(386) In order to enable some idea of the class and weight of the travellers used, the relative speeds of front roller and spindles, and production, a table is appended to this chapter in which a few representative counts are selected. Other tables give the result of a number of tests made with the Emerson Power Scale and other instruments, which enable the amount of driving power required to be ascertained.
(387) The consideration of the various machines employed in spinning being now concluded, a few words may be said generally about the whole system. Before doing so, however, it may be as well to define the meaning of one or two words which are habitually used to define the relative fineness of the yarn. It will be noticed in the table appended to Chapter X. that the roving was described as such a “hank” roving, while the yarn is said to be of certain “counts.” Although apparently contradictory, these terms are not really so, being simply different expressions of the same fact. The standard upon which all definitions of the fineness of yarn are based is the “hank” of 840 yards. A hank is the thread wound into coils of 54 inches circumference until a length of 840 yards is obtained. That forms the basis by which the “counts” of yarn are calculated, and the “counts” are simply the number of such “hanks” in one pound weight. In ascertaining the “hank” of roving a certain length is wrapped into a coil and weighed. The weight is obtained in grains, and that sum is then divided into a constant number obtained as follows: The number of yards of roving taken is multiplied by 100 and divided by 12. This practically means taking 8·33 as a constant number and multiplying it by the number of yards of roving wound. The same procedure is pursued with the lap and sliver on the scutching, carding, and drawing machines. It is no part of the scheme of the present work, however, to do more than glance at these modes of calculation, as there are many books of rules already in existence, but it may just be stated that the amount of twist which is put into any yarn is determined by the following method: The square root of the count is taken as the basis of the calculation, and is multiplied for mule twist by 3·75, for ring frame or extra hard twist by 4, and for weft yarns by 3·25. The product of these calculations give the twist per inch for any counts of yarn it is desired to spin. The three multipliers thus given are sufficient for ordinary uses, but if yarn is spun for doubling purposes the multiplier is 2·75, and if for hosiery purposes 2·50.