I made this with salvaged angle iron and 1 1/2" tubing, 2-golf cart wheels, 8- roller blade wheels, 3-26 " bicycle rims, a motor and pulley from an old piston water pump, and bits and pieces of steel.
I had hoped to be able to build it for free, but in the end I had to buy the 1/2 inch wire mesh, pop rivets and washers to attach the screen to the rims, two 5/8" pillow blocks and a 76" v-belt.
I used a 2" pulley on the motor, then a 10" pulley, then a 2 1/2" pulley to the 26" bicycle rims. I ended up with 31RPM which seems to work perfectly.
Thanks to all the others who posted videos of their homemade compost screeners. I just copied the best ideas them.