MCi Crusader II 1989 Maintenance Manual page 164

Date
1-1-89
Page. __
4_-3_4 _ _ _
MC-9 MAINTENANCE MANUAL
4. Install lock ring or tighten set screw in spacer. Position
brake shoe over spider and tap anchor pin into position with
"flat" in line with lock screw hole. Repeat with opposite shoe
assembly.
5. Install lock screws. tigriten securely and thread with
lock wire.
6. Position felts, retainers and install lock rings.
7. Install shoe return spring. Install slack adjuster on splined
end of cam shaft and adjust as required.
8. Assemble snap rings using washers to take up end play if
necessary.
ADJUSTMENT
New linings should be circle ground and adjusted to a few
thousandths less than drum diameter. Install slack adjuster on
splined end of cam shaft and adjust as required. See Slack
Adjusters in this section.
AIR HORNS ANO VALVE (OPTIONAL)
The purpose of the air horns is to provide a warning signal .of
greater volume and carrying qualities than usually found on
automotive vehicles. The horns are designed on the principle of
a vibrating diaphragm: they consist of die cast bodies. diaph-
ragms. and two black painted horn bells. with the bells m a
horizontal position.
The horns are operated by pushing down on the button of
the foot-operated horn valve. This action pushes down on the
supply valve stem in the horn valve and opens the supply valve.
When air enters the cavity in each air horn on one side of the
diaphragm, pressure builds up on the diaphragm. deflects
it
and the air escapes through the horn bells. This action sets up a
vibration of the diaphragm in each horn bell.
The two different lengths of horn bells give the horn its dual
tone. The vibrations are set up in an air column denser than
atmosphere. due to escaping compressed air. which provides
unusual tone carrying qualities.
:::1
1 6 ~
17--G)
1 8 ~ ·
19-----e
MAINTENANCE AND TESTING
Every 10.000 miles (16,000 km), remove the strainer in the
bottom of horn valve and clean thoroughly with cleaning sol-
vent. Remove dirt screens in the horn bells and clean. Refer to
figure 4-43.
Every 50,000 miles (80,000 km). disassemble the air horn and
clean all parts. Disassemble the air horn valve and clean all
parts.
Operating Test With air pressure in the system, operate the
horn valve and the horn should give a load, clear dual tone horn
blast.
Leakage Test With the horn valve in the released position,
leakage at the delivery port or at the valve stem at the top of the
horn valve should not exceed a one-inch (25.4 mm) soap bub-
ble in one second. With the horn valve applied, leakage at the
stem at the top of the horn valve should not exceed a one-inch
(25.4 mm) soap bubble in one second.
REMOVAL AND DISASSEMBLY
AIR HORN
1 Disconnect the air line to the air horn. Remove air horn
mounting nut and remove horn. Refer to Figure 4-41.
2. Remove the eight nuts and bolts holding the two covers to
the body.
3. Remove the diaphragms from the body of the air horn.
4. Remove the spring contact. springs, and the spring
assemblies from the covers of the air horn.
5. Remove the horn bells from the body.
HORN VALVE
1. Vent the air system. Disconnect air lines to ttie horn valve.
Remove mounting bolts and remove the horn valve. Refer to
figure 4-42.
2. Remove the spring seat from the valve body.
3. Remove the valve stem from the valve body.
4. Remove the strainer and spring from the spring seat.
1. Screen 8. Seat-Spring
15. Coupling
2. Bell 9. Set Screw
16. Gasket
3. Contact 10. Screw
17. Washer
4. Diaphragm
11. Washer 18. Washer
5. Spring
12. Nut 19. Nut
6. Lock Nut
13. Bell 20. Body
7. Cover
14. O-ring
Figure 4-41. Air Horns.