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ProModeler Scorpion Power
RM3

Elite Veteran

Killeen, Texas - USA

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Ok, I just want to know, of those of you that have had a vertical tail bounce (up and down) above a certain headspeed that just gets worse with more headspeed... what was the solution/issue? large helicopters 600 - 800 class.

One to two sentences please.

showing a preference will only get you into trouble, 90% of everything is crap...

10-02-2016 03:17 AM
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fastflyer20

Key Veteran

N. Tonawanda, NY

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I just had this happen and took forever to solve it. Turned out to be a bad swash plate.

Tom
CAUTION - my posts are based on my experiences, yours may be different.

10-02-2016 03:36 AM
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don s

Key Veteran

Chesapeake, VA

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Something wrong with the main rotor system. Tracking, something bent, swash, etc.

E820, Raptor G4N, X50F/E, E620, Forza 450, and some planks.

10-02-2016 03:40 AM
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Slowpoke

Key Veteran

Dublin, OH

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on a flybarless, too much gain

10-02-2016 03:42 AM
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banshee rider

Senior Heliman

n.e. illinois

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Slowpoke
on a flybarless, too much gain
+1

ageing is manditory maturity is optional

10-02-2016 03:55 AM
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gologo

Key Veteran

Sedalia, Mo USA

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on a flybarless, too much gain
Yep, just dealing w. that right now in fact, setting up a new Neo.

10-02-2016 04:26 AM
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RM3

Elite Veteran

Killeen, Texas - USA

My Posts: All  Forum  Topic

on a flybarless, too much gain
not a bobble... but a fast vertical shake.

keep em coming...

showing a preference will only get you into trouble, 90% of everything is crap...

10-02-2016 05:26 AM
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gologo

Key Veteran

Sedalia, Mo USA

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Bent tail shaft, would think that would get worse w. rpm??

10-02-2016 05:37 AM
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Slowpoke

Key Veteran

Dublin, OH

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that would definitely do it.

10-02-2016 05:39 AM
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Dr.Ben

rrMaster

Richmond, VA, USA

My Posts: All  Forum  Topic

Reduce gyro gain to maybe 20%. If it eases, it's gyro. If it persists, it's offen a bent mainshaft, spindle, or head block.

Ben Minor

Team Synergy Team Futaba Team Kontronik USA
Progressive RC

10-02-2016 01:35 PM
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don s

Key Veteran

Chesapeake, VA

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Is this a problem on a new build, or an old build?

E820, Raptor G4N, X50F/E, E620, Forza 450, and some planks.

10-02-2016 03:07 PM
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RM3

Elite Veteran

Killeen, Texas - USA

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Old heli, problem since day one
situation:
_tuned to perfection (out of tune results in side to side vibs)
_new main shaft..no side side slop nor vertical play
_rotor hub/grips balanced and tested for alignment while mounted to shaft
_feathering shaft new (FBL Trex 600 head)
_new Trex600 swash
_all cyclic servos good, no slop.
_all links smooth, no binding, no slop
_gear mesh - smooth
_Torque tube has two bearing supports in boom (unequal spacing)
_tested tail by connecting to dremel and spinning it up... no imbalance vibrations
_No cracks or structure failures, all bolts secured - frame is solid
_main and tail blades balanced with identical CGs
_exhaust is supported
_skids are secure
_boom supports mounted to frame structure, no vibs on boom supports
_drive train (clutch to bell) good
_no binding in drive train

could it be component placement? like resonance?
Will lower the gain on Elevator (adjusted according to CGY750 video by Nick M.)

not sure what else to try...

Heli flies really nice at 1600 HS... but push it to 1700 and vertical tail vibs start, 1800 and you would think the heli was broken.... 1900 is not possible, which is where the engine would make its best power.

can it be the heli frame just cant handle the engine output despite it being balanced and tuned?

showing a preference will only get you into trouble, 90% of everything is crap...

10-02-2016 03:56 PM
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fastflyer20

Key Veteran

N. Tonawanda, NY

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Did you try a different swash?

Tom
CAUTION - my posts are based on my experiences, yours may be different.

10-02-2016 04:04 PM
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Slowpoke

Key Veteran

Dublin, OH

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Ahh! new information... it's a NITRO machine....

Although the vbar is good at handling vibes, double check the mounting of the unit.

Make sure the mounting tape is still good, that it is good and secure.

As a TEST to see if it makes any difference, is it possible to run a zip tie cushioned with fuel line around the unit?

Not saying you should have to do that as a normal practice, but if it does make a difference, it might be vibration is an issue.

10-02-2016 04:10 PM
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ICUR1-2

Key Veteran

Ottawa, Ontario

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something wrong with your clutch

spending time, paying attention

10-02-2016 04:20 PM
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chopper37

Senior Heliman

FL350

My Posts: All  Forum  Topic

Have you checked t/r output shaft, bearings in t/r gearbox, also ck t/r blades for cracks or balance, I've had a few that were not.

10-02-2016 04:34 PM
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RM3

Elite Veteran

Killeen, Texas - USA

My Posts: All  Forum  Topic

clutch works fine... engages when it should, holds during climb-outs good...
swapped engine into another airframe which is shorter tail, 620 blades and belt tail and FB.... and I get no vibs until I get to apprx 2000 which I consider over speed on a 600 gasser.

not a VBAR, a CGY750, not a nitro, gasser

what Im trying to gather is a pile of issues and solutions common to any larger heli that is not tied to the engine or primary drive (pinion/clutch)

looking for out of the box ideas, odd solutions, common solutions to a problem that has been so common that there must be a majority all they way down to the obscure.

then compare that list to what I have done...

showing a preference will only get you into trouble, 90% of everything is crap...

10-02-2016 04:37 PM
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chopper37

Senior Heliman

FL350

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Had also once a bad t/r hub which caused one blade further out which caused a imbalance

10-02-2016 04:40 PM
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RM3

Elite Veteran

Killeen, Texas - USA

My Posts: All  Forum  Topic

bad t/r hub
manufacturing defect?

showing a preference will only get you into trouble, 90% of everything is crap...

10-02-2016 04:45 PM
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chopper37

Senior Heliman

FL350

My Posts: All  Forum  Topic

Yup right out of the bag hub wasn't centered and one of the side grip posts was a diff length, had never seen this before, put a new one on, good to go (its was on a excell 60 years ago)

10-02-2016 04:51 PM
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