hub motor with transmission built in

[California98Civic]

I thought this NSK hub motor pretty interesting.
These could be so great for a parallel hybrid on a front wheel drive car, saving interior space. The problem with the motors I have seen (such as QS-motor) is that most cannot rev fast enough with no load. The best QS motor in this regard revs 1000 with no load: a car would be limited to maybe 70 mph without large tire/wheel combos. (I think I understand that correctly.)

https://www.youtube.com/watch?v=Y2tlXHiPTFY

I imagine like Proteon, Michelin "active wheel," and other motors, it may never go to market (at least it seems that way with these designs).

[rmay635703]

Hmm gear reduction via planetary?

Anyway RPMs are a hub motor issue but only at startup since you don't have enough torque to start the car rolling

Never heard of top speed as being an issue with hub motors,

[California98Civic]

Originally Posted by rmay635703

...Never heard of top speed as being an issue with hub motors,

I could be misunderstanding the specifications I found online. I am new to all of this. But I understood the max no load limit of 1000 rpms on QS Motors' products to mean not only that that's the maximum rpm it hits without any load on it but also that to exceed that in speed would damage the motor. Newbie mistake?

6000W V3 Electric Car Hub Motor(273 Model) - qs-motor.com

[cRiPpLe_rOoStEr]

Since the direct reversibility and the ability to get rid of a transmission are the most highlighted advantages of hub-motors, I wouldn't hold my breath for this setup to become commercially available. But who knows...

[rmay635703]

Originally Posted by cRiPpLe_rOoStEr

Since the direct reversibility and the ability to get rid of a transmission are the most highlighted advantages of hub-motors, I wouldn't hold my breath for this setup to become commercially available. But who knows...

Yes but no commercial hub motor has enough starting torque to move a car.

They are only used on bikes because the person can "push off" to get the thing moving.

So I suppose the worlds first usable automotive hub motor might sell.

Actually if the thing is reliable it would be the first to work on a car.

I think that is important, just have to wait for China to clone it so it's cheap enough to use for hybrid conversions

[California98Civic]

They don't seem to intend to bring the whole design to market, just some of the parts, such as a bearing they designed for it. I guess they realized--maybe from the beginning--the limitations you both are pointing out.

[puddleglum]

Originally Posted by California98Civic

I could be misunderstanding the specifications I found online. I am new to all of this. But I understood the max no load limit of 1000 rpms on QS Motors' products to mean not only that that's the maximum rpm it hits without any load on it but also that to exceed that in speed would damage the motor. Newbie mistake?

6000W V3 Electric Car Hub Motor(273 Model) - qs-motor.com

I would interpret the "1000 rpm max" to be the free run speed of the motor at 72 volts (rated voltage), not the max rpm that the motor can be spun up to without power. It's max safe rpm is probably a lot higher. It says it can be run at 144 volts which would double the rpm right there. there is still the issue of the anemic torque output though which would limit its use in a car unless you were going to fit 4 of them.

On the other hand, that NSK motor looks like it would be pretty cool and might work really well if you were rich enough to afford a couple.

[thingstodo]

Originally Posted by California98Civic

They don't seem to intend to bring the whole design to market, just some of the parts, such as a bearing they designed for it. I guess they realized--maybe from the beginning--the limitations you both are pointing out.

From what I read, the bearing design is quite important.

Other hub motors that I have read about ... the motors wear out and fail (quite spectacularly) before the first set of tires is worn down.

There is not much clearance between the rotor and stator on a modern electric motor of any type - induction, PM, BDC. There is a lot of load on the bearings - since that is what is holding the car off the ground ... and taking the bumps since the motor is unsprung ... no suspension to smooth things out. Only one bearing on one side gives the hub motor a couple of additional challenges. After a few thousandths of an inch of wear on certain parts of the bearing ... some part of the stator meets some part of the rotor and *BAD* things happen.

From my limited understanding, the bicycle hub motors benefit from having support on both sides like a traditional motor. Both ends are connected to the bicycle frame. And bearing wear is not nearly such a big deal.

[NeilBlanchard]

Originally Posted by rmay635703

Hmm gear reduction via planetary?

Anyway RPMs are a hub motor issue but only at startup since you don't have enough torque to start the car rolling

Never heard of top speed as being an issue with hub motors,

I think it is because they want to reduce the weight of the motor units, that requires the reduction gear. They avoid mentioning the reason that weight is the issue - unsprung weight is the main challenge of hub motors.

The obvious answer is to use tandem motors with half shafts. Then you don't have gear losses, and you have much lower unsprung weight, too.

[California98Civic]

Originally Posted by puddleglum

I would interpret the "1000 rpm max" to be the free run speed of the motor at 72 volts (rated voltage), not the max rpm that the motor can be spun up to without power. It's max safe rpm is probably a lot higher. It says it can be run at 144 volts which would double the rpm right there. there is still the issue of the anemic torque output though which would limit its use in a car unless you were going to fit 4 of them...

This discussion got me reading further online (Endless-sphere site and such places). It seems a 30% buffer above max load is a common saftey design feature. But that means with tall tires on 15" wheels this hub motor would start to come apart at about 80-85mph MAX.

Originally Posted by thingstodo

... There is not much clearance between the rotor and stator on a modern electric motor of any type - induction, PM, BDC. There is a lot of load on the bearings - since that is what is holding the car off the ground ... and taking the bumps since the motor is unsprung ... no suspension to smooth things out. Only one bearing on one side gives the hub motor a couple of additional challenges. After a few thousandths of an inch of wear on certain parts of the bearing ... some part of the stator meets some part of the rotor and *BAD* things happen. ...

Yeeoww! Makes sense though. Seems like it is not the kind of thing to try on a daily driver, hahaha!

Originally Posted by NeilBlanchard

... The obvious answer is to use tandem motors with half shafts. Then you don't have gear losses, and you have much lower unsprung weight, too.

But that takes more space. A hub motor set up would save cargo space and it seems like an easier conversion. But the hub motors obviously need more development.