Scrapheap Challenge Season 3, Episode 7: Giant Mower

Demolition

The teams each have to build a machine capable of demolishing a set of industrial outbuildings at an old power station in Norwich. Sadly, no explosives are allowed, but they manage all the same. The Beach Boys, a group of twentysomething surfers, decide on a straightforward, human-powered battering ram, and do something no other team has ever managed — they finish building before time is up. The Chaos Crew keeps the Junkyard Wars tradition alive, with a great, big, nasty-looking machine. They build a big hydraulic claw that can rip down walls.

Aerial Bomber

Teams must build a nonpiloted flying vehicle that can accurately drop paint bombs on a target on the ground. Both teams need to go with radio-controlled vehicles, but that's where the similarities end. Three Revs a Minute are three trainee ministers (Get it? Revs?) who decide to build a working model airplane. Their opponents, The Mothers of Invention, go for a big blimp made of Mylar. The challenge begins at 3 a.m., since both teams want to avoid any wind.

Underwater Chariot

In this challenge, The N.E.R.D.S. (New England Rubbish Deconstruction Society) — the first American team to compete in the show — take on The Dipsticks, three undersea-oil-drilling platform engineers. The task of the day turns out to be a minisubmarine, which can pull two scuba-clad divers around an underwater obstacle course. The Dipsticks create an elaborate vehicle to ride in. The N.E.R.D.S. stick to their KISS (Keep It Simple Stupid) philosophy and build a James-Bond-style diver tow, a submersible engine and a propeller, which pulls the divers behind it.

Windmill

The Techno-Teachers go up against The Manic Mechanics to see who can harness the forces of Mother Nature and build a windmill to power a machine crucial to life as we know it — a coffee grinder! One team constructs a conventional fan-bladed windmill, while their opponents go for a vertical-axis Savonious rotor. Quick on-screen sketches reveal which is best for which wind conditions. But a half-hour before the competition, the weather services release a gale warning, forcing one team to clip the blades off their windmill for fear of having them ripped off. But at competition time, the wind doesn't get over 2 miles per hour.

Missile Launcher

This time, a team called Filth goes up against the winner of Demolition (Chaos Crew or Beach Boys) to design and build a machine that can throw a rugby football as far as possible using only their own muscle power, so no motors allowed. They have to create something that can store muscle power gradually, then release it in a controlled burst. Filth decides to ignore their expert and creates a huge cross-bow-type machine. The other team decides to pump up an air cannon to shoot the ball. And while the winner can't be revealed, one team captain manages to throw his rugby ball farther than his machine could.

Bridging Machines

Brothers in Arms go up against the winner of Bomber (3 Revs a Minute or Mothers of Invention) in a challenge to build a vehicle that can carry all four members across a 30-foot ravine. The vehicle must also be capable of both deploying a bridge and retrieving it once the team is across. The Brothers go for a van-based bridger, while their opponents use bikes.

Steam-Powered Car

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.

Final: Fireboat

In the championship match, the two surviving teams see who can build a boat that will go across a lake and put out a fire in a burning building. One team builds a Land-Rover-based fireboat with an amazing pump, but their boat is less maneuverable than they'd like. The other team's pump is not as strong, and their boat keeps taking on water.

Grand Final: Dragster

Drag racing. Nothing gets a Junkyard Warrior's blood stirring like sheer speed. In this special match-up, the Season 3 champs go up against last year's winner to see who can go as fast as possible while staying on the ground. The champs go for a classic dragster car, but when their gearbox blows up, they have to flip the back axle upside down, making reverse gear push the car forward. Last year's winners go for a trike, which increases the possible speed, but takes much more precision to build.

Christmas Special: Car Crusher