Hey, Cammy mentioned Lego! :crazy:
When I used to have the stuff out (Some years back now, now all in storage) the last things I was building were “avoider robots” (One which worked with some novel gearing and just one motor - Still reversed and turned left/right as appropriate) and another RCX based one; as well as working lego engines - The biggest being a 4-cylinder in-line hulk (Cylinders were bricks, pistons were flat plates) that ran off a vacuum cleaner, along with a single cylinder version (~1000rpm) and a dual cylinder, fully valvegear-reversable engine using the conventional lego pneumatic cylinders.
Just thought I'd bring the car and lego topics into line :-D
Hodgkinson.