The Impact of Needles on a Knitting Cam

High-speed film of the motion of knitting needles in a conventional cam system showed that most needles changed direction smoothly, without bouncing, on impact with the cam track. However, an occasional needle did appear to bounce. This be havior is investigated.

It is shown that there is a maximum cam angle; making the cam steeper than this maximum would cause the needle to jam in the angle between the cam face and the trick wall. Just below the maximum is a range of cam angles for which the needles would change direction smoothly, without bouncing. For still shallower cam angles, the needles would always bounce in the track. The various critical angles mentioned above depend on the elastic and frictional properties of the needle and trick and cam track surfaces. Some numerical estimates of the critical angles are given.