. The Street railway journal . ive-eighths inch is now probably the most usual sizeadopted, while a decade ago two inch was most favored. Pulley Diameter—The rules for the least pulley diame-ter given in the foregoing, viz., thirty rope diameters forcotton and forty rope diameters for manilla, cannot bedisregarded without impairing the durability of therope. If in any case the use of a smaller pulley becomesimperative, the load on the rope should be correspond-ingly reduced; the use of hard, or tightly twisted ropeshould in this case be carefully avoided. As in belt driv-ing, the slack side of
. The Street railway journal . ive-eighths inch is now probably the most usual sizeadopted, while a decade ago two inch was most favored. Pulley Diameter—The rules for the least pulley diame-ter given in the foregoing, viz., thirty rope diameters forcotton and forty rope diameters for manilla, cannot bedisregarded without impairing the durability of therope. If in any case the use of a smaller pulley becomesimperative, the load on the rope should be correspond-ingly reduced; the use of hard, or tightly twisted ropeshould in this case be carefully avoided. As in belt driv-ing, the slack side of the rope should, if possible, alwaysbe uppermost. With a lair length of drive the slack ofof the rope will increase the arc of contact with bothpulleys, thus augmenting the resistance to slipping, whilenecessitating less initial tension and its correspondingdisadvantages. If the slack side is below, the reverseaction takes place, each arc of contact being lessened andthe risk of slipping correspondingly increased. For dyna-. F1G 2. mo driving 10 per cent, should be deducted from thepower of the ropes to allow for this effect. Length of Drive—In mill driving no difficulty is usuallyexperienced in obtaining an ample length of drive, but inthe dynamo room economy of space is usually a muchmore important consideration. To ensure satisfactoryresults, the distance between the centers of the drivingand driven shafts should not be less than one and a quar-ter times the sum of the diameters of the two for pulleys of twelve feet and four feet diameters,respectively, the distance between the shaft centers shouldnot be less than twenty feet. This rule is a somewhatelastic one, but for all ordinary ratios of pulley diameterslikely to occur in dynamo driving, it may be followed. Asthe difference in the diameters of the pulleys becomes less, the length ofdrive may be re-duced if desired,W//A but if the pul-leys differ greatlyin size a lesserlength of drivethan given by theru
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Keywords: ., bookcentury1800, bookdecade1880, bookidstreetrailwa, bookyear1884
