RunRyder RC
WATCH
 2 pages [ <<    <    ( 1 )     2     NEXT    >> ] 351 views Post Reply
Home✈️Aircraft🚁HelicopterHIROBOHirobo Freya › Eagle 3 shaft drive vibration and wobble
05-17-2021 12:04 AM  36 days ago
Topic Vote0Post 1
gdesdigu

rrNovice

China, France

MyPosts All Forum Topic
Eagle 3 shaft drive vibration and wobble
Hello everyone,

I just finished building and made the first few flights on my new Eagle 3 shaft drive and I have two problems:

1/ A nasty high frequency vibration on the tail. The horizontal stabiliser is shaking so much on the tips that it becomes blurry but the vertical stabiliser doesn't vibrate as much. The vibration intensifies as I increase the rpm and it then creates a humming sound at around 1750 and 1850rpm in idle up 1 and 2.
Changing the boom brace anchor points did not help. Changing tail blades neither.
The only reason I can imagine is that the rubber part on the two bearing holders of the torque tube are a bit small and don't create a snug fit in the carbon tail boom thus allowing it to shake inside of it. I saw it when building it, the torque tube slides in the boom a bit "too" easily, as in I could push it in with my pinky. I wrapped some blenderm around the bearing holder's rubber but maybe not enough?
The other source I can think of could be a bent tail shaft but since it is new I kind of doubt it.

2/ The Heli has a longitudinal wobble lasting up to 2 seconds after a kind of sharp longitudinal cyclic input. I'm not talking as in 3d flying but a gentle and light stick bump. This wobble appears regardless of the rpm. The same kind of wobble appears at the end of an auto too.
Is the damper rubber too soft? It is the SSR 7 head.

I would really appreciate your help guys, the Eagle 3 is a rare machine, especially the shaft driven one so it is very hard to find informations on it.

SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
05-18-2021 08:55 PM  34 days ago
crflyer

rrApprentice

Maine

MyPosts All Forum Topic
Just a long shot here, but on some shaft driven tails its recommended that the center bearing not be located in the center of the tail boom, but just off center forward or back.
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
05-19-2021 08:59 PM  33 days ago
gdesdigu

rrNovice

China, France

MyPosts All Forum Topic
Yes that was exactly my first thought, as the bearing supports are equally spaced on the shaft thus being on a vibration nod.
Sadly the bearings mounts are VERY firmly glued to the shaft and I cannot space them un-evenly to my liking...
The one thing I have not tried yet is to do exactly as the manual says which is to just insert the drive shaft into the boom without tampering with the support bearings rubber like I described in my first post. In this case however there is a little bit of play between the rubber and the boom inner diameter.

see attached pictures: We can clearly see that the shaft is not well supported, not only is the rubber not even squished in the boom, but there is space between the rubber and the boom at around 12 o'clock. If I tip the boom slightly the driveshaft just slides out...

How do you guys do it on your E3s with shaft driven tail???

SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
05-19-2021 10:37 PM  33 days ago
Rojoalfa

rrKey Veteran

Punta de Mata, Monagas-Venezuela

MyPosts All Forum Topic
/
/

As you explained, you need to isolate the problem.

1. Check pinion driven by autorotation spur.
Look for broken theets.

2. Install the boom with torque tube and tail box without grips and blades.
Run the helicopter looking for Vibrations.
Check tail shaft for bending.

3. Balance tail grips with blades and install.

/
Saludos cordiales,
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
05-19-2021 11:48 PM  33 days ago
gdesdigu

rrNovice

China, France

MyPosts All Forum Topic
Yes I will try removing everything from the tail shaft next time I'll go test it out and gradually add the assembly back together. I would be surprised if anything is out of balance as the whole thing is new with a shaft drive conversion. The tail blades used to be on my caliber 90 that is butter smooth so I know they are good too.
As a last ressource I'll replace the tail shaft, hub and grips with the ones from my Turbulence D3 that I know is good too.

If none of that work I'll just bite the bullet and get the actual carbon drive shaft intended for the E3, maybe that will end the ghost hunting...

