For clearness we will exaggerate the differences in diameter in the sketches and figure the speeds that the different size ropes would produce. We will take _A_ as normal, _B_ 1 inch farther out of the groove, producing a difference in diameter of 2 inches; _C_ 1 inch deeper in the groove, producing a difference in diameter of 2 inches. In Fig. 85 assume for the normal diameter of driver and driven 40 inches, 42 inches for _B_ and 38 inches for _C_, with a speed of 200 revolutions per minute for the driver. Either _A_, _B_ or _C_ will give 200 revolutions per minute for the driven sheave, omitting slippage, of course. In Fig. 86 say the normal diameter of the driver for rope _A_ is 60 inches and of the driven 30 inches, a speed of the driver of 200 revolutions per minute will give the driven sheave a speed of 400 revolutions per minute; _B_, with the driver 62 inches and the driven sheave 32 inches diameter, will give the latter a velocity of 387-1/2 revolutions per minute. With _C_ the driver is 58 inches, the driven 28 inches, and the speed given the latter 414-2/7 revolutions per minute. In Fig. 87, the normal diameter of the driving sheave being 30 inches and the driven 60 inches, a speed of the driver of 200 revolutions per minute will give a speed of the driven member of 100 revolutions per minute. With _B_, if the driver is 32 and the driven 62 inches, the driven sheave will have a speed of 103-7/31 revolutions per minute; _C_, with the driver 28 inches and the driven sheave 58 inches, will give the latter a speed of 96-16/29 revolutions per minute. So it will be readily seen what effect a large or a small rope would have.
There are some who claim that slack ropes will transmit more power owing to more wrap on the sheaves, while others claim that tight ropes are better. If a drive with all the ropes slack gave trouble by the ropes slipping, the first remedy tried would be tightening the ropes. But if the conditions were like Fig. 87, it would not be particularly harmful to have some of the ropes longer than others; in fact, it might be well, as the longer ropes would not make a complete circuit as quickly as the shorter ones; consequently the position of the splices would be continually changing. However, it seems more natural to have about the same pull on all the ropes, that is, not have them as shown in Fig. 88. In conclusion for the system, it should be noted that it has no means of tightening the ropes except by resplicing; it is not as well adapted to various conditions as the other forms; it is the cheapest form to install and in some cases should give excellent satisfaction.