I would like to make a buffer with two pillow block and a shaft with a pulley. My motor run at 3400 RPM, but what size of pulley I can use to reduce half speed (to 1700 rpm ) ? (small one on the motor and big one on the shaft ? But, which size to have the ratio 2:1 exactly ?)

Alain M-D

Hi Alain,
Welcome to the forum. You are right about the pulley setup. To reduce speed. at a 2:1 ratio, the diameter of your pulley on the buffer shaft has to be twice the size of the one on your motor shaft. (circumfrence= diameter x 3.14).
Here is a good page for speed conversion: www.baumbearing.com/calculators.htm (http://www.baumbearing.com/calculators.htm)
Regards, Greg

The larger the pulley on the motor, the slower it goes. You can also put a step pulley on the motor and have a variable speed machine, but you have to put the motor on a pivoting base, that can be securred at any speed.

Quote:
"The larger the pulley on the motor, the slower it goes."

Gene,
Didn't you mean "The larger the pulley on the driven shaft ..." ?
Regards, Greg

Yep.
Another dumb mistake I made.SORRY.
Had it backwards alright.
Another late night of forging made me dingy.
I even posted on Pat's signiture line again. :)
I'll be OK after a knap.

Thank you for the "speed conversion calculator" address ! That will be very practical ...
It is exactly what I sought

Alain M_D