Side to side vibration

[Rchelipastor]

Hey guys!
I finally maidened my 766 today and it was awesome...at roughly 1600 rpm with 766 blades it seemed fine. at 1760 and 1890 (especially 1890) in a hover is had a side to side shake. if you were to look at it in a hover (tail in) the skids would shake from side to side...any idea what that might be reflective of? BTW, even with the shake it flies incredibly...no problems....
may god bless you all,
James

[Robert "Full" Montee]

Typically shake is the head and hum is the tail.
With that said on a newly built Heli I'd review some things.
Does head gain changes, change the shake.
What FBL controller do you have on your 766?
Are the blades tracking, could they track better?
Lastly is anything loose after the maiden?

Look forward to hearing back from you and congratulations on your new Heli!!!

[Richard Rollins]

Hey James,

I had the same results with my new 766. I would suggest flying it and seeing if that smooths out / breaks in so to speak. Mine was pretty tight and I know that these machines were designed to last so because of that things may be a little tight in the beginning.  I have about 15 flights on mine now and every flight its getting smoother. Hope this helps. You can also play with your gains but at first my gains did nothing , just need to fly it.

[Rchelipastor]

Robert,
1) Ill double check the tracking and get back to you...at the time the tracking seemed dead on...
2) Lowering the cyclic gain seemed to help a little, but very subtle..barely noticeable.
3) Spirit Pro Flybarless with Jeti Radio (REX7 receiver)
4) I'll Check again for anything loose but from a preliminary post flight inspection everything appears well.

Richard,

Your response is incredibly encouraging! I'll get back to you after about 15 flights...I've only put in 3 flights...I'll let you know as things progress...

Thank you guys...you both give reps in the hobby a great name!

James

[al_voisine]

On my E7se there is a head speed at which it would oscillate.  above or below and it is fine.  You might have the same issue with the 766.

Hope this helps.

Al

[Kevin Feil]

Also be mindful of the dampeners, if you have put a number of flights on it. Make sure that your gap between the head block and the blade grip is even. I have seen with these new machines that with the new style dampeners, before they have a chance to break in, you will notice that the spindle is rather tight moving from side to side (blade grips removed) this will at lower head speed especially sometimes cause your head "not to center properly" meaning you get a bit of elliptical rotation as opposed to a centered rotating mass. Also to add the 766 heads have about 25mm in/out play, with this being said like previously mention you want to shim the head axle tighter. Don't be surprised if you end up running a double 90 dampener on both sides and shimming out the in/out play. My recommendations are to check those measurements and shim accordingly. And if you still have an issue go 90/90.  Keep us posted and glad to see you up and flying.😎

BR,

K

[Danny Dugger]

I'm another vote for dampers, they can take some flights to wear in. As Kevin mentioned checking the gap between the head block and grips, also make sure the dampers look the same on both sides of the head block. (Dampers on both sides should look even in reference to the sides of the head block). If you run 15-20 flights and it doesn't clear up feel free to shoot me a PM and I'll try to help you work through it.

[Charles Rosario]

Did you check the balance and CG of the main blades?  How tight do you run the bolts holding the main blades?

[rcnut]

Dampner break-in and blade grips too tight will cause this...as well as proper shimming.

[Rchelipastor]

The blades are pretty snug...ill check the dampers and loosen the blades a bit. You guys are awesome!

[Rchelipastor]

Ok guys, 40 flights later and the problem never went away. As a matter of fact, I had a crash that appeared to be the result of some type of mechanical failure that I have yet to identify. Any other ideas guys?

[Robert "Full" Montee]

May we have more details about the crash, for example what was going on when it happened?
Is the problem still there after the crash?
What parts were replaced after the crash?

Regards,

[J Anthony]

Damn. That sucks man. I'm really sorry to hear that. I haven't built my 766 yet but I'll be watching this to see what the answer is. Good luck.

[Grees01]

Sorry to hear that you had an accident pastor. I thought that maybe we could meet each other back when you were building your 766 and had the bearing retainer bolt problem. Seeing as how I live close to you. But anyway let us know if your able to identify the part failure. And give us a little more details about what happened when you crashed. Best of luck on the rebuild.


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[Grees01]

Hey Pastor. Just thought I'd check in and see how things are with you. Did you get your 766 back together?  Were you ever able to identify the problem that caused the crash?


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