What Formulas are Needed to Calculate Rotational Force and Power for an Electric Bicycle Motor?

[aliaze1]

Hello everyone,

My brother and I are designing an electric motor for a bicycle (just for fun). Assuming a 200 lb person rides the bike, there is a normal force on each wheel of 100 lbs. We forgot the formulas related to rotational motion and power (watts, horsepower, torque) for this situation (finding the wattage required to turn the wheel at a certain rate carrying a person of that weight). Thanks!

 

[Andrew Mason]

Hello everyone,

My brother and I are designing an electric motor for a bicycle (just for fun). Assuming a 200 lb person rides the bike, there is a normal force on each wheel of 100 lbs. We forgot the formulas related to rotational motion and power (watts, horsepower, torque) for this situation (finding the wattage required to turn the wheel at a certain rate carrying a person of that weight). Thanks!

The normal force is not really an issue.

If you want it to duplicate the power output of a human, you will need an electric motor that will have a power output similar to a human. A physically fit human can produce about 200 watts on a sustained basis and much more in a sprint. See: http://en.wikipedia.org/wiki/Human-powered_transport

AM

 

[astrokreng]

Hello there,

It's great to see your interest in designing an electric motor for a bicycle! To answer your question, the formulas you are looking for are related to rotational force and power. The formula for torque (rotational force) is T = F x r, where T is torque, F is the force applied, and r is the distance from the axis of rotation. In this case, the force applied is the normal force of 100 lbs on each wheel and the distance from the axis of rotation would be the radius of the wheel.

To calculate power, you can use the formula P = T x ω, where P is power, T is torque, and ω is the angular velocity (rate of rotation). To find the required wattage, you would need to determine the desired angular velocity and then plug in the values for torque and angular velocity into the formula.

Additionally, to convert from watts to horsepower, you can use the conversion factor of 1 horsepower = 746 watts. So if you calculate the required wattage and want to know the equivalent in horsepower, simply divide the wattage by 746.

I hope this helps with your project! Good luck and have fun designing your electric motor for the bicycle.