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| Low ground clearance could be a problem for some |
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| 'Pump up the volume' the GGs uprate their suspension |
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| Oooff you could have somebody's eye out with that steel-toothed mud mangler! |
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| Chaos' ingenious two engine four-wheel drive |
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| 4x4 denied. Boat Buoys chassis offers a web of cross struts |
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| Barleys reap the rewards of a top 4x4 conversion |
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Science
 Off-road driving
Diesel, petrol and water
A stable grip
4x4 transfer
Off-road driving
As you can imagine, off-road driving with its axle-twisters, ruts, water and mud requires a different type of skill from road driving. A serious off-road driver will walk the course to try and 'read' the problems ahead, examining the landscape for ideal routes and noting any dangers. A typical method involves driving very slowly over difficult terrain, letting the vehicle pull itself gradually over obstacles in low ratio gears while the driver steers with their thumbs outside the steering wheel so they don't damage their hands from a serious kick-back after an impact. The theory is that the vehicle needs to work with the landscape and be driven appropriately in order to traverse it comfortably.
That's fine for rumbling along, but when you have to race against the clock, you need power and grip. Our battling teams aimed for the thrashing style (apart from the outstanding, paced drive by the Barley Pickers) and trusted to speed and bravado to whisk them to the end of the course.
Diesel, petrol and water
Diesel engines work on compression to ignite their fuel/air mixture. This means that, apart from electrically-powering some heater plugs (to gain optimum firing temperature) and a starter motor to turn the engine over, the diesel engine will perform perfectly in wet conditions once running.
On the other hand, the more powerful petrol engines require an electrically-generated spark, fired in perfect time into each cylinder to ignite the fuel/air mixture. This requires either a distributor or electronic ignition system to be wired to the spark plugs. As most people who have tried to start their car on a wet and cold winter's morning will know, the slightest hint of damp can interfere with an efficient spark. A large pool of muddy water can really throw a spanner in the works.
A stable grip
A well-balanced vehicle is a huge benefit off-road. The Barley Pickers even filled their tyres with water to add stability, but the best adaptation for this show has to be the outrigger wheels on the Megalomaniacs machine. Nosher and the lads attached two halves of an axle to the rear sides of their manic three wheeler. These were angled off the ground and had wheels attached. If the trike started to roll, the outriggers would stabilise the whole machine. They were also great for upping the confidence of the driver of the three-wheeled whippet.
The Megs outrageous steel wheels may have appeared slightly bizarre, but the theory was good – it's all a matter of grip. Many vehicles working on difficult terrain don't use conventional tyres. Some forestry machines are equipped with massive outsized wheels with huge spade-like treads to enable them to drive through forest and mountain extremes. Some earthmovers are shod with wide, steel rims covered in spikes to enable them to move over the soft ground like that found on landfill sites, and cars that race on ice use rubber tyres encrusted with needle-like metal studs.
4x4 transfer
With all this talk of 4x4 and transfers, you'd be forgiven for thinking you'd overheard a football commentary. For those without a solid grounding in Series III Land Rover tinkering, here's the low-down: 4x4 is the same thing as four-wheel drive and that's exactly what it does. Most cars on the road have front or rear-wheel drive, which means either the front wheels are pulling or the rear wheels are pushing the car along. Whichever configuration, only two wheels are actually driving the car. With a four-wheel drive, both axles are powered and all four wheels are driving. If one set loses grip and spins, the other set will continue to drive. This is great for off-roading, but a bit of a waste if you're just driving the kids to school.
A transfer box is essentially a component in the line of transmission which takes power from the main gearbox and transfers it equally via two prop shafts to each axle. This enables all four wheels to be driven at once. Early off-road vehicles provided the option to select between two or four-wheel drive, but most new four-wheel drive vehicles on the road today have four-wheel drive engaged permanently.
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