[cajunfj40]

Hello HaroldinCR,

I have NO problem with mechanical stuff here. Just wait until I get ready to start trying to make a 2 speed electronic transmission. Y'all are in for some REAL sufferin.

Great, I can keep ranting. As for the 2-speed electronic transmission, do you mean electronically controlled mechanical, or some sort of Wye-Delta electrical shifting? The first is solved if you don't mind harsh shifts, look up electro-pneumatic control of Lenco and Powerglide drag-racing automatic transmissions. Somebody may even have come up with a solenoid valvebody for a Powerglide, though I haven't looked for such a thing.

Hello again thingstodo,

Originally Posted by thingstodo

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.

Your impression is correct. There's just this odd corner of the performance envelope with "locker" or really aggressive "clutch type posi" rear ends that I've read about that can cause odd handling in very low traction corners.

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?

NOTE: I'm being theoretical. I've not yet driven an auto-locker equipped vehicle. The "aggressiveness" of the torque transfer will be the deciding factor in the road manners on low-traction surfaces in corners. If it happens relatively slowly/smoothly, no issue. You will have the ability to spin all four wheels, but you will be able to creep up on it. If it is fast/harsh, the vehicle will be twitchy.

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.

I'm no racer either. It will probably work fine for the mud situation. Having 1/4 of the vehicle's max torque capability at any one wheel will allow for continued forward movement when 3 of 4 wheels are slipping, provided the available torque and traction at that one remaining traction-available wheel is high enough to overcome the drag on the vehicle.

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.

Note that you need constant tension in order to have simple reverse as well. Backing up with a plain tensioner won't work - the belts will slacken.

You can use two tension wheels, tied together, or use a bolt-adjustable tensioner rather than a spring-adjusting tensioner. No need for two belts.

Please note that for any belt final drive to work you pretty much must have what amounts to a straight trailing or leading arm suspension. Otherwise the belt has to twist and change length as the suspension moves. Add dirt/mud/water/etc to the situation and it gets really difficult to keep the belt on the pulleys.

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.

Benefit to using an existing driveline: you can get every part you need by purchasing a wrecked/non-running whole vehicle. Craigslist or local equivalent. The most difficult challenge here is coupling each motor output to it's individual wheel. You have two practical off-the-shelf solutions available (ie, figured out and used a lot):

1: Drive the inboard end of a standard CV axle half-shaft, use conventional IFS/IRS suspension/hubs/etc. Pretty easy to get AWD, all you need to engineer is the mounting for the inboard ends of the CV axle half-shafts and their drive pulleys, plus the remaining mounting for the motor and any jack-shafts needed to get the reduction ratio you need. Flange-mounted CV's could allow just sandwiching the pulleys between the CV and the diff, and just gutting the diff of everything not needed to hold the drive flanges in and concentric.

2: Use a set of straight trailing swingarms in the rear - essentially two motorcycle rear ends, mirrored side to side so the pulleys are on the inside. Drive pulley is concentric with swingarm pivot, tension is set by moving the wheel/driven pulley closer to/further from the pivot. Pretty easy to get 2WD IRS this way, so long as you are OK with zero camber change with body roll/suspension travel. Doing leading or trailing arms for the front means figuring out how to bolt a CV jointed steering knuckle off the outer side of said arm, and beefing it up against the resulting twisting forces. Not easy.

Going with one bigger motor allows you to use complete standard AWD/4x4 driveline bits, with the only required mechanical engineering being adapting the motor to the input shaft. Use a recent traction-control equipped vehicle and the computer uses the brakes to slow down the spinning wheel, forcing the differential to shove an amount of torque equivalent to the braking force over to the wheel with traction. Add a Tor-sen or similar, and you get a 2.5-3.5 or so multiplier for that brake torque.

Two motors - one for each end - can still be run off the single controller, but you have double the amount of mechanical speed reduction hardware necessary, and still need to do the traction control for the left to right mechanically.

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

IIRC they use open diffs. Not sure what year they put in full TCS, but it uses power reduction and brake application to try and limit wheel spin. If there is not enough traction available from static friction, you're not going anywhere. Most of these systems don't allow you to rely on dynamic friction (spinning all the power-able tires), though the SUV's and sportier cars tend to have a way to disable the power-reduction part of the traction control. 3rd and 4th gen Ford Explorers apparently can do this, though it requires steady throttle control to keep it from "freaking out" and no longer working as desired. CAN bus controlled module to do it, too. Beyond my ken at this time, though I would LOVE if I could retrofit the newer ABS module, powered brake servo, and wheel sensors on both rear wheels (mine has just one on the pinion) to get it.

Note that brake-application traction control necessarily turns some of your battery power into heat while it is working. Dunno how more or less efficient that is than running at higher slip on the other motors.