Dynamical Theory Of The Pendulum Yarn Testing Machine

Dynamical Theory Of The Pendulum Yarn Testing Machine

Author: S. A. Shorter D.Sc. And W. J. Hall, B.Sc., A.R.C.S.

Year: 1924

During the course of certain work on yarn testing we had brought to our notice a form of autographic machine based on the ordinary pendulum machine. The records made by this machine had a peculiar shape, which we felt certain did not correspond to any peculiarity in the elastic properties of the yarn. This opinion was verified by testing a piece of thin copper wire (0.005 in. diameter) in the machine. A similar curve was obtained. The curves given by the machine were wavy, indicating quite wrongly an extraordinary relationship between stress and strain (even in the case of a copper wire!). In the case of ordinary worsted yarns the effect is so marked than no autographic arrangement is needed to show it: it can be seen by simply watching during a test the pointer of an ordinary Baér, Schopper or Goodbrand machine. The pointer moves from rest, suddenly stops for an instant, moves on again, stops again, and so on:- the motion appearing to consist of a series of jerks. These jerks often become less marked after a time, the motion in the later stages appearing much smoother.This peculiar motion is familiar to the more observant users of the machines. The writers have heard the opinion e