15·27
0·23
= 1½ per cent. shrinkage
15·50
picks.
When quarter-picks are required exactly, by changing one wheel only—multiply 507·5 by 4, and the product of the two drivers A and C must equal this. Then every tooth in the driven wheel B will represent a quarter-pick per quarter-inch.
There are many methods of letting off the warp positively, but none are likely to succeed in displacing the older and quite satisfactory method of levers, ropes, and weights. The very fact of making the let-off positive, causes too great a rigidity in the hold of the warp, which is detrimental to the yarn. The frictional let-off is not likely to be replaced in cotton goods weaving unless it be in some of the heavier kinds of fabrics. Where it is a question of putting in as much weft as possible, the positive let-off has an advantage.
CHAPTER III
DROP-BOX LOOMS
WHERE more than one kind or colour of weft is used in a fabric, it is, of course, necessary to change the shuttles automatically. Sometimes two or more different counts of weft of the same colour are used, and sometimes different colours of weft. Checks of all kinds, extra weft spots, and others are the chief classes of fabrics which require change boxes.