JBee
Well-known member
- First Name
- JB
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There is a lot of threads on here with discussions about how good torque vectoring is offroad in comparison to lockers.I’m not sure that bit about crawling is true. The two rear motors are virtually lockable in the tri motor vs mechanical locking in the dual. The end result is likely the same.
There are a couple of points to consider here:
1) Electric motors have something called "Stall Torque" which is when they are operating at very low RPM, like when climbing, with 1-2RPM. This means they do not produce full torque, or sometimes even enough torque to keep momentum, unlike two wheels joined by a locked diff, where the toque can vary between axles without TC/TV interfering with RPM. This is a common issue with Rivian QM.
2) The other point is that TC/TV only has a about a 25Hz feedback loop to the wheels, a diff lock is nearly "instantaneous" in that the only fluctuation is the tyre deformation from acceleration. This means there is "no figuring out" of differential traction of the ground, the amount of torque required, or can be applied to the ground for what level traction there is in that split second of time, or the the ability of the motor to deliver it etc. despite position sensing being done in the motor itself. With a locker the toque is evenly supplied to wherever there is the most available traction mechanically, without any systems interfering at all, and not reduction in RPM that kills momentum.
3) the same applies for going downhill or off camber, in that toque vectoring of undulating and varying traction terrain leads to instability and loss of vehicle control on the limits of traction. And open diff, without a locker on, is far superior here, in that any torque on one wheel will be compensated for by the other side instantaneously and directional control is maintained even whilst the wheels are slipping down the hill. The point is you don't want lockers or TV here.
In the case of TM having a locker and open diff up the front will help, but without evidence to the contrary, and development of the TV to replicate the positive dynamics of a locker, it's unlikely to be as good in rock crawling as a DM. But as stated, as soon as you have some RPM on those wheels, the TV will allow for better on-road handling and dynamic control of the rear end, and even torque steering/drifting.
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