Chief Delphi - Bumper Bot Schematics

Ara,
A real simple solution it to have a simple monostable multivibrator. It can be built with two transistors a few resistor and a capacitor. The object is that the circuit remains in one state until it is triggered, i.e. one transistor is high and one is low. Then when a trigger arrives, the transistors reverse, i.e. the first transistor goes low and the second goes high. The length of time this state remains is dependent on the capacitor and resistor in the timing circuit. Use one of the transistors to drive a DPDT relay. The relay is wired so that in one state it feeds voltage to a motor in a normal manner and in the other state it reverses the voltage to one motor. Use a switch on the front of the car that will close when the car bumps into something. Wire the switch as the trigger, and calculate the length of time a wheel motor needs to reverse to get 45 degrees of rotation. Use that calculation in determining the timing components.

A 555 timer can be wired as a monostable and is almost as simple and cheap as a two transistor monostable MV.