----- Original Message ----- From: "Robert J. Chassell" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, December 29, 2003 9:13 AM Subject: Re: Efficient bus
>Rob sez: >> The inverted rotor/stator design is such an obvious and elegant >> solution to an electric drive for vehicles that one does wonder >> why it hadn't been thought of before. > > It has been thought of before. To my personal knowledge, it was > thought of at least 40 years ago. Then my wonderment was not for naught. <G> > > There are several reasons the design was not used in cars: > > * Motors like this make for heavier wheels; the `unsprung weight' > increases. I have yet to read a discussion of how important this > factor is now; all I know is that engineers have always told me > that an increase in `unsprung weight' is a problem. Thats quite interesting. I can see where increased mass of the wheels could cause metal fatigue and/or deformation due to greater inertia, especially on a rough road. Do you think that the newer generations of lighter weight permenant magnets would alleviate this concern? > > As far as I know, this is, or was, the key problem. > > In the 1960s, Wyle Labs developed a hydraulic resevoir and motor > that would have been fine for cars except for this problem. (I am > told it ended up being used by NASA; devices may have gone to the > moon.) I don't know whether modern designs for either electricty > or hydraulics weigh less. Yes, the moon buggies were electric driven. I wonder if there is a blow-up of the design somewhere online? > > * In the 1950s, it was less expensive to build cars with an internal > combustion engine driving a clutch, a differential, and wheels > than to build cars with an internal combustion engine driving a > generator and then motors on wheels. > > Remember, car manufacturers enjoyed a great deal of sunk > investment in machinery to make clutches and differentials. A > different technology could not simply be a little better; it had > to be sufficiently better that the oligopolists of the time had an > incentive to shift. Moreover, California smog regulations did not > exist, so companies were not encouraged to design hybrids with > less smoggy engines. I can see that. I think that is a good example of an entrenched design moderating a manufacturing economy. Kind of funny, but last night I was talking with Steve Sloan and his dad about how entrenched designs prevent innovative thinking. Well.....mostly *I* was talking about this, but what I am thinking is that when a technology becomes deeply invested and large numbers of engineers and technologists are trained in the specifics of that technology, they become stuck in that technologies paradigm and truely innovative thinking becomes more difficult. One example of this is the situation where auto manufacturers have claimed to have "rethought" the automobile when what you actually find is another assembly line product varying only slightly from other assembly line products. A stronger example is the current generation of hybrid electric vehicles. Its just an ICE with an electric motor tacked on. Not really much different from what we are all driving today. > > * In the past, and perhaps in the present, I do not know, engineers > have been worried about keeping connections in a wheel from > shorting when the car drives through puddles of water. A thorough examination of E-Tractions website shows one of their motors being used as a generator in a water wheel. IIRC this implimentation had been running for over 2 years in what appears to be a very wet enviroment. > > Would the inverted rotor/stator design be for direct current, > which was the least expensive before modern controls and which has > the best low power torque? If so, the problem of shorts becomes > very serious. I get the idea (and this is just a guess) that since all their calculations are at 48V and 96V that they are running DC. The only frequency drives I have ever worked with run at 480V AC, so I wouldn't want to guess at the operation of such motors at such low voltages. I think it is important to note though, that the design they show for passenger vehicles is a remote motor with a drive shaft. > > * In the past, speed control mechanisms were more expensive than > now; the price of modern electronics has dropped markedly over the > past half century. True. Frequency drives are quite common these days. > > Incidentally, I do not know how a car was supposed to respond to a > foot on the pedal in the past-- would it increase the fuel flow to the > engine, which would generate more electricity, which would provide > more power to the wheels, thereby obviating the need for expensive and > unreliable batteries, or would pressing the accelerator increase > electricity from a battery, the draw on which would cause a govenor to > increase fuel flow to an engine? Remember, batteries are temperature > sensitive, and their use through the winter is difficult, though not > impossible. I haven't looked to see myself, but I expect that speed control and engine speed would packaged as part of a solid state design. Its probably a modification of a standard ICE computer ignition. It might even control the regenerative braking system. It would be interesting to find out! > > I personally have always wanted to see an inverted rotor/stator design > for cars. It is a beautiful design. I'm impressed! xponent Electra 288 Maru rob _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
