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Author Topic: Could car wheels be modified to act as generators?  (Read 34938 times)

satguy1

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Could car wheels be fitted with windings and magnets to make them generate electricity as they turn? The car would be a gas/electric hybrid. The batteries would be charged any time the vehicle was in motion.
« Last Edit: 06/02/2009 22:58:18 by chris »

lightarrow

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Re: Could car wheels be modified to act as generators?
« Reply #1 on: 06/02/2009 17:19:10 »
Could car wheels be fitted with windings and magnets to make them generate electricity as they turn? The car would be a gas/electric hybrid. The batteries would be charged any time the vehicle was in motion.
If they only generates electricity you wouldn't get an hybrid, but electromagnetic brakes. If those brakes acts also as electric engines, than you have made a kind of KERS (Kinetic Energy Recovery System) even if usually they use a mechanical, instead of electric, system:

http://en.wikipedia.org/wiki/Regenerative_brake#Use_in_motor_sport_.28KERS.29

Vern

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Re: Could car wheels be modified to act as generators?
« Reply #2 on: 06/02/2009 17:51:37 »
When a good clean design finally settles in I suspect they will have motors in each wheel. When breaking the motors would generate power back into its storage system which could be some combination of battery and / or gyro-generator. If electrics caught on my guess is that batteries would be rapid change things that service stations owned and leased to users.

To fill-er-up you just zip into the station and change the quick-connect battery.
« Last Edit: 06/02/2009 17:53:10 by Vern »

LeeE

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Re: Could car wheels be modified to act as generators?
« Reply #3 on: 06/02/2009 19:15:38 »
Could car wheels be fitted with windings and magnets to make them generate electricity as they turn? The car would be a gas/electric hybrid. The batteries would be charged any time the vehicle was in motion.

If you generate energy by taking it out of the wheels' rotation it'll just mean that the engine has to work harder to keep the wheels rotating at the same rate.  Also, as you're introducing another stage in the power chain, which will not be 100% efficient, you'll end up with s slightly less efficient system overall.  As the others have said, it's only real benefit would lie as a braking system where some of the energy used to brake the car can be recovered instead of being wasted as heat.

lyner

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Could car wheels be modified to act as generators?
« Reply #4 on: 07/02/2009 00:39:12 »
This seems to be just another version of "Is perpetual motion possible?"
And it isn't.
Of course, motor/generators in wheels are the way to go, however.

LeeE

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Could car wheels be modified to act as generators?
« Reply #5 on: 07/02/2009 16:43:34 »
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Of course, motor/generators in wheels are the way to go, however

Weeell, I can't unconditionally go along with that.  This is because putting the motors etc in the wheels increases the unsprung weight.  This not only adversely effects performance, in terms of response times, damping and forces when the wheel goes over a bump, but also as a consequence, results in increased wear, both on the tyre and the road, which then reduces efficiency as a consequence of those increased forces.

lyner

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Could car wheels be modified to act as generators?
« Reply #6 on: 07/02/2009 17:07:59 »
I agree; perhaps I should have said "for each wheel" rather than "on each wheel". Having said that, motors can be made extremely light these days

LeeE

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Could car wheels be modified to act as generators?
« Reply #7 on: 07/02/2009 17:57:42 »
Perhaps one solution would be to move the suspension from between the hub and the chassis to between the hub and the rim?  Off-set spoked wheels provide a degree of suspension, as well as reducing the unsprung weight, so perhaps some type of 'intelligent' curvy-type hollow graphite spokes, filled with a lightweight damping fluid, might work.  I suppose that it might also be possible to incorporate 'intelligent' spokes in an integrated active hydraulic design for the hub/rim assembly.  Effective braking might be more difficult to achieve with the suspension between the hubs and rims though.

Vern

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Could car wheels be modified to act as generators?
« Reply #8 on: 07/02/2009 21:19:31 »
I was thinking of the wheel itself being the motor / generator. It need not necessarily be all that much heavier than a wheel that is not a motor. This would then allow software control of differential forces etc.

LeeE

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Could car wheels be modified to act as generators?
« Reply #9 on: 08/02/2009 00:19:56 »
I was thinking of the wheel itself being the motor / generator. It need not necessarily be all that much heavier than a wheel that is not a motor. This would then allow software control of differential forces etc.

How could it not be heavier than a comparative wheel that does not incorporate all the motor stuff?  The only way this could work is by comparing dissimilar wheels, which rather invalidates the comparison.  You can't use exotic lightweight materials in the motor wheel and compare it with an ordinary wheel made out of pressed steel, and then claim that it's not much heavier; you'd need to compare the motor wheel with a motorless wheel made using the same technology.

lyner

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Could car wheels be modified to act as generators?
« Reply #10 on: 08/02/2009 14:29:28 »
A drive shaft with a flexible mount for each motor would do the job. The effective unsprung mass would be the same or better than using the present system. You would need only one universal coupling, too. FWD would also mean less unsprung mass per wheel.

