Overview: In the second semifinal match, the challenge is to make a vehicle that drives on steam power. One team finds a weird little three-wheeled car and adds a steam engine, their opponents decide to build a dragster. But don't think that these machines will be on the roads anytime soon. A broken drive shaft on one car has to be welded back together mid-race, while the other car has no brakes, and must be thrown into reverse to make it up hills.