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TEXT ONLY | CREDITS | APPLY FOR SCRAPHEAP 2005 | |||||||||||||
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| DON'T MISS SCRAPHEAP ON CHANNEL 4 EVERY SUNDAY, 6.30PM |  |
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Chariots | |
Result | |
Anoraks' diary | |
Hogs' diary | |
Science | |
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All challenges | |
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Science
 General science The designs Pros and cons
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General science Background The chariot was the earliest and simplest type of horse-drawn carriage and is primarily thought of as used for war and sports rather than goods hauling. Chariots are probably best remembered from the climatic race around the spectacular Circus Maximus in the film Ben Hur. Chariots were dangerous to drive and positively suicidal to manoeuvre at speed so it's a fitting theme for our Scrapheap Challenge series final. How to drive a chariot Some chariots had very basic suspension in the form of a leather grid which the driver stood on – but the thin wheels and need to turn very sharply meant the chariots could often tip on one wheel and even flip over. To counter this, the driver would lean, much like a modern motorcycle rider, to keep the vehicle's balance. Our teams had to be particularly brave to shift their weight around their unstable chariots. The challenge The challenge was to build a motorised chariot. The chariot had to be at least 2.5m away from the iron horses (axle to axle) and controlled remotely. The teams could use any appropriate combination of powerplant and control system but the machine had to able to carry all four team members, be hitched and unhitched quickly and allow the team to attack targets. |
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The designs Hairy Hogs With their love of all things Harley, the Hogs were happy to use a powerful motorcycle as their power unit. They ditched the front wheel and used burley Conn to yank the bike round on the pivot point of the back wheel. This was connected to the chariot trailer, which was made up of an old axle, a box and some sheet steel. What was not usual though was the quality of the finish, it really was worth close inspection. The key to the design was to find the machine's centre of gravity, to ensure the motorcycle was correctly balanced. If the Hogs couldn't do this, the motorcycle could collapse or be uncontrollable. The steering mechanism used a set of handlebars on the chariot trailer which could be quickly coupled to the bike. The bike's brake cables were run to a nifty pedal on the floor of the trailer and the bike's gears were engaged through a cable which ran to an old automatic shifter mounted on the trailer. The Anoraks The team planned to cut and shut a rare car and have a four-wheeled 'horse'. They scavenged a DAF Daffodil (how the DAF club would weep) and (a first on the heap) put a variomatic gearbox into action. This crazy gearbox uses a series of cones and rubber bands to allow the engine to run at optimum speed at any point in the range. Continuously variable transmission (CVT) is, in theory, better than fixed ratio transmission and more efficient than using torque converters which take a lot of power from the engine. Ford, Nissan and Honda have all brought out CVT cars but they are still not as popular as standard manual or traditional automatic transmissions. The DAFs never really took off – the rubber belt drives slipped off and they got a reputation for unreliability. Despite this, the Dutch Army used a truck fitted with a variomatic gearbox and the Daffodil was even exported to the USA. Once the team had cut and shut the DAF, having got as much broken glass into the rubber gearbox as humanly possible, the chariot was then connected to the 'horse' with a conventional ball and hitch. This left plenty of opportunity to jack-knife on the course. The Anoraks then spent the rest of the day arguing about the control method. They eventually settled on using the world's longest steering column built out of a CV (constant velocity) joint from a scrap car with UJs (universal joints) along the shaft to absorb the various forces which would have snapped a rigid system. The gear changer was put in to place on the bar surrounding the chariot with a Heath Robinson system of wires running to the box. The engine speed was controlled with a wire running to the engine – just as it would on a boat. |
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Pros and cons Hairy Hogs Pros
The Anoraks Pros
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