Wheel Hub Motor on future vehicles and its effects
Wheel Hub Motor on future vehicles and its effects
(OP)
I have been researching future trends in vehicle design lately and there seems to be a clear trend that most major manufacturers believe wheel hub motors will be used almost exclusively.
I can see the benefit in doing this because you are able to use the large wheel diameters to reduce motor currents, among other things.
The one side-effect I can see is the additional weight of a wheel/hub motor design compared to a traditional wheel/rim design and the effect of this extra weight on the suspension. Specifically the increased un-sprung weight versus the reduce body weight of a future vehicle (reduce body weight that would be needed to make an electric vehicle really viable).
Electric motors have come a long way, but so far, you cannot escape the need for lots of copper for high power/current designs that would be needed for a vehicle drivetrain.
I am more or less interested in what you folks have to say on this topic. I work in the robotics field but have always been interested in vehicle design.
Thank you up-front for your opinions.
I can see the benefit in doing this because you are able to use the large wheel diameters to reduce motor currents, among other things.
The one side-effect I can see is the additional weight of a wheel/hub motor design compared to a traditional wheel/rim design and the effect of this extra weight on the suspension. Specifically the increased un-sprung weight versus the reduce body weight of a future vehicle (reduce body weight that would be needed to make an electric vehicle really viable).
Electric motors have come a long way, but so far, you cannot escape the need for lots of copper for high power/current designs that would be needed for a vehicle drivetrain.
I am more or less interested in what you folks have to say on this topic. I work in the robotics field but have always been interested in vehicle design.
Thank you up-front for your opinions.





RE: Wheel Hub Motor on future vehicles and its effects
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Wheel Hub Motor on future vehicles and its effects
Various forms of "sprung hubs" have been around for nearly a century. Problem is, when they run out of travel, the situation becomes worse than ever.
It would be nice to come up with some kind of progressive and powerful compounding for re-generation. That way the brakes could finally be almost eliminated.
In a fashion somewhat similar to hydraulics, why can't powerful magnetic pulses be sent through the upper and lower control arms?
RE: Wheel Hub Motor on future vehicles and its effects
Another thing comes to mind. If you have the suspention built into the wheel hub itself, then you would essentially be reducing the available volume of which to package your motor/gears. Isn't this counter productive? Whatever the amount of suspension travel you have would take-away from your motor diameter?
RE: Wheel Hub Motor on future vehicles and its effects
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Wheel Hub Motor on future vehicles and its effects
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Wheel Hub Motor on future vehicles and its effects
the are equally bad. The point i was was trying to make is that whatever suspension travel you have with a wheel hub motor/suspension design takes away from the max diameter you can have for a motor.
Assume a 20" Wheel ID and 5" of total suspension travel. With a conventional suspension you could have a max motor OD of 20". With a wheel hub/suspension design the max motor OD would be 15".
Motor OD, or more specifically working diameter of the stator/magnets, is a direct function of motor output torque and therefore motor current. Motor diameter is important because the less motor current you have the high effciency you have (in most cases).
RE: Wheel Hub Motor on future vehicles and its effects
The guys that designed the motors are really worried about the unsprung mass of the motors, so we are working on using very lightweight materials to lighten them.
I guess we will have to wait a few months until it is rolling to see what affect the extra unsprung mass will have
Ryan (New Zealand)
RE: Wheel Hub Motor on future vehicles and its effects
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Wheel Hub Motor on future vehicles and its effects
The only way that we figure to counteract this is to use active damping, which is coming on leaps and bounds recently. This should hopefully elleviate all handling problems, and allow the suspension to handle as you desire.
RE: Wheel Hub Motor on future vehicles and its effects
How are you going to get the power to drive the active dampers? What makes you think that you can resolve all handling issues (eg aforesaid gyroscopic effects) with dampers? Do you really have a source for them in the timeframe of your project?
I've made a suggestion, instead of chasing rainbows, why not try the experiment and see if it matters?
