Spring of balance line from post to end
of arm. A slight curve is permissible. If
position properly on to pinion (14 figure
spring has more than a slight curve after
2- 2), size pointer hub with broach (table
it is set, it may be too weak and
. If pointer hole diameter
assembly should be checked by placing
compress hub with collet In
altimeter in pressure chamber and
jeweler lathe and resize for positive fit
subjecting it to a minus 1,500 feet, then
c. Hold mechanism dial vertical with 0 on top. Tap
to maximum range of instrument.
Balance assembly must not contact
stand and note reading.
Turn instrument 90
mechanism assembly or diaphragm.
counterclockwise. This places 0 at left (9 o'clock). After
q. Check alignment of balance link assembly with
tapping, note indication of hand. If hand has moved
slot in arm of rocking shaft. Balance assembly must be
clockwise (plus error) by more than 30 feet, correct error
adjusted so link is parallel with slot, to move in slot
by shifting position of sector counterweight toward
without binding. Insert link in slot and secure link with a
rocking shaft. If error is minus by more than 30 feet,
new bearing pin.
counterweight should be moved away from rocking shaft.
Alternate between two adjustments until a
mechanism body. Replace jewel settings assembly (13)
maximum position error of + 5 feet is obtained.
e. Temperature compensation of an altimeter is
and adjust it until an end play of 0.003 inch is obtained.
Secure jewel setting assembly with screw (50).
necessary only if bracket or adjustment nuts have been
s. Secure rocking shaft hairspring so it has from
disturbed or if compensator pins have fallen out and their
three-fourths to one turn tension.
original location cannot be determined.
f. Temperature compensation is greatly facilitated if
When applying tension to wheel assembly
hairspring as described in preceding steps l and m. 6 3/4
a chamber is used in which air temperature can be
regulated to give an overall change of 80C (144F).
revolutions (27 spokes) tension must be applied to
hairspring for this type of instrument.
This allows testing and adjustment of altimeter
2-8. Position Error Adjustments.
temperature compensation with great convenience. If
such chamber is not available. altimeter mechanism can
be subjected to required variation of temperature by first
placing it in a cold bath of kerosene (item 5. table 1-2) or
Adjustment procedure as outlined in the
compass fluid, then in a hot bath: or if only one vessel is
following paragraphs applies to all
available. cold reading of mechanism can be taken at
altimeters covered in this publication,
room temperature. followed b. heating bath to a
regardless of their range.
temperature 80C (144F) above room temperature
a. Balance arm on rocking shaft controls position
before taking second reading. If liquid baths are used.
error of instrument in normal operating position and 180
there should be a third bath maintained at room
temperature. Mechanism should be transferred to this
from this position. The sector counterweight controls
position error at 90 and 270 from normal operating
bath before being immersed in extreme temperature
bath to permit it to change temperature more slowly!-
b. Mount mechanism in stand assembly, part no.
TE1357-5003, so wheel assembly is at 0 position, and
place stand, dial up, on bench. Lightly press balanced
hand-on-hand-staff pinion so it indicates 0.
compensation in a chamber in which air
mechanism in stand assembly and hand pressed onto
temperature can he regulated is same
hand-staff pinion at an indication of 0, hold instrumental
as that described below for liquid bath
dial vertical with 0 on top. Tap stand and note reading.
Turn instrument 180 (this places 0 at bottom) and, after
method of temperature compensation.
tapping, note indication of hand. If hand had moved
clockwise, (plus error) by more than 30 feet, correct error
by shortening effective length of calibration arm to which
balance is connected. If error is minus effective length of
Change 4 2-10