# Determining required torque for a chain and sprocket conveyor belt

I am working on a project for an electronics class, but need some help with one of the mechanical details. My job is to program a stepper motor to move a conveyor belt back and forth as specified. The "belt" will have a chain and the shaft of the motor will have the sprocket. But before I choose my stepper, I need to know what the required torque for my stepper motor is. Unfortunately my physics knowledge isn't great, so I googled to find the equation I should use. This is what I came up with.

I also found this equation which comes out to be similar to the above equation except this one doesn't have the efficiency and gear ratio involved.

So I have 3 questions:

1. what kind of force would I calculate for F? If the object is laying flat horizontally, what kind of force would be pushing against it east to west?

2. the two equations give me very different results due to the efficiency and gear ratio. when would I use one equation over the other?

3. where would the required speed come into the picture? if I want to move my object quickly vs slowly, would this affect the torque needed?

If you are still reading this, I thank you for your time, and hope you could help me with any or all of my questions...

Thanks :)