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Mark _australia said...Ian K said...Mark _australia said...GreenPat said...Mark _australia said...
any real 4WD will do it just fine with open centres.
What are these centre diffs of which you speak? None of that fancy-shmancy trickery on the 1982 Hilux. Same power to the front and back axle regardless. Just don't drive it in 4x on the blacktop, the tyres will work against each other and wear out quick smart, plus you'll struggle to shift out of 4x to 2x with all the torsion in the drive shaft (reverse a little can help).
I was talking about diff centres, not centre diffs.
Your Hilux still has open (not LSD or locked) diff centres so still suffers from the wheel in the sky = no forward motion.
Shouldn't the wheel by wheel electronic braking of new-age stability control systems soon be fitted to all 4wds and make these fancy diff centres obsolete?
( Then again if the manufacturers of 4wds got serious about hub electric motors they could do away with diffs altogether.)
No, cos
(1) the best thing for offroad is locked diffs all the way, no slip at all. Of course they need to work on road to, so diffs are normal open centres or LSD's and serious 4WD crew replace them with an airlocker.
But like I said it is not needed for just beach driving
and
(2) all the ESC / traction control stuff is great - till you hit sand. In deep sand momentum is important, even if you are spinning wheels. Especially in a climb.
All the new fangled sh!t just gets you bogged - as when you give it a bit of loud pedal, wheels spin and in response the system brakes the wheel, which is the total opposite to what one wants on sand.
To get down the beach a real fourby with a transfer case (not an AWD) and normal tyres (let down) and clearance, is all one needs. An AWD is fine as long as it has a centre diff lock.
I can't think of anything other than a sand hill where wheel spin rather than traction is important? Maybe you should term it "jet propulsion" rather than "momentum". Throw sand backwards to get push up the hill? But that's specialised stuff, if you're right into that sport fair enough, but you won't have the time or money left to windsurf.
Back in the day traction was the go even in sand, the best sand tires had fine tread, and were also useful on bitumen.
It is possible to provide the function of a fully locked system with electronic stability control. You just tweak the electronics so all wheels are braked to the rate of the slowest wheel. This allows all 4 to spin if you wish. The only disadvantage of using brakes to keep all wheels spinning at the same rate is that power lost as brake friction. But 4wds have heaps of power these days so for the odd occasion that it's needed, not a problem.
Part of the modern 4wd's undoing is the requirement that they be reasonable on road. They use heavy stabiliser bars so they don't lean in corners. Offroad this exacerbates the diagonal wheel unloading. I recall a story about a country town 4wd show. The Ford dealer, with not much to contribute, took a falcon ute, had the mechanic weld up the rear diff, disconnected the stabiliser bars and left the local Nissan dealer in the bushes. (He claimed this was Ford's inspiration to produce the Falcon RTV)