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TESTING OF YARNS.

WILLIAM MYERS, Lecturer on Textiles, Municipal School of Technology, Manchester, Eng.

In dealing with a subject of this kind it is well at the outset to consider the nature of the tests to which yarn should be subjected, and the best and most efficient methods of applying those tests.

Nature of Tests.-Yarn must be tested for count or number, strength, elongation to breaking point, elasticity if possible, twist, regularity, cleanliness, moisture, and diameter. It is proposed to deal with several of these in this paper, and the remainder will be dealt with in a subsequent paper. The reason for adopting this course is that the whole subject cannot be adequately dealt with in one paper.

Condition of Material to be Tested. A good deal depends upon the condition of the yarn as to the kind of apparatus which may be used. Yarn may be tested from the cop, the ring bobbin, the hank, the ball warp, the beam warp, and from the woven texture.

Testing for Count. - Assuming that the bulk of the yarn which has to be tested for count will be in the condition in which it has left the spinning machine, it may be well to discuss and determine: first, the most suitable length of material to test to arrive at an accurate result; second, what are the differences to be found in the count of a yarn when various lengths are tested; third, the effects of testing the material from various parts of a cop or bobbin and to note what differences, if any, exist; fourth, the most suitable method of measuring the yarn, the tension to be put

on during reeling and the effect on the length of yarn reeled due to tension and possibly the speed of reeling.

The most common way of testing yarn for count is to wrap a lea from each of several cops or bobbins taken at random

from a delivery of yarn, using a machine of the type shown in Figure 1. Now whilst there may be no particular objection to this plan, it will be found advantageous to vary this procedure and take a number of tests from the middle and near the finish of a cop or bobbin.

The graphic diagrams, Figures 2, 3, 4, 5, show the variation in count from two cops of reputed 46 mule twist. The tests. in each diagram include the whole of the cop (30 tests), and it will be seen that whilst the average count is not much below the reputed, the variation is considerable, extending in cop I from 43.6 to 48.4 (mean 45.36), and in cop 2 from 43.86 to 47.39 (mean 45.16).

Figure 6 shows the variation in count from cop 3 of 46s mule twist and whilst with 57 half-lea tests the average count is still nearer the reputed count, the variation is much greater, extending from 42.35 to 48.8 (mean 45.69), and in Figure 7, cop 4, 70 tests of 40 yard lengths shows a mean count of 44.8 with a

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Break 46° Mule Twist Sp2. Cop I Break 46 Mule Twist Spinner 2 Cop II

30 Lea Breaks.

30 Lea Breaka.

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FIGURES 2, 3, 4, 5, 6, 7.-VARIATIONS IN COUNT.

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variation extending from 41.5 to 49.3. The variations in count from other yarns are shown in the figures illustrating the variations of strength in another part of the paper. All the yarns used to illustrate this paper have been spun commercially.

Now having these variations and averages in mind, does it not seem reasonable to suggest that occasionally at least the whole instead of a part of several cops might be tested for count; and whilst there is variation, if it is found that the net result is a good average count, then the manufacturer has had delivered to him all he is entitled to, so far as count is concerned, because in a fabric or in a wrap the average count must be taken into account, as it is this which determines the weight of the texture. This of course assumes that the variations from the reputed count are not excessive. As regards average strength, that is a matter for further consideration.

In connection with the diagrams given, it should be mentioned that the yarns have all been reeled at the same tension, and as far as possible at the same speed. The wrappings have all been weighed on a chemical balance, and readings to of a grain recorded. In all cases the wrappings have been taken consecutively, and thus the variations may be readily traced.

Measuring the Yarn. - Regarding the most suitable method. of measuring yarn, it may be said that an expert reeler can adjust the tension by hand, and with constant practice he can. reel the yarn at a regular speed, but it is desirable that there should be some more reliable method of obtaining regular results as to length and tension. To remove some of the possibilities of variation, a few spinners and manufacturers have their wrap reels driven mechanically at a fixed rate, and the tension may be regulated by passing the yarn amongst a series of glass tension rods.

At the testing house of the Manchester (England) Chamber of Commerce, there is a specially constructed wrap reel with a measuring, tensioning, and stopping device. Figure 8 shows a front view of the reel with the device attached. The mechanism is constructed to put a definite amount of tension upon the