FEATURE
Build a drone
KEEPING IT
IN THE AIR
Flight
component
choice
nce you have chosen your
frame, the choice of all flight
components – propellers,
motors, motor controllers, and
battery – stem from the frame’s
characteristics. The size of the
frame dictates the size of the
propeller you will use, which in turn dictates the size
and characteristics of the motors that will drive them,
and then the appropriate motor controller to drive
that, and ultimately the size of the battery required to
provide enough power to keep the craft in the air.
The first of those choices is relatively simple. There
is only a certain amount of space for a propeller on
a given multirotor frame without adjacent propellers
getting too close to each other, so a certain size
range will be a natural progression. For example, our
450 mm frame has a recommended propeller size of
8–10 inches, so we have gone for 8-inch propellers.
There are two figures to look at when choosing
a propeller. One is the size, which we have already
discussed, while the other is its pitch, or the angle
of its blades. This is quoted as the number of inches
that represents a theoretical distance it will travel
for a single rotation. Going into the full detail of the
mechanics of propeller design is beyond the scope
of this article, however we are fortunate in that there
is usually a recommended pitch range for a given
propeller and frame size.SPIN ME RIGHT ROUND
Propellers are normally sold in packs of two,
containing both a clockwise and anti-clockwise
component, and are quoted as a four-figure number,
denoting their size and pitch. Our 8-inch propellers
have a pitch of 4.5, and thus are 8045 propellers.
If you are not a propeller guru, and we certainly
aren’t, look online at similar builds to the one you are
embarking upon, and base your choices upon theirs.
The propeller will sit upon a motor, in almost all
cases except small toy machines, a brushless motor.
These are motors that accept their electricity as three-
phase AC over three wires, and require an electronic
motor controller for operation. There are three figures
that matter with a brushless motor, a figure that
represents its dimensions, one that represents its
speed, and the voltages and current it is designed for.
The dimensions of the type of motor you will
use on a multirotor are expressed as a four-figure
number that simply expresses its width and height
in mm. So, our motors have a figure of 2212, they
are 22 mm wide and 12 mm high. Your frame willO
Below
One motor and the
end of its arm