[LINK] Standards, please! The third coming of electric vehicles
francisoconnor3 at bigpond.com
Sun Apr 22 10:24:43 EST 2012
Use bigger brush motors
Put the motors on bearings on the outer axle, and attach the wheel to the bearings.
Mess with the suspension
Nothing is insoluble ... solutions abound ...
My point remains ... the energy loss and inefficiency of using a single direct drive motor is unacceptable in the context of the technology. Energy is lost ... big time ... on the extended drive shaft, at the differential, on the axle cogs and on the axle ... at unacceptable rates. It is simply inefficient to persist with a design that is more suited to a radically different type of engine.
You want to design an electric car, then design a car that plays to the electric motor's strengths, not to the strengths of its competitor.
On 22/04/2012, at 10:09 AM, David Boxall wrote:
> On 22/04/2012 2:02 AM, Frank O'Connor wrote:
>> - Why not install multiple smaller engines in an electric car?
>> - Why not install them in the wheels?
> A small matter of physics. That arrangement might work at very low
> speeds and/or on extremely smooth roads. The problem comes when you hit
> a bump.
> Hitting a bump accelerates the wheel upward. The degree of acceleration
> is a function of the nature of the bump, speed of the vehicle and
> diameter & width of the wheel, among other things, but the wheel ends up
> going upward at a given rate.
> The suspension is then required to stop the wheel and return it to the
> road without adding to the problem by slamming it down too hard. That's
> usually done with a spring and a shock absorber. The spring absorbs the
> energy of the ascending wheel and the shock absorber slows its return,
> so it doesn't rebound violently.
> So far, so good, but the energy required to stop the wheel's upward
> motion has to go somewhere. It goes into the body of the vehicle, where
> it's ultimately felt by the passenger(s). The amount of energy absorbed
> by the vehicle is a function of the speed and weight of the wheel.
> Adding a motor increases the weight of the wheel. Vehicles employing
> so-called wheel-motors have been made (might still be in production),
> but none give a very comfortable ride, particularly at speeds above
> walking pace.
> One solution is to move the motors back into the body of the vehicle.
> That reduces the weight of the wheels, while increasing the weight of
> the body. The increase in body mass increases its capacity to absorb the
> energy of a (now lighter) upward-moving wheel, further enhancing ride
> characteristics. Unfortunately, the necessary axles and constant
> velocity joints add to costs, though you can get away with using cheaper
> motors (wheel-motors, needing to minimise weight, are notoriously
> David Boxall | "Cheer up" they said.
> | "Things could be worse."
> http://david.boxall.id.au | So I cheered up and,
> | Sure enough, things got worse.
> | --Murphy's musing
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