# How to calculate the torque required to move the gear?

1. Apr 9, 2013

### aiklone1314

1. The problem statement, all variables and given/known data
Given

Where gear 1 is start from the bottom right gear and ends with gear 7 which is located at the top middle.

The shaft length are 20cm between gear 1 and gear 2,15cm between gear 2 and gear 3 and 15cm between gear 5 and gear 6. The material of the shaft and gear are made up of acetal which density is 1410kg/m3.

May i know how to calculate the input torque required in order turn all the gear?
no load are at the end of the gear, only mass moment of inertia of the gear and the shaft need to be consider. TQ for helping.

2. Relevant equations
Torque= mass moment of inertia*angular acceleration
...

2. Apr 9, 2013

### haruspex

Merely moving the gears requires no particular acceleration; it can be extremely small. As a result, there is no minimum torque required by that equation. In practice, there is a minimum torque, but that comes from static friction at the axles.

3. Apr 9, 2013

### aiklone1314

if mass moment of inertia of the gear and the shaft are needed to be consider? i am required by the lecturer to do that calculation

4. Apr 10, 2013

### haruspex

I just realised you left something out. You wrote:
But what you meant was
May i know how to calculate the input torque required in order turn all the gear at the specified accelerations? ​
Now it makes sense. All you need to do is calculate the MI of each gear and shaft, multiply each of those by its required acceleration, and add them all up. But you cannot do that for the shafts without knowing their radii. Do they matter? I would not have thought so. The shaft lengths are irrelevant.

5. Apr 10, 2013

### aiklone1314

TQ so much.

Sorry that i miss out the acceleration and the radii of the shaft.
The acceleration is 9.81m/s2 and as the shaft is to be designed by me and no specific radii is given to it, thus the radii of the shaft i would like to use the following formula to find:

As the bending moment of the shaft are negligible small, the midrange and alternating bending moment is ignored, only torsion need to be considered.
May i know how to calculate for the alternating torque, i was told by the lecturer the alternating torque is superposed but may i know why is it superposed?

I just realised the shaft length are irrelevant in the formula. Just ignore it.

Do i need to use this formula to calculate the gear torque
total torque on A to accelerate A and B :

= Ia alphaa + n2 Ib alphaa
= ( Ia + n2 Ib ) alphaa

that are found in this website:
http://www.tech.plym.ac.uk/sme/mech226/gearsys/gearaccel.htm

May i know do i implement the shaft mass moment of inertia into it?