I developed stand, method and software for balancing of motors and propellers to perfection. It is very cheap.



Before balancing:



After balancing:

(work was carried out at the resonance frequency)You can balance without removing from stand. Better results can be archived with free dangle mount. The best ones are with resonating wobbly frame.

The sensitivity of resonant platform:1. Arduino (I have Pro Mini USB\UART adapter and Bluetooth module 2. Accelerometer with SPI communication protocol (it is important because sampling frequency is 3.2KHz)3. Optical speed sensor with comparator that provides discrete signal. I have this one to work with lable on the motor body and this one to work with the propeller.Connection schemeDescription Pro Mini pin ADXL345MISO 12 SDOMOSI 11 SDASCK 13 SCLData Ready 4 INT1Chip Select 10 CSOptical input 2Connect power and LED being controlled by pin 3 for firmware v2 (not mandatory).You can download firmware here (N.Esenin.zip) (Dynamicbalancingstand.zip) . With firmware v1 you need to glue label on the motor body (if body reflects infrared light then you need to glue a piece of black electric tape else a piece of aluminum foil). The firmware v2 is designed for sensor that detects the reflected light from the propeller. It remember blades order and the LED indicates after stopping the propeller for which blade we had been sending signal.



There is a vibration source - our motor with (or without) propeller. We are going to record the vibration (associated acceleration) with the accelerometer. We are concerned with just one axis. In my firmware it is X. So you should attach sensor to the rest correctly. If it is horizontal rest (see first two photos) the axis should point to center of rotation. In case of wobbly frame axis should be positioned vertically. Firmware v1 works with label on the motor body. Firmware v2 detects IR light reflected by propeller (sometimes it detects sunlight and that's bad. And not every propeller reflects IR light). I recommend to use v1 if possible. It's simpler to work with it. In fact, the firmware does one simple thing: collects 550 values from accelerometer and speed sensor (only 550 can fit in memory), and sends them to the port. Data series being sent are delimited by the word "end" to separate the data on your computer.The magic begins on the computer (photos by order: not balanced/almost balanced/perfectly balanced):



Software for computer is in N.Esenin.zip but you need to install following modules: http://www.ni.com/download/labview-r...-2013/4059/en/ and http://www.ni.com/download/ni-visa-r...e-5.4/4231/en/ . After start program chooses random serial port and starts. You need to stop it (error message can be shown). Then choose desired serial port and press arrow button. Sourse files for LabVIEW 2013 is in the main archive (still need visa and robotics modules ).1. Select revolutions to get maximum sinal aplitude (sinewave at our revolution frequency is better recognizible).2. Attach the flyweight to figure out where we have overweight. Correct phase difference.3. Remove flyweight and rotate at matching revolutions looking at what angle we get desired offset (if additional angle is +180 then it is clear where to glue the flyweight). Then if your sensor detects propeller label and loose initial blade go to 3.1 else to 4.3.1. Attach small flyweight and look at the amplitude change. If it is increased then you missed. Attach flyweight at the same angle but relative to another blade.4. Attach flywight and look at the amplitude at desired frequency (revolutions per minute multiplied by 60 seconds). Repeat until it decreases to minimum.During the balancing you can forget relative to what you measure the angle and where to glue the flyweight. It is simple to use 2 flyweights. Glue first to the propeller, second to the motor body at 90 degrees (it turns out as 2 perpendicular axes). Then move center of mass to the center of rotation by ajusting these 2 flyweights. As a result the impact of center of mass displacement on the total vibration becomes less than impact of the other factors (switching the windings, bearings, natural vibrations of different parts and so forth) and futher balancing doesn't make sense.For example rctimer 5010-14 360KV has such a disbalanceSometimes happends like this

While SunnySky X4108S was perfectly balanced.Sometimes propeller adapter doesn't fit well (mounting holes in propeller displaced). In such case only motor-propeller combination as a whole can be balanced. My stand allows to do it very quickly and accurately.Best result. Even wires doesn't move while propeller rotating and start/stop doesn't affect on them.Process of balancing