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The cutter bar of a mower, swather, or combine is said to be askew when the center line of the guards, in the plan view, is not in the direction of travel. For pull-type vehicles (mowers, swathers, and combines), the cutter bar is askew if its outer end lags behind the inner. The lag is what commonly occurs and is a function of the crop, the rolling resistance, and the ground slope. The cutter bar will be askew for self-propelled and pull-type vehicles on turning, if the turning center is not located on the axis of the cutter bar. The lateral motion of the guard, due to the skew of the cutter bar, deflects the stalks out of the vertical prior to shearing, thus increasing the variation in the stubble height. If the deflection is large, the guards may be unable to penetrate the stalks satisfactorily. When this occurs, the crop will not be cut and the cutter bar may plug. For example, Harrison et al (4) experienced plugging with some pull-type mowers due to skew if the crop density and the ground speed exceeded specific values. For a pull-type swather, Harrison and Reed (3) observed that the crop would be cut satisfactorily even when the skew was 15
an analysis of cutter bar skew
Harrison, H.P. 1972. AN ANALYSIS OF CUTTER BAR SKEW. Canadian Agricultural Engineering 14(2):101-104.
101 - 104