The wiring within this circuit is planned to be at as low resistance as is possible to ensure the motor is driven with as much current as it requires. (something between 20-30amps)
So, say the regulator is removed, and the 555timer is inserted. My thought for this is everything is off before the triggerswitch is pushed and the timer is reset. Once the trigger is engaged, the motor spins as it should. Once the trigger is released, Q1 begins switching it's state, the mono-stable timer is triggered, and it's initial current flowing from the output pin is spent charging C5. once C5 is nearing 67%, the signal inverter is powered, allowing Q2 to change states (after Q1 has changed it's state), creating a resistance for the already spinning motor until it comes to a hault, at which point the timer will have completed it's cycle.
any thoughts, major errors, comments, suggestions?
This here is a similar circuit to one kchriste had helped me develop in a much earlier thread (when looking at the FET's), but all of the logic has been removed/replaced with the timer.
Schematic is attached below: