Fig. 25 Angular Misalignment
PULL AND BEARING LOADS for further instructions on summing vectors.
Idler Force: Belt installation tension can also be applied by exerting a force against an idler
pulley within the system that is used to take up belt slack (see Figure 23). This force can be
applied manually, or with a spring. Either way, the idler should be locked down after the appropriate
tension has been applied.
Calculating the required force will involve a vector analysis as described previously in the shaft
Sonic Tension Meter: The Sonic
Tension Meter (Figure 24) is an
electronic device that measures the
natural frequency of a free stationary
belt span and instantly computes the
static belt tension based upon the belt
span length, belt width, and belt type.
This provides accurate and repeatable
tension measurements while using a
measurement process itself doesn't
change the belt span tension). A
measurement is made simply by
plucking the belt while holding the
sensor close to the vibrating belt span.
The unit is about the size of a portable phone (8-1/8" long x 3-3/4" wide x 1-3/8" thick or
206mm long x 95mm wide x 35mm thick) so it can be easily handled. The sensor is about 1/2"
(13mm) in diameter for use in cramped spaces, and the unit is either battery operated for portability
or AC operated for production use. The unit measures virtually all types of light power and
precision belts. A gain adjustment allows measurements to be made in environments with high
noise levels. Data can also be collected through an IBM Compatible RS-232 serial port, if desired.
For additional details, see the product section of this handbook.
SECTION 11 DRIVE ALIGNMENT
11.1 Angular And Parallel
Drive misalignment is one of the most common sources of drive performance problems.
Misaligned drives can exhibit symptoms such as high belt tracking forces, uneven belt tooth wear,
high noise levels, and tensile cord failure. The two primary types of drive misalignment are angular
and parallel. Discussion about each of these types are as follows:
Angular: Angular misalignment
results when the drive shafts are not
parallel (see Figure 25). As a result,
the belt tensile cords are not loaded
evenly, resulting in uneven tooth/land
pressure and wear. The edge cords on
the high tension side are often
overloaded which may cause an edge
cord failure that propagates across the
entire belt width. Angular misalignment
often results in high belt-tracking forces
as well which cause accelerated belt
Fig. 23 ldler Forces
Fig. 24 Sonic Tension Meter