Woollen mules are made with several hundred spindles and of varying pitch to suit particular requirements. Thus if the mules are to follow a set of say three machines with a tape condenser, and are required to spin fine counts, the pitch of the spindles may be much finer than ordinarily, but a greater number will be re quired to work up the sliver delivered by the set of machines. There are many other details which require careful consideration; the inclination of the spindles, for example, must be suited to the material to be spun.
The mule-frame to which reference has been made is a ring spinning frame arranged to spin condensed woollen slivers con tinuously, thus producing about double the weight per spindle as compared with the intermittent mule. Drafting-twist is introduced in this case between two pairs of drafting rollers by a "twizzler" which, however, only inserts false twist. The true twist is inserted later by the spindle and traveller. This method of spinning neces sitates more twist than that necessary in mule spinning so that "frame" woollen yarn is most suitable for warp and is usually not soft enough for weft yarn.
The yarn as delivered by the mule is "single" and will serve as warp or weft for the great bulk of woollen cloths, warp being as a rule twisted harder than weft. Sometimes for strength, sometimes for colour, however, it will be necessary to twist two or more of these single strands together. This is best effected on a twisting frame of the ring type, which consists of delivery rollers, to de liver a specified length of yarn in relationship to the turns of the spindles, and the spindles, which serve to put in twist and to wind the yarn upon the bobbin or tube, which they effect by reason of the retarding action of the traveller. Fancy twists such as knops, loops, stubs, etc., may also be produced if the frame is fitted up with two pairs of delivery rollers and two or three special but simple appliances.
For woollen and worsted weaving, see WORSTED MANUFACTURE. (A. F. B.)