FED-STD-791D
4.1.4.1 The system is charged with approximately 30 L (8 gal) of lubricating oil,
type MIL-PRF-7808 or SAE J1966. The support oil temperature measured at the
distributing manifold, is maintained at a specified value of 74 2.8C (165 5F), by
means of electrical heaters located in the sump, and a water cooler located after the
pump, through the action of thermoswitches. Pressure lines from the distributing
manifold lubricate the bearings and helical gears, as well as the adapter housing and the
step-up gearbox back to the support oil sump.
4.1.4.2 The action of the load oil circuit for the WADD gear machine is shown
on Figures 2 and 3. Oil from the load adjusting valve, Figure 2, enters the WADD gear
machine through the load chamber located at the rear of the driven shaft. Sufficient oil is
provided to maintain a constant "load-oil pressure," and to allow for leakage past the load
chamber seal. The load bypass valve is opened when it is desired to release the load-oil
pressure quickly, such as at the end of a test run. The optional automatic recording load
oil system, shown on Figure 3, affords automatic loading of the machine and a
continuous recording of the load-oil pressure. In operation, the desired load is set on the
indicator, the load is then automatically changed at a constant rate to the preset value and
is recorded. The load is automatically released at the end of each test run by solenoid
valves which release the control air pressure to the pneumatic valves allowing the valves
to return to their respective normally closed and normally open positions.
4.1.5 Test-oil system. A test-oil system capable of maintaining a test-oil
temperature of 205C (401F) is used with the WADD gear machine for
high-temperature gear load-carrying capacity evaluations. A schematic diagram of the
test-oil system is shown on Figure 4. The capacity of the test-oil system is 1 L. Test oil
is supplied to the test gears by means of a pressure pump through an inline filter and then
to the jet, located on the unmeshing side of the gears. The oil is gravity drained from the
test section through the flow check chamber and returned to the sump. Oil temperature to
the test gears is maintained at 205 2.8C (401 5F) by means of two electrical band
heaters located on the outside of the test-oil sump.
4.1.6 Radiometer. A Barnes R-4D1 industrial radiometer, or equivalent, is used
in conjunction with the WADD gear machine to measure the narrow test gear
temperature during test. The industrial radiometer consists of two components: (1) the
temperature sensing optical head which is located inside the test cell, approximately 137
cm (54 in) from the end cover of the WADD gear machine, and is aimed at the web of the
narrow test gear through the hole provided in the gear machine end cover, and (2) the
electronics and readout unit which is located in the control console of the test rig.
4.1.7 Induction heater. A Lepel T-5N-3, or equivalent, induction heater having a
5 kW output at 450 kHz with a wide range continuous grid control is used to heat the test
gears to the desired test temperature.
4.1.7.1 A load coil transformer is used in conjunction with the induction heater to
minimize power loss from the induction heater. The load coil transformer is mounted
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