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The Build
The Extinguishers
The firefighters got straight down to business and decided on a mountain board-style design – the wheels would be outside the board, rather than directly underneath as on a conventional skateboard.
To steer, they'd have to lean left or right, compressing car springs that would push on the axle. The boys figured that a motorbike would be the best bet to push them along. The plan was to cut off most of the bike, leaving just the powered wheel as one of their skateboard back wheels.
The low 'drop deck' design, while stable, reduced leverage and made the design of the trucks critical – they needed the springs to compress quickly and then return to centre as fast as possible.
Scavengers Bob and Pete came up trumps with a 125cc scooter. It proved to be a decent runner and made Lenny happy by turning up a supply of decent checker plate (Lenny was adamant the board would look the part and not 'scrappy').
An old Escort was the donor for one of the axles. It was sufficiently lightweight but a pain to gas axe off – on one occasion Bob nearly lost his eyebrows as the fluid in the shockers flared out of control.
While Bob and Pete enjoyed playing with fire, Lenny and Captain Simon had been busy completing the powered rear axle and were itching for springs for the steering mechanism.
An old Vauxhall seemed a good idea and the scavengers began to take off the springs, but it proved a nightmare job. Minutes turned into hours and the lead they had built up began to slip away. Shame it took them nearly two hours to realise they could just use the springs off the axles they had already gas axed! Doh!
With the springs in the build bay the boys had finally gathered all the parts they needed and the spring trucks took shape fast. When the board was mounted on the trucks they had an impromptu test and sure enough the compression on the springs pushed the axle round.
Not only did the board look perfect but it seemed to work perfectly as well. The Extinguishers were as surprised as the crew to find themselves finished ahead of time with a good chance of test success.
The Steaming Scots
The Steaming Scots decided to go for a classic 70s-style skateboard, with the wheels mounted underneath the board and with weight transfer turning the axle with a standard king pin design. They wanted good torque so an electric motor seemed the best bet to push them down the course.
Unlike the firemen next door, the Scots' scavenge took a long time to pick up steam, with Laura and Hamster discounting one electric motor after another.
Back in the build bay, expert Tom and Captain George were left kicking their heels until Laura discovered an old street cleaner. With the axle, motor and controller in hand it looked like their build had turned the corner. Everything else they needed was super simple – like metal, old tyres and axles. Laura got straight to work as master welder.
But while the motor looked powerful there was a lot of doubt that it could turn normal-sized car wheels so Hamish was sent back onto the 'heap, returning with dinky forklift wheels.
To get the tilt of the board under control, the Steaming Scots came up with the simple idea of using car tyres on either side of the pivoting board. They would compress down and rebound as they leant the other way. They could control how fast the board tilted by raising or lowering the amount of air in the tyres.
Once the trucks were mounted on the central rib it was time to test the critical kingpin. For a skateboard truck to work effectively the pivot pin must be able to rotate to allow the axle to turn when weight is distributed around the board.
Sadly for the Scots they had welded the pivot pin solid and when they stood on the edge of the board the pin was unable to rotate and broke free with a sickening crunch.
It wasn't looking good. No-one could figure out a simple way for it to work, until Laura had an epiphany. If they sleeved the pin in a section of pipe it would rotate as the board tilted, pushing on the axles; so they would turn, while still being secure.
With the crux point passed they pressed on, making sure the electric motor controls would work and ensuring they had a grab rail surrounding the board. When time was up, the board's steering looked weak, but the electric drive looked OK. How would they fare on the slalom course?
