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Head Setup:
In
order to achieve the best flight charactoristics for upgraight and
inverted flight, the head must be properly set up. This means the
head should be symetrical about the positive pitch side as well as the
negative pitch side. Servo travel should allow full range of
pitch motion but not excessive.
NOTE!!!
: Perform this work with 2 of the 3 motor wires disconnected and in
Idle up 2 with a symetrical pitch curve (0, 25, 50, 75, 100)Servo
balls on the cyclic servo arms. There are variations between servos
that make full servo travel (100% to -100%) vary from servo
manufacturer to servo manufacturer. Here are some guidelines
1) All 3 cyclic servos should be the same brand and model type.
2)
All 3 cyclic servos should have the distance from center radius to
servo ball be the same distance. This distance should typically be 13
to 15mm. 13.5 is the default Blueray RTF setup. Too large a
distance and you will have alot of pitch range but less effective servo
strength and less servo resolution. This will cause more "bobbing" of
the helicopter. Too short of a distance and you will get less
pitch range, but the effective servo strength and resolution will
increase.
3) If you are
changing servos or are using building an ARF kit, use the thickest
widest servo arms that came with the servos. This will yeild less twist
in the servo arm and will provide better response.
For setting up the head and servos from scratch, I recommend this process:
1) Start with the Linkage lengths given by the Trex 450 SEv2 manual. I have these measurements available in this photo: Linkage Lengths (enable pop ups to view).
Don't forget, linkages only go on one way. One side of the black
plastic linkages is larger than the other. That side goes towards the
ball as you push it onto the ball.
2) Adjust the linkage lengths
until you have as good of a symetry as possible for the mixing arms and
zero main blade pitch. Adjust the paddle angles if necessary. Photo 1 (enable pop ups to view), Photo 2 (enable pop ups to view). Note:
It is best to always measure EACH main blade from the same position. I
typically will measure with the blade rotated towards the front. This
will eliminate bias of the swash tilt so that the blade pitch is near
equal as possible. Otherwise, if the wash is tilted, you could be
setting some error in the blade pitch which would manifest itself in not only error in your settings, but typically bad initial blade tracking.Follow the Trueblood Engineering Swash leveling procedure.
Note: Step 8 is NOT required for the EXI Squadron or
Blueray helicopters. Set those servos up level. If you do not
have a swash leveling tool, you can still follow the procedure but try
to just eyeball the swash at zero, min and max pitch.
After
following the Trueblook Engineering procedure, Put the head back on and
check your center stick is Zero Pitch on the blades. If not, then
adjust the 3 linkages that go from the OUTSIDE ring of the swash to the
servo arms. Adjust them inwards or outwards with equal full turns. Do
this until you get Zero Pitch at 50% collective Pitch stick throw. Many
Transmitters will show you the current stick position to help you
determine center stick.
Now,
verify that full positive Pitch and full negative pitch are equal.
Once again, measure the pitch at the same point of rotation.
Beginner/novice Tip for better helicopter stability while learning to hover.
TIP: I have seen some novice pilots who are just learning to hover have sucess at doing the following:
1)
Use the next hole inward on the servo arm (less than 13mm). This will
yeild a pitch range less than +/-9 degrees typically (with swash mix
set at 60%)
2) Follow the above procedure then determine your
max/min pitch value. Take your max value and subtract that value
from 9. Then adjust both (A) links until you have that value as
the pitch value at center collective stick:
For example:
Using a servo ball distance of say 11.5mm I end up with +/- 6
degrees of pitch (total 12 degrees of pitch range). 9 minus 6 =
3. Now adjust both (A) links until center stick (50%) is 3 degrees of
pitch. This should then give you a pitch range of +9 to -3
degrees. Your hover point will be slightly above center stick.
You will have to move your collective stick a little more up/down
during hover but the servos will be stronger. You can also adjust
your pitch curve to change the feel of the collecitive movement.
You
are sacrificing total pitch throw for more servo mechanical advantage
and resolution. This is fine for hovering and basic forward
flight but not good for aerobatics and totally unacceptable for
inverted flight.
If you don't find you like it, switch it back :)