TM 9-1829A, April 1944
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2021-07-07
No. 00 grease, O.D., in the top groove of the pinion carrier. Assemble the star pinion in the top groove of the
pinion carrier with the six even teeth to the left. Assemble pinion carrier on the odometer shaft with slot over
retainer on field plate. Make sure that one of the short (or half) teeth on the right side of the star pinion is
assembled toward the outside diameter of the figure wheel, and that it is not engaged with the two gear teeth
on the left side of the figure wheel. If this is assembled incorrectly, odometer will lock. Assemble a figure
wheel, then a star pinion and carrier on the odometer shaft, continuing assembly in this manner until all figure
wheels, pinion carriers, and star pinions are assembled. Next assemble odometer spacer on shaft and press
shaft on through left side of frame and secure in position with odometer shaft retainer. If other than a zero
setting is desired, it should be done at this point. Disengage transfer pinion from 20-tooth side of wheel to be
moved. When desired figure is up, re-engage with pinion. Check to make sure wheel figures line up and are
not
1
/
2
figure off. If wheel is
1
/
2
figure off, disengage from pinion again and move wheel one tooth to bring in
line and re-engage. Adjust each succeeding wheel to be set in the same way. Do not disturb the star pinion
settings. The dial may be temporarily positioned to check alinement of figure wheels. Check end play of
odometer and insert split space washers to gain end play of 0.009 inch to 0.018 inch.
k.
Appearance:
Wipe excess lubricant and finger-prints off figure wheels with lintless cloth or soft chamois.
l.
Install dial and pointer:
Install dial on jewel bracket and retain with two screws. Place the pointer on the
spindle so it points to about 30 miles per hour, and twist gently back to zero against speed cup stop while
pressing lightly down. Tap pointer very lightly with small wooden-handled screwdriver to secure in position.
m.
Calibration:
The speedometer or tachometer should be calibrated at this stage of the assembly procedure
(par. 9).
n.
Install case, bezel and glass:
Install dust washer around neck of frame and reset shaft if used. Drop case over
neck of frame and retain with two screws and lock washers. Install into new bezel the outer gasket, glass,
inner gasket retainer, and gasket. Invert the case in the bezel assembly, and secure bezel with crimping tool
(T-178730, figs. 74 and 75).
o.
Moisture- and dustproof the unit:
Brush sealing or plugging cement on all joining surfaces and allow 15
to 20 minutes for drying. Butyle methacrylate can be thinned with toluol or equivalent.
9. Calibration
a.
General:
The calibration of a speedometer or tachometer is the operation of electrically balancing the magnet
with the hair spring so that the unit checks at least three points of its scale with a master head. In the following
instructions, it is stated that the magnet should first be overcharged by at least 50 percent, and then
demagnetized to a state of correct balance with the hair spring. It is very important that this initial overcharge
be given, otherwise the unit will gradually read lower.
Note: For example, if a pail is filled with water to the
rim, some water will be splashed out as it is carried. However, if before carrying the pail of water, a little is
intentionally spilled out, then the remainder can be carried safely for a long distance. In much the same way,
reduction from maximum magnet strength has the effect of “setting” the magnet permanently at the desired
strength. Some manufacturers accomplish a similar result by a three- to six- month aging process.
b.
Charging the magnet:
Connect the magetizer (T-189785) to a 12-volt direct current source, preferably two
12-volt fully charged batteries in series. Clamp the magnetizer poles over the speedometer field plate. Turn
the magnet by hand until it is at right angles to the magnetizer poles. Press the magnetizer button firmly for
2 or 3 seconds.
Figure 23: Charging AC speedometer or tachometer magnet, using magnetizer (846294)