LeeE

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Could car wheels be modified to act as generators?
« Reply #11 on: 08/02/2009 22:41:24 »
Umm... the present system is to use a chassis mounted engine with flexible drive to the sprung/suspended hubs.

Now with a hydraulic drive system, on the other hand, not only do you get a very flexible drive transmission to the wheels but the weight of the drive rotors could be off-set against a reduction in weight of the braking system components because the hydraulic system could also supply the dynamic braking requirements (you'd still need a parking/hand-brake though).

lyner

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Could car wheels be modified to act as generators?
« Reply #12 on: 08/02/2009 22:59:33 »
I had a 2CV with inboard discs! Revolutionary.

LeeE

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Could car wheels be modified to act as generators?
« Reply #13 on: 08/02/2009 23:09:52 »
I had a 2CV with inboard discs! Revolutionary.

Well yes, until you put the brakes on, at which point they would stop revolving, hopefully  ;)

lyner

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Could car wheels be modified to act as generators?
« Reply #14 on: 09/02/2009 18:54:15 »
 ;D

lyner

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Could car wheels be modified to act as generators?
« Reply #15 on: 09/02/2009 18:56:52 »
LeeE
Quote
Umm... the present system is to use a chassis mounted engine with flexible drive to the sprung/suspended hubs.
But the engine (/gearbox) is not on a flexible mount in the conventional system - you need two UJs on each shaft.

The motor could be at the centre of radial motion of the wheel suspension - very low moment of inertia and hardly affecting the total effectively unsprung mass.
« Last Edit: 09/02/2009 18:59:00 by sophiecentaur »

LeeE

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Could car wheels be modified to act as generators?
« Reply #16 on: 10/02/2009 17:08:05 »
Apart from the engine mounting bushes, to deal with low-amplitude, high-frequency vibrations, you don't want the engine to be flexibly mounted in the chassis; that's what stops the engine from turning itself around instead of the drive shafts.  The suspension then, is located between the chassis and the hubs, so it's only the wheels that are unsprung and the UJs are there just to cope with the changing geometry between the essentially rigidly mounted engine in the chassis and the suspended hubs.

Although brakes seem to be mostly mounted on the hubs these days, I can remember some older designs where the disks were mounted in-board i.e. on the drive shafts close to the UJs, which effectively reduced their unsprung weight.  The trouble is, it makes them harder to maintain as you've got to lift the entire car up to service them, instead of just taking a wheel off.

I don't have a problem with using multiple engines on an engine per wheel basis but there is an issue with ensuring that each one supplies the right amount of power;  should one of the engines suddnely brake down or drastically lose power it would be like applying the brake on that wheel only, which would make the vehicle very unstable and possibly uncontrollable - not good.  Even then though, I see no benefit to mounting the engines outboard of the UJs, which you'll need in any case if any of the weight of the engines is to be sprung; if you don't mount the engines on something that is attached to the chassis then you're right back to unsprung engines again.

lyner

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Could car wheels be modified to act as generators?
« Reply #17 on: 10/02/2009 18:51:49 »
My flexible mounting would be gimbals - not rubber! I don't understand your comment about mounting motors outboard of UJs.

ABS manages to balance the braking effort pretty well so I doubt that balancing the load on four Electric Motors would present a serious problem with modern control systems. As for one motor fault producing serious consequences - siezed brakes, broken wheel bearings and broken half shafts on a limited slip differential can all give their own problems.  Not to mention collapsing suspension (been there!).
Any decent control system could switch to two wheel drive to give good control whilst you bring the vehicle to a halt.

LeeE

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Could car wheels be modified to act as generators?
« Reply #18 on: 11/02/2009 13:11:43 »
I think we may have gone running off in different directions here and are talking at cross-purposes; I can't quite see what, or where you'd be mounting anything, on gimbals.  Looks like we may have to resort to diagrams.

But apart from that, while ABS manages a reasonable, but not perfect, job of preventing wheel lock-up during braking, just by comparing the rotation of each wheel in comparison to the others, it doesn't try to balance brake forces; it would need to be a pretty expensive high-performance car to justify the cost of an active/intelligent braking/traction control system.

While I agree that a sort of drive-by-wire system would probably be able to cope with the potential problems inherent in a design using independent engines for each wheel, aren't you just adding one system to deal with design problems in another when the design problems could be avoided in the first place?  Sure, any many different faults can occur to just one wheel in a multi-wheel design utilising a single drive source anyway, but why add to their number?

