lightwieght pulleys, pistons, flywheels, driveshafts

[oldcorollas]

stock pulleys on 4A's also fail.... esp GZE... due to large load from SC (20-30hp?)
that the keyway also widens indicates that the pulley is moving on the crank and smashing the keyway, so it may be more of a design problem inherent to the 4A, than the fact that the pulleys are undamped..

fwiw, i have a vague recollection of calculating inertia of drivetrain vs weight of car for a mouldy rolla... in first gear, it was something like 20 or 25% of the inertia? might be completely off, but that is the kind of magnitude you are looking at... for first gear....
and it just reduces from there.

flywheel is the single biggest "adjustable" item.

light pistons/rods are done for engine rev limit and efficiency (reduction of energy losses), as opposed to directly altering the revvability of motor.

pulleys are aguably a waste of time, as their inertia is relatively low (ie, compare inertia of a water pump pulley.. vs say.. an alternator....)

alloy or carbon fibre driveshaft? hmm... sometimes shaft becomes too long, but more likely it is not well made to get the vibrations... it is easy to fark it up.... the inertia of driveshaft is relatively low (slow speed of shaft and small diameter), so it is often the last place of all to look for savings...

[brett_celicacoupe]

i suspect that the combination of all 4 wheels and brake rotors would be equivelent to the flywheel on its own.

the flywheel spins about 4 times as fast (in top gears) so its got a moment of interia 4 times greater relevant to the wheels.

if your going as deep as pulley weight reduction then id also look at rims and brakes

[Rodger]

Removing weight from items turning at engine speed equates to 15 times that off a static weight. IE 1kg off a flywheel is 15kg off the car.

Removing weight from an item turning at road speed equates to a 3 times saving of the static weight. IE 1kg off the rim is 3kg off the car.

So as has been said, lighter flywheels have the most dramatic effect.

Change from a 12kg flywheel to a 6kg one, you would need to take 90kg from the car to have the same effect.

Regards

[Kyosho]

Removing weight from items turning at engine speed equates to 15 times that off a static weight. IE 1kg off a flywheel is 15kg off the car.

Removing weight from an item turning at road speed equates to a 3 times saving of the static weight. IE 1kg off the rim is 3kg off the car.

So as has been said, lighter flywheels have the most dramatic effect.

Change from a 12kg flywheel to a 6kg one, you would need to take 90kg from the car to have the same effect.

Regards

So basically, it'd be cheaper to just not have passengers?

[brett_celicacoupe]

Removing weight from items turning at engine speed equates to 15 times that off a static weight. IE 1kg off a flywheel is 15kg off the car.

Removing weight from an item turning at road speed equates to a 3 times saving of the static weight. IE 1kg off the rim is 3kg off the car.

im not sure how you can come up with these presise numbers.

in 4th gear, the relative intertia of the components spinning at engine speed is going to be exactly your diff ratio times more then the stuff spinning at road speed. your assuming a 5:1 diff ratio above

its much like the people that say their speedo is out by 10km/h. to which you reply "so it reads 10km/h when stationary?"



removing 1kg of mass from the flywheel at the 4" diameter mark is equivelent to removing 4kg from the flywheel at the 2" diameter mark

I=(1*4^2)/2
=8

I=(4*2^2)/2
=8

[Rodger]

I'll head back into my reference books and check the reasoning behind these numbers. I should have referenced where I got them from, hey.

Regards

Rodger

[brett_celicacoupe]

they'll only ever be a very rough guide but its probably best you acknowledge that when you use those rules of thumb

[Rodger]

Found my reference in:

Chassis Engineering, Herb Adams, (Chapter 15, Rotating Inertia); New York: HP Books, Berkley Publishing Group, 1993.

Regards

Rodger

[Esteban]

While rotationally heavier, 2 Piece Driveshafts apparently save you some unsprung weight in a live axle setup, though you'd have to have an alloy diffhousing to notice it in my opinion...