Heavy Hub Motors: Unsprung weight issue solved: Hub motor = in wheel active suspension system!?

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Logic11

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The unsprung weight of hub motors is a huge issue in EVs, which is why you don't see them at all in production EVs. (Well... not that I'm aware of..?)

In wheel suspension, between the hub and rim, would be 'The Cure', but that's noT! easy:
The inventions so far just dont look trustworthy.
They look like they may well ingnore your stearing input and prefer input from road bumps and angles.
They also look like they will wind up the suspension when you try to brake and accelerate. (maybe a good thing too get some rpms into a hub..?)

Here are 2 such inventions:
www.wired.com

An Ingenious Shock-Absorbing Wheel for Bikes and Wheelchairs

Riders can traverse stairs and curbs nearly as easily as gliding down a ramp.
www.wired.com www.wired.com
Both seem to have been renegaded to wheelchairs.

But how about a system that turns a hub 'motor' into an active suspension system!?
discourse.odriverobotics.com

In wheel motor and active suspension

Hi, I am developing an in wheel motor and active suspension system. Please see these animation on you tube. My knowledge of BLDC motors, Odrive, Python is 100% “armchair”. I am hoping that the Odrive community could get involved in building a controller for this...
discourse.odriverobotics.com discourse.odriverobotics.com

It still looks a bit spindly to me, but is as clever as FreeHub IMHO.

This is noT the kind of thing that will suddenly appear in an EV, but may well appear on something here..?
Thoughts?

(No I'm not associated. It's just that really clever ideas like this 'blow my skirt up!' :D )
 
They've been around since the 1800s but hardly ever had any kind of popularity. Not that they don't work, most of the early designs weren't ideal but several major auto manufacturers have shown concepts using them that are totally viable other than additional cost for minor benefit over conventional suspension. Hub motors might just be the the tipping point, they're so obviously the correct path for power transmission but hit a brick wall for unsprung mass, the obvious routes forward are either massive weight reduction or in wheel suspension.
 
I remember many years ago, when steel rims in car wheels were the norm and aluminium ones were an expensive novelty, the main argument for switching was that aluminium is lightweight and therefore the unsprung mass is reduced, which is good thing.
Now the aluminium rims are the norm. But take a typical modern rim made of aluminium - it weights much more than a steel rim of the same size. Like 2-3 times more. With larger wheels the difference is even more stark, the steel ones feel very lightweight.

All in all, i don't think the 'unsprung weight' is that important, especially for bikes.
 
Thanks for sharing, I personally haven't seen an idea like this before which is so clearly demonstrated. I can't weigh in on the practicality or whatnot, but it's cool to see that other smarter people are working on it with some result.
 
rafalg said:
I remember many years ago, when steel rims in car wheels were the norm and aluminium ones were an expensive novelty, the main argument for switching was that aluminium is lightweight and therefore the unsprung mass is reduced, which is good thing.
Now the aluminium rims are the norm. But take a typical modern rim made of aluminium - it weights much more than a steel rim of the same size. Like 2-3 times more. With larger wheels the difference is even more stark, the steel ones feel very lightweight.

All in all, i don't think the 'unsprung weight' is that important, especially for bikes.
Click to expand...
It defines comfort, it's the main thing that makes a luxury car "luxury", that plush ride quality. They're invariably heavy and that gives a very high ratio between sprung and unsprung mass. It's also an essential part of good ground contact but that's pretty much the same thing, the ratio between sprung and unsprung mass. In an ideal suspension the vehicle is an immovable object, infinite mass. Everything in the real world is a compromise to that ideal, making the best of what we have and every single gram of difference makes that harder.

Alloy and steel rims work out almost the same weight strength for strength, alloy has the edge because it can have greater stiffness for the same weight but it doesn't always work out that way in practice. Good quality metal alloys can offer significant advantage, half the weight or less for the same strength but the alloys generally used are generally poor, even from major manufacturers and most aftermarket parts are absolute dirt, extremely poor quality material.
 
Interesting idea! Failure can cause wheel lockup, loss of control leading to serious accident?
 
i'd rather use a smaller diameter wheel with a really big tire. Then the tire becomes the shock absorber and there's no unsprung mass at all.
 
Sounds cool but you still have these things going against you vs an inboard geared motor:

- The larger cost of materials for the motor
- The additional cost of the in wheel suspension, startup costs and testing costs will make this high
- The additional weight of both systems

I think the inboard motor will continue to win on the car for many of the same reasons mid drives are winning on the ebike.
 
Good point, there's no major price gain from DD hubs anyway so no margin for anything to make headway unless it's super cheap and effective. Can't see that happening, there are some elegant designs using composites but even at their simplest they wouldn't come anywhere near the cost of conventional rim and spokes.
 
I think hub motors will eventually find a place in urban people movers and cargo vehicles, but only after we have tamed the street environment to serve modes other than cars and trucks. Increased payload capacity per vehicle volume is a point in favor of hub motors.

Either lower operating speeds, better surfaces, or some of each would make the dynamic shortcomings of hub motors much less of an issue. And we can have both if we put oversized, overpowered ICE vehicles on a short leash.
 
