Ideal Mechanical Advantage of this bicycle?

AI Thread Summary
The discussion focuses on calculating the ideal mechanical advantage (IMA) of a bicycle wheel with a diameter of 73cm driven by a chain on a gear with an 8.5cm diameter. The formula for IMA is correctly identified as IMA = de/dr, where de is the diameter of the wheel and dr is the diameter of the gear. Participants clarify that the values mentioned (8.5cm and 73cm) represent distances, not forces, and emphasize the need to apply the correct mechanical advantage formula. The concept of viewing the system as a third-class lever is introduced, with the axle as the fulcrum and the chain applying effort. The discussion ultimately seeks to clarify the calculation of mechanical advantage in this context.
Rionic
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A bicycle wheel has a diameter of 73cm and is driven by a chain on a gear of 8.5cm diameter

What is the ideal mechanical advantage?

I know that IMA=de/dr
But I'm not sure which one is de and which one is dr.
 
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billy_joule said:
I'm not sure where you got that equation from but the normal form is:

MA = Force in / Force out

https://en.wikipedia.org/wiki/Mechanical_advantage

Can you find the MA now? If not, can you identify the force in and force out?
Force input= 8.5 and force output=73?
 
Those are distances, in cm, not forces.
But your idea is right and will give the right answer.
One way is to consider it as a 3rd class lever, the axle is the fulcrum, the effort is applied via the chain and the load is at the tyre contact point.
 

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