
04-23-2008, 11:48 AM
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Nothing scares me anymore
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Join Date: Dec 2003
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Re: Reverse diff concept
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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??
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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.
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