Vibration

[rippa55]

Hi all. i have just upgraded to kora 15/14 on 5s with a 19 pinion. but i can only get the throttle upto 62% before a vibration sets in. i have not put a tac on it yet, but its not that fast.i will be doing so soon. does anyone know where it could come from, or had the same experiance, have checked everything and all is tight and balanced. also, has anyone used the top or bottom holes on the main shaft yet? thanks for help, andy

[Jafa]

If you do a search you will find this has been discussed a lot

I am absolutely sure it's the dampers hanging onto the spindle too tightly
It used to happen to me quite often when the heli was new
I could land, pull the spindle in the direction I felt it needed
then spool up and the vibrations are gone
After 150 flights it rarely happens now

The other cause is the stock white blades that came with the heli
Some sets are good and others are not - check the balance and C/G

[Rush]

Jafa - how did you know which side it needed to be pulled on? you just pulled on the blade grip in that direction?

I have the same problem. At 85% TCV, 2600 RPM i get high frequency vibration from the tail. It's ok so long as i stay below that... but my Stunt Curves are at the 100 - 90-80-90-100% (2900 - 2800 -2700 -2800- 2900 rpms) points.

I saw an earlier post of yours. I have a 0.1mm difference in one of the blade grip distances from the rotor housing hub... is this significant enough to cause vibes? There is absolutely no play in the grips when i measured that.

Thanks in advance

[Jafa]

To be perfectly honest, I just eye ball it and pick a side
8 times out of ten I pick the right side
If it still shakes when you spool up again you spool down and yank the other one
So you do need to mark one grip and note which one you yank on

Yes - the vibes show up in the tail for sure
The 1st time it happened I actually thought I had a bent tail output shaft

2600 is ok on the Lepton in the 1st few months
But once you get used to it and want more then you go looking for 2800+

The 0.1mm is an issue I feel - simply due to the very high HS we run
If you can pack the other side with a 0.05 washer it would help

[Rush]

The head doesnt shake during spool up. I only get that really irritating high frequency vibration on the tail.

I want to run 2800 immediately. I just balanced the tail assy, main blades, lubed the spindle. I can now run below 2800 w/ minimal tail vibrations. If i go above that 2870, then the vertical fin becomes a blur due to the vibes.

i have that 0.1mm difference as well... i was looking at some of the shims i have here.. the thinnest i could find was 0.2 mmi just may sand that down a bit to get 0.1 mm and put it in.

Still waiting on masa to reply on the parts i want. its been over a day now. he does take his time doesnt he...

[Jafa]

Yeah - shen I say the shakes I do mean the tail tail vibrating left/right very quickly