PULLEY SIZE AND RPM

 
Supply any 3 of the following and calculate the fourth:
Pulley A Pulley B
SIZE SIZE
RPM RPM
 

 

Example:

On a ground driven planter unit, the drive wheel is 125 cm in circumference and turns a 13-tooth sprocket, driving a chain up to a 20-tooth sprocket. The 20-tooth sprocket is connected to a shaft which turns a 17-tooth sprocket that is connected to a 28-tooth sprocket which in turn spins the 45-cell planter plate. This is a compound drive system and will set the spacing of the seeds down the row.

 

Problem:

How many seeds will drop per revolution of the 125 cm drive wheel?

 

Calculation: (A compound drive is handled as 2 individual calculations)

 

Part #1:

Pulley A Pulley B

Size

13-tooth

Size

20-tooth

RPM

1

RPM

0.65

 

Part #2

Pulley A Pulley B

Size

17-tooth Size 28-tooth

RPM

0.65 RPM 0.395

 

Answer:

The Cell-plate (45 cell)   x    0.395 RPM   =   17.76 seeds drop in one revolution.

Seed spacing down the row then is:   125 cm / 17.76 seeds = 7.04 cm

 

The formula:

As = (Bs * Br) / Ar

Ar = (Bs * Br) / As

Bs = (As * Ar) / Br

Br = (As * Ar) / Bs

 

where

As = pulley A size, Ar = pulley A rpm, Bs = pulley B size, Br = pulley B rpm