How to Wrap or Upgrade a Brushless Outrunner Motor


Introduction: How to Wrap or Upgrade a Brushless Outrunner Motor

A brushless motor uses a pulsed current that alternates between three wires. This fact about them can make it seem confusing about how to make one. There are a few different ways to wrap a brushless outrunner, but I will show you the easiest and most common way. Once you know how to wrap a brushless motor you can change the performance of your motors to have different outputs such as higher torque, higher RPM, and higher tolerances. You have a few different options when wrapping the coils of wire on the stator. More wraps or turns around each pole gives the motor more torque and a lower kv (rpm per volt). More turns will allow the motor to turn a bigger propeller, and fewer turns will limit the torque so it can turn a small prop at high speed. You can use any guage of wire that will fit the motor and you can wrap multipule wires at once for better performance.

Brushless outrunner motor
(small bell style motors as shown are easiest to work with)
400 grit sandpaper
enamel coated wire

Step 1: Taking Apart the Motor

Taking apart the motor you want to modify is easy. Start by removing the "C" shaped washer on the back of the motor. Pliers should be able to sqeeze it off. Then pull the outer part of the motor off of the stator (the part that has the coils). Unwind the wire on the motor and be sure to count how many turns are on one of the poles so you know what to change the number to. Some times the wire is glued on, so carefully cut it off.

Step 2: Winding the Motor

There will be at least three  main wires that will have to be wound on (usually made of several strands to handle more current). I color coded the wires in the picture, so you can tell them apart. Each wire will be wraped on every third pole. So, on a 12 pole motor as shown below each wire will be warpped around a total of 4 poles. Each wire would be wrapped around 3 poles on a 9 pole motor as shown. Be sure that each coil is wrapped in the same direction on each pole, with the same number of turns , and in the same order.

In the picture the three different colored wires at the bottom go to the ESC.

Looking at the yellow wire, start wrapping on the bottom pole after leaving enough left over wire to go to the ESC. Then, after wrapping the desired number of turns, continue the wire to the pole on the right, then the top, then the left. Do the same for the remaining two wires. Then, you should be left with three loose ends (shown in the picture on the left side of the stator with the bare copper exposed).
Use the fine grit sandpaper to sand off the layer of enamel on the tips of these loose ends until the shiny copper shows. You can either solder them together as shown, or twist them together. This is a Y wiring configuration which will provide the most torque and least kv. The picture where the ends of the wires meet up with the ends of wires of a different color is the most common configuration called Delta. It provides less torque and more speed.

Step 3: Finish

Reassemble the motor and test it out.

For the motors shown in the intro which are about 25-30mm in diameter I got these results:

12 pole motor Y configuration:
4 turns had about 3000+kv
12-16 turns had about 1000-1300kv
20-25 turns had about 700-850kv

9 pole motor Y:
20 turns about 900-1100kv
40 turns about 500 kv



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    12 Discussions


    1 year ago


    I still didn't get the part of how do you calculate the KV and why as you put more windings it gets a lower KV isn't that suppose to be the opposite?

    Say I have a 5065 motor with 270kv and I want to get it down to around 170 kv how do I know how to wind my motor?

    6 replies

    Calculating KV is complicated and is determined by many variables that include efficiency variables. Variables include:
    exact magnet type and dimensions,
    number of magnets,
    magnet to stator air gap,
    stator material, dimensions and lamination thickness,
    number of stator slots
    friction from air and bearings,
    and of course the number of turns, Y vs Delta termination, and wire resistance.

    Estimates work well though if you have a starting point, so for your motor rewind it the same way as it was made except with 1.6 times the original number of turns if my math is correct. More turns can be compared to more leverage and slower speed since more wire is acting on the magnets if that's a good way to visualize it. I'm no expert on these, so that's my best example. I guess it is kind of like a compound pulley system where a long wire pulled it's length moves the output end of the pulleys a certain distance, but it takes a wile to pull that whole length of wire and in the mean time the leverage was increased to lift more weight. If you turn the system around so you pull on the output end of the pulleys you pull a very short length of rope and move a very long distance on the output end. So more turns = more torque and lower kv, less turns = less torque and more kv

    But I know most of the variables you said to start since I'm working with a ready motor.

    also is the amount of windings the biggest factor of determining the KV? say I put twice as many windings with with 270KV would I get 135KV?

    and what about wire diameter I'd have to get half of the diameter of the original wire the get twice the torque wouldn't it affect the KV as well?

    biggest factor that determines kv is equally windings magnets and stator dimensions.

    You are correct on the kv

    Wire diameter has to decrease from the original because more turns means more wire volume, and the stator slots can't hold that, so the diameter has to degrease ideally only enough to keep the slots full or almost full for air to still go through. Smaller diameter wire will decrease torque to the extent that less amps can go in before the motor overheats, so less power can go in. In general motors are limited to a certain power output based on size which is a major cooling ability factor. Because you end up with a lower kv you can use more voltage to still get the same rpm out, using more voltage means you can get more power through the motor before it overheats, in general amps causes most of the heating, but watts contributes, so in the end you shouldn't loose power output. The decreased wire diameter can lower the kv very slightly due to higher resistance, but using higher voltage can help counter that. It will probably be a very small kv drop. Too small of ESC or too weak C rating lipo can affect the kv too, so to find the true kv it is best to use an over sized battery (capacity and discharge rate wise) and ESC and measure the no load rpm at full throttle. Many cheaper motors are not accurately rated just so you know.

    Well thanks that helps do you know of any guide to calculate motor states according to windings and all the other dimentions with numbers?

    Perhaps maybe do it your self.

    I don't know if you saw my post BELOW about doubling dimensions. Other than that, with experience with different motors you can carefully make good educated guesses on different designs. The farther you go from an untested design the farther from reality your estimates will likely be. Otherwise There are probably college textbooks that explain it all, it would take a while to learn with lots of hard math involved. There are CAD programs with simulators that designers and manufacturers use which cost hundreds or more and usually require an expensive class for a few days just to use them let alone learning the math and terminology.

    With a lot of experience and thinking things through and a little research you can with good accuracy know the performance of a motor you design and build. The math helps get performance numbers according to specifications, the experience is important for knowing how your materials will affect things, whether or not you math is accurate, and you could just look at your design and see it's limitations without thinking through much math.

    motors's kv and torque is easily estimated with proportions: double length and halve kv and double torque, same for doubling diameter, same for doubling turns, same I think for doubling magnet number. Y vs D termination I don't think has an easy proportion.


    2 years ago

    What gauge wire are you using?

    If it has 16 magnets then yes. If it has 14 then check my other instructable. Just know that each time a motor is disassembled the bearings get stressed and can go bad. It usually only takes doing this 2-3 times to significantly damage the bearings.

    This wiring method doesn't work for all motors, if it doesn't work see my instructable (coming soon) for 12N14P motors.