[Clev]

Originally Posted by Christ

That statement is exactly the sole reason that MasterLock is still around.

People perceive weight to be strength.

Which has nothing to do with motors. An electric motor is about torque, and bigger IS better. Thicker shaft, more magnets, more insulation...

Think about it like this. If you wanted to make an MIW EV, you wouldn't have to use that 48V motor. You wouldn't have to use a single 30HP motor mounted to the transmission. The motor wouldn't weigh in at 60-100 lbs.

You would be using 2-4 motors.

Now, worst case scenario, the each motor is 24V, 15HP, and only weighs 30-50lbs... roughly the same weight as many cars' wheel and tire combo.

Or about 60-70 pounds with tire... EACH.

Divide the original motor between 4 wheels, and you've got 4 motors, each 7-8HP, each 15-20lbs, each 12V.

Even when you consider removing the engine and transmission, drive line (CV axles or drive shaft) etc, you still have removed more weight than you're adding on.

Lets say that you take a 1989 Honda CRX HF (lighest, smallest engine), remove the engine, transmission, both axles, and all eletronics associated with both.

The engine weighs in at least 230LBS,
Tranny is another ~100LBS,
Axles are close to 40LBS,
Remove engine wiring, fuel tank, pump, lines, filler nozzle, filter, charcoal can, associated equipment ~30LBS (rough estimate)
Remove complete exhaust ~30LBS (depending on cat/muffler, etc.)

In total, you've lost ~400LBS.. now you can add those 4 EV motors at 60LBS each, and still be ~150LBS lighter... add in the electronics to run them, and you're ~100LBS (I have no true idea, that was a guess.), Add the batteries, and now you're JUST starting to get overweight.

Replace those 60LB EV motors with 20LB EV motors, that run on 12V, and produce 10HP each, and you've got roughly the equivalent of a bone stock Geo Metro anyway, as far as HP.

You have the equivalent of a bone-stock Geo Metro perpetually in 4th gear. Without any kind of gear reduction, you're at basically a 1:1 fixed ratio between the motors and wheels. 10hp is about 7,460 watts, or 621 amps at 12V (not counting sag at the batteries.) That's to produce the same base horsepower at the wheels. Plus, add some weight (or exotic materials) to be able to hold together and absorb pothole impacts at 60 mph, and you're talking about a lot of weight, money or both.

And now you're looking for a wheel motor that can handle 621 amps at 12V for the amount of time required to climb a hill, and that motor can only weigh 20 lbs. Then add the 1/0 welding cable to each wheel to handle the amps, and you're dangerously close to being back at that 100 pounds you saved by dumping the transmission. Add four times the electronics for a controller that can drive four motors, and you're talking a lot of money for not a lot of advantage.

Acceleration will probably be faster, since you're not waiting for the engine to get into it's "torque range"... E-motors have a torque figure while idle (potential torque), and you're not experiencing ANY drivetrain losses.

Compared to the ICE, maybe, but compared to the simple forklift motor/transmission combo, I'd put my money on the forklift motor. The drivetrain losses will be traded for resistance losses because of the lack of gearing, as the motors struggle to translate 600+ amps into forward motion from a stop.

Now, you could still attach those motors to the chassis of the car, and attach from the chassis to the hubs using CV axles, but you'd experience at least some drivetrain losses, have another breakable component in the mix, be adding another 80LBS of weight (All 4 corners). And adding almost no benefit, other than "less unsprung weight" which isn't helping you at all anyway.

I wouldn't underestimate the impact of an extra 20-30 pounds of rotating mass at each corner than needs to be accelerated. Couple that with 1:1 gearing, and you're talking about a system that will cost at least 4 times as much, but actually do worse. At least with axles, you can go with a lighter weight motor, as it only has to deal with rotational stresses--something every cheap motor can do. A transmission provides even more protection, as the clutch and transmission/engine mounts provide some cushioning as well.

Personally, I think that if you want to eliminate the transmission, go with a motor coupled via a differential and axles. You can gear it properly to match your speed range and RPM range, and you can use standard proven brakes, wheels and tires, motors, controllers and wiring. Plus, your motor can be out of the salt and dirt, and it'll be far cheaper to boot.