Next time if I can get it in the air without too much vibe I'll try to solve the wobble after a sharper longitudinal cyclic input by trying different blade tightness and rpm and also see if I can reproduce the issue upstairs.

BTW is "mast bump" the same as a "wobble" from a bad rpm range? Because my problem is a for/aft only rocking motion, the problem cannot be reproduced by a sharp aileron input.
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
05-20-2021 03:27 AM  33 days ago
Rojoalfa

rrKey Veteran

Punta de Mata, Monagas-Venezuela

MyPosts All Forum Topic
/
/

Before installing the boom, lets check it on a flat table for bending. The boom has to make a "smooth sound". If the boom make a "wooble" sound, replace it.

/
Saludos cordiales,
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
05-20-2021 09:16 AM  32 days ago
gdesdigu

rrNovice

China, France

MyPosts All Forum Topic
It is the carbon fiber boom and it is not cracked whatsoever.
Next time I'll test it out I'll go one step further and mount make a test with and without the driveshaft.
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
05-20-2021 03:51 PM  32 days ago
crflyer

rrApprentice

Maine

MyPosts All Forum Topic
I've done shaft drive conversions on some of my Hirobos,the bearings seem to fit tighter on the aluminum tail booms.
Seems like there is a lot of play with the carbon boom.
I've never had vibration issues.
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
05-20-2021 04:21 PM  32 days ago
Krister T

rrApprentice

Sweden

MyPosts All Forum Topic
Sometimes its not a "vibration" problem. Its more the sum of all vibrations that develope resonance.

That is proberly what you are searching for.
If you run the helicopter without the tail fin or horizontal fin or just one of them installed, do you still have vibrations? If so then its proberly not resonance.
Hirobo have these 0404-819 for soft installation of the fin.
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
05-20-2021 05:22 PM  32 days ago
gdesdigu

rrNovice

China, France

MyPosts All Forum Topic
@crflyer Yes I have a spare aluminium boom, I've fitted the driveshaft in it but in my case I doesn't seem much tighter.
I start to feel like my rubber grommets shrunk with time...

@Krister T Absolutely right, This is why next time I'll test everything I'll remove the driveshaft and reassemble everything just to see if the boom is not amplifying something coming from the pod.

Could it be a misaligned clutch and start shaft causing the vibrations?
I'll replace the tail shaft just to remove a variable from the equation.
How do you guys remove the pin from the shaft holding the pinion in place? Is there a special tool?

I have flown with and without the carbon horizontal fin, with and without the tail brace, and tail brace anchored at different positions on the frame. The tail is still making that whining resonance sound no matter what I do, just a little bit less loud without the hor. fin. The braces vibrate a lot too, I can see two of them in flight...
The vert. fin's tip vibrates a little just like any other nitro helis, the hor. fin and braces serve as a visual indicator of the problem.

I really don't know what to make of that last statement since if only the hor. fin and braces vibrate that much and the vert. fin stays still, one would believe that it could be the symptoms of a unbalanced element of the tail assy. or a bent tail shaft, not a loosely guided drive shaft...

I'll make the described tests, hope to find the culprit and keep you guys posted.

Thank you for helping me, It is the first time a Heli gives me so much trouble...
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
05-20-2021 07:46 PM  32 days ago
dgoss999

rrApprentice

UK - Lancashire

MyPosts All Forum Topic
If you have a mechanical vibration (rather than vibration due to blade balance), run the machine up to hovering speed with no blades on and lightly touch parts of the machine with a finger. You will be surprised how easily it is to feel exactly where the source of the vibration is. If you feel nothing, you have a blade balance issue....

DG
https://www.facebook.com/scale.skids.52
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
05-20-2021 07:59 PM  32 days ago
gdesdigu

rrNovice

China, France

MyPosts All Forum Topic
This is how I tested everything up until now. All I see is that it gets worse past the boom support
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
05-20-2021 09:19 PM  32 days ago
dgoss999

rrApprentice

UK - Lancashire

MyPosts All Forum Topic
Can you verify the torque tube has no kinks or is even bent. The positioning of the tube bearings can be critical to stop harmonics on the tube. Also check the tail rotor shaft is straight and the tail hub is in balance... If everything is straight and true there should be no buzz on the tail boom..

