# Torque and Power required to turn a plate

1. ### superman22x

4
I have a question. I am working on a small project for class. We have locking Geneva mechanism that turns a table made of cast iron 72* in .5 seconds. The table mass is calculated to be 7300 kg (D=1.25m, h=.350m).

Based on the 72* in .5 seconds, I calculated alpha to be 10.08 rad/s^2. Using I=m*r^2/2, I calculated I to be 612.3. Torque (Nm)=alpha*I=6172N*m.

For power, I used the equation P (Kw) = (Torque*2*pi*rpm)/60,000. And I used alpha*t to solve for the RPM, which ended up being 5.04 rad/s = 2888 rpm. My power required ends up being 1867Kw which seems ridiculously high. Am I calculating this correctly?

Let me know of any other info you need.

2. ### willem2

I didn't know what a Geneva mechanism was before this thread.

http://www.brockeng.com/mechanism/Geneva.htm

5.04 rad/s is < 60 rotations per minute.
2 pi rad/s is 1 rotation/second = 60 rpm, so I don't know where you got 2888 rpm.

A bigger problem is that the continuously rotating wheel accelerates the slotted wheel for the first 0.25 seconds, but decelerates it in the next 0.25 seconds, and it will probably get most of the kinetic energy from the first 0.25 seconds back. The continuously moving wheel will than have the time that the slotted wheel is stationary to get back to its origional speed.