247 (#321) ############################################ PRINCIPLES AND PRACTICE An important distinction should be drawn between calculated and actual twist. In fact with reference to all textile machinery there is room for much research on the reason for the marked difference between the theoretical and actual results obtained. An approx- imation of theoretical and actual results should be diligently sought for. With reference to all these spindles and their equip- ment the following points should be specially noted :- 1. the driven parts_flyer or spindle-should be well designed to stand running for years at normal speeds and easily oiled ; 2. the driven parts should be driven under con- ditions which will ensure absolute regularity of running from day to day and week to week -chain drives wherever possible ; 3. the system of control adopted should be certain, easy to manipulate, and should give no occa- sion for the taking-in of grit or for the splash- ing of oil on to the yarn during spinning; 4. the lifter-or ring-rail-should be under delicate control-positive or negative and it should be impossible for it to give any other distribu- tion than that demanded from it* ; 5. the system of yarn-control due to the relation- ship of front rollers and spindles should be such as to give the necessary support to the thread during twisting, and to direct it satisfac- torily to its position on the spool or bobbin. Lifter Motions. The distribution of the delivered thread on to the spool, bobbin or tube is a fascinating * The problem of obtaining a stationary ring-rail in ring spinning is of much moment. Reference is made to this type in Chapter IV. 247
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