Hi All,

I'm not sure if this is the forum to place this, but it just might be interesting to some of us..

A while ago I was waiting for having my car-tires balanced when I thought that must be possible with my motor-prop combination as well.
So what I did...
Got an old 9DOF razor board from Sparkfun, a motormount, a laserpointer, old transistor uses as light sensitive element, ESC and some programming skills and assembled this into a "Dynamic outrunner and propellor balancing Unit".
The razor board is equiped with an 8 MHz Atmega 328 chip that drives the ESC and reads the light sensitive transistor. Communication to a PC application is done by serial I/O
How it basically works:

- connect the razor serial port to your PC running the visual basic application.
- place the outrunner with propellor mounted on the stand. This stand is flexible mounted on the wooden base plate.
- mark one blade of the propeller with a marker. With each succesive balancing-run this marked blade should be on the same starting position.
- on the pc-application click the "RUN" button.
- now the motor runs from 1000 to 3000 RPM while the accelerometers on the razor board are constantly read. The measurements are sent to the PC-app.
- this pc-app shows the place where a counterweight should be put. It also kind of indicates the mass of it.

Done this several times to test the system and till now it works very well :-) I noticed that not only propellors need balancing, but also the outrunner itself. Could just be poor chinese quality as well :-(
All video's I shoot with my quad are without any halo-vibration-effect since and the quad is vibration free.

What else did I do:
- motors are mounted with shock absorbing supports.
- I removed the circlip from the outrunner-axle. This not only makes the balancing action very easy (just pull off the propellor unit) but also saves the bottom ball-bearing from excessive wear. I know some people may say
this is dangerous, but I never experienced a lost propellor. Every 50 flying hours I replace all bearings with quality european bearings.

motors: 4 X KDA 20-22L from Hobby King
Prop: APC SF 4,7 * 10
APM 1.4 Hotel & Oilpan with selfmade MS5611 baro-modification
ESC: Turnigy 25A basic 3.1 met simonk firmware, all calibrated manual
3DR radios 900 Mhz, HF decoupled by ferrite ring
sparkfun compass removed from frame by Starship Enterprise construction, shielded cable
Ublox LEA-6 GPS
RX/TX 40Mhz Robbe/Futaba F14 8 channel, ch5:6-way diy-mode-switch, ch6:potty, ch7 extra switch
No sonar
Lipo 4000 1p3s
2 X ubec DE-SW050 Fixed 5V switching regulator(http://www.dimensionengineering.com/products/de-sw050) both with 220uF, 10uF tantal and 100nF parallel. One system for apm + RX, the other for, leds, 3DR radio
4 Ledstrips, discrete driver 2n2222 (yes, leftovers from the stone age)
quad made of: carbon en forex (= foamed PCV). The carbon arms are two crossed rods of 1 meter each.
motors on flexi mounts
apm, dampening with 2 millimeter neoprene + aluminum.
Powerboard: diy 2 * Y, wires to motors not yet twisted, but no effect on compass
No bullet connectors to ESC and motors, all soldered
Camera Canon A3300 with CHDK hack for interval shots and RAW images, even movies are good (love it)
Camera gimball: some chinese carbon thing, works well. 2 X Hitec HS-322HD servo

Total weight: 1.8 Kg w/ camera & gimball, Flighttime 10 min, without camera 12 minutes.
Size M2M diagonal 75 cm

See attached files for pictures and pc app screen dump

Off course, I'll be happy to share code and more insight information if anyone is interested.

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A few months ago I started doing something similar but because of not having spare accelerometer I tried to use piezoelectric element (it generates voltage while changing its shape) but I stopped the development on early stage.

Nice job!

which gimble are you using?

WOW Frank

Great Idea.  I'm following this post but please make sure to include me for any "kits" you may make available!! :-)

That's another way of doing it :-) I started using an old speaker, mounting the cone to the motor mount. Didn't work good enough...

The adxl save a huge amount of work, is small and cheap. Love it :-)

Yes Tom, you're on the list!

When it's available I will anounce it in this thread.

It may take a little while, I'm currently working together with Marc on a way to only balance the motor using this gear and program.


Any late breaking news on this topic.  Really am interested in the balancer and would be willing to be a beta tester if/when  :-)

Hi Tom,

Sure you can help with testing too. Marc Kulhavy has already done a tremendous job helping me get the software on a decent level. I guess it's ready to take the next step. The hardware is DIY so you will have to make a flexible motormount yourselve. Also an optical system is needed. Of course I help you with these items, it's not that hard :-)

All files are now available in http://dpb.frankshuis.mooo.com/dpb_all.zip

Before installing extract all files in the datafiles directory to directory c:\dpb (mandatory), then install the PC-software and load some sample files. See how a very tiny piece of Schotch Tape changes the "overweight spot" and the mass (direction and thickness of the green line). Yes it's sensitive...

If you drop me an message, we can continue offline, not spamming this thread.

Regards, Frank

Will do Frank

Hi Frank ,

Great work ..any news in this development ? this very very interesting ...please keep giving news



This sounds very promising. I hope you share a video with us. I am eager to see how it works.

Hi CyberCrash,

That's a very good idea..,

A demo can be viewed at: http://youtu.be/eWWOqcSu8IY

We still have some issues in Tom's setup, but the video will give you an impression how it works at my side. I got all my motors/props balanced perfectly :-) Still not have tried 2.9.1 because I'm waiting for a bit warmer weather in the Netherlands.

Regards, Frank

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