rotating mass equation
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From: mansfield, ohio, usa
rotating mass equation
ok im trying to teach a younger person about cars and physics but dont remember the exact numbers that go into the rotating mass equation grams per hp.. anybody know the exact numbers?
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Re: rotating mass equation (fkncivic)
It's not a direct relationship of weight to power. Rotating mass is just momentum just like making your car heavier or lighter. Reducing the rotating mass in the wheels or in the flywheel is equivalent to making the car lighter. It's NOT equivalent to making the engine more powerful.
You can remove 10 pounds of weight from the car itself & get better acceleration. There's no rotating mass involved in that.
If you remove the same 10 pounds of weight from the axles, it would be barely any better. That's because the axles are very close to their own center of rotation.
Remove the 10 pounds from the tread of the tires, you'd get twice the improvement. So that would be worth the same as 20 pounds from the back seat.
Removing weight from the flywheel includes another couple factors for the overall gear ratio & the radius of the flywheel. Still, it's equivalent to a reduction in weight, not equivalent to an increase in power.
Some dynamometers will measure an increase in power from lightening the flywheel, but it's a kind of misleading measurement. It's related to the dyno operating by inertia rather than braking.
You can remove 10 pounds of weight from the car itself & get better acceleration. There's no rotating mass involved in that.
If you remove the same 10 pounds of weight from the axles, it would be barely any better. That's because the axles are very close to their own center of rotation.
Remove the 10 pounds from the tread of the tires, you'd get twice the improvement. So that would be worth the same as 20 pounds from the back seat.
Removing weight from the flywheel includes another couple factors for the overall gear ratio & the radius of the flywheel. Still, it's equivalent to a reduction in weight, not equivalent to an increase in power.
Some dynamometers will measure an increase in power from lightening the flywheel, but it's a kind of misleading measurement. It's related to the dyno operating by inertia rather than braking.
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From: mansfield, ohio, usa
Re: rotating mass equation (JimBlake)
ok but by using a lightened flywheel or pully's you dont gain hp you nearly retrieve lost hp im just looking for the formula cause i know i have seen it before.. i understand the concept of rotating mass very well..
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Re: rotating mass equation (fkncivic)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fkncivic »</TD></TR><TR><TD CLASS="quote">ok but by using a lightened flywheel or pully's you dont gain hp you nearly retrieve lost hp im just looking for the formula cause i know i have seen it before.. i understand the concept of rotating mass very well..</TD></TR></TABLE>
This is an artifact of the testing method because the drive train is accelerating during the dyno test. The term that you seek is rotational inertia.
http://en.wikipedia.org/wiki/Rotational_inertia
This is an artifact of the testing method because the drive train is accelerating during the dyno test. The term that you seek is rotational inertia.
http://en.wikipedia.org/wiki/Rotational_inertia
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