415
OF ENGTN"EBING FOBMULÆ.
High-speed Belting.
The formulae above apply to ordinary cases,
but are inapplicable to cases in which very small
pulleys are driven at very high velocities; ns in
some wood-cutting machines, fans, &c., the acting
area of the belt on the circumference of tlie driven
pulley being so small that either grant tension or
a greater breadth than that determined by the
formula is required to prevent the belt from slip-
ping.
In such extreme cases of high-speed belts, find
the breadth of the first-motion belt (the belt
which imparts motion to the driving pulley) by
1100 HP
the formula for ordinary belting, W =------------->’
then, if
A = Acting area of first-motion belt,
r = Velocity of first-mut':on belt,
a — Acting area of high-speed licit,
V = Velocity of high-speed belt,
A v
a ~ ’
The noting area of cither belt = I X o.
Where I = length of circumference of driven
pulley embraced by the belt,
b = bicadth of belt,
b — 7 in the case of the high-speed belt.
If there is no first-motion belt exclusively for
the machine, it will be easy to suppose n hypo-
thetical case, from which the breadth of the high-
speed belt may be calculated.
Long belts arc more effective than short belts.