VIBE RATIONS !!! OS 55 PROBLEM ???? THE VIBE HUM ? HELP Please !

Ok here goes I have a problem with Vicky my Vibe 50 flybarless.

From new I have chased a small high frequency Vibration which can be clearley heard in flight at a certain rpm , roughly 1750 ish.

Any way I fitted a second torque tube bearing , balanced the tail, and tail blades and in an effort to cure this I removed the engine , ballanced the clutch & hub (needed no weight) and dialed the hub run out down to less than one thou.

After this the vibe is worse :(:( to the point of making the tail drift in hold.

I have noticed the fuel is absolutly boiling in the tank upon starting the os 55 up and the vibes from the engine are making the tail pushrod and fin vibrate hugely at just idle !!!

Forget engaging the clutch I am not getting that far !!!!

Oh I also replace the bearings in the OS 55, as just to get the fan off you have to push the crank out.

What can I do next should I change my balancer , a highpoint one as to my surprise everything was bang on and needed no balancing.

Things are much worse since removing the fan and changing bearings.

Any Ideas ?????


Thanks X Rachel

[sacko]

Maingear mesh perfect?

[rachel]

Hi yes but this vibration is before the clutch even turns so I don't think it's the maingear ? but thanks for the input anything helps.
x Rach

[Ross Northcott]

This might not be relevent but i had a small tail vibration so i replaced the torque tube and added 2 number bearings and guess what the tail is 10 times worse, i would of thought that a additional bearing would help but i reckon it magnifies any vibration.

[sacko]

I have a dubro balancer you are more than welcome to borrow, but not sure how straight the rod is on it.

May get a replacement as it must only be a 5mm rod.

[forbsy]

I had a very similar problem on mine.I changed the tail output shaft and the vibes were near enough gone.Once i had greased the tail grips the problem went.Mine is flybarred though and is not called vicky:)

[J-S-Q]

I'm not sure how much use there is in balancing the clutch because the balance could be different once it is engaged anyway.

[rachel]

[QUOTE=forbsy;640091]I had a very similar problem on mine.I changed the tail output shaft and the vibes were near enough gone.Once i had greased the tail grips the problem went.Mine is flybarred though and is not called vicky:)[/QUOTE]

Hi thanks it must be engine as it vibes before the maingear / tail even turns.
Thanks for the input though.

[pgkevet]

If the vibe happens before clutch engagement then hunting should be easy enough... pull the blades and whole boom and see if it's still there..then boom and no tail grips etc..

If it's in the frame system then front TT system or just a loose something setting up a harmonic, clutch stack bearings etc..

[sooren]

How well is that engine tuned Rachel, Unless it is just right it can cause vibration and resonance at certain levels.
Regards
Paul

[Mr.Brown]

It may help if you tune the engine with the idle screw!?

[rachel]

I am sure the engine is set ok I will do a video and you can see what you think .
Thanks again all for your input.

[derrick]

Have you not got an old 50 you could try in it, then at least you would know if it's the motor. good luck with it.

[Pitman]

[QUOTE=derrick;640129]Have you not got an old 50 you could try in it, then at least you would know if it's the motor. good luck with it.[/QUOTE]

We can lend you an OS 50 to try if you like, Rachel. Just let me know.

[Steve]

If you Google Vibe Hum, you should find various references to it on US forums. I've read about this a long time ago when I first got my V50, and the general consensus was to use 92mm Radix tail blades. Not the stock kit plastic ones or 95mm tails. I've always had Radix 92s on mine and have also always had two torque tube bearings at unequal spacings, and have never had the hum in 3 years of flying the heli. Reports from across the pond suggest that if you get the hum bad, the tail boom simply snaps off in flight - very high frequency fatigue failure which suggests a tail output issue rather than engine or head etc.

Has this started recently? If so, what (if anything) did you do to the heli before it started?

Just to add - Align 50H and MP5 on mine since new. Smooth and quiet as silk since they day I built it. But I do have a YS56 on its way that should be fitted this week.