STRICKLAND, Tate wrote:
>
> The point is to slow everything down by a good margin, but just slow
> the alternator down a bit - or perhaps none at all. As for 5 pulleys,
> the first thing is looks - all of the pulleys the same is sharp! Also
> I forget the term, but there is a term for weight that has to be
> moved.
In this case, the term is "rotational inertia". In the
general case, "inertia".
> It is much more important than weight that doesn't.
If you don't have to move it, you don't care how much it weighs :-).
[snip of "less weight equals more fun" section]
> Point is that they look great, removes a little bit of the most
> important type of mass (moving) and the horsepower is free - i.e. it
> doesn't affect dependability if done properly.
>
As someone else mentioned, lowering the mass while keeping
the radius of the pulley the same is the best way to do it.
You'll get a benefit from reducing the radius as well, but
at the expense of reliability/drivability.
A better strategy would be to not only look at shaving
weight off of the pulley train, but also installing
accessories that have low internal friction on their
driveshafts, or which _themselves_ have low rotational
inertia (lightweight alternator assemblies, pumps that
are pushing fluids with lower viscosity than stock, etc.).
Reducing spots of rotational inertia in your engine
(crankshaft etc.) will give you gains up to a point,
depending on what you plan on doing (street vs. full race).
Use your own disgression; better yet, look at the total
performance profile for what you do with the vehicle
before you start going crazy with aluminum and aggressive
milling :-). You'll be surprised at what you find; after
a while, it's cheaper to hit the treadmill and drop 20 lbs.
than it is to find ways to shave weight off of a vehicle :-).
Also remember that inertia is part of the momentum equation
(an object in motion will stay in motion barring any
other external force upon it). Reducing momentum within
an engine can be bad after a certain level, especially for
daily drivers and weekend warriors :-).
For a streeter, reduce the pulley mass and keep the stock
radius, and keep your eye out for street performance
accessories (pumps, alternators, etc.); for racers, go whole
hog and reduce the radius to whatever suits your pleasure, or
don't drive accessories at all. Quite frankly, most real races
don't last long enough to require turning a water pump, or even
having a radiator. In fact, one of the sure ways to spot if a person
is sneaking a little nitrous into the mix is if they have a radiator
in the racer; the nitrous usually gets hidden there. A good thing to
watch out for if you're racing for money or slips at the track
(or in a back alley 8-) ).
Have fun,
--
John Bell johnb@pswtech.com http://www.psw.com
"You're not foolin' anyone, y'know..." - Monty Python
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