CROSSED ROPE DRIVING.

There are several methods of dealing with driving in reverse direction. One is by means of single ropes for each set of grooves and so threading them in pairs that the tight sides run in unison between the slack, thus modifying the scrubbing

which would otherwise take place. It is necessary however to have two empty grooves for each couple of ropes to allow space for crossing which means six grooves for four ropes.

Another and in many respects better way is by a continuous system limited to each pair of ropes, making a double crossing. The chafing is by this means still further reduced on account of the central overlap running in the same direction for which sufficient room is allowed by the single empty groove on each pulley. We are indebted to Messrs. CROFT and PERKINS of Bradford, Yorks, for these wood cuts which describe themselves.

Figure 31 shows how to arrange the rope before fixing it in position. A folds to A and B to B.

A

B

B

FIGURE 33. — CROSS DRIVING.

Vertical half-cross driving may be successfully carried out after the fashion of Figure 33 either with multiple ropes, the leading side of which takes direct lines, or on the continuous plan either with or without tension pulley.

As however, proximity intensifies the angular wrench on the pulling side, the length of the drive between rims should not be less than five times the largest pulley.

Well polished grooves are a necessity in such cases and it is always as well to provide long keyways so that the pulleys may be adjusted to the best position in actual practice. This also applies to other awkward conditions.

FIGURE 34.—

VERTICAL HALF-CROSS

Hitherto we have confined our attention to what may be designated main driving, either from the engine or from the line shafts. Now let us proceed DRIVING. a step further and discuss the equally important question of driving machinery when the motion.

is not constant.

By an arrangement of fast and loose rope pulleys (which my firm introduced some years ago) ropes have superceded belts in many of our cotton mills.

From Figure 35, which reproduces a room interior of a mill where this system of driving has met with great success, it will be seen that the power is entirely transmitted by ropes from a central shaft running the whole length of the room thence along a series of ring spinning frames and over guides down to the

encased driven pulleys near the floor. By this means a much longer horizontal than vertical span is secured for the ropes, which owing to the weight between the sustaining points are maintained at an easy driving tension.

The ropes upon these frames are from 3/4 inches to 18 inches diameter and cost about one sixth that of the 31⁄2 inches or 4 inches leather belts they replaced.

Figure 36 displays the shifting gear which puts the rope in and out of action. This is simply an ordinary radius fork bent to the curve of the pulley operated by a small lever outside the box.

This sectional drawing shows the entire combination of grooves including a shallow central one in which the rope gains a start before passing to its work.

Nor is the employment of fast and loose rope pulleys restricted to spinning frames. They are most effectively used on many other classes of light machinery.

A remarkable effect of their use in connection with textile machinery is the annihilation of static electricity generated by slipping belts, which is so pronounced in some cases as to cause the fibres to bristle up instead of lying close when spinning.

Before dismissing the purely mechanical side of the question. a most important item still awaits our careful consideration, that is the construction of grooves. The fact that when loads are constant the trailing span curves by its own gravity down upon or away from the pulleys, according to the direction of rotation, and is ejected so to speak without any disturbance or apparent effort; also that a cotton rope may be pressed as tightly as possible round the entire circumference and will yet fall away immediately the ends are liberated; pretty conclusively demonstrates the futility of seeking easement in curvatures to match in some measure the roundness of the rope itself.

FIGURE 38. CURVED SIDED GROOVES

Curved sided grooves having proved not only an impedence to driving force. but also a stimulus to that destructive rolling action which is the very antithessis of good practice, should therefore always be discouraged.