76 (#124) ############################################# WOOLLEN AND WORSTED SPINNING Ń fibre length The formula is simply a suggested 3 basis for deciding the matter of wire length; if adopted it would still require modification in the light of certain empirical knowledge. It does, however, give some approximation 'to present-day practice. The length of wire should probably be taken into account along with the space interval—at least in the true carding ” positions (worker and swift). If the length of the wire above the knee be taken as the carding length, then the three factors : length (approximately) of swift wire, space interval, length (approximately) of worker wire should be just equal to the minimum fibre length to ensure equal carding conditions for the fibre. This condition is probably attained in carding short fibres of fairly average length, but in carding longer fibres there is a marked discrepancy. This is due partly to the “lie ” of the fibres upon the revolving cylinders, partly to the resist- ance offered during transference from cylinder to cylin- der--even in stripping, and partly due to air friction. It is difficult to see how the practical nece ties can here be met with any other method than empiricism, but the value of having mental vision of what is happening, and some basis of reference, is still strongly in evidence. (c) The combination of foundation and wire to meet the requirements of the various and different activities observable in every carding engine, and also to meet the *requirements of carding engines designed to card par- ticular fibres, must now be considered. Differences here will be found to be due to 76
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