I
use what is called an adjustable servo reverser.
It allows for servo matching
adjustment from one pot only (centering). Seems to work OK for the 18.00 or so
they cost (25.00 if built into a Y-harness). The 2 servos are connected to a
Y-harness with the reverser in one leg. I use heavy gauge wire reversing-y's
only.
Not sure if it would be adequate for digitals. There is a unit called the
matchbox from JR would give much more latitude and fine adjustment. But is much
more exp. (69.00) Link at end of notes.
I used 2 identical servo wheels and I rotated the wheels until I got
the drive hole where it was needed. Keep in mind that there is spline offset on
Futaba servos. I believe JR's are the same. 12.5 deg per spline or something
like that and because of this, rotating the servo wheel can be used to get the
servo output holes located correctly. I will have to look for my data on it for
the exact specs as to degrees change per spline rotation.
This basic procedure will get you there using one of the following: a servo
reverser, a spare channel and mixing, or the JR "Matchbox" (equal
drive arc).
01) Do prelim set up with servos out of the machine. Long leads from an
installed RX will work for the setup.
02) Make sure that the servos are facing the same direction on the bench when
doing this set up, i.e., wire to the left-output spline to the right as an
example.
03) Plug in the servos to the Reversing -Y and Rev-Y into lead into the RX.
CAUTION: BEFORE turning on the power to the RX, Center the Pot on
the Reverser. Failure to do this can strip the gear train in the servo!
Do NOT test how far the pot will rotate your servo with the power on. It can
bind and damage gears and case.
04) Turn on Radio but DO NOT turn on the RX.
05) Set the ATV collective channel on the TX to desired (guestimated or known)
value.
06) Set Trim and sub trims, etc., for collective channel to 0.
07) Center the Pot on the Reverser. Check it!
08) With servos plugged in, turn on the power to RX and TX and Reverse the
servo at the Reversing-Y pot.
09) On the servo that does not go through the reverser, install one of the
servo wheels.
10) Make Sure that a line drawn through the servo drive hole passes through the
center of the servo wheel, and is parallel to the long side of the servo case.
Note: Re locate the servo wheel on the splines until this is accomplished.
11) Mark this servo wheel with a
permanent type mark with 2 "nicks"
side by side at the drive hole location.
12) Follow the same procedure for the other wheel on this same servo as used to
do the first.
Mark this second wheel with 3
"nicks" on the same end of the servo, at the drive hole location.
Install the servo wheel screw. I also mark
the servo it "belongs" to
Note: 1 mark can easily happen in a crash, 2 and 3 nicely placed marks are not
likely to "happen". (for rebuilding/repair purposes)
13) Install the first marked wheel onto the servo in the Rev-Y so the
"marks" are at the same end of the servo as the first, without
retaining screw.
14) Adjust the centering pot on the Reversing-Y until the servo is centered as
close as possible to the first. You may need to play with moving the servo
wheel a spline in either direction as well as adjusting the pot. Install
retaining screw and ball studs into the servos and wheels.
15) When ready to install into machine, locate one servo to the original
collective pocket so that it has the correct rotation as needed for collective.
If the servo you choose is wrong rotation, the other is correct.
16) Do not install and then reverse the servo to get correct rotation. You will
have to reset everything on both servos.
ALL 5 servos are spaced out by way of added shim under each -- about .250 in.
I will check exact dimensions. Basically all of the servo grommets are even
with the "top" edge of the servo box each sits in. when tightened
down using Raptor supplied servo screw plate on top, the plate is just above
the edge of the servo "Box"
New ball-stud drive hole in "collective" seesaw must be accurately
positioned same as original, although the JR matchbox would make this less
critical due to wide adjustment capabilities.
A longer link rod is needed for the new servo. As the servo location is the
same fore/aft as the original there is not a problem with driving the seesaw.
The linkage travel arc will be identical if all else is same except for the
"height. of each servo
I run a 1900 mAh pack most of the time. I use a Dymond Super Turbo charger
and charge after 3 flights.
I will add further detail and pics as I get the time, but this should
give you something to mull over :)
