Home-Built Brushless Models

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Motor Building Info

Tips and "How -To"s are on the FAQ page

Some useful information & tools for
designing and building outrunner motors


Winding Diagrams


The 'standard' Star diagram for
9-tooth stators & 12 magnets

Star (Wye) Connection

Similar to the Star diagram above
for 9-tooth stators & 12 magnets

Delta Connection

The winding leads connected together
in pairs to create a Delta connection


For 12-teeth stators
(10 or 14 magnets)

Distributed Winding

For 12-teeth stators
(10 or 14 magnets)

Winding Scheme Calculator

For other combinations of
stator teeth & magnets

Winding Scheme Table

A very handy table showing
winding schemes for teeth/pole

Calculators, Spreadsheets & Tables

Wire Size Calculator

Airgap calculator for outrunner motors
Magnet Coverage Spreadsheet
Wire Conversion Table
AWG to Metric
Wire Cross-Sectional Areas


or the same number of turns and wire thickness:

DELTA gives 1.73 higher power and amp draw than STAR

DELTA Kv (RPM)  = 1.73 higher than STAR Kv while the Kt (torque) = 1.73 lower

With a STAR connection, 1.732 less turns need to be wound to get the same power (and Kv) as with DELTA

In case you're wondering: 1.73 = sqrt(3)


How to wind a typical CD-ROM motor

This is the winding instructions for the
Apex Mini300 motor, but CD-ROM
motors are exactly the same

How to determine the Kv of a motor

Method 1 (by Ron van Sommeren)

A quick'n dirty method:

Drive your motor with a power drill.
Measure RPM and voltage generated.

Kv = RPM / voltage

- - -

Method 2 (by Neil Stainton)

Run the motor without a load at full throttle at various input
voltages and measure the RPM and controller input voltage.

You can measure the no load RPM by marking two stripes

on the bell with an indelible pen. Then shine a torch on the
rotating bell and tach the reflected light.

To find Kv either:

a) graph RPM vs Voltage, the slope of the line is Kv


b) for each voltage divide RPM by voltage, and

average your results.

Theoretically, a) is more accurate.


I post as Skylar on RCGroups.com
and also on


E-mail: Christo van der Merwe   ---   Skype name: Christo1636