Vibration Troubleshooting - Help!

[aelaron]

Hi There,

I've got a nano cpx and have owned it for about 1 year now. In that time I have learned to fly (crash) and replace many parts.

Today, I am attempting to troubleshoot some vibration in the heli.
Blades are balanced, just installed a new stock main motor.

on spool up, the heli shakes, but smooths out at full head speed.
However, i am left with the skids and tail fin vibrating in a blur.

Any suggestions on where to start looking for the culprit?

Thanks!

[merch@nt]

Maybe give the new motor time to break in or spindle is to tight loose even bent,main shaft out of wack just a few things to check.

[mnipjy]

The most common reason causing vibrations I've ever experienced was bent spindle.
And you should keep the spindle nut at the sweet spot - not too loose nor too tight.
Sometimes blade grip bearings wobble in the blade grips because old plastic grips can't hold bearings tight enough, and this causes vibrations too.
In this case you should replace blade grips, or you could use metal head set if you wanna be free from this issue.

[HEXAHYDRATE]

There is a rubber collar on the mainshaft that holds it from having up and down play. Grab the head and see if there is any play in it. That rubber sleeve may have slipped on the mainshaft. This causes exactly what you are explaining. Just slide the rubber back into place if this is the case.

[d12bn]

Check the spindle or maybe blades are too tight

How to check if helicopter Feathering Spindle shaft is bent without removal (2 min 0 sec)

[aelaron]

Thanks for the advice everyone. I'll recheck the spindle. It's new, with appx 10-15 flights, and no crashes. The grips/bearings might be a place to look, so I'll check that tonight.
Any concerns (eg. not enough power) running stock motor with a metal head/grips?

[Pabling]

If everything seems ok with the spindle, main shaft, blade grips etc. try checking the main gear, sometimes the hole in the main gear is not centered and that will cause vibrations when the motor spins, to check this hold the heli with your hands and spool it up slowly, look at the main gear and see if it shakes from side to side, if it does then the hole isn't centered.

I've always kept my nano cpx as stock as possible, as it is a bit underpowered which becomes worse when you upgrade to metal parts. If you feel it doesn't have enough power to drive the head I suggest you upgrade the motor to a MMW motor. I'd stay away from the HH brushless kit as I have never had a good experience with them.

[hellyflyer1]

Couple of things to try
1. Make sure main and tail blade is balanced even if its new it may require some tape
2. Make sure main blades are sloppy loose

[aelaron]

Hi Everyone

Thank you for the tips. turns out when i reinstalled the motor, i installed my main gear upside down. (not sure if that matters), but by flipping it, i got rid of 90% of the vibrations.

The tail fin still has some horizontal vibration, but the bird is much more stable now.
Any suggestions on the tail fin vibrations? I've read that maybe the tailboom may be cracked.

[MariaFan]

The stock, hollow boom can crack very easily.
Try holding the boom mount in one hand and gently twisting the tail motor mount with the other, looking for any sections that seem to "bulge" or simply move with the twist. If the boom is OK, you should see no deformations at all.

[aelaron]

Hmm...so I can rotate the boom almost 120 degrees without resistance. Time for a trip to the hobby store.

[MariaFan]

Here's a thread for some ideas when it comes to the tail boom.

https://www.helifreak.com/showthread.php?t=711850