FED-STD-791D
4.1.5 Drive system. As shown in Figure 1, the Ryder Gear machine (A) is driven
by a 50 hp induction motor (B) through a dynamic coupling (C), a step-up gear box (D),
and an adapter (E). The test gear speed is controlled by adjusting the field excitation of
the dynamic coupling. By this means, accurate speed control from standstill to well over
the specified test speed of l0,000 rpm can be attained.
4.2 Instrumentation and controls. All of the instruments and controls that require
constant attention during test are located on the control console (Figure 2). Items that do
not require frequent attention are located on the test stand. The functions of most of the
instruments and controls are apparent. Therefore, only selected items will be explained
further.
4.2.1 Speed measurement and control. An electronic counter (Figure 2, item 4),
located on the control panel, measures the speed. This instrument is actuated by pulses
supplied by a variable reluctance pickup (the variable reluctance being provided by a 60-
tooth gear operated from the driven shaft of the step-up gear box). The rpm adjustment
control (Figure 2, item 20), located on the con-sole, regulates the field excitation of the
dynamic coupling and thus the gear speed.
4.2.2 Control of test run duration. An electric timer (Figure 2, item 10) located
on the console, is used to control the duration of each test run. As soon as the desired test
load has been reached the timer is started at the determined test duration setting. After
the run is over the timer automatically turns off the drive motor and opens the
load-bypass valve. The timer switch must be turned to the "stop" position prior to the
next run.
4.2.3 Support-oil controls. The support-oil pump buttons (Figure 2, item 11) on
the console are connected to the support-oil pressure pump as well as the three scavenge
pumps. Pressing the start or stop button controls all four pumps at the same time. The
support-oil heater buttons (Figure 2, item 12) control both the electric heaters and the
water cooler through the action of thermoswitches (Figure 6). The support-oil chamber
vacuum is measured by a water manometer located on the test stand. A valve connecting
the chamber to a vent (Figure 6) should be adjusted to give a chamber vacuum of 2.5 to
10.2 cm (1 to 4 in) of water under normal test conditions. If this value cannot be
maintained, the shaft and shaft seals should be inspected for leakage.
4.2.4 Control of load oil pressure. The control of load oil pressure has been
explained in 4.1.3. Of the three valves in the load oil circuit (Figure 6) only the bleeder
valve is not remote controlled. However, this valve need only be set to give the desired
sensitivity for load control during installation of the tester. As a rule, adjustments are
seldom necessary thereafter. The load adjusting valve is air actuated and is controlled by
the load adjust control (Figure 2, item 9) located on the console. The load bypass valve is
solenoid actuated and is controlled by the load bypass switch (Figure 2, item 13) on the
console. During the test run the load bypass switch is in the "close" position and the load
bypass valve is closed. At the end of a run, the solenoid circuit will automatically be
opened by the electric timer. This opens the load-bypass valve, but the load bypass
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