Abstract:

The paper presents a new method for determining yarn twist that eliminates the drawbacks of the presently used ‘reverse-twisting method’. The new method may be described as a ‘two-end untwisting/twisting method’. In this method, the test sample of a yarn is subjected to untwisting and twisting by two clamps rotating in opposite directions. Pre-tension of the test sample is effected by loading it at its mid-length point, by virtue of which the sample takes the shape of a broken line instead of a straight line. Owing to the use of two rotating clamps and pre-loading the sample at its middle point, there is no ‘ballooning’ of the sample during testing. The ballooning phenomenon occurring in the reverse twisting method is responsible for uncontrolled elongation of the test sample, due to slippage of the fibres. The two-end untwisting/twisting method is much less sensitive to the amount of pre-tension applied to the test sample. For the purposes of this method a special twist-meter, described as CZ/V-1, was designed and made. On comparing the results of testing twist by the ‘reverse twisting method’ on the Zweigle twist-meter D-314 and the results obtained by the ‘two-end twisting method’ on twist-meter CZ/V-1, it was found that the new method of two-end twisting was at least 50% more accurate than reverse twisting.