Trevor,
Thanks, I think you got the point in your first response - even in my
generator equipped TR-3, the ammeter reads to the + side most of the time,
meaning I have current to spare, meaning an electric fan is not going to
sap any more horsepower. Unless you want to atart calculating the
requirements for the extra weight.
Bobk
>Kinderlehrer's wrote:
>> Ok, now I'm very confused. The output of the alternator is dependent on the
>> rotation speed of the armature, ie RPM of the engine.
>> I put an electric fan in the car, then I have to go faster to get more
>> horsepower to the fan motor??
>
> Not really. Most of the time, there is current to spare. The
>battery will be fully charged, all accessories can work, and the
>alternator has excess capacity. LUCAS alternators have
>low output, but British cars tend to have few accessories
>so it works out.
>
> Running a fan isn't likely to put you over a limit unless you
>are too close to it anyways.
>
> My modern car has an electric fan that only comes on
>when required. I almost never hear it on. The only time it
>comes on is at idle. I often hear it when I get out
>of that car to jockey spots with my LBC. I have an inline
>parking spot, so as I am starting up the Midget I
>often hear the idling Celica start it's fan behind me.
>
> So when you calculate your current demands for the fan,
>you want to be able to run it often but in all likelihood
>you won't.
>
>> I guess I'm lucky because I have a TR3 with a generator which is far less
>> than 100% efficient. It keeps on turning even after the battery is charged
>> up and it isn't really needed, so I can use those wasted revs to drive my
>> electric fan (when I get one).
>
> The generator suffers from the same problem, just at
>a greater level. Not only does the generator produce less
>current, but it also often requires higher RPMs to do so. Often
>while idling the generator cannot help at all
>because the regulator will not get enough juice from the
>generator to complete the charging circuit.
>
> Your TR3 has an ammeter, so you can watch the effects
>of various conditions. If your ammeter is below zero,
>you are losing the battle. Unfortunately idling is
>when the fan is needed most and there is the least
>current to drive it.
>
>--
>Trevor Boicey
>Ottawa, Canada
>tboicey@brit.ca
>http://www.brit.ca/~tboicey/
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