
TM 9-1829A, April 1944
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2021-07-07
The reversing swivel joint (T-178704) is used with tachometers having a counterclockwise face dial. The
following adapters are furnished with calibrating machine:
T-170852 - For 0.104-inch square male thread drive
T-170863 - For 0.187-inch square drive
T-170886 - For 0.104-inch square female thread drive
T-178719 - For connecting flexible shafts supplied with calibrating machine to test instruments while
mounted on vehicle.
Insert swivel joint into proper spindle connection (par. 66) and tighten knurled screw. Place proper adapter
in swivel joint connection and set instrument on adapter. Hold instrument in left hand while turning speed
control wheel with right hand and proceed with test or calibration of instrument. When finished, slow down
calibrating machine (returning pointer of master to zero), then turn motor switch to “OFF” position. An
important step in calibrating some makes of speedometers and tachometers is “demagnetizing” (fig. 156).
When this is done it is advisable to hold one finger between the field plate and the pole presented to it, thus
preventing the magnetizer and demagnetizer tool from being pulled into contact with the field plate and
completely discharging the magnet.
Figure 156: Demagnetizing, using special tool (846294) while operating speedometer on calibrating machine (T-170645)
67. Lubrication
a.
Every two months inject a few drops of light motor oil into the four spring-capped oilers (one on front motor
armature shaft bearing hub, two on rear motor hub, one on driven pulley shaft bearing). Two openings on
each side of the case and a door in the rear of the case make these oilers accessible. About once a year the ten
plugs must be removed from the small gear housings and housings filled with No. 00 grease, O.D. About
every six months the motor rear thrust bearing should be removed and packed with high-temperature grease
(OFSB6-2). To gain access to these lubrication points it is necessary to remove electric cord, speed control
wheel (one screw), spindles (by removing one screw each and unscrewing spindles), and 20 screws around
base of machine. Entire case can then be lifted off mechanism. The two swivel joints (T-176827 and T-
178704) must be lubricated with No. 00 Grease, O.D., about once a year.