ROBBE HeliCommand 3A Mode D'emploi page 16

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Installation
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Mounting the unit on the tail rotor servo
Especially with small models, it makes sense to install the unit as high as pos-
sible in order to obtain maximum ground distance. This means: as close as
possible under the fl ybar, with a safety margin for maximum fl ybar travel. The
mounting bracket supplied can often be fi xed to the top of the tail rotor servo or
some other support. Do not use foam under the bracket, fi x the bracket rigidly.
Alternatively stick the HeliCommand to the tail rotor servo case (with foam
tape) without using the mounting bracket.
Mounting the unit on the tail boom
Fix the supplied mounting bracket to the tail boom using a cable tie, pulling
it really tight. The HeliCommand can then be fi xed to the bracket by applying
two strips of double-sided foam tape to the back of the unit. Once test-fl ying
is complete, secure it against rotation relative to the boom, using UHU-hart or
cyano-acrylate glue. Double-sided foam tape is too soft for this purpose.
Protect from vibration
Please take particular care to protect the unit from vibration!
Use soft self-adhesive foam tape, but don't apply it to the whole of the surface;
instead just stick two very narrow strips right at the top and bottom edges of
the back panel. This means that the mounting surface must be at least as tall
as the HeliCommand itself.
Ensure that the HeliCommand cannot shift or come loose, as this could cau-
se the model to take up an inclined attitude in auto-pilot mode, rendering it
uncontrollable.
Remove all traces of oil residue before sticking the unit in place.
We recommend that you wrap a thin rubber band round the HeliCommand to
guard against the risk of the self-adhesive foam tape coming loose.
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Electrical earth
An electrical connection must be created as an earth between the tail boom,
the motor crankcase and the helicopter chassis. Note that carbon is a conduc-
tive material. Belt drives inside the tail boom are particularly dangerous, as
they act as a high voltagte generator. If you ignore this, cables running along
the tail boommay conduct sparks (which have already caused servos - not the
HeliCommand itself- to run to one end-point).
On-board location
The higher the installation in the model, the smoother the stabilisation effect
in position mode at very low altitude, and the larger the gain setting you can
safely use. In many models a suitable location is one side of the tail rotor servo,
or - using the mounting bracket supplied - the tail boom, the tail rotor servo, the
chassis or the fuselage nose.
The mounting surface should be solid and should not "give", as this could ge-
nerate resonance effects.
Installed attitude
Vertical, with sensor facing down.
Any of the four possible directions can be used.
Unobstructed view between the sensor and the ground
The cross-section of the vision cone is square, with an open angle of 15° x 15°.
For this reason you must arrange an unobstructed square vertically below the
sensor, with at least the side length
S = window size (15mm) + [0,28 * distance from window]
(see drawing).
It is important that neither the aerial wire nor anything else can get in the way
of the vision beam!
Installation in an enclosed fuselage
Cut an opening in the fuselage (see above for size); alternatively do not cut a
hole (no sensor view), and manage without position mode. In this case cover
the sensor window with dark adhesive tape.
If you do this, you can only exploit horizontal mode, and not position mode.
Horizontal attitude
Set the unit as close to vertical as possible, i.e. parallel to the main rotor shaft!
The electronic compensation means that an angled installation would only be
noticeable when the pilot gives a tail rotor command.
Miniature helicopters with particularly large blade pitch angles invariably hover
with a more pronounced tilt; this is necessary to counter-act for the greater tail
rotor thrust. You can compensate for this tilt using the PC adaptor, or see the
page 38: „fault-fi nding".
Notes regarding internal combustion engines
• The unit must be installed as far from the exhaust as possible.
• Effective vibration protection is very important, as invisible vibration from the
engine can be a particular problem. If you can feel the HeliCommand unit
vibrating when the engine is running -even though it is installed as directed-
we recommend additional vibration damping measures. Velcro (hook-and-
loop) tape behind the cell foam is often a suitable solution.
The safest option is a metal plate (3 mm aluminium or 1.5 mm steel) which
is fi rst stuck to the HeliCommand; the foam strips are then applied between
this plate and the mounting surface. Additionally secure the HeliCommand
with thin rubber band.
Alternatively you could consider installing the unit in a different location,
where vibration is not so severe.
• Avoid running the motor unnecessarily rich, to avoid clouds of smoke
confusing the sensor.
• To prevent soiling we recommend that you install a protective tube,
or (better) a cubic box under the sensor. Its internal dimensions must take
the vision cone into account. Be sure to clean the window regularly right to
the edges.
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