FED-STD-791D
and main shaft support bearing, P, together with a separate oil system. The test and support
sections of the bearing head are separated by a screw-thread seal, H, to prevent mixing of the test
and support oil.
4.2.1.1 Test-oil jet. The test-oil jet, F, is a nominal 0.1-cm (0.040-in) diameter jet
located at the 12 o'clock position on a 6.668-cm (2.625-in) radius from the center of the bearing
machine end cover. Prior to test, the size of the jet is checked with standard plug pin gages,
0.099-cm (0.039-in) diameter gage go, and 0.104-cm (0.041-in) diameter gage no-go. In
addition, the condition of
the jet is observed under flow condition by connection to a pressurized water line. Water
flow through the jet is maintained by a 103.4 kPa gage (15-psig) pressure. The jet should deliver
an essentially solid stream in axial alignment with the jet orifice. Corrections for size and axial
straightness of jet flow are made by replacing the jet plug or the entire test-oil jet as required.
4.2.2 Test bearing. An unshielded 100-mm straight-roller bearing (Rollway P/N RCS
120-560, or equivalent) is mounted on the free end of the shaft in the test-oil compartment of the
bearing head. Load is applied to the bearing shaft, C, and hence to the test bearing, by means of
a hydraulically controlled load pis-ton, E, acting through the load bearing, as shown in Figure 1.
The test bearing is lubricated by a single jet, F, which supplies essentially a solid stream of oil
midway between the I.D. of the outer race and the O.D. of the roller retainer at the top or
unloaded position of the test bearing.
4.2.3 Test-bearing mount. The bearing is made with an outer race removal feature which
permits the removal of the bearing outer race for cleaning and inspection. Three spot-type
thermocouples are located 120 apart (radially) around the I.D. of the bearing mount and indicate
the skin temperature on the periphery of the outer race of the test bearing, which is pressed into
contact with these thermocouple junctions when it is installed in the bearing mount. One of
these three thermocouple leads is connected to the West bearing temperature controller, or
equivalent.
4.2.3.1 Test bearing outer race thermocouples. Insert fiber glass sheath, 20-gage,
iron-constantan thermocouple wire through the three drilled holes in the heater mount from
outside to inside. Silver-solder each thermocouple junction leaving spherical bead on the
junction about 0.32 cm (1/8 in) in diameter. Peen each bead back into the hole. Remove excess
silver solder leaving just enough material to insure contact between the heater mount and the
bearing outer race. Each of the three thermocouple leads is brought out directly through the
bearing housing at 120 degree intervals.
4.2.3.2 Thermocouple packing. Polytetrafluoroethylene, or equivalent, is used to
insulate all thermocouple leads where they pass through the housing or end cover fitting. This
also applies to the two bearing heater terminals where they pass through the end cover.
4.2.4 Test-oil system. A schematic of the test-oil system is shown on Figure 2. The
test-oil cycle starts at the sump where external heaters maintain the desired bulk-oil temperature.
Sump heaters, except for the uppermost band heater which is controlled by a manual switch, are
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