnets are strong enough to force both motors to turn at the same speed. If you reverse one of the motors, the magnets alternately repel and attract. This either forces the machine to drive in a straight line, or to pivot about its center, respectively. They also have an optical interrupter on one gear so the CPU can tell how far the motors have turned. It had a hookup to dump the trailer, and I think some other options that never were released. It was a pretty cool toy. A quick web search found this: BigTrak User's Guide: http://www.comp.lancs.ac.uk/computing/courses/year3/358/cwk/brown/BT_UG/ BigTrak Simulator Project: http://www.comp.lancs.ac.uk/computing/courses/year3/358/cwk/corke/ BigTrak Repair Service: http://www.lavalamp.demon.co.uk/bigtrak/bigtrak.htm Bill Richman incolor.inetnebr.com/bill_r (Home of the COSMAC Elf microcomputer simulator!)