450 My tail wags through vibration "hotspot" on spool up, then runs perfect.

[orbi]

I have a problem with starting up now. I get a quick tail wag half through spooling up, then as I get towards 60% it stops and I get the most beautiful balanced heli I ever saw. She hovers real well, tracks up spot on, in fact she s perfect. ( Pro 450). with 306 turnigy MG HV servos, (like silk) Futaba 9257 tail. I have been looking at the boom braces area, my brain although still in its "newbie" state tells me there is a fault there but hey what do I know?
Any ideas? guys

 

[Tony]

Sounds like a resonance vibration to me. As long as it goes away, you should be okay. But just to make sure, recheck the balance of your blades, make sure your main shaft is straight as well as the feathering shaft, and make sure yoru tail braces are not coming loose on the ends. Take them off on one side, and if you can twist the end off with your hand, they were coming apart. Put some CA on it, align it with the holes so that it's flat and let it cure. then, loosen the horizontal stab bracket, bolt up the braces, and push that stab up until there is no play at all in teh supports. Mine is actually pushing my tail up just slightly.

 

[treff]

Hi, I had this exact problem (amongst others lol) and it turned out to be the tail hub grub screw was loose. The tail would start to spin but the hub would spin on the spindle causing vibration but then would sort of catch up with the belt drive and go smooth.
It looks smoother than normal only because of the vibration suddenly going away. Hope this helps. Your problem maybe different. Cheers

 

[orbi]

It could well be the braces. I only recently got this Pro back up running, been waiting on parts etc. inthe mean time I pinched the braces for my Sport. I started the heli up and saw straight away that I had no braces, the tail was wagging violently. I put on a bodged up set that I managed to mackle up that I thought would do,they seemed strong enough and were fairly tight, I guess they need to be more solid than I expected.
The old Pro heli flies/ hovers way way better than my new Sport, sounds way better too.


Thanks guys

 

[Lee]

Resonant frequency can be many things. Just a slight bit tighter or looser on the screws in the tail clamp can reduce or even get rid of it. Same with the boom brace.

 

[pvolcko]

You can also go a little crazy trying to chase down spool up vibrations. There is almost always going to be a resonant point in the spoolup where it will shimmy or vibrate, especially if the blades aren't perfectly straight, until you get it up to a certain rpm and things spin out and settle in. The important thing is does it have bad vibrations at or near your flight rpms in either normal or idle up modes?