Tail shakes on Evo 50

[tplummer]

Hi guys,

Flying an EVO 50 here. I just rebuilt this one after a crash a while back and can't seem to get rid of a shakng problem (not the one that requires a beer).
Really need some advice on this one. I've already tried the standard proceedures on the shakes but just can't seem to solve this.


The problem

High frequency vibration on horizontal and vertical fins. Higher RPMs produce more pronounced shakes.
Fuel as visibly being shaken up during flight. I noticed the other day that the fins vibrate even when the heli sits at idle, suggesting
it's the engine?? The OS-50 Hyper I have in this machine is only 4 months old. Could a bearing be out in this or something??


What I've tried

Replaced main shaft
Replaced Center Hub
Replaced flybar shaft
Replaced Cross Shaft
Replaced tail boom
Checked tail struts for tightness
Checked main blades for balance
Checked thrust bearings in tail and main grips
Checked belt tension
Checked engine\clutch alignments
Getting my local pro to adjust the engine properly at high and low ends. He says it's fine.


Options


Replace all bearings on main shaft (probably should have done this already after crash).
Inspect and or replace counter gear assembly
Replace tail shaft (It looks fine though)
Check bearings in engine.


Of the options above (feel free to suggest more) what would you guys shoot for?


Thanks,
Travis

[Major_Smackdown]

I bought a used xspec and it had a tail shake, a local said it was probably the gyro gain too high - but I didn't think that was it - I got rid of the plastic fan and got one of them cnc machined aluminum fans, and on top of that verified it was perfectly balanced after putting in my gov. magnets - that's all I did and it cured a pretty good tail wiggle.

balance your hub/flywheel/fan assembly

I just saw another inexplicable tail shake on a buddy's heli - looked at everything but then figguhd out it was loose double sided foam tape holding down his gyro. easy cure.

you could also pull your tail shaft and balance it with your tail blades.

roll that tail shaft on glass, while you're at it.

if not those things - then keep looking.

good luck

[eeeyal]

Things to look for:

Are the tail blades balanced?
Do the tail blades track true?
Is the tail shaft straight?
Is the hub true?
Are the blade grips equal distance from the center of the hub?
Is the tail shaft loose in the bearings?
Are the bearings in the tail case good?
Are the pulleys true? (If not, they will vibrate the belt in the tail boom :roll: )

[Jafa]

If the fins are shaking at idle it's a good bet that it's either the clutch run out or you are running lean...Go half a turn rich on the main needle, if no change then dial the clutch. Also check the fan and hub for damage...

There are many things that can cause this problem, you just gotta work through them all.

Tracking and both the tail shaft and tail spindle are other things to check.

Good luck

[BarracudaHockey]

Dial indicate the start shaft.