I'm a newbie, but here goes: Why don't cars use hub motors?

MikeFairbanks

MikeFairbanks

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Couldn't four hub motors be regulated to have the same output (or output distributed as needed) on a car?

Why do golf carts and other electric vehicles still use some kind of differential or transmission?

Is this a dumb question? If so, disregard.

I ask this because there are remote-control helicopters that are actually quad designs, and a central chip controls each propeller, enabling the helicopter to not only hover in place, but can be program to follow GPS coordinates by tracking over a dozen satellites at a time.

And these little helicopters are available to the public (although quite expensive). Check it out:

http://www.draganfly.com/uav-helicopter/draganflyer-x6/
 
Probably because if you get in some kind of crash, you get to replace your motor.. uh yeah.. screw that :)

Also.. gear ratios are gonna be an issue. Okay so you could probably do a planetary geared transmission, but... why would you want two transmissions when you only need one?

Also, changing tires is gonna suck when your wheel is 50-100lbs.

I could go on..
 
There have been a few hub motor powered cars, but having all that weight in the wheel makes life very tough for the suspension as it just adds masses of unsprung weight. PML produced a Mini as a demonstrator using their hub motors: http://www.youtube.com/watch?v=XdRS7eVVZbU and here: http://pmlflightlink.com/ but it's never made it into production.

Although using hub motors seems like an attractive packaging arrangement, as it removes the needs for a transmission etc and leaves more room for batteries, you can't get away from the fact that high unsprung weight is always going to make the ride and handling poor, particularly at speed, which is almost certainly why the only real use for hub motors commercially, AFAIK, is slow moving equipment, like the big, slow trucks used in quarries an open cast mines.

Jeremy
 
In addition to unsprung weight as Jeremy mentioned, it's also rotating mass, which is a double strike against hub motors. In some cases the benefits outweigh the drawbacks though. Design flexibility is awesome, no losses in drive shafts getting to the wheels is a beautiful thing.
 
In 1898, Ferdinand Porsche and Jakob Lohner worked together to build an electric car with hub motors known as "System Lohner-Porsche". That system was later used as part of a more reliable hybrid system. History has some interesting examples of modern technology :)
 
Amazing that Ferdinand. Everywhere he worked in those early years he dramaticly improved the cars coming out the factory.

Too see real hubmotors in action, look at the biggest mine dump trucks in the world. All run on 4 hubmotors. Required so they don't burn out regular brakes descending into the open pits. Hub motor braking is the solution.
 
grindz145 said:
Design flexibility is awesome, no losses in drive shafts getting to the wheels is a beautiful thing.
Click to expand...
I'll take the axle losses and move the motors inboard.
 
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