GRAUPNER heim Bell 230 Instructions D'utilisation page 59

8. Gyro adjustment
Gyro systems damp out unwanted rotational movements around the vertical (yaw) axis of the
model helicopter. They do this by detecting the unwanted motion and injecting a
compensatory signal into the tail rotor control system, and in order to achieve this effect the
gyro electronics are connected between the tail rotor servo and the receiver. Many gyro
systems also allow you to set two different values for gyro gain and switch between them
from the transmitter via a supplementary channel. The extra channel is controlled via a
proportional slider or rotary knob, or a switch, depending on the gyro system.
If your gyro features an adjustor box with two rotary pots for two fixed settings, and you can
switch between them from the transmitter, it is best to set one adjustor approximately to
centre (50%), and the other to 25%. If the gyro system provides proportional control between
the two set values, then the one pot should be set to "0", the other to about 80%.
If you have a gyro system whose effect cannot be adjusted from the transmitter, i.e. there is
only a single adjustor on the gyro electronics itself, the pot should be set to 50% gain as a
starting point.
Check that the direction of the gyro's compensatory action is correct, i.e. that it responds to a
movement of the tail boom with a tail rotor response in the opposite direction. If this is not the
case, any yaw movement of the model would be amplified by the gyro! Most gyro systems
are fitted with a change-over switch which reverses its direction, and this must then be
moved to the appropriate position. However, some systems have no such switch, and in this
case the solution is to mount the gyro inverted.
One factor which all gyro systems have in common is that flight testing is necessary in order
to establish the optimum settings, as so many different factors influence the settings.
The aim of the gyro adjustment process is to achieve as high a level of gyro stabilisation as
possible, without the gyro causing the tail boom to oscillate.
Notes regarding the use of the Graupner/JR „PIEZO 450...5000" piezo gyro system in
conjunction with a computer radio control system (e.g. mc-12 ... mc-24)
The advanced design of this gyro system necessitates a different set-up procedure to the one
described above. Please keep strictly to this procedure:
1. 1. Set the servo travel for the tail rotor channel to +/-100% at the transmitter.
2. If you have a gyro mixer („Gyro-Control") which suppresses gyro gain when you operate the
tail rotor control, it is essential to disable it permanently.
3. Disconnect the tail rotor pushrod at the tail rotor servo.
4. Operate the tail rotor control at the transmitter; at about 2/3 of full travel in either direction the
servo should stop, even when the stick is moved further (travel limiting).
5. Connect the tail rotor pushrod to the servo in such a way that the tail rotor's mechanical end-
points in both directions are the same as the travel set by the travel limiter (servo should be
just short of stalling on its mechanical end-stop at this point).
It is essential to make these adjustments mechanically, i.e. by altering the linkage
points and pushrod length. Don't try to do it electronically using the transmitter's
adjustment facilities!
6. Now correct the tail rotor setting for hovering, i.e. when the collective pitch stick is at centre,
using the servo travel centre adjustment facility at the transmitter.
7. Gyro gain can now be adjusted between „0" and maximum effect via the auxiliary channel
only, using a proportional control on the transmitter. If required, maximum gain can be
reduced by adjusting the travel of the auxiliary channel or by adjusting the transmitter
control. This gives you a useful range of fine adjustment for tailoring gyro response to your
requirements.
8. If you find that the tail rotor control system is too responsive for your tastes, adjust it using
the exponential control facility; on no account reduce servo travel, as it must be left at +/-
100%!
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Bell 230