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Synergy Electric Helicopters => Synergy 766 => Topic started by: Rchelipastor on May 13, 2016, 03:14:34 PM

Title: Side to side vibration
Post by: Rchelipastor on May 13, 2016, 03:14:34 PM
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
Title: Re: Side to side vibration
Post by: Robert "Full" Montee on May 13, 2016, 03:47:33 PM
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!!!
Title: Re: Side to side vibration
Post by: Richard Rollins on May 13, 2016, 04:08:31 PM
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.
Title: Re: Side to side vibration
Post by: Rchelipastor on May 13, 2016, 05:28:25 PM
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
Title: Re: Side to side vibration
Post by: al_voisine on May 14, 2016, 07:08:15 AM
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
Title: Re: Side to side vibration
Post by: Kevin Feil on May 14, 2016, 03:08:29 PM
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
Title: Re: Side to side vibration
Post by: Danny Dugger on May 15, 2016, 05:16:44 PM
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.
Title: Re: Side to side vibration
Post by: Charles Rosario on May 19, 2016, 08:11:36 AM
Did you check the balance and CG of the main blades?  How tight do you run the bolts holding the main blades?
Title: Re: Side to side vibration
Post by: rcnut on May 19, 2016, 10:58:50 AM
Dampner break-in and blade grips too tight will cause this...as well as proper shimming.
Title: Re: Side to side vibration
Post by: Rchelipastor on May 20, 2016, 04:26:25 AM
The blades are pretty snug...ill check the dampers and loosen the blades a bit. You guys are awesome!
Title: Re: Side to side vibration
Post by: Rchelipastor on July 12, 2016, 04:33:05 AM
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?
Title: Re: Side to side vibration
Post by: Robert "Full" Montee on July 12, 2016, 01:29:22 PM
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,
Title: Re: Side to side vibration
Post by: J Anthony on July 15, 2016, 08:52:58 PM
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.
Title: Re: Side to side vibration
Post by: Grees01 on July 18, 2016, 06:14:15 PM
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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Title: Re: Side to side vibration
Post by: Grees01 on July 30, 2016, 03:55:23 PM
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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Title: Re: Side to side vibration
Post by: curmudgeon on July 31, 2016, 06:47:58 PM
I just maidened the 806 today.  Six flights.  I am also encountering the side to side shake during hover.  Side to side shake goes away when the helicopter is moving (not in a hover).

Rail 806/116 blades
14S
12T pinion
25T tail gear for 5.1:1 tail gear ratio
KDE 700XF-455kv-G3 motor
Kontronik 200HV, BEC set to 7.4v, using Kontronik governor
BK BLS 8002HV cyclic and 8005HV tail
Spirit Pro FBL
Jeti REX7 receiver
Stock Head Dampers:  80D Orange inside, and 90D black outside

At 80% Kontronik governor throttle (about 1,740rpm) I get pretty bad side to side shakes.  Decreasing the cyclic gain all the way down to 20% (minimum cyclic gain for Spirit Pro) does not improve the side to side shake.  Decreasing the head speed down to about 1600rpm makes the side to side shake go away almost completely.  I like how the 806mm blades sound at 1740rpm.  What can I do to minimize the side to side shakes at 1740rpm?  If I need to change the dampers, should I do all dampers black 90D or all dampers orange 80D?

BTW, this heli is a beauty!
Title: Re: Side to side vibration
Post by: Danny Dugger on August 01, 2016, 05:28:05 AM
You can run any damper configuration, I've tried them all. personally I like the stock configuration best. 80/80 will likely run smoothly but it will also have a softer response/feel. The most important thing is that the dampers measure the same thickness on each side of the head block. Sometimes it will take a handful of flights to seat the dampers and smooth out, so don't give up after the first flight.
Title: Re: Side to side vibration
Post by: FlamingHomer on August 01, 2016, 06:33:25 AM
How strong did u tighten your blade screws?
I had the same issue with my N7 on cold temperatures...the i see that one blade was very hard to turn in the grip. After loosen it a little, the Heli runs smooth... please check that.
I fly mine 766 with 766 blades between 1100 and 2090rpm without a shake or wobble. I use the stock damper setting in the Head!

Greetings from switzerland
Chris
Title: Re: Side to side vibration
Post by: curmudgeon on August 01, 2016, 10:58:57 AM
I tried both ways, tight and loose.  It did not make a difference
Title: Re: Side to side vibration
Post by: Matt Botos on August 01, 2016, 08:50:42 PM
There are a few theories on this including servos and dampers. Servos with sloppy centering might cause this or stiff/new damping may also cause the wobble.

Also..... Dampers need to break in, give it about 20-30 flights. Mine as well as a few other Team members experienced the same thing. Keep flying!

Matt
Title: Re: Side to side vibration
Post by: Rchelipastor on August 03, 2016, 03:28:30 AM
I came to the conclusion that my BK servos were acting up. I'm rebuilding my 766 as an 806 with MKS X8s. ill report back as soon as i re-maiden it...
Title: Re: Side to side vibration
Post by: Mike Spano on August 03, 2016, 08:34:39 AM
MUCH better servo choice!
Title: Re: Side to side vibration
Post by: curmudgeon on August 03, 2016, 09:22:39 AM
I came to the conclusion that my BK servos were acting up.


I am also using BK servos.  BK BLS-8002HV cyclic servos (http://www.bkdesignsllc.com/product-p/bkbl05.htm).  This is my first time using these servos, so I have no other experience using them in other helicopters.  I am OK installing other servos if that is what would solve the side-to-side shake.  However, I don't want to spend the time installing new servos and readjusting the head only to have the side-to-side shake continue.

