tion, before any attempt is made to replace the
heater elements.
(1) P o s i t i o n two serviceable heater ele-
m e n t s in their respective position in
versing switch access door (high voltage com-
the magnetic motor starter and secure
partment) (fig. 6). Unscrew the four binding-
w i t h the four binding-head machine
head machine screws from each heater element
and remove the two heater elements from the
screws removed in b a b o v e .
m a g n e t i c motor starter.
(2) C l o s e the drive reversing switch ac-
cess door (high voltage compartment)
h e a t e r elements for burned-out, cracked, or
(fig. 6) tightly.
broken condition.
Note. The key numbers shown below in parentheses in this section refer to figure 64 except where otherwise
indicated.
VARIDRIVE ASSEMBLY AND TACHOMETER
Section IX.
GENERATOR GROUP
m e a s u r i n g the actual speed (rpm) of a gen-
175. Description
erator or alternator, which is indicated on the
a. Varidrive Assembly. The varidrive as-
tachometer indicator meter (3, fig. 16) on the
s e m b l y is a self-contained unit, embodying a
meter panel.
m o t o r and a built-in speed transmission, all
shock mounted on one base to prevent vibration
176. Maintenance
o f the control panel. Constant horsepower is
a. General. Organizational maintenance is
maintained through its infinite range of speeds,
l i m i t e d to such removal and installation re-
a n d any desired speed (rpm) can be obtained
quired to replace the V belt (18) and tachom-
by merely turning the handle of the speed con-
eter generator (2).
t r o l (32, fig. 16). Rotating the handle of the
b. Removal.
speed control in a clockwise direction actuates
(1) S t a r t the test stand by sliding the
a pivoted strut which slides one of the lower
safety clip (33-B, fig. 16) off the stop
varidiscs (11) on the rotor (motor) shaft (13)
button (33-C, fig. 16) and depressing
toward its companion varidisc, thus causing the
t h e start button (33-A, fig. 16) (do
V belt (18) of the varidrive assembly to climb
not hold the "START" button de-
u p w a r d on the tapered varidisc to a larger
pressed more than 10 seconds).
diameter. Simultaneously, the V belt causes the
s l i d a b l e upper varidiscs (15) on the driven
(2) Turn the handle of the speed control
( d r i v i n g heads) shaft (17) to retract against
( 3 2 , fig. 16) fully counterclockwise
a spring, permitting the V belt to assume a
until the varidrive assembly is operat-
s m a l l e r diameter on the upper varidiscs and
i n g at minimum speed. Stop the test
increasing the speed of the driven shaft. Thus
s t a n d by depressing the stop button
the speed of the driven shaft is increased but
(33-C, fig. 16).
the rotor (motor) shaft speed remains constant.
Warning: Disconnect the external
R e d u c e d speed in any degree is obtained by
power supply source and place the
r o t a t i n g the handle of the speed control in a
on-off input power toggle switch (fig.
counterclockwise direction.
11) in the "OFF" position before any
attempt is made to perform proce-
b. Tachometer Generator. The tachometer
dures in (3) through (10) below.
g e n e r a t o r mounted on the end of the driven
(3) Open the drive reversing switch access
(driving heads) shaft (17) of the varidrive as-
door (high voltage compartment) (fig.
sembly with a coupling adapter (5) and a
6 ) and remove the three 100-ampere
f l e x i b l e shaft coupling (built within the ta-
600-volt fuses (fig. 12).
c h o m e t e r generator (2)), provide a means of
