MicroBots
Here are some pictures of my first MicroBot. Her name is Lishka, which means Fox in Czech. It was created out of boredom and fulfills the need for something to amuse my cats when I am too lazy to do so myself. The two motors are from a Wang DAT (Digital Audio Tape) drive. The racing slicks (tires) are rubber firewall grommets that were originally too large in the I.D., but Mr. Hot Gluegun fixed that! The front "wheel" is simply a machine screw which really does nothing else but keep her nose off the floor. Steering can only be accomplished by, 1. ramming and deflection, 2. varying the speed of the motors. I concluded that a single bearing point in the front reduced friction as well as keeping the front end from looking "two screwy". I originally wanted to use wheels up front, but after considering the complexities of the steering geometry and mechanisim, my design group (8 cats and a Magic 8-Ball) came back and told me I was screwed! Yeah, that's it! After I bought a round for them (Lil' Bits 'O Ham) I installed the monopod. I plan to machine a threaded Teflon rod, rounded on one end to replace the screw. I'll address the other parts with the pictures.
Anatomy Of A Bot
The colors indicate the organs of interest

BLUE- This is the "brain", all 8 neurons of it. Through a series of DIP switches, Lishka can be "programmed".

YELLOW- Speed control. A Bourns 10-turn 10K pot. The negative return from the motors is run through it. I chose to do it this way because Ineeded to control the voltage, therefore speed of the motors without dropping the control voltage to the relay coils.

GREEN- A JUMBO LED so I won't forget I left the power on! Also serves to attract the kitties (like motion and sound isn't enough!).

RED- These are Teledyne M39016 DPDT DIP relays. They work great! The DIP package makes them a breeze to place and has the same footprint as a 8pin IC. They're rated at 12vdc but they'll go as low as 7.5v to actuate and hang-on til ~2v.

PURPLE- The electrochemical fuel cell (9volt battery).

ORANGE- The motors. Lil imported 8-12vdc @ ~25 quadrillion RPM. Got 'em from an old DAT deck. You should be able to find these in any old tape deck, disk drives, CD-ROM drives, etc. Get creative, think like a tiny motor.
A top view of Lishka.
Here you see the top of the relays with schematics painted on at the factory. In addition, you can see the brain, throttle pot, LED, and modular connectors for the motors. I installed the modular connectors as a way to be able to remove the powertrain from the motherboard without desoldering. They were on the PCB from the DAT deck. Her motion can be pre-set through the brain DIPswitches. Switch 1 puts power to the +9v bus. Switch 2 sends power to the relays which goes through the default contacts to the motors and results in forward motion. Switch 3 reverses the righthand motor resulting in a CW spin. Switch 4 reverses the lefthand motor resulting in a CCW spin. When switches 3&4 are switched on, Lishka will go full tilt reverse.
Right side of Lishka.
Roll over! Good bot!
A close-up of her wiring. I wired the relays opposite of each other so the motors would spin in opposing directions (cause they're mounted back to back, this works great).
The resistor is a current limiting resistor for the LED. The globs at the top are hot glue to attach the nerf bar that protrudes from the front.
A view of the powertrain. The "frame" or motherboard is made from perfboard, available at Radio Shack's everywhere. The powertrain strip is hot glued to the underside of the motherboard. Perfboard and hot glue go together like PB+J. The holes allow glue to flow through and create "fingers" that provide far more shear strength to the joint than if it were two flats glued together. Think of it as almost nailing the perf together. The hot glue itself dampens vibration as well.
Close up of one of the "tires".
Lishka going full tilt in a spectacle reminiscent of the Whirling Dervishes. The cats are very curious when she spins.
Rear view.