What is the Torque at the rear wheel in this gear setup ?

In summary, the gear setup of the bicycle consists of a small gear and a large gear with a gear ratio of 5:1. The electric motor turns the small gear, which is connected to a large gear on the bottom bracket shaft. Another small gear on the opposite end of the bottom bracket shaft is connected to a larger gear on the rear wheel shaft, creating a further gear ratio of 5:1. This results in an overall gear ratio of 25:1 and increases the torque at the rear wheel.
  • #1
ramonegumpert
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Dear Experts


A bicycle has the following gear setup. I like to get your advice what is the effective gearing and torque at the rear wheel that is being turned by a electric motor that is turning the whole gear set using a chain.

There are 2 gear sizes : small gear and large gear. Their gear ratio is about 5:1.

A electric motor is mounted onto the bicycle. It has a pinion gear of the small gear size.
This gear is connected to a large gear mounted on the bottom bracket shaft.

There is another small gear connected to the other end of this shaft. This is same size as the motor's pinion gear. This gear is connected to another big gear mounted on the rear wheel shaft via another chain.

I am not sure what is the gearing effect at the rear wheel.

I suspect, its like this :

1. when the motor turns, its pinion gear turns the bottom bracket large gear at a stepped-down ratio of 5:1 increasing the torque by 5 times.

2. The small gear at the opposite end of this large gear rotates at this stepped-down speed with this same torque even though the gear is smaller.

3. The Rear wheel rotates at a even slower rate because of the gearing ratio of a further 5:1 increasing the rear wheel torque to be more than the torque at the large gear mounted on the shaft in the bottom bracket.

Thanks for reading my question and hope to hear your advice.

Have a nice day.

regards
Ramone
 
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  • #2
ramonegumpert said:
Dear Experts


A bicycle has the following gear setup. I like to get your advice what is the effective gearing and torque at the rear wheel that is being turned by a electric motor that is turning the whole gear set using a chain.

There are 2 gear sizes : small gear and large gear. Their gear ratio is about 5:1.

A electric motor is mounted onto the bicycle. It has a pinion gear of the small gear size.
This gear is connected to a large gear mounted on the bottom bracket shaft.

There is another small gear connected to the other end of this shaft. This is same size as the motor's pinion gear. This gear is connected to another big gear mounted on the rear wheel shaft via another chain.

I am not sure what is the gearing effect at the rear wheel.

I suspect, its like this :

1. when the motor turns, its pinion gear turns the bottom bracket large gear at a stepped-down ratio of 5:1 increasing the torque by 5 times.

2. The small gear at the opposite end of this large gear rotates at this stepped-down speed with this same torque even though the gear is smaller.

3. The Rear wheel rotates at a even slower rate because of the gearing ratio of a further 5:1 increasing the rear wheel torque to be more than the torque at the large gear mounted on the shaft in the bottom bracket.

Thanks for reading my question and hope to hear your advice.

Have a nice day.

regards
Ramone
The gear ratio is: 25:1

Work it out this way: if the small gear has T teeth, the big gear has 5T teeth. So when the small gear turns twenty five complete revolutions (i.e. 25T teeth), the first big gear turns 5 revolutions (i.e. 25T teeth = 5 (5T) teeth). This means that the small gear to which the first gear is fixed also turns 5 complete revolutions (5T teeth). When the small gear turns 5 revolutions (5T teeth) the second large gear turns 5T teeth = 1 revolution.

AM
 
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  • #3
Thanks AM

for confirming that my assumption is correct.
yeah!

I wish you have a nice day.
 

Related to What is the Torque at the rear wheel in this gear setup ?

1. What is torque?

Torque is a measure of the rotational force that is applied to an object. It is typically measured in units of newton-meters (Nm) or foot-pounds (ft-lb).

2. How is torque calculated?

Torque is calculated by multiplying the force applied to an object by the distance from the center of rotation. In the case of a gear setup, torque at the rear wheel is calculated by multiplying the force applied by the gears by the radius of the wheel.

3. Why is torque important in a gear setup?

Torque is important in a gear setup because it determines the amount of power that is transmitted from the engine to the wheels. Higher torque allows for better acceleration and the ability to overcome resistance, such as when climbing a hill.

4. How does gear ratio affect torque?

Gear ratio is a measure of how many times the output shaft of a gear rotates compared to the input shaft. In a gear setup, a lower gear ratio will result in higher torque at the rear wheel, while a higher gear ratio will result in lower torque but higher speed.

5. Can torque be increased in a gear setup?

Yes, torque can be increased in a gear setup by using a lower gear ratio, increasing the force applied by the gears, or increasing the radius of the rear wheel. However, it is important to note that increasing torque may also result in a decrease in speed, as the energy is spread out over a larger area.

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