The key material in the SIM-WIL's in-wheel motors, DuPont's Zytel HTN polyphthalamide (PPA), is used in the motor bobbins shown here. The material is stronger, lighter, and more cost-effective than what it replaces. (Source: DuPont Performance Polymers)
This seems like a great example of engineers thinking out of the box. Maybe I dont' know enough about the space, but putting motors in wheels as a means of increasing mobility on a single charge seems pretty unique--and compelling. Is any one aware of others using this as a mainstream approach?
Beth, acutally this is the way electric cars should be designed. Having one big electric motor is really a legacy of the ICE design philosophy. Of course, it made sense there. I always assumed that this is how electric cars would be designed, and I believe that over the years there have been such prototypes or design studies. Locomotives, for example, the real model for how we should be designing electric and hybrid vehicles, use a motor for each driven axle. Of course, becuase they run on rails they don't need one for each wheel. In the conventional vehicle world, companies like Audi have long touted all wheel drive, where power is feed to each wheel in an optimum way. With modern control systems and, of course, innovations in the motors themselves, this should be a no brainer for the modern electric or hybrid vehicle.
I have to say, that I have heard of this design approach before (motors in wheels) but not sure if it was ever on a vehicle intended for production. Makes perfect sense, though. No more drive shaft tunnel or heavy gearbox and differential. I'll bet it's low maintenance as well. Total cost of ownership/operation is probably pretty good when compared to gasoline and hybrid models.
While I would agree that there is indeed some ICE legacy to the single motor design direction there are other considerations.
Placing the motors in the wheels increases the unsprung mass of the vehicle and this has an adverse effect on the performance of the suspension. Typically both ride and handling charateristics deteriorate when the ratio of unsprung to sprung mass increases. For the locomotives in your example, traveling on a smooth rail this is farless of an issue.
One possiblity is placing the motor very near the wheel with a short drive shaft. Yes the complexity of the sytem increases, but it may still be better than the centrally located motor without the drawbacks of placing the mass outboard of the suspension.
abq-engineer, thanks for that link. What fun! It sounds like a very similar design concept to the SIM-WIL. Of course, as the article points out, it weighed a lot because of the 1.8 tonnes (metric tons, or 1.984 US short tons) of batteries needed.
Ann, I have a feeling we'll look back at this period as an explosion of innovation in the auto industry. I would guess a lot of the technology that's getting developed to support hybrids and EVs will also be handy when used to meet the higher mpg standards in conventional autos.
Thinking about this, the idea of a plastic body for a car with hundreds of watt of energy flowing through it is very smart. I've shocked myself touching the body of a normal auto when static electricity had built up, and it was not fun. Amplify that by a factor of, oh, maybe 200 to 400, and wow! the advantage of using non-conductive parts begins to sound really intelligent. So I'm all in favor of it.
The unsprung weight of the car due to motors in the wheels would certainly reduce its handling capability. And I'd sure hate to hit a big pothole; you'd be out shopping for a new tire and wheel immediately, as soon as your teeth stopped rattling.
The range sounds almost too good- I wonder if it's anywhere near that far at freeway speeds.
But why do they insist on making these things look dorky? Did someone pass a law against making them look like a Tesla?
Ann, one of the major drawbacks of any EV is its less mileage. So any innovation, which can increase the mileage, may get more appreciated from both market and customer side. But am not getting how its possible to deploy one- one motor for each wheel
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