The mechanical design and fabrication was largely dictated by the resources available to me at the time I began this project. The main structure is made of three flat, circular levels, supported by steel threaded rod beams. The levels are made out of sheet styrene, which was chosen because it is easy to cut and relatively strong.
The cylindrical bump skirt is constructed out of aluminum sheet stock, and is supported from the second level of RYOBOT by 18-gauge wire. When complete, RYOBOT's extrernal appearance should be essentially that of a festive little trash can on wheels.
The wheels of RYOBOT are connected directly to the output shafts of my gearmotors, since I do not expect RYOBOT to carry much weight. The gearmotors are surplus which I got through Edmund Scientific. They are bolted to an aluminum bracket which is in turn bolted to the first level of the robot. The output shaft is connected via a shaft coupler (not shown in the drawings) to a MECCANO shaft which mates with the MECCANO wheel. The shaft couplers were far and away the most difficult part to source for this design, and finding them delayed the construction for a long time. The drive assembly on the first level is the bulk of RYOBOT's weight.
The Rug Warrior board is the brain of RYOBOT. It is a commercially available circuit board, available from various vendors in various forms:
See a full description and design drawings at http://world.std.com/~pbrennan/ryobot.html