| 40 × 840 | |
| = 60's counts in worsted. | |
| 560 | |
| 40 × 840 | |
| = 131·25 counts skeins. | |
| 256 |
Example 10.—Find the yards of yarn in 3 lb. of 2/48's worsted and ¼ oz. of 60/2 spun silk respectively.
In 2/48's worsted 24 × 560 = yards in 1 lb., ∴ 24 × 560 × 3 = 40,320 yd. in 3 lb. 60/2 spun silk = 60 × 840 = yards in 1 lb. or 16 oz., and to obtain the length in ¼ oz. divide by 4 × 16—
| 60 × 860 | |
| = 787·5 yd. | |
| 4 × 16 |
Weight of Knitted Fabrics.—These calculations lead to examples where the weight of knitted fabric has to be found. The ordinary plain knitted loop in which the bulk of textures is worked consists really of a weft structure, that is, the yarns run predominantly crosswise, and are intersected with the preceding loops in the manner already described. In determining the weight of a given length of plain knitted fabric we require various factors, these being taken as they are on the frame. It is essential in the first place to know the counts of yarn employed, and the number of courses inserted per inch into the fabric, and again it is essential to know the width at which the fabric is being worked on the machine. Finally, it is necessary to estimate what is known as the "take-up," for the yarn is pushed into curved formation which "takes up" yarn about twice the width of the fabric by the intersecting of the yarn over the needles and this has a very definite influence on the weight.
Example 11.—Find the weight of 10 yd. of knitted fabric made from 2/20's worsted yarn with 18 courses per inch at a width of 32 in. on the needles. The take-up is 2, that is, to form one course of loops, a length of yarn equal to twice the width is required.
If the question of take-up be ignored for the moment, let the yarns be inserted as weft threads crosswise in the fabric and we shall have in 1 in. of cloth 18 courses or threads each 32 in. wide. This gives 18 × 32
36 = yards of yarn in 1 in. of cloth or 18 × 32 × 36
36 yards of yarn in 1 yd. of cloth × 10 for 10 yd., but from the yarn counts we know that the size is such that 2/20's worsted = 10 × 60 = yards in 1 lb., so that dividing the latter by this number of yards will give the weight of the fabric in pounds, thus—
| 18 × 32 × 36 × 10 | |
| = 1·03 lb. as the weight of 10 yd. of fabric. | |
| 36 × 10 × 560 |
But this is the weight if the yarns are straight in the fabric, which they are not, for there is a take-up of 2, that is, the weight has to be doubled—
1·03 × 2 = 2·06 lb. weight.