How to find cause of vibration

[Chris Corbett]

Hello All

I have a rather strange question, here goes;

My swift was flying beautifully until I crashed it the other day. I rebuilt it using new spindle, main shaft, flybar and blade grips.
At the same time I treated myself to the alloy head block and guide.
When test flying it I notice a rather nasty tail vibration (everything else ok) and I can't for the life of me think what is causing it.
I wondered if it was the new alloy head and if anyone has had an issue with this upgrade although I think why anyone would!
I also just want to get advice on where to start looking for the cause. I have stripped the heli down and can't find anything obvious.
Any guidance much appreciated

[Chris Corbett]

Hello All

I have a rather strange question, here goes;

My swift was flying beautifully until I crashed it the other day. I rebuilt it using new spindle, main shaft, flybar and blade grips.
At the same time I treated myself to the alloy head block and guide.
When test flying it I notice a rather nasty tail vibration (everything else ok) and I can't for the life of me think what is causing it.
I wondered if it was the new alloy head and if anyone has had an issue with this upgrade although I think why anyone would!
I also just want to get advice on where to start looking for the cause. I have stripped the heli down and can't find anything obvious.
Any guidance much appreciated

[SteveH]

It depends on how it is vibrating. If the tail boom is shaking up and down, look for a tracking problem, bent flybar, misaligned paddles, etc. If the tail if vibrating the vertical stab side to side, look for something wrong on the tail rotor such as a bent output shaft, bent hub, etc. That should give you a start.

[RAV50]

Did you check the tail rotor output shaft? It has a rotor at the end of it too. So just as your mainshaft can bend when the mainrotor meets the ground, so can this smaller shaft.

[Chris Corbett]

hi there
Thanks for reply. I forgot to mention that I changed this as well so it's not that I don't think.
I was wondering if I should mod the spindle which although is to reduce shake on spool up it might help? What do you think?

[Coolice]

Hey,

Check your tail belts tension as I along with another member of my club have experienced tail vibes when the belt has been too loose.

With the ali head, while I have had no problems try to make sure you tighten the clamping screws equally just incase it can pull the head offline but I dont really think it can. I seem to rememebr someone saying they had experienced this themselves but I have not seen it myself.

Also, I had another bad spell of vibes occur while flying and it turned out the be that I had not aligned the flybar correctly and one side was marginally longer than the other :arggg:
.

[Chris Corbett]

thank you for this, very helpful. I have since also discovered that my lhs has sold me the wrong part for the head. The seperate sleeve with pins I think is for the predator as the pins are too thick to give easy movement in the washout slider. I read somewhere else someone had this problem as the part numbers are very similar. This wouldn't be the cause would it?