« Abu Dhabi group to produce 160km/h electric car | Main | Coming soon, maybe - another electric supercar »

Why in-wheel motors are the silver bullet for EVs

Any boy racers out there should be asking this question. Why are major manufacturers not putting more emphasis on in-wheel electric drive systems?

So often EVs are dismissed by drivers as glorified golf carts, but if you look at the performance claims of the electric cars that have in-wheel motors, they promise a satisfyingly white-knuckled experience for the most ardent petrolhead. Take the ZAP-X that I wrote about last week - its in-hub electric motors deliver 644 horsepower in all wheel drive mode and a top speed of 155mph.

Then there's the PML Mini QED that was show-cased last summer. With four 160 horsepower electric motors it can reach 150mph and does 0-60 in 4.5 seconds. I'm not remotely technical, but even I can see that there's something going on here.

And it gets even better. Apart from performance, there are many more advantages to having your motors tucked away inside the wheels.

For a start, in-wheel technology is adaptable to other vehicle chassis, so there's no need to design from scratch and you can benefit from all the work that's gone into low cost component sourcing for a production vehicle.

These motors also save masses of space and weight and use energy more efficiently by allowing for a four wheel drive system without need of transmission, driveshafts, differential gears or other complex mechanical components. The resulting extra space facilitates the storage of batteries, giving the option of allowing for extra modules to be fitted to improve power and range - or just making more space for passengers and their clobber. There's loads more, so if you want the full science bit, here it is. Dazzling stuff.

The reason that PML originally chose the MINI to demonstrate their technology was because of its broad appeal and iconic styling. It's also heavy for its size and doesn't offer much space to integrate the component set required for a top performance electric car, so they took the view that if they could successfully convert this vehicle, anything else should be a dawdle by comparison.

Starting with a standard BMW Mini One, PML discarded the engine, the disc brakes, the wheels, and the gearbox. These components were replaced by four electric wheels, a lithium polymer battery, a large ultra capacitor, a very small ICE with generator (so small it almost fits alongside the spare wheel), an energy management system and a 'sexy' in-car display module. It's worth having a look at the specification just to begin to understand what fabulous technology has gone into this car.

PML proudly claims on its website that "(This) is truly an outstanding example of British innovation at its best!" I'm totally with them on that one and I'm just wondering what it takes for them to be discovered by more EV manufacturers. And just imagine what they could do for multi-wheeled truck and bus manufacturers. 

The whole auto world seems to be battery-obsessed at the moment, but I'm starting to think that in-wheel motor technology is much more of a silver bullet when it comes to creating an electric car that ordinary drivers will actually desire.

Posted on Friday, February 16, 2007 at 05:02PM by Registered CommenterChristine Gupta in | Comments10 Comments | References1 Reference

PrintView Printer Friendly Version

EmailEmail Article to Friend

References (1)

References allow you to track sources for this article, as well as articles that were written in response to this article.
  • Response
    Response: cialis
    cialis online cialis http://www.youtube.com/user/mcialisdailym [url=http://www.youtube.com/user/mcialisdailym]cialis[/url] buy cialis http://www.youtube.com/user/mcialisdailym [url=http://www.youtube.com/user/mcialisdailym]buy cialis[/url]

Reader Comments (10)

Except, that inwheel motors have one ( arguably huge ) drawback.
Unsprung mass.
To illustrate shortly, the more mass you have not held up by suspension, the rougher your ride. Now, inwheel motors can completely do away with mechanical brakes, so that is going to save some unsprung mass, and some transmission parts are also going to go away, which again are partly unsprung mass.
But still, a lot of copper wire in the wheels is going to weigh some. In short, in-wheel motors require amazing power-to-weight ratios to compete in handling and ride comfort with "normal" motor placement.
Whether the benefits ( more room in body, precisely electronically controlled AWD, less moving parts ) are going to outweigh the drawbacks outlined above, is to be determined hopefully by open market competition.
February 17, 2007 | Unregistered Commenterkert
Kert, The other big benefit is achieved when you combine in-wheel motors with digital control.Because of weight savings by no longer needing heavy components for drive train,transaxles, diffs etc you can specify lighter suspension and this could be smart suspension like in electro-megnetic particle systems. Overall you save so much weight that you obtain efficiency in power to weight, and even the structure can become composites. You do need all wheel control software but now days this is no longer rocket science. This has to be a design engineering option for the next gerenations of EV's as the added range and performance pluses are a strong argument to shape basic design. I have driven a beast with 16 driving wheels and articualtion and it was as smooth as silk!
February 21, 2007 | Unregistered CommenterAsh Gupta
Ash I'm very curious - where was this 16 wheel drive vehicle? any pictures/specs?

it does occur to me that the future ev might as a matter of economics have say 6 smaller lighter/cheaper mass produced inwheel motors configured not to be in parallel rows so that a light weight active suspension [on license from Citroen perhaps?] could be very effective at providing a truly smooth ride [even at 20mph over road humps!]

if a standard small inwheel motor could be agreed on then heavier larger vehicles could just add additional wheels and plug them into the CAN bus. Also when a delivery vehicle is running empty it can just hoist the unneeded wheels of the road, as many ICE trucks do at the moment.
February 26, 2007 | Unregistered CommenterTaranga
Are the motors sealed so they can handle the water and also in climates like Canada we have snow so they have to be able to deal with the salt?

If you do the motor in the wheel do you regenative braking?
April 19, 2008 | Unregistered CommenterSEO Company
Thanks a lot for the tips................!
i will keep visit your blog later again........!
February 9, 2009 | Unregistered Commenternoleaeron
I love the idea of in-wheel motors. I am soooo looking forward to napa and carquest coming out with kits for switching your current truck/car to a in-wheel drive. and the way I see it. even if I have to pull the big V8 and drop in a 4CYL and throw a 60kw gen in place of the tranny. I think the gas mileage improvement of a hybrid would be great. and why am I worried about unsprung weight. my truck rides rough already. its suppose to. its a truck. if I want a smooth ride I will invite a few of the great USA over weight people along :-) besides when I strap my 4300 lb travel trailer on my truck it rides like a dream. and 600hp is double what my poor old tired V8 has now (200,000 miles) and think of how much more quieter that little 4cyl pumping out 60kw would be then the big V8. if my 20 gal gas tank could run the generator for say 10 hours. I could make close to 500 miles per tank instead of 180 miles per tank now. like I said .... NAPA bring on the kits. I am totally ready to convert my GMC.
June 12, 2009 | Unregistered Commenterwyoguy
This has to be a design engineering option for the next gerenations of EV's as the added range and performance pluses are a strong argument to shape basic design. I have driven a beast with 16 driving wheels and articualtion and it was as smooth as silk!
January 6, 2010 | Unregistered CommenterMoby Wrap
First of all, I would like to appreciate the effort that you have put in making such an informative blog. I enjoyed this post of yours and I must say that every time I come back to your blog, I always have something new and informative to read. Thanks for keeping me updated
Atypical this submit is totaly unrelated to what I used to be looking out google for, but it surely was listed on the first page. I assume your doing one thing right if Google likes you enough to put you at the first web page of a non related search.
Ban on women driving should be considered world wide... :-) I would never allow my wife driving my car.. :-) fgvoup fgvoup - <a href="http://www.gianmarcolorenzishoes.org.uk">Gianmarco Lorenzi Shoes</a>.
December 2, 2011 | Unregistered Commenterxotmro xotmro

PostPost a New Comment

Enter your information below to add a new comment.

My response is on my own website »
Author Email (optional):
Author URL (optional):
Post:
 
All HTML will be escaped. Hyperlinks will be created for URLs automatically.