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PULLEY SIZE AND RPM
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| Supply any 3 of the following and calculate the fourth: |
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