Having said that, I'm still not sure what sort of design you're thinking of now, so perhaps it's benefits would outweigh the potential problems.  I'm a bit confused.

lyner

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Could car wheels be modified to act as generators?
« Reply #19 on: 11/02/2009 15:11:07 »
A picture is worth a thousand words.
Actually, it may only need a horizontal pin through the motor, but a vertical axis would probably be needed too in order to get the geometry right.
The longer the shaft, the better, probably.
It is likely that suitable wiring / cross coupling of the motors could  act as a differential. It's amazing what you can do with electromagnetism, geometry and phases.

teragram

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Could car wheels be modified to act as generators?
« Reply #20 on: 11/02/2009 18:28:15 »
I think this might be of some interest
http://www.youtube.com/watch?gl=GB&hl=en-GB&v=i1uTR-8KarE

LeeE

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Could car wheels be modified to act as generators?
« Reply #21 on: 12/02/2009 17:13:09 »
Right - I'm with you now.  There you have an engine rigidly mounted in the chassis and driving the suspended hubs.  You'd need a UJ/flexible joint at each end of the drive shaft though (think about it - it's rotating).

I think the only real factor governing the length of the shaft is the amount of movement of the hub you want to accommodate, primarily in the vertical plane, but also for general changes in geometry due to flexure of the wishbones and their bushes.  A longer shaft allows a greater range of movement but increases mass and is more susceptible to torque-twist.  Mounting the brakes inboard, near where the arc is in your drawing, reduces the unsprung weight, but like I said earlier, makes them more difficult to maintain, and perhaps, cool.

lyner

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Could car wheels be modified to act as generators?
« Reply #22 on: 12/02/2009 23:23:48 »
You don't need a UJ on the inboard end because the motor 'casing' can rotate about two axes (gimbals - see my 'pin' on the diag.) to accommodate the up/down and fore/aft movement of the hub. Some spline joint may be needed if the radius  of rotation of the suspension is not the same as the length of the drive shaft.

Inboard disc pads are as easy to change as outboard pads. The motor would probably be as easy (and cleaner) to remove as a wheel and would allow a disc (which could be right next to it) to be replaced. Actually, the disc could even be mounted on the other side of the motor - if the shaft passed right through the motor.  Inboard discs represent less unprung mass, too.

The movies in teregram's  links show a substantial extra unsprung mass is involved. With an 'active' suspension, this could be coped with, however.

LeeE

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Could car wheels be modified to act as generators?
« Reply #23 on: 13/02/2009 00:01:05 »
So you want movement of the wheel to not only move the entire drive-shaft but also the motor too???

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Inboard disc pads are as easy to change as outboard pads

I can assure you that they're not, at least not on anything larger than a go-cart, although I do agree that inboard disks represent less unsprung mass.  I think I've already said that.

Using an active suspension system could alleviate most of the control issues that come from increasing the unsprung weight, but they can do nothing to deal with the unnecessarily increased forces and wear upon the tyres and road that would also result from increasing the unsprung weight.  It's a bad solution to an unnecessary problem.

You should stop and ask yourself why, if this is such a better way of doing things, aren't they already being done this way?

lyner

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Could car wheels be modified to act as generators?
« Reply #24 on: 13/02/2009 17:16:23 »
So you want movement of the wheel to not only move the entire drive-shaft but also the motor too???
The motor would be extremely light compared with an 'engine' and it would be right at the fulcrum. That would mean a very low moment of inertia, which corresponds to a low unsprung mass (just think of the small angle of rotation of the shaft / motor around the fulcrum). I would envisage the drive shafts being almost full width of the car - not unlike some of the torsion bar suspensions.
Quote

Quote
Inboard disc pads are as easy to change as outboard pads

I can assure you that they're not, at least not on anything larger than a go-cart, although I do agree that inboard disks represent less unsprung mass.  I think I've already said that.
I don't know which veh you worked on but for me it was a piece of cake. You lift the bonnet and reach in - take the pins out and off comes the calliper. You don't even need to take off a wheel - I've done it in ten minutes. In a system with regen braking, it's unlikely that you'd need to change them very often in any case.
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Using an active suspension system could alleviate most of the control issues that come from increasing the unsprung weight, but they can do nothing to deal with the unnecessarily increased forces and wear upon the tyres and road that would also result from increasing the unsprung weight.  It's a bad solution to an unnecessary problem.

You should stop and ask yourself why, if this is such a better way of doing things, aren't they already being done this way?
I agree - except the active suspension keeps your ride with 'g' pointing down. Dunno how your eyes deal with the horizon waving about tho'; that demo car looked like a scary ride, actually. It may be an acquired taste or it could just be a lot better.
They aren't being done the 'new way' because it's not been feasible until lately.
My suggested system is more basic and cheaper.

 

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