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On seed screening and cleaning machines the motor is chosen by the motion the machine produces: the eccentric screen box, aspirator fan, indented cylinder and feed roll are different loads. Power and speed for each come from the existing label or the machine maker; the most sensitive point on a seed cleaner is that speed directly affects separation quality.
Why does speed decide separation quality?
The number of strokes per minute of the screen box sets how far the grains travel across the screen surface. In the aspirator, air flow varies roughly in direct proportion to fan speed; if speed rises, plump seed can be drawn off along with the light grains. Fitting a 2-pole motor in place of a 4-pole one without changing the pulley therefore throws the machine's setting off completely. When replacing, keep the pole count and pulley ratio.
Motors on a seed cleaner
| Section | Function | Selection note |
|---|---|---|
| Screen box | Separates grains by size | Eccentric vibration wears the bearing and foot bolts |
| Aspirator | Removes light grains, husk and dust | Damper position changes the motor load |
| Indented cylinder | Separates by grain length | Turns slowly, usually geared |
| Feed and elevator | Supplies product evenly to the machine | Loaded start and setting of the feed rate |
Dust and treated seed
Fine dust released during screening settles on the motor fins and weakens cooling. If seed treatment is done in the same plant, chemical dust in the air can be corrosive to the motor frame and terminal box. Since such an environment is listed among the conditions not covered by the warranty, the treatment unit should be kept apart from the cleaner motors and cleaning done regularly.
Matching dimensions
Seed cleaner bodies are often compact; the motor base or flange is built into the machine chassis. Comparing the new motor's shaft height and shaft size with the old one is needed to keep the pulleys aligned.
For machine examples see the grain cleaner motors and grain screening and cleaning motors pages, and filter your chosen power and speed in the shop.