328 (#424) ############################################ WOOLLEN AND WORSTED SPINNING and of subsequent setting of the irregularity rather than its redistribution. 6. A periodic roughening of the yarn, or even a periodic tightening of the yarn due to an irregular "run-off” during weaving, will also tend to produce a marked defect. The careful consideration of the pick" on the spool for weft yarns for Italians, cash- meres, etc., cannot be over-estimated. The actual appearance of these repeating defects in the loom may now be briefly considered. Three main conditions are in evidence : 1. In which the repeat of the defect on the yarn is less than the width of the cloth into which it is woven ; and is a measure of, or has a measure in common with; or is not a measure of, or has not a measure in common with, the width of the cloth into which it is woven; 2. In which the repeat of the defect is the same as, or is a multiple of the width of the cloth into which it is woven; and 3. In which the repeat of the defect is greater than, and has or has not a measure in common with the width of the cloth into which it is woven. In Fig. 99 these conditions are illustrated. The effects produced under (c) 4 are often clearly recorded by Neate's extensometer tests as shown in Fig. 97. But a volume of this size might well be filled with records of defects of this type. This section may well be concluded by reference to the useful method recently introduced into the University of Leeds of testing yarns for spinning efficiency or thread/ fibre strength by first testing the fibre strength by bring- ing the jaws of the testing machine close together and carrying out a series of tests, and secondly testing the same yarn well over the fibre length-say 18 in. If, then, the 18 in. tests be put into terms of the jaw tests we have 328
77 77 Textile Machine
292 292 Textile Machine Part
295 296 Textile Machine
228 229 Textile Machine