specially designed transformer, resistors, and a rectifier.
The resistors are usually in series and one is manually
adjustable to compensate for wheel wear. Refer to
f. The indicating instrument is of the D'Arsonval
permanent-magnet moving coil type of design. Handle
the indicator with care to avoid damaging jewel
bearings. Do not hammer on the panel on which the
indicator is mounted. Check that the pointer is on the
zero-set adjustment. Refer to paragraphs 97 through 99
for adjustment instructions.
27. Air System
a. Compressor.
(1) This 4-YC air compressor is of the two
cylinder, two stage, air cooled, pressure
lubricated type.
It is suitable for
continuous service against 115 pounds air
pressure at speeds up to 610 rpm.
Figure 4. Bell ringer operating valve.
Inasmuch as the locomotive engines
operate at idling speeds when the motive
by position of cam edge of rotor lapping control port.
power is not needed, and the compressor
runs continuously, a load and unload type
pressure is exhausted (fig. 4).
control is provided to maintain the main
c. An occasional drop of light oil is all this valve
reservoir pressure between the desire
will require to provide years of trouble-free service.
limits. Refer to paragraphs 110 through
Refer to paragraphs 105 through 107 for maintenance
instructions.
the compressor governor.
(2) The belts should be maintained tight
26. Speed-Indicating Equipment
enough to prevent excessive slippage, but
a. The speed-indicating equipment is designed to
not tight enough to place undue strain on
give a continuous indication of train speed.
the motor and compressor bearings which
b. The complete speed-indicating equipment
will result in excessive heating of these
consists of three units.
bearings and increase tile power required.
When belt replacement is necessary,
(1) A tachometer generator.
replace all belts with a matched set.
(2) Transformer-resistor box.
Refer to TM 55-2034 for maintenance
(3) D indicating instrument.
instructions.
c. The indicator scale is calibrated in miles per
hour, thus making it possible to read the train speed at
and maintenance of the airbrake equipment.
the instrument panel.
locomotive.
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