XC. HERBERT KE, ROSS, 
was made in a transmission of about 160 h.p. at about 4000’ per 
minute. The rope system and belt system each being tested at 
what was believed to be the best working conditions. The result 
was that the efficiency appeared to be the same for both ropes and 
belts. The question of working cost was not examined in the case 
mentioned. It would generally appear, however, that ropes are 
more costly to maintain, for, though costing less, the wear is 
excessive and renewals are comparatively frequent. The use of 
heavy grooved pulleys adds to the cost of installation, and the 
efficiency being no greater, no doubt accounts for the limited 
application of this system of driving, except for great loads, or 
high speeds up to 6000’ per minute. 
While the subject of belts at low speeds may be readily 
examined by existing formule, additional factors enter into con- 
siderations of high speeds which very considerably modify the 
results. It is an American contention that an air pressure, due 
to rarefication of air near the pulley rims, causes a greater pressure 
normal to the belt on the pulley than that due to the tension only. 
And the contention is borne out by results, notwithstanding the 
counter influence of centrifugal effect, which is easily subject to 
calculation. 
Again, at high speeds adherent air is carried under the belt and 
so reduces the friction coefficient. This has led to a system of 
perforating the belt or the pulley with satisfactory results. There 
is little doubt that the efficiency of the link-belt at high speed is 
as largely due to its open texture as to its superior flexibility. 
Thus the system of high-speed driving, brought about by modern 
electric generation, has opened up a new field for investigation. 
The use of link belting is advocated for high speeds rather than 
for high tension and heavy loads, being favoured for its smooth 
running qualities, and capacity for large transmission at high 
speeds. Its low tensile strength renders it unsuitable for slow 
driving, except for governors and mechanism absorbing small 
power but demanding easy running. 
. 
