PALMER: THE DESIGNING OF CONE PULLEYS. 63 
Rules for Proportioning the Steps of Cone Pulleys. 
For ready reference, and for the use of those who may not care 
to follow the discussion presented in the preceding sections, the 
simple graphical method there deduced at length will now be taken 
as fully demonstrated and a brief rule given without proof, for each 
case of proportioning the steps of a pair of cone pulleys which may 
occur in practice. 
REMARKS. 
CONES ALIKE, OR UNLIKE. 
Whenever the features of a design will admit it is always desira- 
ble to have the two pulleys of a pair just alike, so that the same 
pattern will serve for both. In such instances as a cone on a 
machine to run with another cone on the countershaft overhead, it 
is almost always possible to have the cones alike, and they should 
be made so. But, on the other hand, there are very many times 
when the nature of the machine on which the cones are to be used 
is such that it is impossible to make them alike. 
SPEEDS IN GEOMETRIC SERIES. 
In all cases, except when there is some very special reason why 
there should be a certain definite number of revolutions produced 
for the driven shaft, each time the belt is shifted from one pair of 
steps to the next the series of resulting speeds should form a geo- 
metrical progression. 
That is, it 1s desirable that when the belt is shifted the number 
of revolutions of the driven shaft shall be a certain number of times 
(whole or fractional) the revolutions before; and that when it is 
shifted again to the next pair, the next number of revolutions will 
be the same number of times this speed. 
This geometrical series is well established as always desirable, 
and should be attained whenever possible. 
THE SIZE OF STEPS. 
The relative size of the steps has no apparent relation, whatever, 
in general, to the proper series of speeds. If the steps of a cone 
are made with the same differences in diameter throughout the 
cones will, in general, be wrong. <A pair of small three-step cones, 
with a large distance between centers, may have the same differ- 
ence between the diameters of any two successive steps, but in no 
other case can this be true on both cones of the pair. 
