2.0 END MOUNTING
Figure 5 shows some of the ways the prestressed metal band can be secured to the output drum. In
general, any mounting method should follow these rules: (1) the fastener should not protrude above the
circumference of the output drum; and (2) the contour of the mounting drum surface should be such that
the band lies flat without any abrupt discontinuity.
3.0 GENERAL DESIGN CONSIDERATIONS
The major advantages of the constant-torque spring stem from its ability to operate at exceptionally high
apparent stress levels. As in all types of springs, stress is an important determinant of endurance, and this
is especially true of NEG'ATOR bands repeatedly stressed in service as springs or motors. Fortunately, these
values and their effects can be calculated and predicted for practical design because the high allowable
apparent stresses result from the favorable residual stresses imparted to the spring during the
manufacturing process.
The design charts which complete this section tabulate the size-load-life relations.
TEMPERATURE
Application of the constant-torque motor in temperatures exceeding 160ºF should be undertaken only
with the guidance of our Engineering Department.
SPEED AND ACCELERATION
Free release of a charged motor, or any condition approaching free release, may permit the output drum
to throw off material faster than the take-up drum can coil it up. No such limitation exists in the "pull-out"
or charging part of the cycle, except for extremely sudden decelerations. Wherever high-speed operation,
sudden stopping or sudden release are predictable service conditions, experimental models should be
employed to verify performance and endurance characteristics.
TOTAL DISPLACEMENT
The principal limitation on the total number of rotations is the space requirement of the amount of
material involved.
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