On Wed, 17 Oct 2007 11:59:26 -0000, Tim wrote:

Any alternator that has to run a full load full time will burn out. If
you are pulling a 110 amp load don't expect a 110 amp alternator to
last very long.

I don't dispute what you say, but I may quibble over terminology.

Maximum load and full load are not exactly the same thing. Full load
is really max continuous, as opposed to short term emergency, load.
What do you think the term 'overload' means? I believe it means enough
more than continuous power to cause overheating. The copper and iron
take time to heat up which is why you can get away with stuff for a
while. They seem to lie about the ratings is all, and the warning is
good.
If you say they all do it, I will keep that in mind. All the AC
electric motors I have wired or used have been good for the rated
power full time, with I think, no more than a 40C temperature rise.
Starter motors put out about ten times what their size indicates they
should and can easily be burnt up if you have a good battery. Thirty
amp generators used to be the size and shape of the starter which
would draw 300 amps or so.

Another question. How can an alternator eat belts if the manufacturer
picks the belt size. Do the crankshaft designers get to pick? the guys
that design those things know how much power a given belt will safely
carry. Do they come with a naked shaft, buy the pulley separately?
Cars are not that way. This takes arithmetic and a catalog, nothing
exotic. A second year engineering student could do it. So can many
shade tree mechanics.

So what gives with belt eating? Is everything as light and cheap as
possible? On cars the things always last at least hundreds of hours.
Spark plugs last 100 000 miles.

Gardner used to build a 250 horsepower, six cylinder, diesel you could
start by hand if the electrics all went west. Too bad you have to buy
a $500 000,used, boat to get one. You can get home after all the
electrics take a dive, which is not true with many power boats. Oil
lamps anyone? Maybe tick tick chronometers and sextants, mechanical
taffrail log and paper charts? Tahiti is, supposedly, easy to find,
the airliner contrails point right to it. Like following roads with a
plane. You don't even need a map. Or so someone said, I never tried
it.

Twelve volts isn't really enough, which is why so many airplanes use
twenty-eight, so called. You can always get by with less copper if you
double the voltage. Less current, smaller wires. The battery can stay
the same size, with more and smaller cells. After all the power it
takes to crank an engine doesn't change, so doubling voltage halves
current and minimum wire size.

Casady