Loss of traction, skidding...

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discool said:
On a D1 with one wheel spinning then you will be going no'where unless diff-lock is engaged and the hopefully a wheel on the other axel is not spinning as well, if it is then you are still going no'where.
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Yep, something I've been trying to explain to all the people that say to me... 'Oh you're alright in this weather, you've got a 4x4' .

Only solution to this from what I understand are those aftermarket axle lockers (ARB and the like). Mate's got one on the rear of his 90 (for when he finds it a bit tough pulling on his drive in the Newbury area :D )
 
bluea35 said:
Sorry, I meant the bit about locking diffs to apply to both statements, but I still think you are wrong. A 4x2 only has one driven wheel;if you have a locking diff ( or indeed a limited slip diff)you will then get 2 wheels powered on the one axle.
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Don't agree!

4 x 2 has one driving axle, with two wheels.

If there is an ordinary diff, BOTH wheels MUST ALWAYS apply power equally, and so if ONE wheel slips, NEITHER wheel drives.

If there is a locking or limited slip diff, if ONE wheel slips, the diff will lock up, thus maintaining drive to the ONE wheel with some grip.

CharlesY
 
smarty1972 said:
Me too, isn't that where the term 4x4 comes from? Whether a wheel on a driven axle can spin independently or not doesn't matter.
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Yes.
Four by Four
Four wheels, and drive applied to each of them.

Usually there are three differentials, one in each axle and one in the middle between the axles. If these are plain diffs (not locking or limited slip) then each wheel gets exactly the same drive force applied to it as the other three, and if ONE wheel slips, ALL drive goes down the pan on all four wheels immediately.

The wheels are MUCH LESS likely to slip in the first place because the total driving force is shared equally among FOUR wheels, not just two, and this is like magic on the slippy stuff.

If ONE wheel slips, drive from BOTH axles ceases. This is why we can lock our centre diffs, and when the centre diff is locked and a wheel on one axle slips, the OTHER axle tries to maintain drive. As we all know, on the rough stuff, and at slow speeds, locking the centre diff can make a HUGE improvement in traction.

Gaylanders do it another way.

CharlesY
 
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One thing this thread has done, it seems to have brought out all the know it alls that have a 4x4, and they dont know how, why or what........


If one wheel only is driven out of the 2,4, 6,....would we not go round in circles.. just like a skid steer but to a lesser degree?
 
Big Stu 12 said:
One thing this thread has done, it seems to have brought out all the know it alls that have a 4x4, and they dont know how, why or what........


If one wheel only is driven out of the 2,4, 6,....would we not go round in circles.. just like a skid steer but to a lesser degree?
Click to expand...

Would depend on coefficient of friction to surface, angle of surface, pulsating of brake and steering angle - tractors had separate brakes for getting out of sticky situations
 
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All 4 wheels have drive, if diff lock is not engaged and 1 wheel is spinning its because its the easiest route of drive. Dosnt mean its 1 wheel drive its just how a diff works, my disco 2 has traction control which works similar to diff locks. It locks the spinning wheel and puts drive to the other wheels with grip. Am I right?
 
disco2shaun said:
I know it dosnt work on the diff, but through the brakes. With similar effects to difflock
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correct on your assumption, done through ABS system locking the wheel that has lost traction so it fools the diff into sending poweer to the stationary wheel, all Land Rovers have the system fitted - called left foot braking to create the same effect as you have with traction control
 
disco2shaun said:
All 4 wheels have drive, if diff lock is not engaged and 1 wheel is spinning its because its the easiest route of drive. Dosnt mean its 1 wheel drive its just how a diff works, my disco 2 has traction control which works similar to diff locks. It locks the spinning wheel and puts drive to the other wheels with grip. Am I right?
Click to expand...

Not quite,generally traction control detects excessive speed on affected wheels with abs sensors- this may cause brake to be pulsated on affected wheel. This corrects speed without skid when driving at speed. So a good system will not lock wheel but use brake to create artificial load to split output equally instead of all power to wheel with no grip.
Depending on system,may operate differently at different speeds, steering angle and engine output may be reduced as well.

Traction control is like electronic load balancing and airlockers if that makes sense
 
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Big Stu 12 said:
One thing this thread has done, it seems to have brought out all the know it alls that have a 4x4, and they dont know how, why or what........


If one wheel only is driven out of the 2,4, 6,....would we not go round in circles.. just like a skid steer but to a lesser degree?
Click to expand...


Yes indeed, but not usually to the extend you suggest.
The vehicle will tend to veer away from the driven side, but the driver will probably be able to control direction, though he will also probably feel the need to hold the steering firmly towards the side with the grip.

In practice, to skid steer a Landy as you suggest, the surface would need to be extremely slippery, and if it was that slippy it is doubtful if the one wheel would get enough grip to overcome the others, and drive the car. Probably just as well, or we'd all be driving up our own exhaust pipes!

Moral : KEEP YOUR THUMBS OUT from the steering wheel, ALWAYS.

My tractor is a 4 x 2 (no front drive)and has independent brakes on the big wheels. If I stomp hard on the left brake pedal then drive off, it does exactly what you suggest - the big RIGHT side wheel drives, and it does a full skid steer turn to the left. It can turn more or less in its own length.

CharlesY
 
whatever the physics and science... ive just sat on the ice in the fourtrak in rear wheel drive going nowhere , press the switch to drive the front aswell and it pulls away as if on dry tarmac..... the ability to flip in and out of two axle drive soon teaches the differenses in traction , grip under braking and steering between rear axlel and both axle drive. personally i dont give a stuff whether its 1,2,3 or 4 wheels actually driving as long as i get where i want to go without any unwanted excursions into the ditch
 
ricc said:
whatever the physics and science... ive just sat on the ice in the fourtrak in rear wheel drive going nowhere , press the switch to drive the front aswell and it pulls away as if on dry tarmac..... the ability to flip in and out of two axle drive soon teaches the differenses in traction , grip under braking and steering between rear axlel and both axle drive. personally i dont give a stuff whether its 1,2,3 or 4 wheels actually driving as long as i get where i want to go without any unwanted excursions into the ditch
Click to expand...


EXACTLY!

I like this bit specially!
personally i dont give a stuff whether its 1,2,3 or 4 wheels actually driving as long as i get where i want to go without any unwanted excursions into the ditch

CharlesY
 
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