In this, the first semi-final, it's the NERDS (who defeated the dipsticks) versus the Beach Boys (who defeated Filth and the Chaos Crew) in a steamy challenge. The teams must build a four-passenger steam-powered car. They'll have to race it three times around a 700yard course, making one pit stop for coal and water. The winner advances to the finals.

Bothe teams need the same parts. A boiler, steam engine and a car chassis to stack everything (and everyone) onto. A steam powered vehicle works by boiling water (in a boiler) and producing steam. The steam flows through pipes to the steam engine. The steam enters the top of a chamber, driving a piston down then a valve opens letting steam into the bottom of the chamber, driving the piston up. This up and down motion is transferred to a fly wheel which gets connected to the drive system. The hotter the fire, the more steam you can produce, the faster you can go. The limit, however, is about 1/4th that of a conventional combustion engine.
 
 
 

The expert helping the Beach Boys is Adrian Grimmett	For the NERDS, expert Richard Gibbon
The essences of a steam system.  From r to l: water tank, boiler and engine	Take a little time to enjoy the view
The Beach Boys have found a large steam engine...	...and the right sized, massive, boiler to go with it.
Meanwhile, the NERDS have found the small engine...	...and the tiny boiler to go with it.
See, the steam drives the piston up&down to drive the wheel and valve	"The ugliest car we've ever had on the scrapheap"
I love it when they rip the roofs off of junked cars and vans	The judge is Allan McEwan
What on earth is that for?	When you're done rotating the tires, could you look at the brakes?