DG
https://www.facebook.com/scale.skids.52
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
05-21-2021 09:43 PM  31 days ago
gdesdigu

rrNovice

China, France

MyPosts All Forum Topic
The driveshaft is straight, the two support bearings are however dead evenly spaced so they can absolutely cause a harmonic resonance. They are very firmly glued from the factory to the ally shaft, I used a torch to heat up the glue joint up to the point of cooking the bearing's grease to no avail...

The tail shaft looks straight when I spin the tail, It turns true when I look at the hub and by the amplitude of the vibration I have, the tail shaft would have been very bent to cause them.

To test the tail hub I have made the little experiment described in the pictures. It is pretty self-explanatory. The observed difference between the two blades is around 1mm so again, I don't see this minute difference alone causing such a ruckus.
It could trigger the driveshaft to enter in harmonic resonance though.

For me I am almost certain that it is the driveshaft entering in harmonic resonance and/or because it is not well supported in the boom. The only way to confirm this is to run the heli on the ground without the blades with and without the driveshaft to isolate the problem.

I don't have the time to test this weekend so next weekend I hope...

SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
05-21-2021 11:42 PM  31 days ago
dgoss999

rrApprentice

UK - Lancashire

MyPosts All Forum Topic
Sounds like a great plan. Run the head up to hover speed and remove parts 1 by 1. I would take just the tail rotor shaft out first and leave the rear most torque tube bearing. If you have resonance your issue is the torque tube itself or its bearing placement.

DG.
https://www.facebook.com/scale.skids.52
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
05-21-2021 11:51 PM  31 days ago
dgoss999

rrApprentice

UK - Lancashire

MyPosts All Forum Topic
gdesdigu The observed difference between the two blades is around 1mm so again
This can be deformity in the tail hub itself. The mounting screws can be bent if the tail is knocked in transit (with the blades on). I have bent shuttle tail hubs this way.. This mis-alignment could be the start of your vibration...
https://www.facebook.com/scale.skids.52
SHARE  PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
05-22-2021 08:03 PM  30 days ago
gdesdigu

rrNovice

China, France

MyPosts All Forum Topic
Good idea, I'll remove the output shaft and just leave the input dog-bone to isolate the issue to the drive shaft itself.

I have swapped the tail hub and grips by the unit from my Turbulence D3.
My god I love Hirobo's parts interchangeability... Some of them are the same on my E3, D3, SDX and Lepton!
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
05-22-2021 10:28 PM  30 days ago
Rojoalfa

rrKey Veteran

Punta de Mata, Monagas-Venezuela

MyPosts All Forum Topic
/
/

Tail shaft runs 4 time faster than main shaft... So, a little difference on balance are also big problems!

I am sure you are going to find the issue, isolating the Thing.

/
Saludos cordiales,
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
05-28-2021 10:22 AM  24 days ago
jxtee

rrNewbie

Petaling Jaya

MyPosts All Forum Topic
Hi gdesdigu,
Just curious, did you happen to check run out of (flywheel+Clutch shoe+clutch shaft tip) during assembly?
SHARE  PM  EMAIL  Attn:RR  Quote
05-31-2021 05:26 AM  22 days ago
John Benario

rrVeteran

Las Vegas

MyPosts All Forum Topic
Have you balanced the tail rotor blades? The drive shaft likely doesn't have the energy to make the horizontal fin go into resonance.

It sounds like the tail hub is bent
Team highest quality
Futaba radios
Cool Power fuel
John's Ultimate building school
Custom gear manufacturer
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
WATCH
 2 pages [ <<    <    ( 1 )     2     NEXT    >> ] 351 views Post Reply
Home✈️Aircraft🚁HelicopterHIROBOHirobo Freya › Eagle 3 shaft drive vibration and wobble
Print TOPIC

 5  Topic Subscribe

Tuesday, June 22 - 9:01 am - Copyright © 2000-2021 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online