Disconnecting alternator from car....

"M.A. Stewart" > wrote in message
...
> "Existential Angst" ) writes:
>> "hls" > wrote in message
>> ...
>>>
>
>>> "Steve W." > wrote in message news:il5j3s$ef8>
>>>> With it disconnected you might gain about 2 HP. Of course after you
>>>> drive
>>>> till the battery discharges plan on buying a new battery. Oh and if you
>>>> connect up the alternator to charge the battery back up plan on buying
>>>> a
>>>> new one of them as well. They are not designed for long term high
>>>> output
>>>> any longer. Most will fry if they have to put out much over half the
>>>> rated max for any length of time.
>>>>
>>>> --
>>>> Steve W.
>
>>>
>>> I agree.. A 100 amp alternator putting full current would be about
>>> 1300-1400 watts, just about 2 hp. But in real life you dont pull that
>>> much
>>> current all the time, most likely.
>>>
>>> In rough terms, 2 hp compared with 200 hp (when fully putting out),
>>> would be 1%. And 1% would probably resolve to 0.2-0.3 mpg.
>>>
>>> At least the boy is using his thought processes. Thought experiments
>>> worked well for Einstein, Hawking, Penrose, et alia.. But on cars, it
>>> is better to engineer it and test the result
>
>>
>> Do you really need to test the fact that at 60 mph, a small car is
>> drawing
>> 10-20 hp, and not 200 hp?
>> In rough terms, 2 hp is then 10-20%, not 1% -- which, btw, I already
>> pointed
>> out.
>
>>
>> And, altho the electrical draw on average may be modest, the residual
>> frictional load is proly on the order of a better part of a hp. You
>> could
>> have an engineer test that particular detail.....
>> --
>> EA
>>
>
>
> Frictional load is nowhere close to a hp. Have you ever spun an alternator
> by hand? Its almost friction-less. The only effort needed is to rotate the
> mass and that is only when accelerating it to a higher speed. You do know
> that
> alternators by their very nature are automatic... they automatically
> respond to electrical load presented... no electrical load presented, no
> magnetic drag... an electrical load presented, a corresponding magnetic
> drag.
>
> You know you can achieve the same thing WITHOUT disconnecting the
> alternator. Actually you can achieve more... the equivalent of a belt less
> disconnected alternator, and still produce electricity! All you have to do
> is weigh all the rotating mass (pulley that drives the belt, belt that
> drives
> the alternator rotor, the alternator rotor itself) and add a small
> fraction of a percent for the bearing friction, brush friction, and
> windage (air that the rotor pushes around) and then remove "meat" from the
> flywheel! Not enough "meat" on the flywheel to equal the rotating mass?
> Remove "meat" from the pistons, piston pins, connecting rods, and
> crankshaft! Be careful though... removing "meat" can be dangerous to the
> health of an engine! Think "balance". Also check out the availability (and
> weight savings) of titanium connecting rods for your engine.

from a recent post on rcm:

> I think that automobile alternators are reluctance-type.
> They're flexible but not particularly efficient.

I see where Bosch are touting their new 70% efficient 'smart'
alternator that allows digital control so that field
current can be turned off during acceleration and
cranked up during braking, boosting engine efficiency
by as much as 3%. Smart Indeed!

http://csr.bosch.com/content/languag...ENU_XHTML.aspx

------------------

If they're claiming 3% just by tweaking an alternator, imagine disconnecting
it.

Apropos of other comments/realities, not saying disconnecting the alternator
is currently the best idea, but mebbe it would be a good idea for mfr's to
make such a provision.
--
EA




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