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a double inclined plane
The wedge differs from the inclined plane in that it is intended to be pushed under or into the load instead of having the load pushed or pulled up along the plane. Familiar machines using the wedge principle include the axe, chisel, knife, nail, and sewing needle.
A wedge must overcome the resistance of friction, as well as the resistance of the material it is being used on. The ideal mechanical advantage of the wedge is the ratio of its length to its thickness at the blunt end -- the angle of the wedge's working point. The greater the angle between the surfaces of a wedge, the greater the force needed to advance it. If the wedge angle is too great, it is impossible to drive the wedge into the material, no matter how strong the wedge or how weak the material. The limiting angle varies from 90° to 180°, depending on the amount of friction acting on the wedge surfaces.
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This page was last updated on June 20, 2017.