Static and dynamic influence of forces on a being threshed corncob

BACKGROUND: With the use of high-speed shooting, it was found that the corncob, getting into the gap of the threshing unit, generally, takes a position parallel to the drum axis. Let us accept that the plane of operation of the working body of the threshing drum – the beater – coincides with the generatrix of a cob. The cob changes the motion mode because of the impact of the threshing machine beater on the cob. The impact can take place in the moment when the cob even does not hit the deck cleats, so the cob gets a flying kick.

AIM: Deriving the static and dynamic influence of forces on the being threshed corncob. Defining the necessary force of corn seeds breaking-off from the cob in dependence on the friction coefficient.

METHODS: The value of mechanical impact of working bodies of the orienting-metering loading device and the threshing-separating device on a corn seed is limited not only by strength properties of the protecting corn cover, but by the link strength between a seed and a cob in the nose, middle and root areas. Knowledge of this mechanical-technological property helps to increase the level of variability of force impact in corncobs from the side of working bodies of the used machinery. It helps to transport the corncobs without husk, to orient them in space, to supply in small increments for the proper processing and, in addition, to thresh without causing any macro- and microdamages to the seeds.

RESULTS: The seed moisture change and, consequently, the seed-to-seed friction coefficient change also influences on the ratio between the applied force P and the reacting force N. With the same load P applied to the dry and the moisty cobs, the pressure N on the dry seed is higher than on the moisty one, and seed threshing from the dry cobs is conducted with lower external forces P at free direct impact.

CONCLUSION: The process of the flying kick threshing becomes more difficult with the increase of corncobs moisture due to increase of seed-to-seed friction. The flying kick threshing of corncobs stops at the seed moisture which corresponds to the friction coefficient f = 0.22. The obtained theoretical principles are confirmed experimentally.