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The position of the immersion roller in the size has some effect upon the amount of size retained on the warp, as by sinking the roller lower in the box the yarn will remain longer in the size, and will therefore absorb more. This roller is also mounted so that it can be lifted out of the size altogether when the machine is stopped. The larger cylinder is usually 6 feet to 7 feet diameter, and the smaller one about 4 feet diameter, and both are heated with steam.

Some machines have a revolving brush between the size-box and the cylinder. This brush is usually driven from the fan shaft, and its object is to lay the projecting fibres, and so strengthen the yarn. Brushes are only used in some fine-weaving districts, and not always there. The brush gives the threads a round, smooth feel, and prevents them sticking together. Under the brush which brushes the yarn a smaller brush is placed, running at a slower speed than the one above it; the lower brush is placed a short distance into the upper one, and serves the purpose of cleaning it as it revolves.

The marking mechanism in the slashing frame usually consists of a tin roller wheel, B ([Fig. 24]), driving the wheel D, called the “stud wheel”; a screw or worm, E, on this stud drives the bell wheel F. The marking hammer L is situated immediately above a vessel containing colouring matter, and is lifted by a cam, P, driven from the tin roller, and dropped suddenly on the warp, marking it to the required lengths.

The length between each mark is regulated by the wheels used. The tin roller wheel being the driver, if this is divided into the product of the stud wheel and bell wheel, it will give the number of revolutions of the tin roller for each mark, and this multiplied by the circumference of the roller will give the length of the mark. The formula will stand thus—

stud wheel × bell wheel × circumference of rollertin roller wheel = length of mark.

FIG. 24.