Metso MP1000, Technical Reference Manual

Page: 179 / 180

SECTION 5 - ECCENTRIC ASSEMBLY
MP SERIES CONE CRUSHER TECHNICAL REFERENCE MANUAL
5-3
matches the pitch diameter of the pinion. A tool is
available for this method and Tables 5-1A, B
(MP800) and 5-2A, B (MP1000) list the backlash
requirements based on the type of gear set provided
with your Crusher. A distance out from the
countershaft greater than the pitch diameter of the
pinion can be used but a correction factor must be
applied to calculate the corresponding
circumferential motion at that distance. See the
formulas in Table 5-4 for measuring
circumferential motion at a larger diameter than the
pitch diameter of the pinion. The second method
for measuring backlash is to measure it directly by
the use of feeler gauges. This method is used only
on the straight bevel gear sets because you need to
measure the backlash at the center of the tooth face.
See Tables 5-3A (MP800) and 5-2C (MP1000) for
acceptable levels of backlash when using this
method.
If the backlash measured using either one of these
two methods is outside the acceptable range, the
backlash must be adjusted by adding or taking out
the appropriate amount of shim thickness from
under the lower thrust bearing. See Tables 5-3A, B
for the appropriate amount of shim thickness to add
or take away based on the amount of backlash
change required.
When setting the height of the eccentric to achieve
an acceptable level of backlash, be aware that the
eccentric rests on top of the upper and lower thrust
bearings. These two parts are designed to lap
together which will reduce the backlash slightly.
For this reason it is important to continue to check
the backlash at regular intervals. It is also the
reason it is a common practice to set the backlash at
the high end of the acceptable range. If in the
process of lowering the eccentric to reduce the
backlash on a worn set of gears, the root clearance
reaches the minimum limit, the root clearance will
then be the limiting factor to assure that the teeth do
not bottom out. Refer to Figure 5-2.
Care must be used to see that the worn profile does
not interfere with the tips of the gear or pinion teeth
as the pinion is rotated. It may be necessary to
remove by grinding any ridge that may have
formed to provide clearance for the tip of the teeth
to pass.
To check or adjust backlash or root clearance,
proceed as follows:
5.2.2.1 For Spiral Bevel Gear Sets
Because of the spiral cut on the gear teeth, it is not
possible to measure the backlash at the center of the
tooth face with feeler gauges. The only acceptable
way to measure the backlash on spiral bevel gear
sets is by the circumferential motion measurement
method.
1. Remove all clearance between the eccentric
bushing and the main shaft by placing a
hydraulic jack between the inside diameter
of the frame and counterweight, in line with
the counterweight location dowel in the
eccentric flange, pushing the thick side of
the eccentric towards the main shaft. Use
only enough force as is required to slide the
eccentric assembly toward the main shaft.
Using excessive pressure could tip the
eccentric assembly and give incorrect
readings. While maintaining pressure on the
eccentric, pull the countershaft outward to
take up the end float and rotate the shaft
clockwise and counter-clockwise to reach
the limits of motion allowed by the
backlash. Using a dial indicator, measure the
circumferential motion at the outside
diameter of the pinion pitch diameter. Refer
to Table 5-1A (MP800) and 5-2A (MP1000)
for the acceptable level of circumferential
motion and minimum root clearance. A tool
is available that slides onto the countershaft
and has marks at the pinion pitch diameters
for both the spiral bevel and the straight
bevel gear sets (refer to Figure 2-19). Make
sure that you are measuring the
circumferential motion at the correct pinion
pitch diameter mark. If other circumferential
diameters are used for measurement, use the
equations shown in Table 5-4.
2. Then measure and note the root clearance.
3. If the backlash and/or root clearance is
found to be less than that which is specified
in Table 5-1A (MP800) or Table 5-2A
(MP1000), the eccentric assembly is to be
removed and metal shims of the proper
thickness are to be added under the lower
thrust bearing as described in Section 3
under
Lower Thrust Bearing and Shim
Replacement . Refer to Table 5-3A. Adding
shims will raise the eccentric assembly and
move the gear away from the pinion, thereby
increasing the backlash and root clearance.
NOTICE
V-belts or flexible coupling must be loose
before proceeding with the measurements.