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FOR R/C
PLANES & PARTS
(Example: Hitec HS-55 Servo)
Brushless
motor designations
Axi:
The first two digits of the number are the stator diameter in mm: the
second two, its length. The full designation of the motor includes the
number of turns of the winding, found after a slash. For example, the
2212/34 has a 22mm diameter stator that is 12mm long, and it has 34
turns of wire.
Mega motors:
Similiar
designations - Mega 22/30/3 has a 22 mm-diameter case x 30-mm-long
rotor, and a three-turn stator.
Aveox:
An Aveox 27/13/3 seems to use the following: 27-mm diameter of
the outside of the motor (not the rotor!) and 13 mm is the length of
the rotor while three is the number of turns of the stator.
Hacker:
A Hacker B20-26S is 20 mm in diameter, with the “S” indicating short
length (L is for long) and is a 26-turn stator.
KV ratings:
Kv gives the rpms produced by a motor per
volt applied, i.e . if the
motor has a Kv of 2000 and you run it on 6V it will turn at 12000 rpm.
Number of Turns:
Turns are much like gearing! The higher
the number of turns, the larger
the propeller you can swing, however, the lower the maximum current it
can withstand. Brushless motors that come in 1-, 2-, 3-, 4-, and 5-turn
varieties are usually the internal-rotor type (but not always like the
Hacker!). Brushless motors with high numbers of turns (say 10-30) are
usually the external rotor (outrunner as we call it) type like AXI,
Nippy, PJS, and the new little Hacker Baby.
GEARING:
Gearing allows our motors to turn
high rpm at low amps while swinging efficient propellers. For example
an Aveox 1406/3 speed 600 size motor on 7 cells will turn an 8 x 4 prop
at 13,000 rpm for a prop speed of 50 MPH while drawing 28 Amps. If you
use a 3:1 ratio gear box with an 11 x 11 prop the rpm goes down to
5,100 while the prop speed goes up to 53 MPH and the current goes way
down to only 15 Amps. The end result is a cooler running, more
efficient motor and almost double the flight times.
The drawbacks to gearing are that the
gear box can block cooling air to the motor, add to the weight of the
plane, and add to the length and sometimes circumference of the motor.
The motor also has to be retimed to run in the opposite direction from
the prop. If the plane has a narrow nose it will probably need a
planetary in-line gear box. These gear boxes have little or no prop
shaft offset, allow the motor to turn in the same direction as the
propeller and are usually more expensive than standard gear boxes. Belt
drives allow the motor and propeller to turn in the same direction, but
can be large and heavy
Inrunner vs.
Outrunner?
Inrunners are "standard" style motors.
Meaning the can is stationary and the shaft spins inside.
The latest type of brushless motor available is the so-called
"outrunner" like the Model Motors AXI types. At first sight these are
rather odd. They are arranged the same way as a brushed motor with the
coils in the center and the magnets on the can. But...it is the CAN
which rotates NOT the center armature. This means they are a bit tricky
to mount since you obviously can't just clamp them down but it does
have one BIG advantage. These motors generate much more torque than a
conventional arrangement. In practise what this means is that they will
turn a much larger and more efficient propeller without needing a
gearbox. Gearboxes of course add complexity, cost and weight so that's
a real advantage.
Has produced
a HUGE Database of Electric Motor info
The Great
Electric Motor Test #5
Featuring
Hacker, Jeti Phasor, Krontronik, Mega, Model Motors (AXI),
MP Jet, Uberall Nippy, PJS, Plettenberg, and Typhoon Motors
The entire Motor Test Results have
been compiled in a 108 page PDF
available
for downloading here
Buy Your Parkjet Motors and Supplies from
Grayson Hobby!!
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