Assembling The Model; Preparation, Explanatory Notes; The Retract System - GRAUPNER NH90 Bedienungsanleitung

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NH90

1. Assembling the model

1.1 Preparation, explanatory notes

The numbers in (brackets) refer to the part numbers as printed in the parts list (see end of instructions).
The fuselages are hand-moulded and are likely to exhibit minor variations and irregularities on
the inside, especially along the central joint seam. Before finally installing any part check
carefully that it fits, trim where necessary and carry out a „dry run" (without glue). Take your
time and work steadily and patiently. All screwed joints except those involving plastic and those
with self-locking nuts must be secured with thread-lock fluid; this is a basic rule, and is not
mentioned at every stage in the instructions.
Where extra items and accessory components are used they should be prepared and installed
as described in the instructions supplied with them.
1.1.1 Mechanics
In these instructions we assume that the main mechanical system for the model is already
completely assembled. It is a good idea temporarily to remove the rotor head from the mast, as
this makes it easier to trial-fit and install the system in the fuselage. We recommend the use of
the optional silencer console (4450.149) which supports the silencer against the mechanics.
In contrast to the normal configuration of the mechanics, the receiver battery should be installed
in the extreme nose of the NH 90, as this makes it much easier to establish the correct Centre
of Gravity. The connection from battery to switch harness should consist of cable of at least 2.5
mm² cross-section.
The gyro platform behind the main rotor shaft cannot be used, and should be removed complete
with the gyro platform bearer; in this model the gyro system is mounted at the front on the (now
vacant) battery console. In this position it is subject to much less severe temperature
fluctuations than in the original position above the silencer.
As the mechanical system is screwed in place from above, the skid mounting brackets
1291.21A (with insert) must either be drilled out to 3 mm Ø, or replaced with the skid mounting
brackets 1291.21 (no insert). These must be installed with the recessed section facing up.
You will need a 2.5 mm allen key about 30 cm long to install these parts. If you cannot obtain
such a tool, you can make one yourself by extending a standard allen key with a brass tubing
shank.
1.1.2 Fuselage
Glued joints: the inside of the GRP mouldings must be roughened thoroughly at the joint
positions using coarse abrasive paper, otherwise there is no chance of a durable, permanent
bond. The openings for windows, cooling air etc. are machined out as standard. Various holes
have to be drilled in the course of assembly to accept further screwed joints, and these are
described in the instructions. Where parts have to be glued inside the fuselage, it is best to
apply the adhesive on a long wooden stick or similar. All wooden parts to be installed must be
sealed to prevent fuel absorption; applying thin cyano to the surfaces works well.
The upper fuselage fairing, tail rotor fairing and tail cap must be trimmed carefully to fit on the
fuselage. The machined openings in the fuselage will need to be cleaned up using fine abrasive
paper, and trimmed where necessary.

1.2 The retract system

1.2.1 Preparing the main undercarriage
Apply bearing retainer fluid to the M4 threaded rods (F2) and screw them into the threaded
holes in the two undercarriage legs (F1); they should project exactly the same amount on each
side. Fit an M4 hexagon nut on both sides and tighten them fully to lock the studs in place. Now
screw the pivot shafts (F3) on the projecting ends of the threaded rods (F2), again after applying
bearing retainer fluid, with both flanges facing the undercarriage leg (F1). Tighten them firmly
against the locknuts.
Glue the plastic bushes (F5) into the four main undercarriage support bulkheads (A7, A8) using
cyano. Note that in each case the smaller bulkhead (A7) must be on the outside, and the larger
one (A8) on the inside; each pair supports one undercarriage leg between them. For this reason
the bushes (F5) must be fitted with the flange facing the undercarriage leg; be sure to produce
two handed pairs of bulkheads: one right-hand and one left-hand.
Fit the support bulkheads (A7, A8) the correct way round on the pivot shafts of the undercar-
riage legs, followed by the collets (F6); each collet is secured using two grubscrews in such a
way that the wheel legs can still rotate freely on their bearings without significant axial play.
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