What makes you conclude that the BK servos are the cause of the side-to-side shake?
Title: Re: Side to side vibration
Post by: Rchelipastor on August 05, 2016, 03:10:48 AM
specifically, the 8002 servos (I had the same ones) have a ridiculous amount of play around center. As a matter of fact, with the newer BK servos on any of my 700 hell's it's almost impossible to use the soko heli tool to set it up because of the slop around center. The readings can vary by as much as two degrees of pitch. with my MKS, Futaba, (Or even my high end JR) servos, i don't have that problem. As for my 766, i now believe the slop from my new BK's were causing that problem. At lower head speeds, there is less force which would explain why there is no shaking. At higher head speeds, the servos weren't holding as well. I think that at one point, after 40 or so flights, the shaking finally caused some of the linkage to fail which caused me to drive in the machine.  To matt's credit, his design is so good that my 766 held up pretty well in the crash (considering how hard it fell). Boom, TT, Canopy, main blades, and linkage...
Title: Re: Side to side vibration
Post by: curmudgeon on August 18, 2016, 10:03:49 AM
I had used very little Tri-Flow synthetic grease on the feathering shaft and the dampers.  I decided to take the head apart to apply a healthy amount of grease to these parts.  That's when I found out that I had built the head very poorly.  The dampers were holding unto the feathering shaft so tightly that I had to tap the feathering shaft out with a rubber mallet.  The dampers were set so tight within the head that I had to use a hook to pull them out.  For the rebuild, I saturated the dampers and the feathering shaft with Tri-Flow synthetic grease.  It was a very messy, with lot of excess grease to clean off at the end.

Now the side to side vibrations went away at my desired head speed of 1750rpm (80% Kontronik gov).  Interestingly, I encounter pretty bad vibrations at 1650rpm (75%), but no vibrations at 1530rpm (70%).

So the solution for me was to not go so cheap with the Tri-Flow synthetic grease.
Title: Re: Side to side vibration
Post by: Cliff Chmiel on August 23, 2016, 01:00:37 PM
Wow that's tight, mine I use the thumb, if I can push from one side to the other it got enough grease, I also grease the dampers when I put them in.
Title: Re: Side to side vibration
Post by: Rodney Kirstine on August 23, 2016, 02:43:37 PM
I was having the same issue and mine were so tight I really struggled to get them out, too, even though I had greased them initially.  This time I made sure there was plenty of grease, inside and out of the dampers, and now mine is flying really smooth.
Title: Re: Side to side vibration
Post by: TokenLefty on June 18, 2017, 02:29:58 PM
Old Thread I know. But I struggled a little with the aileron wobble as well and finally understand and corrected it. Pretty much the same as everyone else. Wobbles in a hover, goes away in forward flight. Hoping this will help with anyone experiencing the same.

I was running stock setup. Black dampeners outer, orange inner. 766 rail blades with head speeds 1660, 1860, 1960. Always got a wobble that started around 1800 and got worse with increased head speed. (I almost always fly 1860rpm) I spent the weekend rebuilding the head into a few different dampener configurations and testing at different head speed.

swapping Orange Outer, Black inner. - The softer on the outer moved the harmonic up to around 1900 head speed. No wobbles below that. But wobbles above 1900.

All 4 Orange - These 80 durometer dampeners fly smooth up to 2060. No vibs, no wobbles. However, they are a little slow off center for my liking. I'm not a smack pilot by any means but I like the connected feel with the stiffer head.

Now that I finally understood what people were telling me, and understanding how stiff the head really is in the 766, I started backwards and playing with cyclic gain. In the Vbar NEO  control manager, I had the following set when the dampeners were set up stock (black outer, orange inner) and wobbles. 

(OLD Values)
Style 90
Agility 90
Gyro Gain 90

When setting up the cyclic gyro gain initially, I did what I always do; Slowly increase it, perform fast aileron and elevator stops and look for overshoot in the control loop by observing oscillations on the stops. The 766 basically never would do this. So I kept cranking in the gain and at some point decided that 90 was enough. The only hint Vbar manager gives you is a pointer to around 70 for a "TDR". My Logo 700Extreme used 57. (Those should have been a hint)

I want the head stiff so it performs off center, the only thing I can do is adjust the gain back down, test response, and check for wobbles. I could have left it with Orange dampeners on the outer, but decided almost everyone else is flying with the blacks outer by the manual with no issues so I would stick with that setup. I initially backed cyclic gyro gain down 10 at a time until I noticed how sloppy the heli felt on stops. This was around 50. But absolutely no wobble at any head speed with this reduced gain. The span on this setting is 40-120. So 90 down to 50 is significant. Then trial and error back up until I found the perfect match between no wobble and crisp cyclic. The value ended up being 61. ( Funny as 62 wobbles and 60 feels a little slow. It really is that close.) In order to compensate for the slightly slower loop, I increased agility a little. My final Values on the Vbar NEO are:

(New Values)
Style 90
Agility 102
Gyro Gain 61

I can't really comment on other FBL controllers. I have flown a few but only the Spartan Vortex and the VBAR NEO on the 766. Hopefully that information will help someone else that has the wobbles.

Mark


Title: Re: Side to side vibration
Post by: Cullen Colapietro on June 18, 2017, 10:12:14 PM
I am flying a used e7se and get wobbles around 1700rpm, but not at 1950. The dampers aren't new, but I'm tempted to rebuild the head, checking for shimming/tightness. It seems the previous owner used a grease that got sticky as it aged, the spindle is difficult to turn with a driver when the blades are removed. I'll report back if I get it sorted

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