Ed Randall - My son Matthew is the model maker, but I dabble here and there!
Focke-Wulf FW190A
Focke-Wulf FW190A, Hasegawa, 1/72nd scale.

This is a joint effort with my son Matthew. He built the kit and I rigged up the hardware and software as described below ...

A small 3v motor from a broken remote control helicopter is wired to one of the motor drive outputs of an Arduino motor drive "shield" (a board that fits on top of an Arduino micro-controller). The output switches between ON and OFF at a selectable frequency (we use 8khz), with the ratio of ON:OFF adjustable in steps between 0 and 255 - so 0 is off (motor stop) and 255 is on all the time (the motor would run flat out). We start off very slowly, actually alternating between 0 and some low number, with short delays in between, to simulate cranking. The engine "catches" by removing the short "off" delays altogether, now it's at idle. It then slowly increases speed up to "200" which is our maximum power, 255 is sufficient to pull the model along the table and in any case we don't want the motor to burn out - the Arduino is driving it with 5v, the original helicopter had a 3.7v lithium battery. After a few seconds the sequence "throttles back" to idle then stops for a while, before repeating.
Focke-Wulf FW190A