Further Adjustments - GRAUPNER Jet Ranger Handbuch

2.4 Further adjustments

If you have made up all the linkages exactly as described in the previous sections, no changes
to the mechanical arrangements will be necessary. The following adjustments can all be carried
out at the transmitter:
1. Servo direction
Set the „sense" (direction of rotation) of all servos as stated in the instructions. Check the
throttle servo in particular!
2. Dual Rates
You can set switchable travels for roll-axis, pitch-axis and tail rotor. As a starting point we
recommend 100% and 75% as the two settings.
3. Exponential
For the basic set-up you should leave all control systems set to „linear".
4. Servo travel centre offset
Do not make any adjustments to this point. At a later stage you may wish to make minor
corrections here.
5. Adjusting servo travel
This is where you can adjust the maximum servo travel. Note that the travels should always
be the same on both sides of neutral, otherwise you will end up with unwanted differential
effects:
For the throttle and swashplate servos (collective pitch function) it is important to check that
servo travels are symmetrical, i.e. with the same values for both directions, and that the
throttle servo can move the carburettor barrel from the completely closed position (motor
stopped) to full throttle, without being mechanically stalled at any point. The collective pitch
function of the swashplate servos should produce a range of blade pitch angles covering -5°
to +13°, also with symmetrical travels; you may find it necessary to remove the servo output
arms, move them round by one spline and fit the retaining screws again.
The mechanics should now be set up virtually perfectly. When the throttle/collective stick is
at centre (hover point), collective pitch should be about 5.5°, and the carburettor barrel
should be half-open.
Note:The collective pitch and throttle curves can be adjusted later to meet your exact
personal requirements. However, if you have already set differential travels in the basic set-
up procedure, as shown in diagram „B" above, any fine adjustments required subsequently
will be much more difficult to get right!
6. Collective pitch and throttle curves
These adjustments are of fundamental importance to the flight performance of any model
helicopter. The aim of the procedure is to maintain a constant rotor speed when the model is
climbing and descending, i.e. regardless of load. This then represents a stable basis for
further fine-tuning, e.g. of the torque compensation system etc. (see also page 38, collective
pitch and throttle curves).
7. Static torque compensation
The tail rotor servo is coupled to the collective pitch function via a mixer in the transmitter in
order to compensate for torque changes when you operate the collective pitch control. On
most transmitters the mixer input can be set separately for climb and descent.
Recommended values for the basic settings are: climb: 35%, descent: 15%.
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Jet Ranger