Power Rower

This week, it's the return of the Anoraks and Maximus. Their challenge is to build power-rowers. That's rowing as in sculling, in-out-ing, propulsion across the water.

Maximus are working with Jim Bond, a mechanical sculptor who specialises in realistic actions. They're using a slow engine, and then will attach a wheel to the engine, put a rod on that wheel, and use an off-centre pivot to generate the rowing action.

Rob Austin is a marine engineer, and he's working with the Anoraks. Their plan is to attach the oars to the wheels of a car engine, and then use row-locks to provide the action.

First, though, the teams have to find their hull. If there's no hull, then the contraptions are never going to appear on "Is It Buoyant?" and that would be a rather large failure. The Anoraks dive on a large hull, but it's not what captain Lyndon wants. He prefers ... a conveyor belt. Maximus have found a couple of pedaloes, and a cement mixer. The mixer will provide a slow turning engine, which will help with the slow turning required for a rowing machine - racing rowers average 30 to 40 strokes per minute.

For the Anoraks, the small boat hull they found is really too small, and find a Morris Minor car. Not for use as a hull, but it's good for an engine. Well, it'll do as an engine - even in lowest gear, it'll turn far too quickly, so a  chain-and-sprocket device will slow it down. Maximus have their engine at the right speed, but first need to chop off the cement mixer it came with.

A stroke of luck for the Anoraks, the Moggie minor axles are just the right length to fit across their conveyor belt frame. Which is a frame, and doesn't exactly have a solid base, so may not float. And a stroke of luck for Maximus, they've quite literally stumbled across a real live yacht hull, so out go the pedaloes and in comes a proper ship-shape ship in the shape of a ship. They can also use the rim of the mixer's drum to attach the oar arm.

Now, the Anoraks have made a rather large decision, to cut down their large conveyor belt into not such a large conveyor belt, now about the size of a skip. This may give them some trouble when they make the water. They have an arrangement of cams, pulleys, row-locks, and telescoping oars that should ensure everything works. So long as it's buoyant, and the patching they've done on the hull keeps the water out.

The question of test day: are the craft buoyant? Maximus's boat clearly is, the Anoraks may need to bail out as they go along. The rule is simple: both teams will make three trips around the Scrapheap out-and-back course, fastest time overall wins.

The Anoraks go first, and they go badly off course before really getting under way. Maximus start their engine, cast off, and proceed at a stately pace of almost no miles a year, as their blades aren't quite making it.

Second time around the Anoracks lose an oar, then a couple more, and come to a grinding halt. "We've ripped our row-locks off," say the team, who have to send for the Scrapheap Divers to find their oars. On their second go, Maximus proceed at the stately pace of exactly no miles a year. They need more engine.

Third time around, the Anoraks take it slowly, slowly, splash a lot, but might have trouble at the turning point. They do actually make it round, and that puts the pressure on Maximus. The Bath side have completely relocated their oars, and are moving, just very slowly. They do reach the finish line somewhere around sunset. To no real surprise, the Anoraks were quicker, and progress to the semis.