Getting into the rough stuff is one of my hobbies, off-roading I mean, and here in Australia there's plenty of opportunity to do so. It's the remote places I like best, the ones which allow me to leave society behind.
Off-roading is something you can't do without a suitable vehicle though; A four wheel drive is required, and the ability to use one safely and effectively also. There's many good examples rolling off production lines around the world, really capable ones, however none of them are completely suitable for off-road work without additional equipment.
I wrote a post a few days ago in which I said I'll talk about some of the systems and accessories I added to a four wheel drive a while back. It was titled Beyond the blacktop. However before I get into those posts maybe some perspective is required; A little understanding about what a four wheel drive actually is, in the context I refer to.
When I say four wheel drive I'm talking about a vehicle with a dual-range gearbox, that drives all wheels, and has the ground clearance, approach, ramp-over and departure angles to tackle rough terrain, steep inclines, declines, creeks and rivers, deeply rutted tracks, sand, rocks, snow and all the other types of terrain getting off the beaten track can throw up. Not a passenger car with All-wheel drive (AWD).
I'll explain how a 4x4 works in basic terms, but first let me cover off on a 2 wheel drive vehicle, in case you don't know. Please keep in mind I'm not a mechanic or technician as they are called now, so it'll be basic.
2x4
Power from the engine goes to a clutch which transmits it to the gearbox, driveshaft, the differential and via the axles to the wheels which turn and move the car. Simple.
Only driving two wheels, the front set, or rear for that matter, doesn't allow for maximum traction and drive, which becomes an issue when in an off-road situation. Slippery terrain underneath the drive wheels will bring the car to a rapid halt for instance. This is where the 4x4 comes into play.
4x4
- Power transmits from the engine through to the clutch and gearbox.
- The gearbox to the transfer-case, in a part time 4x4, and the central differential in a constant 4x4 like my Toyota Landcruiser 200 Series. (A constant four wheel drive vehicle.)
In a part time 4x4
- When 4x4 is selected the transfer-case transmits power to the front and rear differentials then the axles and four wheels. When 4x4 is not selected only the rear wheels drive so it's a 2x4 vehicle at that point.
In a full-time, (constant), 4x4
- Power is constantly sent to both the front, and rear, differentials. The power is rarely, if ever evenly distributed.
- Engaging the centre-differential divides the power equally providing the same amount of drive to all four wheels.
- Generally the transfer-case has two sets of gear ratios in part time and full time 4x4's called high and low range. This changes the power output ratio and speed increasing torque to the drive-wheels when in low range.
- Being able to control that power, the torque, permits for greater drivability, and control, over various terrains.
- Essentially being in low range first gear will increase torque by about 10 to 15 times, and reduce speed by 10 to 15 times allowing for better control and traction for the driver to work with.
A few 4x4 vehicle advantages
- Improved traction in a wider variety of terrains and driving conditions.
- Increased ground clearance allows the 4x4 to avoid ground obstructions often present in extreme conditions.
- Approach angle, ramp-over and departure angle means a 4x4 can enter and exit steep inclines and declines.
- Purpose-designed off-road tyres work to gain additional traction in various terrains and are designed for different purposes. Mud tyres are designed to bite down deep into the soft surface and are designed to shed mud through centrifugal force and clever tread-pattern design for instance. Off-road tyres are also designed to run in a very low pressure condition which is done to increase traction through a larger footprint on the ground surface, and also to mitigate punctures.
- Good 4x4's are a body siting on a steel chassis which improves rigidity, strength and control, plus have the ability to carry greater loads.
There are many concepts around a 4x4, but I wanted to simply, and in a non-technical manner, explain the basic principle of how four wheel drive works. Knowing how these systems work, and their failings, helps a driver operate more safely and allows them to determine whether their vehicle is suitable to tackle a particular obstacle or not. A skill in itself.
Even a four wheel drive vehicle can be brought to a halt though, and additional drive-train and protection equipment is required, like differential lockers, under-vehicle protection, winches, driving lights, auxiliary power systems, bull-bars, extended-range fuel tanks and various load-options. It's a few of these I'll introduce as time goes.
A well-equipped 4x4, when operated by a trained or skilled driver, can go virtually anywhere, certainly anywhere a person would dare to drive. A 4x4 vehicle right off the showroom floor will generally only be suitable for light off-road use, however will never be able to carry its occupants and general load into rougher terrain without additional equipment.
I have been off-roading for over 25 years and have built up many vehicles, that is to say, added essential and desired off-road equipment to improve the vehicles' ability from the factory specification; It's some of these things I'll cover in future posts. I will introduce a few more concepts and elements around vehicle-equipment and talk about some of the equipment I've added to my own vehicles, and why.
Thanks for reading.
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Note: The images in this post are my own, both lego 4x4 vehicles I built a little while ago.