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Originally Posted by cajunfj40
The "higher torque available to the slower motor" issue could cause similar behavior. The inside wheel gets more torque because it is slipping more than the outside wheel (assuming both motors are loaded, so both are going slower than commanded speed), while the body rolls away from said wheel, unloading it. Once the traction drops below what is needed to keep the tire from slipping due to torque, it lets go. No max overspeed, because AC, that's nice. The whole vehicle slows down a bit since it isn't being driven by that wheel anymore. Now the outside wheel is going even slower than commanded, so slip goes up. Thus torque goes up. Traction is higher than it was on the inside (all else being equal, body roll will do this), so it takes longer to let loose, but when it does, now both wheels on that end of the car are spinning and it's sliding out. Again, this would probably happen faster on slick surfaces.
The point being, without an "open" differential, when one tire lets go the other gets the rest of the torque, making it more able to break traction. Hmm. Maybe slap pulleys on either side of a "truetrac" geared limited-slip differential, and run without a pinion or ring gear at all? I wonder if that'd allow the proper torque biasing.
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Hmm. I was under the (mistaken?) impression that transferring torque to the wheel with traction, and not spinning the heck out of the wheel that has just lost traction, is a good thing.
With 4 wheels commanded to turn the same speed, if the inner front one has traction, it pulls you along and you go a bit faster. The other three wheels still have power going to them, just not as much since the have less slip. If the front inner tire loses traction, you should still have traction on the two rear and the front outer, and you go a bit slower. If you break loose with all 4 tires ... 4 wheel skids are not fun ... but perhaps you were a bit aggressive in your driving style for conditions?
I am not a racer - my experience is somewhat lacking here. I just don't want to get stuck in mud, one wheel spinning madly while the other three sit there.
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You still don't want it to slip. The tensioner just keeps the "slack" side of the belt from flopping around. If you want reverse and/or regen braking you will want a "set the tension by setting the distance between the pulleys" setup, else the belt will always slip on reverse and/or regen as the slack swaps sides. A really strong tensioner could work, but might need to be impractically strong to function properly, leading to too much side load on the pulleys.
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Good point. I will likely have little regen in the simple case.
Is there an off-the-shelf mechanism that uses 2 belts on a dual pulley system, where one belt is tensioned to 'pull' at the drive pulley and the other belt is tensioned to 'push' at that same pulley, using idlers of some sort?
That likely does not make any sense without a sketch. I'll add one tonight.
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You may be better off with one motor and the driveline out of something like a Subaru or a 4x4 ATV. Used LEAF motor? Car-part has them as low as $445. More than 4x $85, but you get to use existing driveline parts...
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Perhaps a Subaru AWD would be a better fit for me. But I'm not a mechanic. If I can solve a problem electrically instead of mechanically, I will. The ATV linkages, suspension parts, etc are out of the price range for now. They cost as much as many 4x4 truck parts.
I have little info on Leaf drivelines. Do they use an open differential and activate brakes to transfer torque to the wheel with traction? I would not object to using Leaf parts, I just need to learn a bunch of stuff. There are no wrecks up here to pull from. Leaf drivers seem more careful than Tesla drivers
