185 (#247) ############################################ PRINCIPLES IN WORSTED DRAWING rollers. As a rule it may be taken that the slivers are so firmly gripped by the drafting rollers that there is no slip. Under these conditions there is no half-way house-the fibres are either under the control of the back rollers or of the front rollers, and if there is any question the front rollers assert their strength and the fibres are extended or broken. If, however, the grip of, say, the back rollers is inefficient, then whatever the dis- tance apart may be the front rollers will take off the fibres at different tensions and there is a chance of a looped yarn being produced ; and similarly with a defective grip of front rollers. Thus the following con- ditions of roller-gripping are possible, and the results in each case should be thought out, or, better still, experimented with :- Back rollers failing to grip Front rollers gripping; gripping failing to grip; failing to grip failing to grip; gripping gripping. The last is, of course, the correct condition, and every box should be designed and clothed to effect this. Given, then, the last condition, what possible settings of the ratch” are there? There are three possible settings of the ratch for any given length of fibre, viz. 1. Front rollers taking control of fibre before back rollers release fibres (A); after back rollers re- lease fibres (C); 3. just as back rollers release fibres (B). (See Fig. 55) It is obvious that with modern tops, which may be 60 2. 1 185
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