14
AP Dynamometer Service Manual
Procedure for 20,000 lb
(10000 kg) and Below
Span adjustment procedure
Only Dillon shackles and pins
should be used with the
dynamometer during calibra-
tion or use. For best instrument
performance, use the shackles
and pins during calibration that
are used during routine use.
Typical recalibration interval is
every 12 months, although
more frequent calibration is
suggested for dynamometers
in extreme service.
The shackle bearings included
with the dynamometer must be
used during calibration and
operation. These bearings are
installed in the dynamometer
and facilitate predictable and
repeatable rotational movement
of the pressure arm under load.
We do not recommend that the
instruments be calibrated or
have any type of performance
reviewed with the bearings
removed.
Equipment required:
• load frame, dead weights, or lever system
• applicable fixturing for applying load to the device
• torque wrench with 3/16 inch hex drive socket
The calibration technician must be qualified for and trained in the proce-
dures for operating the calibration machine, adjusting the calibration of the
device, and recording of the calibration data.
1.
Service the dynamometer. Inspect the unit for damage, and the
condition of all load bearing surfaces. Replace or repair parts and
assemblies as required. Leave the crystal off the unit until the device
has been recalibrated after repair.
2.
Dynamometers received for recalibration and repair that are functional
should have “as found” readings taken. Install the dynamometer and
shackles in the calibration machine.
3.
Check the maximum hand adjustment and record the number of
divisions to the nearest half division the maximum hand will move the
dynamometer pointer in a counter clockwise direction.
4.
Exercise the unit three times by applying 1.00 to 1.05 times rated
capacity load and then releasing the load completely. Observe the
smoothness of pointer travel throughout the full range. Zero the pointer
and calibration transfer standard indicator.
5.
Apply four to five point calibration with the pointer and division mark
aligned at each reading as found.
6a.
Apply the rated capacity load with the unit pointer and division mark
aligned. Move the zero adjusting bracket towards the center of the unit
if the load shown on the calibration machine indicator is greater than
the rated dynamometer load. Move the bracket away from the center
of the unit if the load shown on the calibration machine indicator is less
than the rated dynamometer load. Repeat this procedure until the unit
is properly spanned.
6b.
Tighten the zero adjustment bracket cap screws to 144 +/- 8 inch
pounds torque.
7a.
Linearity adjustment procedure. Slight adjustments can be made to the
midrange readings of the dynamometer.
7b.
Loosen the two dial retaining screws. Load the dynamometer until the
pointer and the one half of rated capacity division mark are aligned.
Shift the bottom of the dial to the right if the load shown on the calibra-
tion machine indicator is greater than the half scale dynamometer load.
Shift the bottom of the dial to the left if the load shown on the calibra-
tion machine indicator is less than the half scale dynamometer load.
7c.
Tighten the two dial retaining screws and recheck the span adjustment
of the unit. Readjust the unit span and linearity as required.
