2. How to calculate the size of Pulleys for a machine

As in my 1^st post we calculated the RPM of a machine. Now if I am going to change the motor with a high speed 2800 RPM motor. How to find out the size of pulleys? If we use 2 inch pulley on motor and 14 inch pulley on machine and 1 coupled pulley in center. As below:

 

We can calculate the RPM at middle pulley;

RPM at Center Pulley = Motor Pulley  x  Motor RPM

Center Pully

RPM at Center Pulley = 2 x 2800  =  466.67 RPM

12

Now we had to find out the middle pulley ‘x’ as we know:

RPM at Machine  =     Center Pulley  x  RPM at Center Pulley

Machine Pulley

RPM at Machine  =  x  x  466.67  =  84 RPM

14

=>                    x  =  84  x  14/466.67  =  2.52 inch

Now we have calculated all the required components.