New heli - Bad vibrations!

[wonderd]

Hi there,
Not enough I have a frame vibration in my new Trex700E, now a friend of mine came to me with an almost the same problem:
He has a V90 newly built, the engine is not new - he bought it from a friend.
His heli vibrates pretty hard when he tries to hover, the major issue for me is the fact that the vib. is not constant! it shows up and then after 4-5 seconds it disappears.
I looked at the heli for him - checked the flybar- equal, checked whole head actually, everything is looking good - nothing loose. (BTW, do all V90 have tight links? the whole thing is moving a lot harder then I expected..)

what to do?

Thanks,
Elad.

[Bart101]

Is the engine correctly lined up?? Are the bearings on the TT glued on, in the correct place?? What tail blades is your friend using?? Gear mesh correct??

Seems very odd that it's only there for 4-5sec

[p00rboi]

The links are very tight on the V90. They will wear in after a gallon or so. If you so desire, you can size the links below the head. They take longer to wear in because they don't move as much.

[wonderd]

Originally Posted by Bart101

Is the engine correctly lined up?? Are the bearings on the TT glued on, in the correct place?? What tail blades is your friend using?? Gear mesh correct??

Seems very odd that it's only there for 4-5sec

The only thing from what you wrotethat I think of is the TT bearings..but would they do that problem? it seems like the vib. is coming from the head area and not from the tail..

[DominicD]

Sounds like the feathering shaft set screws were done improperly.

[wonderd]

Hey there,
My friend took apart the grips and head and with my remote assistance reassembled it. I also told him to check the main shaft just to be sure and guess what - it is bent!!
I hope that was the problem and when he gets his new shaft he will no longer have that problem.

I am making sure this time that the feathering shaft is installed right in the center with the screws very tight.

[wonderd]

Hi there again,
We have found the problem source today - after taking the head apart again myself and replacing the main shaft, we tried again and was still vibrating.
We almost gave up when we decided to take out the engine and look in there - we found out that the starting shaft was not the original - the owner broke the original and replaced it with an Align one..the new one did not fit prefectly and was causing the whole clutch assembly to be loose. once we fixed that, the whole vibration went away.

Velocity90 Vibrating (0 min 40 sec)

is a short video of the vibration before we found the problem..

[DominicD]

Great detective work ! I hate tracking down vibrations.

[wonderd]

And the problems continue - today Oren (the owner) was hovering when he heard a strange sound, landed and called me..
I took off the engine and guess what....the clutch was laying there broken!

Could it have anything to do with the vibrations before?

[Bart101]

It could very well be a result of the vibes he had!!

[royroy11]

Originally Posted by wonderd

And the problems continue - today Oren (the owner) was hovering when he heard a strange sound, landed and called me..
I took off the engine and guess what....the clutch was laying there broken!

Could it have anything to do with the vibrations before?

there's no reason for the clutch to just break like that, so i think it's gotta be as a result of the vibrations you had - i would just replace all parts to original (which you already did) and i think you should be fine.

make sure that the starter shaft you put on is the one that came with the kit originally - i bought one from fastlad and it was too long which caused only more problems... the original one has two m4 screws that go into the hex adapter and onto the flat part of the shaft.

where do you guys get parts, by the way?

[wonderd]

Thanks, we replaced that shaft - the original one was broken for some reason on the first try, my friend used an Align one until he got the original and this probobly was one of the problems.
I live in Israel, we have an official supplier here which we purchase from if we get stuck without parts.

[wonderd]

Hey there friends;
I am just updating..everything works good now,
After replacing the main shaft, the starting shaft and the clutch, a friend helped us with the engine tuning. the vibration stopped completly.
The friend also noticed that after putting the engine back into place, the meshing was a little tight..which (I guess) was the cause for the next day main gear tooth strip .

But at least the vibration problem is solved.

Elad.