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33^ BELTS.
Fig. 2 shows an arrangement
by which the direction of motion
of two shafts may be reversed"
when the distance between the
shafts is too short for the use of a
crossed belt or when a crossed
belt, for any other reason, cannot
be used.
Suppose pulley A to be the
driver and to run in the direction of the arrow. C and D are
guide pulleys, and the motion of the driven shaft B is in the op-
posite direction to the shafts. In this case the guide pulley C is
on the working part of the belt, and is the one to which special
attention must be paid in regard to heating. If the direction
of shaft A is reversed, guide pulley D will be on the working
part of the belt.
Crossed Belts.
If the distance between A and B (Fig. 2) had been long
enough, it would have been preferable to reverse the motion of
B by means of a crossed belt, instead of by the arrangement
shown in Fig. 2.
Crossed belts do not work well when running on pulleys
small in diameter as compared to the width of the belt.
Too short distance between the shafts must be avoided.
Wide crossed belts are very unsatisfactory; therefore,
instead of running one wide crossed belt it is preferable to use
two belts, each of half the width, and run them on two separate
pairs of pulleys. Such belts should be of equal thickness, and
the pulleys should be crowned, well finished and of correct
size, so that each belt will do its share of the work.
Quarter=Turn Belts.
Fig. 3 shows a so-called quarter-
turn belt, used to connect two shafts
when running at an angle and laying
in different planes. The principal
point to look out for is to place the
pulleys (as shown in Fig. 3) so that
the belt runs straight from the de-
livering to the receiving side of each
pulley.
The pulleys shown in Fig. 3 are
set right for belts running in the
direction of the arrows. If the mo-
tion is reversed, the belt will run off
the pulleys.
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