So I forget exactly who said it, but in one of the many vibration threads someone made a note about how "maybe a little more mass helped stable out the APM". Now I know there are some neat rigs out there but I want things simple, so for a simple test, I took the heaviest small item I had lying around, a ~90gram foil pommel, and just taped it to my APM.
The results were good. I think a properly sized and fitted plate, maybe on the bottom, would help a lot. Again, I just stuck the weight on there, in the only way it could fit, this was a crude test, but I think it has merit.
(The APM is has two pieces of moon gel between it and the frame and it's secured with a piece of velrco.)
Before: I was +/- 5-6 with a greater min/max change.
After I was +/- 3-4 and much smoother.
ENGINEERING!
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Credit to R_Lefebvre for a great idea!
Let me clarify, I have two pieces of moon gel on the bottom secured by a piece of velcro. Also, I follow 100% what you're saying about helicopters. Oddly enough, I've had less trouble getting my helicopter happy in terms of vibration compared to my quad.
Richard,
I don't think everyone will have the same amount. I added a lot and crudely for this test, but I think better placed mass will do much better. I think this a good example of keep adding or taking away until you get things right. I also have more wires that I'm just not going to bother dampening because I just don't care, and I also don't have OCD over balancing props, so I'll probably end up more mass than the normal person. I like modular systems that can be quickly changed or moved around and there is performance cost for that.
That was me. Yes it works. Though... not quite what you've done.
What have you done? Is there any damping in the system? I just see a lump of metal stuck on the APM?
For my 550 heli that I'm working on, I have a 3" x 3" x 1/8" square of Aluminum, suspended on rubber bulb dampers in the corners. The APM is rigidly bolted to that. I think it should work well. Hopefully test soon, maybe tomorrow.
You do have to watch out with these systems, that you don't drive the natural frequency of the mass too close to the control frequency, or primary vibration frequency of the Copter. This is less of a problem for multi-rotors. The control frequency tends to be low, and the vibration frequency is high. So there's lots of room between the two. However, a Tradheli, the control frequency and vibration (or rather, shaking frequency) of the heli are closer together, so it's hard to come in right at the right spot. Suffice it to say, if you can see the thing shaking, it ain't gonna work.
And again, you want the mass spread out in a flat plane, and the dampers have to be wide-set. Think of a racecar hugging the road. What you have there, is a lot like this. And this didn't work well at all. This was the "Roly-Poly".
I also notice that when I doubled my battery from 4S 5000mAh to 2-4S 5000mAh, that my zAccel went bad and alt hold failed. The copter flew, but alt hold was all messed up. Went from 16:30 to 21:30 in flight time. Either something is out of balance or I'm getting some kind of harmonic at the faster spins on the motors to maintain altitude.