# Homework Help: Need help Solving for torque

1. Jul 4, 2013

### Steve O

I know this may be a simple problem but I don't understand it. Is there information missing or is it just me. Please help.

We have a motor capable of producing 10 n-m of torque. Attached to the motor is a gear with a PCD of 200 driving a gear with a PCD of 400. What is the torque exerted on the shaft of the driven gear?

PCD gear #1= 200
PCD gear #2= 400
Motor torque = 10 n-m

2. Jul 4, 2013

### SteamKing

Staff Emeritus
What do you know about the effect of gear ratio on torque?

3. Jul 4, 2013

### CWatters

So you have motor turning a small gear which turns a larger gear. The small gear is normally called the pinion, the larger gear is the driven gear.

No load is specified but presumably the question wants to know what is the maximum the torque could be produced at the output/driven gear gear.

Ever been on a bicycle?

Last edited: Jul 4, 2013
4. Jul 6, 2013

### Steve O

I don't have extensive knowledge about this subject. I do know that Torque = force x distance. I have the torque, but how do I get the distance?

We have a motor capable of producing 10 n-m of torque. Attached to the motor is a gear with a PCD of 200 driving a gear with a PCD of 400. What is the torque exerted on the shaft of the driven gear?

PCD gear #1= 200
PCD gear #2= 400
Motor torque = 10 n-m

5. Jul 6, 2013

### CWatters

PCD = Pitch Circle Diameter

6. Jul 6, 2013

### SteamKing

Staff Emeritus
You don't need a distance. All you have to know is how gear ratio affects rotational velocity and consequently torque itself.

7. Jul 6, 2013

### CWatters

What Steamking said.

You could work out the force at the teeth using T=Force * distance and then convert that back to torque for the other gear.... but once you have done that a few times you will see the short cut that allows you to work out the torque directly from the gear ratio (which can be deduced from the ratio of the diameters).

8. Jul 7, 2013

### SteamKing

Staff Emeritus