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Oct 08, 2012, 03:26 AM
18t
18t
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dynamic balancing for multirotor helicopters


With all of the variables to consider when flying fpv or flying camera equipment, one keeps coming up. Assessing vibration from components sometimes becomes a time consuming obsession for me. My process is getting easier/quicker these days though. I'd like to put some links up to related info and if anyone would like to contribute any advice or links please do so. I'm mainly concerned with prop balance but vibration isolation info would also be useful.

Ive used a few techniques such as static balancing, and balancing using a laser attached to an arm. Recently I've been using ivibrometer app measuring in m/s2 to get a fairly objective number on how much vibration one motor/prop combo is inducing on the imu or camera.

explanation of a similar technique:
https://www.rcgroups.com/forums/show....php?t=1267814

thread on prop rotation reducing vibration:
https://www.rcgroups.com/forums/show...&postcount=228

how about a mini version of this system? looks like someone makes a small edf balancer like it, this would be awesome:
http://www.rpxtech.com/rpxweb/Dynavibe.asp
edf version: http://www.bobsworkshop.co.uk/outdoo...d-fan-balancer

Thought I would add this in here also for reference, static balance tutorial:
HorizonHobby.com How To - Prop Balancing (13 min 41 sec)

I don't use all of these techniques but I now use his CA hub balance technique. I do like my top flite balancer though.
Last edited by 18t; Nov 08, 2012 at 09:32 AM.
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Oct 08, 2012, 01:11 PM
18t
18t
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Anyone?
Oct 08, 2012, 07:13 PM
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otlski's Avatar
I'm not sure if this is the kind of thing you would like to see or if it is too theoretical. I posted these some time ago.

https://www.rcgroups.com/forums/show...&postcount=241

https://www.rcgroups.com/forums/show...&postcount=243

Cheers,
Dan
Oct 08, 2012, 08:45 PM
13brv3's Avatar
Dynamic balancing is one of my obsessions. I used to balance experimental aircraft props with a professional unit, and it was sweet! I've tinkered with acc and optical sensors and got as far as being able to measure the magnitude and position of the imbalance.

The biggest problem is that we don't have a nice place to put weights like you do on full scale engines. I even made a small flywheel type ring with holes, and tried to use tiny weights in the holes, but anything you use for weight on this scale is just too much.

Another problem is that it's a hassle to set up all the sensors to measure magnitude and position. You do this once for a real plane, unless something changes, then maybe you do it again. For us, it would be a full time job.

What I do now is static balance the prop as well as I can, then I measure the magnitude of the vibration at various positions of the prop on the motor shaft. Usually, there's a pretty nice sweet spot, and I call that good enough. Occasionally, if the prop is too well balanced, position won't matter.

Cheers,
Rusty
Oct 10, 2012, 08:36 PM
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otlski's Avatar
Hi Rusty, the way we do it is to get two set screws, say 4-40 X 1/4" and grind one lighter than the other. So if you "determined" you need 0.0001 lbs at 90 degrees to balance, you would grind one screw 0.0001 lbs lighter and place the lighter one at 270 degrees and the heavier one at 90-deg.

Cheers,
Dan
Oct 10, 2012, 09:29 PM
13brv3's Avatar
Hi Dan,

I've tried similar things by making a small ring with threaded holes radially. My thought was that I could not only change the size of the set screws, but I could also screw them in and out to change their position as an easier way to tune the balance. I had some limited success with that, but it was time consuming, and not something you'd ever consider doing on every prop.

Rusty
Oct 11, 2012, 02:37 AM
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SeismicCWave's Avatar
No to mentioned Rusty has spend quite a bit of time testing a "Canfield" balancer. Now that's a dynamic balancer.
Oct 11, 2012, 08:58 AM
18t
18t
Registered User
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thanks for the responses. otlski, any contribution is appreciated, feel free to post more links if you have them. Thanks for the input 13brv3.


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