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
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.
Great stuff Frank !!!!
I'm certainly following this as well.
this is really cool stuff.
I think everybody would be glad to get more details on this device
I've put the installation files for the windows app on my server for download.
There is a windows XP and a windows 7 version. The latter might also run on W8, but can't test that.
How to do:
Create a directory c:\dpb This is mandatory.
Put all files from datafiles.zip in it.
Unzip the xp version or the win7 version and run the setup.
The program will start automaticaly after installation. If not, check c:\dbp and it's contents.
Start "Load" a file to display it.
The green vector is the overal resulting force. Put weight on the opposite side.
The datafiles are the result of my last runs for all of my motors. No vibration at all, only some torque and bearing-noise!
See what happens if a little piece of tape is put on one blade (load 3-too-much-tape on-refblade) and after balancing (3-rebalanced).
You might notice a checkbox for heli's and an option to change the number of blades. Doesn't work yet, it's a teaser :-)
Have fun and please share your remarks!
btw I'm almost done defining the "new" hardware.
Wow this would be perfect! i have an Octocopter that is used for filming so vibrations are my enemy. I was going to break out the mirror and laser this weekend, but maybe i should just wait and do it properly :)
Can't wait for the next installment!!
Keep us posted
Marc and me currently are beta testing the software and setup procedures.
Meanwhile I uploaded a part of a 4 month old video to show that the Arducopter platform is very well suited for filming :-) Very stable and done without fpv.
Video on http://youtu.be/pqDPZjEVuFc
that's cool, seems to be better then with any type of vibration dampers...
But I found that 9DOF razor board is quite expensive.... for propeller balancing (at least for me).
But any way looking forward to hear about idea development.
The current status of the project is that it has been successfully ported to an arudino pro mini board and an adxl 345 sensor. Frank is refining the software and killing bugs, I am helping a little by building the second prototype, beta testing the software for Frank, and building a frame all will fit in.
Very interesting, sounds very promising!
New hardware is much more realistic also.
Keep us posted :)
Heli option sounds really big too!
What'd also be great is if we could balance the motor alone. I have a few heli motors that have undergone shaft/bearing replacement and I suspect their balance is now way off. Would it be possible to measure RPM directly from the motor like from the fan holes or something ?
the option to balance a motor standalone is on the wishlist, but not yet implemented. We are discussing the possibilities to do that so balancing the motor works for all types of motors.
The current setup with the arduino pro mini and the adxl 345 works good, very much depends on the mounting of the motor and accuracy of the whole setup to get good results.