COTTON-SPINNING MACHINERY. 299 



deKvering rollers and tlie taking-up barrels must also be the 

 same, in order to convey the roving to the bobbins with- 

 out causing any strain or looseness of the rovings. But 

 this applies only to the first few laps of the rovings ; for 

 the barrels are enlarged by the successive coils of roving^ 

 and their rotative motions must be reduced accordingly. 

 As the bobbins are being filled with rovings, their surface- 

 motion must be made to correspond with that of the de- 

 livering rollers, so as to take up equal lengths in equal times. 

 The spindle and flyer that twist the rovings, and the bob- 

 bins that take them up, are driven by separate first motions, 

 whereby their speeds are adapted to the required difierences, 

 to be noted further on. The bobbin and fly frame was not 

 strictly a new invention when first used as a roving-frame ; 

 it was a modification of the throttle spinning-frame of 

 Arkwright. The bobbins used for spinning are about 3 to 

 3^ inches long, and some 2 inches in diameter j those for 

 the rovings are from 6 to 9 or 10 inches long, and 3 to 4 

 inches in diameter. It was thus necessary to adapt the 

 roving-frame to these larger-sized bobbins. But the essen- 

 tial change from the throttle frame consisted in the addi- 

 tion of the new apparatus for driving the bobbins apart 

 from the spindles, by trains of wheels and pulleys, so as to 

 ensure the differential motions for taking up the roving. 

 This separate driving of the flyers and the bobbins was 

 the problem to be solved by the new construction. To 

 explain this, it should be stated that, in spinning, the 

 spindles and flyers are driven to twist and deliver the 

 threads to the bobbius, and the bobbins are carried round 

 with the flyers by the pull of the threads, against a slight 

 friction, as they are taken up by the bobbins ; and the 

 bobbins thus make fewer turns than the flyers, by the 

 number of coUs taken up by them. The tightness of 

 winding on is thus determined by the strength of the 

 threads, and the friction as drag of the bobbins. But as 



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