Dam Busters

Week two: The Dam Busters. This week's teams are trying to emulate Barnes Wallace's famed bouncing bombs. The trick he used in the 1940s was to spin the bombs as they were released, like skimming stones on the water.

Maximus are Paul McGarry, William Trickett, and Dennis Mapp, rickshaw riders from Bath, playing in dark blue, and working with Mike Bretton. The basic plan is to have a very large clay pigeon trap - a giant spring, and an arm that flies up to release their charge.

The Irn Cru are Ben craven, Robin Pollok, and Drew Irvine, from the Glasgow science centre, they're playing in sky blue. Mike Groves is their expert, and his plan is to use a motor to propel a trolley forward, stop it suddenly, and rotate the device over the lake.

Three hours into the build, Maximus have their platform, and eventually find a large orange spring. They now need to get to work and construct. The Irn Cru have turned a 2CV into a very large chassis, but they still need to attach a cable round a pulley to their bomb trolley, drive away, and have the trolley stop very quickly. They stop and think what has a big automatic engine. They've found a couple of cars, but neither of them work.

Lisa and Robert are worried that Maximus are so far ahead of time, they might finish before lunch. Less than five hours in, they're already making their bombs - or discuses, to be exact - from the ends of old beer kegs. The opposition's 2CV has caught afire, and is good for not all that much. On the upside, they've finally got a Jaguar motor running - but it's stuck in the mud, and it's mid-afternoon before the team can begin. Maximus reckon that they may need to strengthen their arm, but they've got plenty of time.

By the time darkness falls, Irn Cru have adapted the 2CV as their launch platform, and have fitted a third wheel to give their bomb some backspin. They're working on a winch, and hope for some rails - or motorway crash barriers - to keep the trolley on target. Or they might use an anchor behind their 2CV. Maximus's large release arm will pack the punch of a charging rhino, and they're working on a release mechanism so they can keep a very safe distance. Lisa and her sniggering sidekick reckon that the only thing that can go wrong is the arm. Or the complex electronic release mechanism.

Final touches: the Irn Cru decide to use a rope attached to a very heavy weight to stop their trolley. Maximus need some guide rails, and actually manage to finish before time expires. Thanks to a little help from the rest of the crew,
the Cru's machine is just about ready for prime-time. Well, maybe.

The dam consists of some beer kegs stacked up 35m away from the shore. It's three points for each bounce, ten points for each keg knocked off, but nothing if the bomb doesn't bounce. Four charges each.

Irn Cru's first charge doesn't quite work - the cable that stopped the trolley wasn't strong enough, and the trolley followed the bomb into the drink. Maximus's first attempt is in roughly the right direction, but takes out some
collateral damage in the form of lakeside trees. Two bounces each tie the scores at 6-6.

Maximus's second shot almost reaches the dam, but doesn't quite have the distance. Three bounces. Their bearing is going, and they're relying on a bit of scaffold pole to stop the thing from going off too soon. Shot three does
reach the dam, but just fails to dislodge anything; only one bounce doesn't help. The steward accidentally sets the trap off, and takes out two kegs. Shot four bounces twice, but goes just wide. Their final total is 24.

Irn Cru's second shot uses the guide rails, but any precision is foiled when they forget to attach the brake cable, and the trolley ends up in the trees. Shot three does have the legs, but the Jag's axle breaks, the trolley is lost
in the drink, and the whole creation is in no shape to launch a fourth time. Maximus takes the win, 24-21.