Harvesting

Cotton is harvested by removing the fiber from the other plant parts. Two different harvester designs are used. These machines are representative of a machine that collects material, sepa­rates the desired portion, and drops the rest back onto the ground in the field. Grain combines, of course, have the same functionality.

The spindle harvester has a picking head with a series of cone — shaped spindles with rows of serrated ridges parallel to the axis. These spindles rotate and wind the cotton fiber around the spindle, thus pulling it from the bole. The picking head rotates as the harvester moves forward and doffers sweep the cotton from the rows of spindles. The cotton is then pneumatically conveyed to the storage basket on the harvester.

The stripper harvester has a mechanism to aggressively comb through the standing cotton stalks and collect the fiber. It tends to collect more plant parts (pieces of stem, leaf, and outer hull of the bole) than the spindle harvester.

Raw cotton collected from the field includes the seed, therefore it is referred to as “seed cotton.” A cotton harvester is actually a mobile solid-solid separator technology. The seed cotton (a solid) is separated from the other plant parts (solids).

Infield hauling is done with side-dump wagons sometimes referred to as “bole buggies.” When the harvester basket is full, the harvester stops, the side-dump wagon pulls alongside, and the basket is dumped (Figure 7.12). The wagon then proceeds to a location where the module builder is parked, typically close to a public road to provide ready access for the module hauler.

The wagons cycle continuously between the harvester and module builder until the harvest of a particular field is complete. Harvesting cost ($/t) is lowest when harvester wait time is minimized. Ideally, the module-building location is chosen to minimize cycle time of the wagons. However, in reality, it must be chosen such that road trucks can get into position to pick up the modules without getting stuck, thus there is a trade — off between wagon cycle efficiency and road truck access.