As we should be. Idk about there but politicians here... I saw the word "sustainability" blathered out 17 times in a single article recently, it was probably only half a dozen paragraphs long! Almost every time it's used these days it's nothing but a buzzword, the only thing any elected official would achieve by making the kind of changes needed for genuine sustainability would be losing their next election. Speed is the number one culprit, we expect to move at a mile a minute or more and while living within our means and that's just not possible.
 
stan.distortion said:
Good point, there's no major price gain from DD hubs anyway so no margin for anything to make headway unless it's super cheap and effective. Can't see that happening, there are some elegant designs using composites but even at their simplest they wouldn't come anywhere near the cost of conventional rim and spokes.
Click to expand...

Yeah, development of the hub motor seems to be frozen in time except for the efforts ebikes.ca is making.
It is probably because watt limits are actually getting enforced in the USA.

The most efficient DD climber i have to date is a RH212 on 52v/40A in a 24" wheel.
Billy goat, but it still needs 2000w of peak power to go up 7% grades and such w/o falling out of the efficiency band and overheating ( you have to go full blast because high RPM is where the efficiency is )

So the rational thing to do as a law abiding citizen is a mid drive for an area like mine ( very mountainous ).

A car doesn't have this legal pressure but motors are expensive, controllers are expensive, and batteries are expensive, but gears and an axle are not, so i think for that reason the inboard motor is a win for the electric car & it would be extremely hard, maybe impossible for the hub to compete there with today's motor technology.
 
For me this post is more about the brilliant idea of having a hub motor be both the motive force
AND
The fully active active suspension.
(that's 2 for the price of 1!)

Here's what active active suspension can do!

Then I'm thinking; there a number of members here capable of making a prototype of this for an E-bike and perhaps it'll take off from there.

Maybe even Justin will be interested?
Combine this with FreeGen and we have a paradigm shift in EV!
 
Active suspension on a hub motor for an ebike?

A suspension seat post would be a lot cheaper.. and not having the suspension in the hub makes for much nicer wheel changes, especially when your low to mid power DD motor is already 15lbs average..
 
My hubs keep braking.

Just parking it for 2 weeks my motor will get stuck. A normal person wouldn't be able to get it working after such an event and the return rate for a commercial product would be 100%.

There were some guys in my land doing it far up north with buses / coaches and they really couldn't keep them serviced. Rather they were quing for the garage rather than being in service shuttling customers.

Company went bust as well as the above "fantasy" one.

I have never seen anyone doing a hub motor and tripple the amount and size of the rubber to get the "hang" on it :D - regarding the care tyre / hub.
 
Do you live in a humid or rainy area?

Water ingress is another serious problem with DDs, of which there are a few cures.
 
Late 1800s: "Why change tires or bother with simple little suspension seat poles when you can just use a horse"
Late stone age: "Why bother saddling and feeding a horse when you can just walk"
Somewhere in between: "Why bother loading shit onto a wheeled cart when we can just carry it all"

Why do we do these things?
We do them not because they are easy but because we're too stupid to realize how difficult they'll be!.. initially...
:D
 
neptronix said:
Yeah, development of the hub motor seems to be frozen in time except for the efforts ebikes.ca is making.
It is probably because watt limits are actually getting enforced in the USA.

The most efficient DD climber i have to date is a RH212 on 52v/40A in a 24" wheel.
Billy goat, but it still needs 2000w of peak power to go up 7% grades and such w/o falling out of the efficiency band and overheating ( you have to go full blast because high RPM is where the efficiency is )

So the rational thing to do as a law abiding citizen is a mid drive for an area like mine ( very mountainous ).

A car doesn't have this legal pressure but motors are expensive, controllers are expensive, and batteries are expensive, but gears and an axle are not, so i think for that reason the inboard motor is a win for the electric car & it would be extremely hard, maybe impossible for the hub to compete there with today's motor technology.
Click to expand...
Regulation stifling innovation
 
Would maglev rims work? Half an inch of gap might be enough but would field windings be efficient with that and would it be possible to recirculate power to 'jack' the rim, pull down one side with load and power up the other?
 
Lotus has a hub motor e-racing program where they clim to have made a Lotus racecar with 4x hub motors corner, handle, and lap better times, than the equivalent modern rwd or awd racecar f a similar class.


QUOTE:
Protean Electric and Lotus found that most negative effects of added unsprung mass could be eliminated by adding suspension damping, and that the ability to utilize accurate torque vectoring actually improved car's handling so much that the net effect of the whole arrangement was positive.
 
DogDipstick said:
Lotus has a hub motor e-racing program where they clim to have made a Lotus racecar with 4x hub motors corner, handle, and lap better times, than the equivalent modern rwd or awd racecar f a similar class.
Click to expand...

Most of us can't count on racetrack quality pavement. I ran over a recessed manhole cover near my house the other day and broke the retaining pins off my battery case.
 
stan.distortion said:
Would maglev rims work? Half an inch of gap might be enough but would field windings be efficient with that and would it be possible to recirculate power to 'jack' the rim, pull down one side with load and power up the other?
Click to expand...
That's an interesting idea stan.
Waaay above my pay-grade though. :)
 
Chalo said:
Most of us can't count on racetrack quality pavement. I ran over a recessed manhole cover near my house the other day and broke the retaining pins off my battery case.
Click to expand...
You should try the 'New South Africa'!
Here the only way to avoid potholes. pot-pits, pot-dongas would be rims the size of the big wheels at fairgrounds with helium filled tyres!
Try a search if you dare!
 
Maglev rims... some magic forces, and look ma, no hands
For the cheapo-tinkering people here, just remember that the solid matter is built from tiny little particles with lots of void between them, everything held by electromagnetic forces. So we got maglev already, everywhere, for free.
 
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