I hope you don't mind, but my .jpg is a little bigger than the maximum (53K vs 50K). My buddy, who scanned it for me, had trouble cutting it down any farther, I started building HARVEY (which, by the way, stands for "Halfway Autonomous Robotic Vehicle") about a year ago and finished him in about 3 months. He has three wheels and utilizes differential steering. The two 4" foam drive wheels are located at the rear with just a single caster in the front. The foam wheels, originally made for an RC Aircraft are great. With the high gear ratio and these "grippy" tires, HARVEY can pull something in excess of 40 lbs (!). HARVEY's frame was bolted together from aluminum bar and angle with overall dimensions of about 18" long x 13" wide x 18" high. The running weight is about 12 lbs. Power is provided by two 12V, 4A-h batteries, not because that much power is required but because the direction switching relays and DC Gearhead motors were rated for 24V and the batteries were left over from another project. While most people would avoid using relays for reversing the motor polarity, I used them for a very good technical reason...I already had them! Front and side-mounted plexiglass bumpers have integral microswitches to sense contact with obstructions. The plexiglass was selected over aluminum for these in deference to the new living room furniture. HARVEY's intelligence is provided by a 8051 with 16KB of RAM and two serial ports. He has an 8 bit input an 8 bit output port, a 1X40 LCD display and an operator keypad for future expansion. All code was done in assembly language simply because that is the only development tool that I happen to have. HARVEY currently spends most of his operational time skittling about the floor showing off his SPO256 based speech synthesizer. He selects and utters random comments from lists of predeveloped phrases and always comments (either positively or negatively) about every encounter with an obstruction. HARVEY was constructed primarily of surplus parts from my junk box...I've got a *really big* junk box. In terms of actual cash money expended, I would guess that I have about $25 invested. The drive motors are Pittman DC gearmotors that probably cost a fortune new, but I found them surplus (but unused) for $0.50 each (2 for a buck!) at a hamfest. HARVEY is a work in progress. Future planned enhancements include, in no particular order: 1. line-following, 2. internal navigation using some sort of beacons, 3. RF link between HARVEY and his development PC, 4. Sonar location of obstacles, 5. A "drive-in" battery charging station, 6. Maze navigation. HARVEY III, an all-terrain outdoor robot, is currently under consideration.