• Sep 1st 2006 at 5:37PM
  • 8
Justin over at Treehugger.com recently wrote about a standard Mini One which was converted into a stunning gas-electric hybrid by the British engineering firm PML. Instead of implementing a complex, parallel drivetrain system that splits power between electricity and gas, this little rocket's wheels are only driven off it's electric motors. There's one in each wheel. The small internal combustion engine only comes to life when the batteries need recharging. Since it's a plug-in hybrid, that shouldn't happen all that often.

The benefits that PML claims their in-wheel drive technology has are as follows:
  • It's adaptable to other chassis
  • It eliminates the need for gearing and a mechanical drivetrain
  • It allows more space inside the car
It's hard to argue when they claim a 0-60 time of 4.5 seconds and a top speed of 150 mph. Each of the electric motors is rated at 160 bhp, hence the 640 horsepower total. Oh, and the range is phenomenal. It can go 200-250 miles on the battery and capacitor combination alone while the inclusion of the combustion engine adds 700 or so miles to your trip yielding a gas mileage of up to 80 mpg.

But aren't hub motors bad? It seems as though every automotive engineer would tell you that overall weight reduction is important, but reducing unsprung weight is paramount in a high performance car. For those of you unfamiliar with the technical sections in the back of your favorite car magazines, unsprung weight is comprised from the parts of your car that aren't supported by the suspension (wheels, tires, the suspension itself and the parts directly bolted to them). It's quite simply a high-performance faux pas. Given the circumstances, I think I could overlook it just this once.

[Source: Treehugger]


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    • 1 Second Ago
  • 8 Comments
      • 9 Years Ago
      Ok, I'm impressed. At least a little.

      I'd be a lot more impressed if they had used a small diesel instead of a gas-powered generator (or better yet, an SVO engine). While it's nice to get 80+ mpg, it would be even better to do that on a fuel we don't have to buy from OPEC. Biodiesel is ideal for engines that are run at constant RPM and load. And SVO would be even better.

      I'd be REALLY impressed if this vehicle was priced under $20,000, and the required battery changeout was less than $5,000. Since neither of those costs was anywhere to be seen in either article, I'll bet that they are considerably higher.

      The 0-60 numbers are double-giant overkill, but they do open up the possibility that this vehicle could be used to occasionally tow a light trailer, which would make it a suitable replacement for my small pickup truck.
      • 9 Years Ago
      4.5 seconds 0-60 is crazy fast, I am starting to find hope with electric cars.
      • 8 Years Ago
      Sounds good, but lets see if it really works the way it is meant too. And see what kinda "bugs" show up.
      • 9 Years Ago
      I am a little bit angry, I have tip you 1 week ago about this news without any response. To bad, tha means you never read your tips!

      That was the last time!
      • 9 Years Ago
      I was going to post a really long answer to this, on the good and bad of electic hub motors, but I did mannage to find out something about the weight on anouther blog that looks promising. Look at comment 29.

      http://www.autoblog.com/2006/07/21/pml-s-mini-qed-boasts-640-in-wheel-electric-horsepower/2#comments

      "First Unsprung weight! The 120kW inwheel motors and magnesium alloy wheels, with the tyres, has a total mass of 24kg. The original assembly mass was 22.5kg! Not much added I think! The ride feels the same. Remember the car has full regen braking so the brake hubs and disc's have been removed."

      I don't remember how much a kg is compaired to a pound... but thats not a bad change at all... they did it probably by removing the standard brakes, a custom designed suspention, and vary light magnesium alloy wheels. They also might of went with smaller rims which can shave some pounds...

      All In all, Im vary impressed if this is true... So impressed I want to drop off a Ford Fiesta, or some other horrible geek ride, and tell them to make me a evil dork machine so I can go chew up Camaros, Mustangs, and whatever else I can find at the local drag strip.

      I will miss the stick shift though... that was fun.
        • 7 Years Ago
        2 Kg is about 4.4 pounds, so that is adding a bit to the unsprung weight.

        I'm a bit leery of the plan to eliminate standard friction brakes. Regenerative braking tends to get less effective at very low speeds, which is why hybrids and EVs shift from regenerative to friction braking at low speeds. Also, what holds the car in place on a hill? Would it have to use electrical power just to stand still on a slope? If the power is switched off or fails, there is no backup brakes!

        PML isn't the only one working on wheelmotors. Siemens is developing a design that is even more compact, incorporating suspension and steering and motor in one compact unit - and it still includes friction brakes!
      • 7 Years Ago
      It seems that you could reduce even further the unsprung weight by integrating the electric motor and the wheel into a unified unit, meaning the wheel __IS__ the motor with a tire mounted on it.
        • 7 Years Ago
        Yes, but unless it was a "run flat" design, that means carrying an extra motor in your spare tire, and it complicates tire changes.
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