lowers the dropout voltage without
fingers. This should normally be 1/8
affecting the pickup. Increasing this air
inch when open.
gap raises the dropout voltage without
91. Relay Panel Type UV-56
g. Another adjustment (which may or may not be
a. This relay panel consists of either two relays
used) is the jumper on the resistor tube but this
and two resistor tubes on an insulating base or one relay
adjustment is determined at the factory and must not be
and a resistor tube on a base. The relays are exactly
changed. If a new resistor tube is installed, take care
alike in mechanical details and coils but may be
that it be assembled with the identification band at the
adjusted to operate at different voltages. The correct
lower end of the relay panel and note the position of the
operating voltages are indicated on figure 44. Each coil
jumper on the old tube. After replacing with a new tube
is connected in series with one of the resistor tubes.
install the jumper on the tap corresponding to the tap on
b. The relay is a clapper type device mounted on
the old tube.
hardened pivot bearings which are covered by a felt
h. If possible remove the relay panel to a bench
washer to exclude dust and dirt.
with a source of variable voltage with a range covering
c. The pivot points are used
to minimize friction
the pickup and dropout voltages. It is possible to adjust
and . counter weight is attached to the armature to
these relays on the locomotive if the circuit to the
balance the moving parts and minimize the effect of
traction motors is broken or it may be possible to adjust
vibration. The moving and stationary contacts have
them while the locomotive is in operation.
contacts with silver tips.
i. Maintain the pickup and dropout voltages shown
d. These relays are adjusted to two voltages. One
on figure 44 by changing the proper adjustment. This
is the so-called pickup voltage which is the voltage at
will only be required at infrequent intervals provided the
which the coil overcomes the pull of the spring and pulls
adjustments are resoldered to prevent locomotive
in the armature. The other voltage is the dropout which
vibration from affecting them. Keep the fingers in
is the voltage at which the tension of the spring
adjustment as they wear. The fingers should deflect
overcomes the pull of the coil and pulls the armature
1A/6 inch when in contact with their studs. Keep the air
back away from the coil.
gap between finger and contact stud at not less than
e. Three adjustments are required to calibrate
3/32 inch and relay should not "float." either in or out.
these relays. One is the tension of the spring, the
second is the air gap when the relay is closed, the third
92. Relay Panels Type UR
is the air gap when the relay is open or deenergized.
a. The relays are simple and rugged and have a
These adjustments have been made at the factory and
clapper type armature with a rocking pivot.
should not need to be changed. These adjustments
armature is held in position by the same compression
have all been soldered so that the vibration on the
locomotive will not change them.
should deflect 1/16 inch on closing and have a gap of 32
f. The effect on the pickup and dropout voltages
inch when open.
of the three adjustments are as follows:
(1) Increasing the tension of the spring raises
voltages are specified on figure 44. The dropout value
both the pickup and dropout voltages.
is not important. The shunt coils of these relays are
Decreasing the tension lowers both the
usually connected in a bridge circuit and therefore carry
pickup and dropout voltages.
very little current during normal operation. For the
(2) With the relay de-energized, increasing
the air gap (by means of the stop screw)
c. Maintenance consists mainly of visual
raises the pickup voltage and does not
inspection to see that the relay is clean and the parts
affect the dropout. Decreasing this air
free to move in the proper manner. Be sure all
gap lowers the pickup voltage without
connections are tight and wires not broken.
affecting the dropout.
(3) With the relay picked up, decreasing the
air gap (by means of the residual screw)