
TM 9-1829A, April 1944
77/100
2021-07-07
Figure 114: Speedometer mechanism (dial removed)
d.
Remove bonnet assembly:
Remove two screws and lift out bonnet assembly (includes hair spring, disk, and
staff; fig. 115) and two bonnet springs. Removal of second gear and magnet from frame, or further
dismantling of bonnet assembly is not recommended.
Figure 115: Speedometer mechanism (odometers removed)
e.
Remove oil wick:
Using punch remove oil wick plug from frame (fig. 63). Then lift oil wick out of frame
(using tweezers).
43. Cleaning, inspection, and repair of parts
a.
General cleaning:
Thoroughly clean third gear, reset gear, tenth dial gear, reset shaft, brackets, springs,
screws, and metal washers with brush (T-170755) and dry-cleaning solvent. Carefully dry parts. Wipe other
parts clean with a rag.
Caution: When cleaning second gear be careful not to touch magnet with steel tools.
b.
Bonnet assembly:
Bonnet assembly should not be submerged in dry-cleaning solvent, but should be carefully
and thoroughly wiped with a clean cloth. Inspect bonnet assembly to see that hair spring and lower pivot are
not damaged. If necessary, adjust hair spring as follows: Turn aluminum disk clockwise until it stops against
bonnet lug. Hold in this position and adjust hair spring (using tweezers) until coils are equidistant from each
other and parallel to the bonnet. At no point of swing should the coils touch each other. To adjust tension,
move regulator (fig. 114) approximately
1
/
4
inch to left, and set tension so that disk returns lightly to zero.
This is done by turning hair spring collet on staff to the right or to the left, as required (fig. 72). Return spring
regulator to center position.
c.
Main frame, second gear, and magnet assembly:
Check magnet shaft for side play and excessive end play
(about 0.003 inch is correct end play). Too much end play can be corrected by using fixture (T-170666 with
Det. 6) to re-flare end of magnet shaft (fig. 92).
Caution: Care must be taken when using fixture to make sure
that it does not come in contact with steel portion of magnet, causing it to be weakened.
Check gear teeth for
wear. If any part is defective, entire assembly should be replaced.
d.
Third gear and trip odometer gears:
Check for excessive wear or broken teeth. Discard if defective.
e.
Odometers:
Wipe dials clean with rag. Do not wash in dry-cleaning solvent, as lubricant will be removed.
Inspect for free turning of dummy wheel on total odometer and tenth wheel on trip odometer. If odometers
are “bound up” discard complete assembly.
f.
Dial supports:
Inspect to see that they have not been bent in disassembly. If so, straighten.