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Wheel Hub Motor on future vehicles and its effects
The project is an ongoing one, so we have no timeframes, but at this stage we do not have any active dampers avaliable, although there is a lot of R&D into them at the moment. I dont believe that active damping will solve all problems but will be able to solve the large majority of problems.
As per the experiment, I will see what I can do, hopefully we will be able to get something like that working to test it out.
Cheers,
Ryan
RE: Wheel Hub Motor on future vehicles and its effects
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Wheel Hub Motor on future vehicles and its effects
Can you give a website link to your design?
I found a few, interesting in-hub motor designs, ranging from mopeds avaialble for sale:
http://www.electricrider.com/crystalyte/index.htm
to an 8-wheel drive vehicle from General Dynamics & the US Army (very skimpy details on page 4):
http://ww
and a DARPA-funded 4-wheeler (General Dynamics, Boeing, US Navy, Magnet Motors): http://www.dtic.mil/ndia/ewc/Kennedy.pdf
The latter two were apparently tested in 2002.
RE: Wheel Hub Motor on future vehicles and its effects
Gyroscopic effects - lift the front wheel of an adult bicycle off the ground and spin it vigorously, then move the handlebars left and right and feel the reactions.
It's called precession. See http://en.wikipedia.org/wiki/Precession
Bill
RE: Wheel Hub Motor on future vehicles and its effects
I have not published my design. I do have a bunch of ideas though.
RE: Wheel Hub Motor on future vehicles and its effects
LOL!!! I've just gotta make it to OZ one of these days. I have a feeling that I'll be right at home.
Rod
RE: Wheel Hub Motor on future vehicles and its effects
what is the typical unsprug weight of a modern passenger sedan? (or better yet sprung/unsprung ratio) at what point would that weight effect ride/handling?
RE: Wheel Hub Motor on future vehicles and its effects
Sometimes the chin is just to far out for me to resist the temptation. I know, self discipline and discretion are desirable traits I sometimes lack.
I am sure you would fit right in here.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Wheel Hub Motor on future vehicles and its effects
I have never done the FORBIDDEN EXPERIMENT, directly, but I invented it due to the repeated mantra about unsprung mass.
We used to have a beam axle and an IRS in the same car, with the same tyres, and the same front suspension. The difference in usprung mass was perhaps 10-15 kg per wheel.
There were certain circumstances in which a difference was easily detectable, but for the vast majority of the time, on the vast majority of road surfaces, the differences were unimportant.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Wheel Hub Motor on future vehicles and its effects
opposite direction (planetary).
I haven't thought of this until now but could you counter balance for added weight?
I know something is wrong with that statement but it works on our large tools.
Cheers
I don't know anything but the people that do.
RE: Wheel Hub Motor on future vehicles and its effects
that's fine, for straightaways!
RE: Wheel Hub Motor on future vehicles and its effects
RE: Wheel Hub Motor on future vehicles and its effects
RE: Wheel Hub Motor on future vehicles and its effects
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Wheel Hub Motor on future vehicles and its effects
Smaller cars dont need the huge amounts of torque, so smaller motors (and therfore wheels) would work.
Ryan
RE: Wheel Hub Motor on future vehicles and its effects
Our car website is www.nzeco.net We are working with Hybrid Auto in Brisbane who are supplying us with the 2 in-wheel electric motors and allowing us to use many components they have developed and helping us with their outstanding expertise and knowledge of electric cars.
Regards,
Ryan
RE: Wheel Hub Motor on future vehicles and its effects
I would like to know more about these in-wheel electric motors from Hybrid Auto. Could you give me a clue how to find more information about that? The link www.nzeco.net does not say nothing about hybrid cars or in-wheel electric motors. I called Hybrid Auto but a man that I contacted said he do not know that they supply nz company with in-wheel electric motors.
Regards,
Dimitar
RE: Wheel Hub Motor on future vehicles and its effects
Forgot to mention the project is for the University of Waikato, not a company and our website expired, so we are working on another one.
Hybrid Auto works out of Brisbane.
Cheers,
Ryan