Outer Limits 4x4 Board

uninformed wrote:

Bush65 wrote:

uninformed wrote:

uninformed wrote:have you thought about chnaging your diff and gear ratios to change propshaft speed to help negate the torque twist from engine rotation?

I would have thought that this would have pricked someones ears up and started a discussion?

I nearly did, but doubt the OP would be interested in the only methods that I know of for countering torque reaction and still be useful off road - probably too much work for what he wants to do.

If he was interested he would have done some research after you posted and found out for himself, or asked appropriate questions.

so im on the right track????

it was a bit of a guess on my half John.....I remember a friend (reliable engineering mind) telling me how noticed the difference when he changed his diffs, and hence ratios from 4.7 to 3.54, transfers where also changed so final ratios would have been similar. i think it got worse when he went to 3.54 as in the front left of the car would lift more at take off and in 2nd when accelerating

if youd like to explain a bit that would be great

cheers,'
Serg

Not quite what I had in mind. But diff ratio is an important factor.

If you want to reduce/eliminate the torque roll, you can employ suspension link forces.

Torque roll comes about from the reaction to the tooth forces (recall Newton stated every force has an equal and opposite reaction) in the diff.

The link forces can be engineered so that there is nett lift on the right side of the chassis or nett pull down on the left side. The other end of the link will have a force in the opposite direction at the axle.

The upper link geometry would normally be set up for this result. The diff ratio affects the link geometry required. But often the diff ratio is not applied because compromises have to be made so ideal numbers are unobtainable and you simply try to get whatever advantage is possible.

Not many bother, but it was being used (maybe not deliberately) by some competition rock buggies (I haven't followed recent trends, so don't know if the have continued with it).

It can be the difference in avoiding roll over in some situations - getting power down on steep side slopes when the left wheels are on the high side. Our original poster appears to be only interested in a cheap bandaid, probably for no other reason than to see if he can go faster at a roundabout.

Thanks John,

the car that my friend had used a rover front end(ie oem radius arms and axle caseing etc etc) rear uses rover A frame.

can you dumb it down a bit for me? is the lift in the front side (left i think) starting with the crankshaft? or more so just the diff and axle?

draw me a picture if you will.....all be it in text.

cheers,
Serg

uninformed wrote:Thanks John,

the car that my friend had used a rover front end(ie oem radius arms and axle caseing etc etc) rear uses rover A frame.

can you dumb it down a bit for me? is the lift in the front side (left i think) starting with the crankshaft? or more so just the diff and axle?

draw me a picture if you will.....all be it in text.

cheers,
Serg

The torque transmitted to the diff pinion results in tangential (and separating) forces between engaged teeth of pinion and ring gear. The pinion tooth pushes the ring gear tooth, and there is and equal and opposite reaction from the ring gear tooth that acts on the pinion.

This reaction tries to rotate the vehicle around the pinion and is resisted by the vehicle weight.

Similar forces and reactions are taking place at the engine and gearbox, but the force and reaction are usually greater at the diff pinion.

A quick translation (sorry John) is the prop shafts try to twist both the motor/gearbox and the driving axles.

But the motor/gearbox is held to the chassis pretty well by the engine mounts so the torque mostly shows up in the suspension as the driveshafts twisting the axle in relation to the chassis.

Geez kids, just to enter in the pissing contest, you supply bulk HP to a constant 4wd and you WILL spin the front wheel no end, I had a 351 windsor in my rangie, which was a nightmare to get away quick from standstill, I used to just engage the CDL for quick launching, then disengage, it caused no harm as the wind up is practically nil when heading straight

I also thought of useing an LSD centre diff, to try get the power to the ground, but alas as you've noted, they are very thin on the ice in aus and had no luck sourceing one, so it never happened

I can;t be of much technical help, but am very much liking your thinking as this is where I was at, now with a turboed 4BD1, I don't have that problem, can barely bark a wheel when given shit, even in its fuelled up state

I'd be useing one of those LSD centre diff's, pulling it apart, and seeing how much shimming can be done, to produce a tight centre LSD

cloughy wrote:I can;t be of much technical help, but am very much liking your thinking as this is where I was at, now with a turboed 4BD1, I don't have that problem, can barely bark a wheel when given shit, even in its fuelled up state

Mine can squeal tyres in second if I give it some revs before the clutch comes out. Second on my Isuzu box is probably a bit taller than 1st on an LT95.
I'm cheating though, smaller tyres.

CDL is a pretty good solution for the OP. That is afterall what it's there for. "Anytime where traction may be lost".