The Marvel Manufacturing Company copyright 2017
3
Balance Procedure
1. Place 3152 Base, hub extension upward, central across blocks.
2. Index and secure adjustable plug section of 2939 Pitch Position Posts at 1
5/16” from end of rod. Install in outer threaded bores “A” of base.
3. Install 3378 Adapter, large end downward, over hub extension of base.
4. Position tail rotor assembly to locate machined static stop surfaces of hub
yoke upward and pitch horns adjacent to position posts. Install on adapter
and seat trunnion.
5. Install 2533 Bushing, knurled end upward, on 3165 Arbor from lower end.
Position near top of arbor shaft and temporarily secure with set screw.
6. Install 2586 Plate an arbor from lower end and position against bushing.
7. Install 3380 Cone, knurled end upward, on arbor from lower end and
position its top surface at arbor scale setting indicated by the installation
illustration. Secure by moderately tightening both set screws.
8. Insert arbor downward thru rotor trunnion and base. Seat cone into
trunnion bore and secure by moderately tightening both set screws in hub
of base.
9. Reposition rotor if necessary and insert large diameter plug of position
posts into bolt bore of pitch horns.
10. Lower plate and bushing on arbor to seat on rotor yoke and secure by
moderately tightening both set screws in bushing. Maintain engagement of
posts with pitch horns.
11. Suspend assembly to clear work support. Stabilize movements and
observe balance condition as indicated by exposure of black disc in top
surface of arbor shaft. Check to insure indications are not affected by
interferences, air drafts or movement of nearby personnel.
12. Refer to applicable helicopter maintenance manual for balance tolerance,
method of correction or other assembly requirements.
