Twin Tweaks ...
PUTTING IT ALL BACK TOGETHER.
A DRIVING BASE FOR THE SAVÖX.
FEATS OF STRENGTH AND SPEED.
64 SERVO 07.2011
PCB on long posts instead of wires. To remove
the pot, we cut it at the posts, with the posts
being the perfect place to mount our
replacement voltage divider. Wires would have
been more of a bother because if they weren’t
long enough to resolder to, they may need to
be completely desoldered from the PCB.
Ideally, we would want our voltage divider
to mimic the voltage of the centered pot. Using
our trusty multimeter, we determined that ideal
resistance to be about 2. 4 kΩ. Not feeling like
taking a trip to the electronics store, we rooted
around our toolbox to see what we had on
hand and determined that a 2. 2 kΩ resistor
would be close enough, leaving the slack to be
taken up by the trim on our radio controller.
To make our voltage divider, we twisted
one leg from each resistor together to make a
Y, with the common lead going to the center
pin on the PCB. The other legs of the Y went to
the other pins, and the only tricky part of the
procedure was being clean with the soldering
and not shorting anything with a solder bridge.
We carefully put the casing back together,
making sure that the legs of the resistors did
not contact the aluminum casing of the servo.
Reassembling the gearbox was straightforward,
and once everything was back together it was
so indistinguishable from its partial rotation
cousins that we had to mark the servo to tell it
apart at a glance.
Another option for a full rotation hack that
we did not pursue is one that keeps the
potentiometer. For some servos, the
potentiometer knob can be shortened so that it
no longer spins with the servo gears. The
shortened knob can be notched so that the
potentiometer can still be adjusted without
interfering with the rotation of the gearbox. A
hole can be drilled in the servo casing so that
the pot can still be adjusted. This, however, was
not an option with the Savöx servo because the
pot was situated directly under the main gear.
We could have possibly shortened the knob, but
replacing the entire pot with the voltage divider
avoided any problems of incidental rotation of
People Livin’ in Competition
Now that we had a full rotation Savöx
servo, we wanted to see how much of its speed
and torque we retained in the hack. This could
be achieved by lonesome tests of strength and
speed, but we are hard pressed to remember
an exciting training montage that led up to a
climax where the protagonist simply went for a