227 (#299) ############################################ TYPES OF DRAWING MACHINES 3. To attempt approximately to lay the slivers side by side. In order to effect (1) it will be necessary to slow down the lifter motion from the first accurate setting to com- pensate for the additional length of sliver per coil- that is, according to the increase in the circumference of the bobbin which will be As r[a + 2 (nt)] : Tea where a = the diameter of the bare barrel of the bobbin and n = the number of coils already placed upon the bobbin, t = the thickness of the sliver. Example If a = 1" (diameter of barrel of bobbin) n = I" and t = "" then As re[a +2 (nt)] : Ta :: Initial speed of lift : speed of lift for 2nd travers = As a [I + 2(1 * £)]: 3.1416 X I = As 3.1416 [1 + 1) :3.1416 As 6•2832 : 3.1416 :: Initial speed of lift : speed of lift for 2nd traverse. This illustrates another of the difficulties involved in cone drawing, for not only must the bobbin be posi- tively driven faster and faster when flyer leads bobbins, or slower and slower when bobbin leads flyer, but the speed of the lifter-plate or rail must be slowed down exactly according to the increased length of the coils being placed upon the bobbin. To effect (2) little forethought will be necessary. The movement of the lifter-plate or rail may be started (a) to lay the coils of yarn actually overlapping one another ; (6) to lay the coils of yarn exactly side by side ; (c) to lay the coils of yarn well apart. . The number of layers to be placed on the bobbins SO 227
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