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FIGURE 5. The popular KK2 2.0 multi-rotor controller.
FIGURE 6. Parallax ELEV- 8.
FIGURE 7. HoverFly Sport.
(First Person View) 2. 4 GHz directive
antenna ground station; there’s a
cable running to an LCD video
display which is out of the picture.
Figure 9 shows two flyers: the test
quad mockup on the right with the
black whip antenna for the video
link, and a hex-modified ELEV- 8 in
the air. One of Parallax’s new
versions will utilize a Y- 6
configuration with GPS and two-way
XBee. “We were inspired to build the
ELEV- 8 because the next
generation of robotics is
clearly taking to the skies, to
the water, and in the
atmosphere, and we want to
be sure that our Propeller
multi-core processors are
prominently part of the new
era of robotics. And there’s
hardly a better application
for a multi-core than
controllers. Each process
(R/C receiver, ESCs,
gyroscope) can be
conveniently managed by
one of the Propeller’s eight
cogs,” Ken commented.
Ken and his crew have
been working on a “really
large version of the ELEV- 8,”
among other flying robot
projects. Some specifications
include two 4 Ahr 18 volt
batteries driving four 770 KV
motors with 14” props and
80 amp ESCs (electronic
FIGURE 8. Hexcopter and video ground station.
speed controllers). According to Ken,
“it will carry lunch for five or a dozen
You can get up-to-date
information on the ELEV- 8 and other
multi-rotor developments at the
Parallax site or Ken’s blog. The original
ELEV- 8 used four 1,000 KV outrunner
brushless motors, turning two pusher
and two standard 10 inch props. The
large version uses 14 inch props.
The reason for using pushers and
standard props in multi-rotor craft is
because you don’t want the torque
from the props to turn the craft. Both
types are puller props in that the
thrust is downward. Two are turning
the opposite direction from the other
two to compensate for the rotational
For those not familiar with the KV
designation for these types of motors,
it does not refer to Kilo-Volts, but to
the torque and current draw for a
specific voltage and rpm of the motor.
In short, the lower the KV rating, the
higher the torque.
Electric motors for winged model
planes have different power
designations such as 280, 300, 400,
480, and 600 which refer to the case
length, and give an approximation of
their power and weight. For example,
a 300 motor has about a 30 mm case
length, is heavier, and is able to deliver
more power than a 280 size motor.
There is a lot of information on
the Internet about brushless motors
and the unique outrunner motors used
76 SERVO 03.2013