Given diameter and pitch of a spur wheel, to find number of teeth.
Set pitch on C to π (3·1416) on D, and under any diameter on C read
number of teeth on D.
Given diameter and number of teeth in a spur wheel, to find the pitch.
Set diameter on C to number of teeth on D, and read pitch on C opposite
3·1416 on D.
Given the distance between the centres of a pair of spur wheels and the
number of revolutions of each, to determine their diameters.
To twice the distance between the centres on D, set the sum of the
number of revolutions on C, and under the revolutions of each wheel on C
find the respective wheel diameters on D.
EX.—The distance between the centres of two spur wheels is 37·5 in.,
and they are required to make 21 and 24 revolutions in the same time.
Find their respective diameters.
Set 21 + 24 = 45 on C to 75 (or 37·5 × 2) on D, and under 21 and 24
on C find 35 and 40 in. on D as the respective diameters.
To find the power transmitted by toothed wheels, given the pitch
diameter _d_ in inches, the number of revolutions per minute _n_, and
the pitch _p_ in inches, by the rule, H.P. = (_n_ _d_ _p_^2)/(400).
Set 400 on B to pitch in inches on D; set cursor to d on B, 1 on B to
cursor, and over any number of revolutions n on B read power transmitted
on A.
EX.—Find the horse-power capable of being transmitted by a spur wheel
7 ft. in diameter, 3 in. pitch, and running at 90 revolutions per
minute.
Set 400 on B to 3 on D; bring cursor to 84 in. on B, 1 on B to cursor,
and over 90 revolutions on B read 170, the horse-power transmitted, on
A.