Harness and Chain Draft
Fig. 1 shows the harness and chain draft of such a web, together with the construction of a properly balanced web for standard goods of 1⅛ inches wide. It will be noticed that the face, consisting of 150 threads, is split up into two warps of 75 threads each. This arrangement is necessary in order properly to weigh them so as to get a good clearance in the shed. The warp has to be divided likewise in the harnesses and put on six harness frames, although the weave could be produced on three. It would not be practicable to crowd 50 threads on one harness frame in the narrow space available, as the harness eyes would shoulder and crowd too much when changing.
In drawing-in this web, one face warp should be arranged so that the threads are drawn on the first, third and fifth harnesses, and the other face warp should be on the second, fourth and sixth. Such an arrangement in the distribution of the warps makes it much easier on the mechanism, and minimizes the risk of breakages. It is also important to make proper divisions of the warps at the back rolls, inasmuch as some of the warps have to be weighted heavily while others are only lightly weighted, and also on account of the different take-up of the varied weaves.
The back rolls should be set in a graded position so as to prevent undue friction of one warp against another. The binder warp should be worked under the front roll on account of the extremely light weight this must carry. Fig. 2 shows the proper position of the back rolls in relation to the harness shed.
In a web of this character where the warp stock is somewhat crowded in the front reed, there is always a tendency for a fibrous yarn to prevent a perfect clearance in the shed, with a liability of producing occasional floats through the shuttle skipping these threads. Such floats will pearl up when the web contracts and make an imperfect face. This trouble may be prevented by setting the back rolls a trifle higher than the breast beam rod, so that the stock in the harness which is down will be slightly tighter than that which is in the upper harness.
The chain draft is so arranged that the face harness will operate to produce a twill which will be reverse to the twist of the yarn employed, and thus reduce the prominence of the twill weave all possible. The filling yarn should be soft, of about 15 turns per inch, and of good uniform quality, in order to produce a nice selvage and not cut the rubber. The reed dent inside the selvage rubber should be carefully twisted at an angle to conform to the nipped in position to the rubber thread, so that the outside edge of the dent will not cut the rubber when the reed beats against the goods at the weaving line.
Fig. 1.—Three Leaf Twill, or Satin Face. Woven in Conjunction With a Plain Back
Fig. 2.—Showing Position of Back Rolls in Relation to Shed