Installing The Bellcrank And Control Bridge - GRAUPNER JetCat 6810 Manual

Helicopter mechanics
with model turbine engine
Now fit the prepared drive shaft assembly into the tail rotor housing, and line up the hole in the
spacer 4618.66 with the hole in the tail rotor housing, then secure it with an M2 x 5 countersunk
screw.
Fit a steel rod (screwdriver blade or similar) through the threaded holes in the coupling 4448.40.
Using the rod as a handle, pull hard on the coupling (against the countersunk screw joint), so
that the tail rotor drive assembly seats itself in the housing with maximum possible gear
meshing clearance between the bevel gears, as if under maximum load. Now check that the tail
rotor gearbox runs smoothly, with just detectable meshing clearance in the bevel gears.
If the play in the gears is too slight, i.e. the gears are stiff to move, you will need to remove the
drive assembly again and remove the shim washer under the bevel gear. If, however, there is
too much play in the gear meshing insert additional shim washers. If you work carefully, making
small adjustments, it is possible to set up the bevel gears so that they work freely but without
backlash. Reinstall the unit, repeat the pulling procedure as described above, and you should
find that the gear meshing clearance is correct.
Note: if you still cannot set the gear meshing clearance to your satisfaction, the problem may be
that the bevel gear on the tail rotor shaft is located too far outward due to manufacturing
tolerances, and is not engaging correctly with the bevel gear on the input shaft. If this is the
case, you will find that the tips of the teeth of the bevel gear on the input shaft are already
fouling the long spacer sleeve, and yet there is backlash in the meshing clearance. In this case
you must shorten the long spacer sleeve and compensate this by fitting shim washers between
the short spacer and the ballrace 4618.69, until the desired slight meshing clearance is present.
Now remove both assemblies again, apply bearing retainer fluid, Order No. 951, to the bearings,
the setscrews, and the bevel gear on the input shaft, re-fit them on the tail rotor shaft and the
input shaft, and assemble the parts permanently.

4. Installing the bellcrank and control bridge

(bag U2-11B)
Press the ballraces into the tail rotor bellcrank 4682.160, not forgetting the spacer sleeve, and fit
the M3 x 22 socket cap screw through the bellcrank. Fit the spacer washer on the screw as
shown.
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