December 11, 2017, 01:21:39 AM

Author Topic: Side to side vibration  (Read 3013 times)

Offline curmudgeon

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Re: Side to side vibration
« Reply #15 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!
Synergy E5:  7S, Rail 556/96, stock 4.0:1 tail ratio, Kontronik Jive 120+ Pro, KDE600XF-1100-G3, Spirit Pro, Futaba BLS255/256HV, Jeti REX7, Kontronik TelMe telemetry.

Upgrades:  E7SE metal tail slider, QuickUK front magnetic mounts, 766 swash.

Head Speeds:  2000rpm, 2200rpm, 2400rpm

Offline Danny Dugger

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Re: Side to side vibration
« Reply #16 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.
« Last Edit: August 01, 2016, 05:31:04 AM by Danny Dugger »

Offline FlamingHomer

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Re: Side to side vibration
« Reply #17 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

Offline curmudgeon

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Re: Side to side vibration
« Reply #18 on: August 01, 2016, 10:58:57 AM »
I tried both ways, tight and loose.  It did not make a difference
Synergy E5:  7S, Rail 556/96, stock 4.0:1 tail ratio, Kontronik Jive 120+ Pro, KDE600XF-1100-G3, Spirit Pro, Futaba BLS255/256HV, Jeti REX7, Kontronik TelMe telemetry.

Upgrades:  E7SE metal tail slider, QuickUK front magnetic mounts, 766 swash.

Head Speeds:  2000rpm, 2200rpm, 2400rpm

Offline Matt Botos

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Re: Side to side vibration
« Reply #19 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

Offline Rchelipastor

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Re: Side to side vibration
« Reply #20 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...

Offline Mike Spano

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Re: Side to side vibration
« Reply #21 on: August 03, 2016, 08:34:39 AM »
MUCH better servo choice!
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Rail Blades
TRM Power
Team Byron Fuels
MKS Servos

Offline curmudgeon

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Re: Side to side vibration
« Reply #22 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.  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?
Synergy E5:  7S, Rail 556/96, stock 4.0:1 tail ratio, Kontronik Jive 120+ Pro, KDE600XF-1100-G3, Spirit Pro, Futaba BLS255/256HV, Jeti REX7, Kontronik TelMe telemetry.

Upgrades:  E7SE metal tail slider, QuickUK front magnetic mounts, 766 swash.

Head Speeds:  2000rpm, 2200rpm, 2400rpm

Offline Rchelipastor

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Re: Side to side vibration
« Reply #23 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...

Offline curmudgeon

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Re: Side to side vibration
« Reply #24 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.
Synergy E5:  7S, Rail 556/96, stock 4.0:1 tail ratio, Kontronik Jive 120+ Pro, KDE600XF-1100-G3, Spirit Pro, Futaba BLS255/256HV, Jeti REX7, Kontronik TelMe telemetry.

Upgrades:  E7SE metal tail slider, QuickUK front magnetic mounts, 766 swash.

Head Speeds:  2000rpm, 2200rpm, 2400rpm

Offline Cliff Chmiel

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Re: Side to side vibration
« Reply #25 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.
Cliff

Offline Rodney Kirstine

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Re: Side to side vibration
« Reply #26 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.
Rodney

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Offline TokenLefty

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Re: Side to side vibration
« Reply #27 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



Offline Cullen Colapietro

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Re: Side to side vibration
« Reply #28 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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