New Electric Motor is 50% Smaller but has 2x More Torque
 

So my question to those wiser than I, is if this is meaningful in vehicle applications.

New Electric Motor is 50% Smaller but has 2x More Torque (!) : TreeHugger

Someone commented that. Isn't unsprung weight weight that is not "sprung" by the suspension? AKA wheels/axles? Wouldn't that make hub motors create more unsprung weight.

For the DIY electric cars, this motor isn't all that special. We need lighter/cheaper batteries.

still, over 95% efficiency, and significant weight reduction is nothing to sneeze at.

For big car manufacturers, it's a great thing. But for DIY batteries are most important, IMHO.

I don't see what the big deal is with having a drive shaft, it would allow you put the motor in a more protected location, reduce your unsprung weight, use a cheaper motor, use better mechanical brakes (yes, you can skid to a stop with regen brakes, or just by shorting the motor, but I like redundant brakes!) with all of that said, I like that motor design, it's close to what some of the wind turbines are using for an alternator, it's also close to what my bicycle uses for a hub motor, of course with a bicycle like mine it's all unsprung weight!

The article is pretty limited in detail and my understanding of electric motors is pretty basic. Does the "2x the torque for the same power output" quote mean that you get more torque per kWh? I'm going to have to break down and buy a book.

*EDIT* or I guess more torque per kW would be more appropriate.

Nah, it means that you get 2x the torque output per area of motor. The efficiency number is what you're going to want to pay attention to when determining the amount of power it will make, and how long it will last on a given pack voltage/rating.

Basically, most electric motors have an armature and a housing. One has magnets, the other has windings (very simply put.) This design takes the armature and puts a splined disc on it (or two, or three, or four) so that it almost resembles a Wankel Internal Combustion Engine, i.e. the "rotors" are tied to the shaft by a splined interconnection (possibly splined, there are other ways, as well) (For the purpose of the explanation, we'll stick with splined, though). On each side of the rotor, there is a set of magnets. What you end up with is something like this:

|:||:||:||:||:||:|

Where : = rotor (with magnets) and | = discs with windings, or vice versa (flip windings and magnets, but then you'd have to add brushes.)

One nice thing about a motor design like this is that if it is lighter weight then it is also useing fewer materials, so it might cost the same because it takes more man hours to build but you can build more motors for a given amount of copper.

I can't speak for everyone else, but my problem with it is that it's unnecessary. Why bother with a drive shaft and axle and friction brakes when you can have AWD and greater efficiency with less overall AND unsprung weight. The hub motor should occupy (I don't know how exactly PML sets their system up) the space formerly taken by the brake disc, and spindle, both of which are fairly solid pieces, so in most cases you'll be trading dead even on weight. The hub motors will need some braking component in them for parking anyway, so there's your redundancy.

On the drive end of the car you'll be shedding weight due to losing the driveshaft, which is unsprung. CV shafts are lighter than the solid axles found in some RWD applications certainly, but you're still losing weight where it counts. Add to that the huge amount of rotating mass you've just eliminated, and I see no benefit to a traditional system with the exception of home conversions. ;)

The parking system won't necessarily add redundancy to the braking system, because it could be as simple as the parking lock in automagic transmissions.

Whens the last time you heard someone say: "O Shoot, Clem, I lost mah brakes, gonna toss 'er in PARK!"