Reducing rotating mass/weight
02-15-2003, 05:56 AM
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Reducing rotating mass/weight I am starting to work on reducing rotating mass
in our 2000 SS (M6). I saw several ads on light weight flywheels (11 vs 24lbs) and also aluminum
driveshafts (any weight reduction there?). These flywheels
are offered by SLP, RK Sport and others - are they
strong enough. My car has around 380..400rwtq.
Any other sugestions?
Thanks for your help,
Gert
in our 2000 SS (M6). I saw several ads on light weight flywheels (11 vs 24lbs) and also aluminum
driveshafts (any weight reduction there?). These flywheels
are offered by SLP, RK Sport and others - are they
strong enough. My car has around 380..400rwtq.
Any other sugestions?
Thanks for your help,
Gert
02-15-2003, 09:37 AM
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Re: Reducing rotating mass/weight It's not just the mass of what's rotating,
what you're looking to get rid of is
angular momentum (to be spun up by the
engine's output). This is mass * radius
(integral of the whole object from its
center of mass).
Flywheel? Designed to apply angular momentum
smoothing to the crankshaft, smooth out the
torque pulses and drag you past the next
compression cycle. You can lighten it but
will want a higher idle, and more finesse
in the clutch foot. No dump & jump when you
don't have that flywheel energy in the bank.
Like a charge card, you pay for that little
impulse purchase cushion all the way down
the track, but doing without it is tougher.
Drivshaft? 2" radius. Forget about it,
other than as a raw weight reduction.
Differential? Kinda chubby, 4" radius,
but a good portion of the mass is concentrated
in the center. So although it's heavy, it's
not as big on angular momentum.
Wheels/tires? 13" radius. Heavy. Mass at the
periphery for the most part. Four of 'em.
Now we're getting somewhere.
what you're looking to get rid of is
angular momentum (to be spun up by the
engine's output). This is mass * radius
(integral of the whole object from its
center of mass).
Flywheel? Designed to apply angular momentum
smoothing to the crankshaft, smooth out the
torque pulses and drag you past the next
compression cycle. You can lighten it but
will want a higher idle, and more finesse
in the clutch foot. No dump & jump when you
don't have that flywheel energy in the bank.
Like a charge card, you pay for that little
impulse purchase cushion all the way down
the track, but doing without it is tougher.
Drivshaft? 2" radius. Forget about it,
other than as a raw weight reduction.
Differential? Kinda chubby, 4" radius,
but a good portion of the mass is concentrated
in the center. So although it's heavy, it's
not as big on angular momentum.
Wheels/tires? 13" radius. Heavy. Mass at the
periphery for the most part. Four of 'em.
Now we're getting somewhere.
02-15-2003, 10:16 AM
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Re: Reducing rotating mass/weight </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by jimmyblue:
<strong> It's not just the mass of what's rotating,
what you're looking to get rid of is
angular momentum </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Ahh, someone who knows their physics!
He is absolutely correct. The biggest rotating mass problems come from the parts that are big diameter like wheels and flywheel. Aluminum flywheels will have to be replaced very often. If you like dropping the transmission all the time, enjoy. Draglite wheels are your best option.
Your crank and pistons are also a form of rotating mass (it is worse in fact, because you need energy to speed them up, then slow them down, then speed them up in the other direction again). When you measure out the length to the pistons, you can see that the overall leverage on the crank is large. Lightweight pistons are a minor plus as well.
<small>[ February 15, 2003, 10:23 AM: Message edited by: 2000WhiteZ28 ]</small>
<strong> It's not just the mass of what's rotating,
what you're looking to get rid of is
angular momentum </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Ahh, someone who knows their physics!
He is absolutely correct. The biggest rotating mass problems come from the parts that are big diameter like wheels and flywheel. Aluminum flywheels will have to be replaced very often. If you like dropping the transmission all the time, enjoy. Draglite wheels are your best option.
Your crank and pistons are also a form of rotating mass (it is worse in fact, because you need energy to speed them up, then slow them down, then speed them up in the other direction again). When you measure out the length to the pistons, you can see that the overall leverage on the crank is large. Lightweight pistons are a minor plus as well.
<small>[ February 15, 2003, 10:23 AM: Message edited by: 2000WhiteZ28 ]</small>
02-15-2003, 10:33 AM
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Re: Reducing rotating mass/weight Skinnies and lightweight front and rear wheels make noticeable improvements in 1/4 mi. times w/LS-1 F-bodies. Even a completely stock car w/light whls and sticky rear tires make a considerable difference. Just make sure they're balanced right on the money, and stay away from rough roads, potholes. They're very fragile. WJ. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
02-16-2003, 05:27 PM
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Re: Reducing rotating mass/weight If you're concerned with rotating mass, you're probably racing. If you're drag racing, that's just fine. But if you're road racing, you'll also need to think about unsprung weight...
Unsprung weight is anything with mass that is not supported by the suspension of the car. The drivers seat is NOT unsprung weight. But the wheel/tire IS unsprung weight. Make sense?
You can reduce weight by running a lighter brake system, lighter suspension pieces, etc.
Overall, by reducting the unsprung weight, you will make the suspension more effective over rough surfaces.
Hope this helps!
-Brad
Unsprung weight is anything with mass that is not supported by the suspension of the car. The drivers seat is NOT unsprung weight. But the wheel/tire IS unsprung weight. Make sense?
You can reduce weight by running a lighter brake system, lighter suspension pieces, etc.
Overall, by reducting the unsprung weight, you will make the suspension more effective over rough surfaces.
Hope this helps!
-Brad
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02-17-2003, 12:32 AM
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Re: Reducing rotating mass/weight SLP does offer a billet steel flywheel that weighs 8 lbs less than stock. It's about $380.
I personally wouldn't use it without some significant weight reduction on the car...you need a heavy flywheel to get a heavy car moving.
I personally wouldn't use it without some significant weight reduction on the car...you need a heavy flywheel to get a heavy car moving.
