Getting stuck in?
Don’t fixate on the fact that you’re stuck. Stop and have a think.
Off-road driving is only possible thanks to 4 wheel drive.
Henry Alexander, Ben Nevis, Model T Ford, 1911. Nutter.
Actually, there was quite a lot of driving in the days before full-time 4 wheel drive, though you’re welcome to recreate it in your daily motor if you want. I’ll pass thanks.
Slipping around on mud is all very well, but when you start driving on tarmac, things get complicated.
The width of a vehicle means that when turning a corner, the outside wheels are always going to travel further than the inside wheels. If you don’t do something about this, the inside wheel will start to spin and you’ll crash. Or the outside wheel will start to spin and you’ll crash. Or the axle will break. And you’ll crash.
To stop all this needless crashing, those clever boffins who made cars turned to the differential. Now for the science bit.
A differential is a particular type of simple planetary gear train that has the property that the angular velocity of its carrier is the average of the angular velocities of its sun and annular gears. This is accomplished by packaging the gear train so it has a fixed carrier train ratio R = -1, which means the gears corresponding to the sun and annular gears are the same size. This can be done by engaging the planet gears of two identical and coaxial epicyclic gear trains to form a spur gear differential. Another approach is to use bevel gears for the sun and annular gears and a bevel gear as the planet, which is known as a bevel gear differential.
Definition courtesy of Wikipedia
What this really means is that you get to go round a corner without crashing; the benefits are obvious.
To put it in a modern context, ie youtube:
Video courtesy of Allegroracing
There are other options; DAF built cars as well as lorries once upon a time. Their engineering was surprising, as was their design. You did away with differentials and replaced them with CVT (Continuous Velocity Transmission) belts. The style baby got thrown out with the technical bathwater though;
The Daf Daffodil. Picture courtesy of Wikipedia.
So if you want to cover all your bases, you need a car with differentials front and back, right?
Of course, you also need to consider the trade-off of differentials, which takes us back to the problem highlighted by those brave Ladies Of The Mud at the top; if you get off the tarmac, you’re going to get stuck.
The solution was obvious. Give up on this car nonsense and stick to horses. Except there was so much money in cars, everyone kind of ignored the horse option.
You can limit the slip of the differential, which comes in handy if you want to go racing and need a little bit of slip in the corners, but more grip on entry and exit.
If things get extreme though, you need to go straight to the locking differential, as the best of both worlds.
A Differential. Exploded.
If you need help getting unstuck, or if you just want to buy Land Rover parts online, visit our website www.mcdonald4x4.co.uk
This article was written by Rupert Astbury.