Rotational weight vs dead weight

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    Rotational Weight
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SUMMARY

The discussion centers on the stability of a motorcycle at a dead stop while the engine is spinning at 15,000 RPM. It is established that the motorcycle's balance is influenced by angular momentum generated by the spinning wheels and the engine. The engine's ability to contribute to stability is limited due to its low moment of inertia compared to the required gyroscopic effect. A calculation involving the engine's power in watts and the motorcycle's mass and center of mass height is necessary to determine if the gyroscopic force can keep the motorcycle upright.

PREREQUISITES
  • Understanding of angular momentum and its effects on stability
  • Knowledge of gyroscopic effects in mechanical systems
  • Familiarity with motorcycle dynamics and balance
  • Basic physics concepts including moment of inertia and rotational motion
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  • Calculate the power of a motorcycle engine in watts
  • Explore the principles of gyroscopic stability in motorcycles
  • Research the impact of moment of inertia on vehicle dynamics
  • Learn about the relationship between RPM and angular momentum
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Motorcycle enthusiasts, mechanical engineers, physics students, and anyone interested in understanding the dynamics of motorcycle stability and balance.

mrwabba
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I herd an argument about a motorcycle that said at a dead stop could a motorcycle balance while turning 15,000 RPM? I know while riding the object being in motion along with the tires rotating keep the motorcycle on 2 wheels. My question is could the engines turning force keep it balanced? The engine is mounted so it rotates parallel to the wheels so it does add some balance and it’s not trying to throw the bike to one side.
 
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mrwabba said:
I herd an argument about a motorcycle that said at a dead stop could a motorcycle balance while turning 15,000 RPM? I know while riding the object being in motion along with the tires rotating keep the motorcycle on 2 wheels. My question is could the engines turning force keep it balanced? The engine is mounted so it rotates parallel to the wheels so it does add some balance and it’s not trying to throw the bike to one side.
Stability has to do with angular momentum. Spinning wheels have angular momentum. The bike will be vertically stable because tipping causes the angular momentum vector to tilt up. In order to conserve angular momentum, the bike has to rotate in the horizontal plane (about a vertical axis). But the friction of the two wheels on the road prevents a rotation of the bike about a vertical axis.

In order for the engine spin to make the bike stable, it would have to create angular momentum to produce a gyroscope effect. Since L = Iw, you need the engine to have significant moment of inertia or high speed or a combination of both. A crankshaft doesn't have much moment of inertia.

AM
 
Take the power of the engine (wattage) and divide this by pi*15,000 rpm.

If this value is greater then half the mass (kilograms) of the bike multiplied by the height of the bike's center of mass (meters) squared, then the bike has some chance of standing up due to gyroscopic force.
 
thanks for both of the replys. how you be able to figure out the power of the engine in watts?
 

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