Reverse diff concept

[AFnut]

Ok this one is a little off the wall, but I need some input. We all know the basic prencipal to the differential, What if you had a diff that transferd torque to the wheel that had the most traction (slowest rotating speed in my concept) insted of the wheel with the least grip? Would applying torque to the inside wheel on a high speed turn make the car handle poorly? What other advantages/disadvantages would I have if I put this on a car?

[Moppie]

Many of the active system in modern cars do exactly that, and it works very well.

[KiwiBacon]

A device to transfer more torque to the wheel with the most traction is basically a limited slip diff. Other arrangements that do the same job are viscous diffs, diff locks etc.

A normal diff transfers equal torque to each wheel regardless of what speed it is spinning at. It does not (contrary to marketing speak) transfer more torque to the wheel with the least grip.

If you talk to anyone who's driven with vicious limited slip diffs or difflocks, they'll tell you that they try to drive the vehicle straight ahead in corners. If the driven end loses traction it happens all at once, instead of one wheel spinning up and the other still having some traction.
They can be dangerous.

[MagicRat]

Welcome to AF.

Unless I am misunderstanding your description, such differentials exist, specifically the Gleasen Torsen and the Detroit locker.

Arguably, a regular clutch operated limited slip differential essentially has the effect you describe.

[Black Lotus]

The Torsen concept address your first sentence. I have a Quaife in one of my cars, the other has the usual limited slip using clutch plates. Neither is perfect, but the Quaife seems to work a bit better.
If you install any sort of limited slip, torque biasing or locker to your car, you may notice more of a tendency to understeer. It's all a matter of shades of gray 'tho, and every car is different. It also may depend on how fast you are driving thru and out of the corner.
The more effectively the inside wheel can transmit the forward driving force of the engine the more of an understeerer you are going to have. But, you might not notice much of a difference.......
Just imagine a rear drive car with an open diff trying to accelerate out of a corner (and doing well enough) until the inside tire starts to spin. The car will hold its line thru the corner well, but won't accelerate very hard because the open diff will simply put the power to the tire with the least traction.
Now imagine the same car with a limited slip. The car can accelerate faster, more load on the rear tires (less on the front).
The inside rear which isn't doing as much of the work of cornering as the overburdened outside tire can now take over much of the job of accelerating. Since the inside tire is inboard of the center of gravity (CG), it will try to yaw the car around so it is trying to point the nose to the outside of the turn. The driver counteracts this with more steering input, and it all shows up as more apparent understeer.
However, if the outside rear tire is well an truly saturated with cornering loads, it may slide the rear end out into more oversteer, and tend to compensate for the understeering (rotating the car around its CG in its yaw axis) effect of the limited slip unit.
Yow!
Like I said--shades of gray.

[AFnut]

Originally Posted by MagicRat

Welcome to AF.

Unless I am misunderstanding your description, such differentials exist, specifically the Gleasen Torsen and the Detroit locker.

Arguably, a regular clutch operated limited slip differential essentially has the effect you describe.

I am not talking about a locker I know those corner like crap, this is an open drivetrain system (the final version might be a limited slip though) I know there are advanced drivetrain systems that do the same kind of thing, but the purpose of my concept is not to surpass curent drivetrain technology, but to make a gearless lightweight drivetrain system, that just so happens to transfer torque to the slower wheel.

[MagicRat]

Originally Posted by AFnut

, that just so happens to transfer torque to the slower wheel.

A true Detroit Locker does exactly this.

[AFnut]

Originally Posted by MagicRat

A true Detroit Locker does exactly this.

How do the Detroit lockers handle in tight corners, and I am just guessing that they work in some sort of ratcheting hub mechinism with a locked center section, am I right? Do they get the off the line traction that a true locker has??

[MagicRat]

Originally Posted by AFnut

How do the Detroit lockers handle in tight corners, and I am just guessing that they work in some sort of ratcheting hub mechinism with a locked center section, am I right? Do they get the off the line traction that a true locker has??

With apologies to the Aussie V8 forum, here is a good description that appeared there:

The Detroit Locker is not really a differential in the sense that the Salisbury and Gleason are. That is, it has no gears at all, and there is no way it can be set up to split torque equally between the two output shafts, while letting their speeds vary, even at very low torques. The locker contains a center element consisting of a dog ring driven by the carrier, like the spider gears and pinions in a Salisbury or an open diff. This central dog ring has dogs on both sides. These mate with driven dog rings on either side, which drive the axle shafts.

The driving dog ring can float a bit side to side. It is held centered by two conical coil springs. When the driving dog ring is centered, it engages both driven dog rings, and we have a locked axle. If the driving dog ring moves to one side or the other, it moves more deeply into engagement with the driven dog ring it moves toward, and if it moves far enough it disengages from the other dog ring. We then have drive to only one wheel.

For a wheel to disengage, it has to overrun the carrier. For this reason, the locker is sometimes called a ratchet. This isn’t really accurate, but the unit is somewhat similar to a pair of ratchets, each driving one wheel, in that it drives the slower wheel and lets the faster one overrun. It differs from a pair of ratchets in that only one wheel can overrun at a time. In decel, the slower wheel sees the engine braking. In a race car, this promotes very free turn-in. If the driver likes to finish braking and then turn, this can work well. If the driver likes to do heavy trail-braking, it may be a disadvantage.

When the driver gets on the power, the inner wheel drives, up to the point where it spins. As soon as the inside wheel reaches the speed of the outside wheel, the unit locks and drives both wheels. The lockup is not smooth at all. The dogs are either engaged, or they’re not. The unit cannot slip. This requires the driver to develop a feel for when the unit is going to lock, and anticipate the change in car behavior at lockup. It also rewards decisive driving. That is, lockers are somewhat unpredictable if the driver is on and off the throttle trying to balance the car. It can be hard to predict whether the rear will be locked or unlocked when the power is reapplied after a brief lift. So the locker responds best to a driver who gets on the power and stays on it.