Motorcycle vs Bicycle chain tension

[asynchronous13]

Trek recently released a belt driven bicycle (instead of chain drive) which led to a discussion among some cycling friends. Which led to discussion of torque, power output, etc. Anyway, I'm trying to compare the chain tension of a motorcycle vs the chain tension of a bicycle. I'm better with electrical systems, my mechanical systems knowledge is rusty.

These specs are from a real motorcycle:
engine makes 16 ft-lbf at 10,000 rpm
primary reduction ratio is 1.9
1st gear reduction ratio is 2.7
Final reduction ratio is 2.7
mass is 420 lbs

Based on the above:
the output shaft of the engine is 30.4 ft-lbf @ 5260 rpm
post-transmission pushes 82 ft-lbf @ 1950 rpm
at the rear wheel (in 1st gear) it's 221 ft-lbf, @ 720 rpm.

Track Bicycle:
Rider is 150lbs
Crank arms are 170mm (0.56 ft)
Gear gain ratio is 3:1 (normal for a track bike)
Mass is 20 lbs

Based on the above:
at the crank, rider makes 84 ft-lbf
at the rear wheel, 28 ft-lbf

I'm not exactly sure how to calculate chain tension from here (or perhaps I've already made a mistake...) I'm thinking that I need to specify an acceleration before I can get the answer. Can't quite recall the appropriate equations...

 

[rcgldr]

I'm not exactly sure how to calculate chain tension from here.

You just need the sprocket size at either end and the torque at the end that you know the sprocket size at. Then the tension = torque at the sprocket / effective radius of the sproket.

 

[astrokreng]

I would approach this question by first understanding the concept of chain tension in both a motorcycle and a bicycle. Chain tension refers to the force applied to the chain by the sprockets, which allows for the transfer of power from the engine to the wheels. In a motorcycle, the chain tension is affected by factors such as the engine power output, gear ratios, and the weight of the motorcycle. Similarly, in a bicycle, the chain tension is influenced by the rider's power output, gear ratio, and the weight of the bicycle.

To compare the chain tension between a motorcycle and a bicycle, we need to consider the different variables and equations involved. In the provided specs, we can see that the motorcycle has a much higher engine power output and a heavier mass compared to the bicycle. This means that the chain tension in the motorcycle will be greater due to the higher forces acting on the chain.

To calculate the chain tension, we need to use the equation T = F x r, where T is the chain tension, F is the force exerted on the chain, and r is the radius of the sprocket. In this case, the force exerted on the chain can be calculated using the equation F = ma, where m is the mass and a is the acceleration.

For the motorcycle, we can calculate the chain tension at the rear wheel by first calculating the force at the output shaft of the engine. This can be done using the equation F = P/w, where P is the power output and w is the angular velocity. Substituting the values given in the specs, we get a force of 30.4 ft-lbf at the output shaft. This force then goes through the primary and gear reduction ratios, resulting in a force of 221 ft-lbf at the rear wheel in 1st gear.

For the bicycle, we can calculate the chain tension at the rear wheel by first calculating the force at the crank. This can be done using the equation F = P/w, where P is the power output and w is the angular velocity. Substituting the values given in the specs, we get a force of 84 ft-lbf at the crank. This force then goes through the gear gain ratio, resulting in a force of 28 ft-lbf at the rear wheel.

From these calculations, we can see that the chain tension in the motorcycle is significantly higher than that in the bicycle. This is due to the higher