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Useful Tips and Tricks for remotely controlled helicopter
models. If you want to help me and provide tips, please
Mail them to me.
 | Throttle Jockey ATV to RPM conversion sheet.
Some people like to have a sheet with all
the RMP's of the Throttle Jockey of
Model Avionics
given a specific ATV value.
For that I have made an XLS conversion
sheet for the Throttle Jockey that provides just that for the
different transmitters. You can give in
your gear
ratio and
print the sheet and take it with you to the field.
Much better, you can also enter the head speed and find the required
ATV values for the different transmitters. Thanks to Bas Delfos for the good Idea.
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| Setting up the 401 gyro.
Setting up the 401 is fairly
simple. First you select a control horn position on the servo such
that the arm length on the servo is about 17 to 20 mm. Next set the
tail control rod length such that when the servo horn is orthogonal to
the control rod, the heck rotor blades have an angle about 10 degrees
(pushing to counter the torque when hovering). Next select the proper
gyro mode for you servo (e.g. DS on for the 9253 servo). Next put the
delay on the gyro to zero (in case you have a fast servo like the
9253).
Put the trim of your rudder channel in
the zero position including sub trim etc. Make sure that there is no
revo or any other mixing to your rudder channel!. Program you Tx such
that you can control the heading hold and rate modes of your gyro
(connect a channel that you can switch to the gain channel). Now put
your tx in heading hold mode, and turn on your receiver and wait for
the gyro to initialize (the led should go on continuously). Now switch
your gyro gain channel such that the gyro goes into rate mode (led
goes off). Now turn down the limit pot on your gyro. Next put the
rudder stick in one of the extremes, and rotate the limit pot until
there is a maximum control throw on the blades without binding (check
both directions). Choose the limit such that there is no binding on
either sides.
Next put the ATV
or EPA values of your TX rudder channel on 100% (reasonable piro rate
for now). If you ever want a faster piro, you can turn up the ATV or
EPA of your rudder channel. Now control your ATV or EPA values of the
gain channel in both directions to 50%. Your basic setup of the gyro
is done.
Go and fly and
check how she feels. You can now turn up the ATV values of the gain
channel in both gyro modes for all your idle ups such there is no
oscillation in your tail (wagging). You can test this best by diving
the helicopter from some height. If it does not oscillate there, then
it is ok. Make sure that your gain is e.g. 5% below your maximum
setting for the different idle ups (less strain on your servo). After
this you can adjust the piro rate to your liking by adjusting the ATV
of the rudder channel.
That’s it, you’re
done.
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Throttle mixing on a TX that does not have a
limit function on the ATV or EPA values (e.g. FF8 or FF9 etc.).
It is not essential to use throttle
mixing, but indeed, for aggressive 3D it is very useful to keep the
revs up. However, the 9C does not have a limit function for the ATV or
EPA. This means that once you have set up the ATV values of your
throttle, that engaging some mix with throttle as slave may result in
overdriving the throttle servo (past the mechanical end point). There
are two options. The first is to move your sub trim and mechanical
setup such that the ATV for full throttle is at 140%. The servo will
never be driven past that point. Then it is safe to do e.g. a roll to
throttle mix. The second option is to make sure that the throttle only
goes to e.g. 85% at full pitch.. You can then add a mix such that at
full pitch and full mixing in (e.g. roll and pitch) the throttle will
go exactly to 100% of the mechanical travel of the carb. Of course
there are mechanical options (special control horns) that allow you to
overdrive the throttle without mechanical problems. That way you can
just engage a ... to throttle mix.
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Maximum differential pitch on your swash plate
Typically the
blade will not stall below e.g. 16 to 17 degrees or so. Since your
heli will probably have a maximum pitch of 9 to 10 degrees, it is
acceptable to put the maximum swash plate tilt such that there is a
differential blade pitch of + and - 7 degrees. However, be careful
that there is no binding at extremes (e.g. maximum pitch, and the
pitch and roll at maximum TOGETHER).
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Loosen up the split gear on a Raptor 50
The Raptor 50 V2 uses a split gear to have a driven tail during
autorotations. However, the gear needs to be loosened up before
installation. If you do that, you loose less energy when going to
throttle hold to enter the autorotation.
The original white gear moves very difficult over the aluminum
autorotation hub. It is designed this way to give the white tail gear
some support since it is pulled towards the back of the heli by the
tail belt. It is supposed to wear in over time, but this takes way too
long. The method described below, will wear in the tail gear so that
it rotates freely, and is still properly supported by the aluminium
autorotation hub.
Just put the main shaft in a drilling machine, and attach the
autorotation hub with the grey gear and the white tail gear to the
main shaft as shown in the picture below.
Now hold the grey gear as shown, and slowly start the drilling
machine. Now increase the speed of the drilling machine, and keep it
rotating until the white gear starts to spin freely. Let it cool down
for a couple of seconds, and feel if it rotates freely. If not, repeat
this a couple of times. This will perfectly match the new white gear
to your aluminum autorotation hub so that it rotates as it should, and
that it is still properly supported by the autorotation hub.
This fix will only take a couple of minutes and is much easier than
grinding or sanding the white gear! Furthermore, this way guarantees a
perfect round fit with good support.
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Saving your Futaba Campac data or
any model data in your TX on to your PC
If you want to make a backup of your Model data inside your TX,
then just copy it to the Campac. Next you can get the hardware from
Model-Gadgets
to read the Campac data from your PC. You can use the Software from
Wallace Louie:
CMS to read and write the Campac from your PC. |
This list of tips will include tips about the following elements in
the future:
| Temperature of different glow
plugs |
| Checking a glow plug. |
| Uniflow setup |
| Extra ring between head
and cylinder if the engine has problems with pre-ignition. |
| Raptor 30 & 50 tips.
 | e.g. piece of tape before the most forward rudder control rod
support to prevent it from moving forward and blocking the tail
control rod. |
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| General Heli setup tips. |
| Correcting the phase error in the head. |
| Engine setup tips. |
This Raptor with an OS 50 engine is running nice and rich, the way it should
be.
| Trimming tips. For now I have just listed a response I gave
to a question at RunRyder why an inverted heli is completely out of
trim on the roll axis.
| Remember that the tail
thrust is there to counter the torque (which it does). However, it
does a bit more then counter the torque, it also generates a side
thrust. As a result of that your helicopter is always tilting to the
right a bit while hovering stable (right hand rotation heli that is).
If the heli would be hovering perfectly level, it would drift to the
left (again right hand rotation heli). You probably have trimmed the
heli to stay put in a stable hover. This effectively means that you
put in a bit of right cyclic by means of the trim.
Now, think about the forces acting upon the
heli while inverted. You will see that the heli should now be trimmed
exactly in the opposite direction for a stable hover. Obviously you
don't do this. As a result of this, the heli drifts to the left while
inverted and you are looking at the nose twice as hard as you had to
correct for in the initial trimming in normal hover (again for a right
hand rotation). You understand that for a left hand rotation the
directions mentioned above are mirrored.
This effect can be reduced by introducing a
mix: pitch -> roll.
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| But there is another thing.
Depending on the vertical position of the tail rotor with reference
to the vertical center of gravity and the main blades of the heli it
will start to roll to the right or left because of the increased
thrust of the tail rotor, and that thrust being above or below the
center of gravity and above or below the average point of sideways
drag of the heli.
This effect can be reduced by introducing a
mix: pitch -> roll.
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