An elementary test

The two best teams that Scrapheap Challenge 2000 has to offer have to battle fire and water if they are to become champions. In one of the most difficult challenges so far, they must build a fireboat to extinguish the flames of a burning waterside building and retrieve a flag, before racing home to victory.

The NERDS, veterans of Mini-sub and Steam Car, face the Brothers in Arms, whose credits include Bridging Machine and Giant Mower, as well as captain Dick's achievement of having competed in all three series so far.

Blinded by science
Both teams get down to it as if they were born to this sort of thing. The Brothers are a little confused when their expert Ian blinds them with science when describing what sorts of pumps they could plump for. Apparently they could choose either centrifugal or positive displacement varieties. Dick translates this into language his brothers will understand: spinning or piston pumps.

They go for the piston pump. The plan is to convert a car engine into a pump powered by a second engine. For propulsion, they will use the pump's output as a water jet, and for a hull, they will chop the top off of a van. This is what the Navy Blues did in Amphibious Vehicle in Series 2 … but with less than spectacular results.

The NERDS decide that centrifugal is the way to go. It is possibly the harder of the two options, but with the potential of being much more powerful – if they can get it right. They need to scavenge oil drums and a four-wheel-drive vehicle. It sounds like the same recipe that the Bodgers used for their winning amphibious vehicle in Series 2 (you know, the one that beat the Navy Blues!). Can the NERDS reprise the Land Rover's winning role for the fireboat challenge? Only time and some brute thought on the part of the team will tell.

Unfazed
Expert Stephen Riley is called over: 'Steve, we need your mass!' shouts Jeff as the NERDS struggle to ballast a quad bike enough to pull a stricken Land Rover. The Brothers in Arms use their expert Ian for more cerebral purposes: he helps them figure out how to join two engines to form the perfect pump. They will need to scavenge a pair of engines and a van. The van roof they settle on does not look in the least bit shipshape – the sky is clearly visible through it. This doesn't faze the soldiers. They make short work of removing it with the reciprocating saws.

For all their computing power – Cathy has taken to referring to Geo as the 'human calculator' – the NERDS still manage to crash the Land Rover into the set on the way in. Maybe it was the discrepancy between UK and US measuring units that had them foxed?

The NERDS' impeller must spin at about 3000rpm so it has to be perfectly balanced or it will tear itself apart. The Brothers in Arms hope to squirt about 100 gallons a minute if everything goes to plan. Fire and rescue training officer Jerry, who is today's judge, points out that this is about one-tenth of the approximately 1,000 gallons a minute achieved by the professionals! Nevertheless he has his money on the Brothers as he reckons their design is simpler and therefore easier to implement. Less specific tolerances are required for the Brothers' machine, but he notes, they will have to unseize their engine if they are to pump even a drop.

Joined at the hip
The NERDS chop the roof off their Landy to shed some weight – crucial if it is to be buoyant. They take it to the weigh-bridge, but to their dismay, it still weighs 1,560 kilograms (3,440lb). Half the day is gone, and the NERDS still need some flotation and to lose more weight off their vehicle. As for the Brothers, they are unable to free the pistons in their old engine and so need a new one.

Geo has a plan: 'Let's abbreviate the whole vehicle!' he exclaims. This is NERD-speak for chopping off the whole back of the car. So they get to work, but still manage to crash into the set on the way out with their surplus rear end.

Luckily for the Brothers, Bobby manages to find an engine that is better than their last one. The new plan is to swap their roles: the new engine becomes their drive mechanism and the old drive engine becomes the pump. This leaves them with one small problem, however. Their new engines aren't a pair at all. They are different sizes and makes, so joining them at the hip won't be easy, but at least they might work!

Ominous sign
Geo has misgivings about the critical tolerances of the NERDS' impeller, which has to rotate at 50 times a second. Cathy comments that, since he isn't given to worrying, this could be an ominous sign.

The Americans have collected 12 oil drums that they intend to weld into water wings for the heavy Land Rover. The Brothers in Arms now have the two engines bolted together, but the whole thing is about 9 feet (2.5 metres) long. With some assistance from Cathy, captain Dick measures their hull and it too is 9ft long. 'Will this be a problem?' asks Cathy. 'No way,' replies Dick in true bodging fashion.

Their real problem is that they have to slow down the pumping engine so that it doesn't create a vacuum instead of pumping water. It has to remain powerful enough to pump a fair distance, though. The Brothers have to get to know their gear ratios in order to cut 1500rpm down to about 300. They also fit non-return valves to stop the pump engine from sending water back the way it came.

Both teams make paddles – just in case. With a few minutes to go, it doesn't look like either team will make it in time. But – you guessed it! – in true Scrapheap style, everything comes together in the last few seconds, including Geo's precious precision centrifugal pump.

Transatlantic tussle
Whether the Scrapheap Challenge trophy will go on a weekend break in the UK or on a fly drive to the US of A is anyone's guess as the teams line up at the start.

The pyrotechnics are set, as are the teams, despite the fact that the Brothers' boat has sprung a leak or two. Their reaction is to laugh it off, aided and abetted by Robert. After all, a bit of water can't stop the army in its tracks, can it?

Turning on the waterworks
The NERDS test their hose, and it's absolutely fabulous, shooting a giant plume of water out across the lake. Geo's work has paid off in spades. The Brothers have a lesser pump but brute force and ignorance in equal measure on board, according to Robert and the judge. It is soon obvious that the NERDS, while creating the super pump, have given little or no thought to manoeuvrability, whereas the Brothers' craft is far lighter and thus easier to paddle into position.

The action heats up
Their heavy vehicle holds the NERDS back once the race is under way, and the Brothers snatch an early lead. However – and incredibly – the NERDS' pump is propelling their craft so well that they have little need to paddle. If the Brothers are able to reach the fire quickly, their weedy pump will be able to extinguish the flames before they really take hold of the timber hut. They do indeed reach the fire first, but it takes them an age to put it out. The NERDS, meanwhile, have caught up and put their fire out in a matter of seconds as their super pump makes short shrift of the conflagration.

The teams flag
The race for the flags is on. The NERDS send Jeff for theirs, but he can't get the box open, which means that he has to drag it to the boat. All the while, the Brothers are catching up, and their brawn comes into its own as Dick races to the smouldering hut. He grabs the flag and powers back to the boat and they're away. The NERDS, stuck in the shallows, surrender their lead to the army team. The lead changes twice more during the race, but it's the British Brothers who turn it on in the home straight to romp home ahead of the Americans.

So the Scrapheap Challenge 2000 trophy stays in Britain, care of the Brothers in Arms. But how will they fare next week against last year's winners, the Megalomaniacs, in the grand final? Tune in to see.

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