Shard

Anybody experience tail "bobbing" on their micro heli? I have an HB clone (Jabo II) and I recently started seeing tail bobbing (up and down) most prominent right after take off. The heli is under control and I have full tail authority but it wobbles from time to time. It stabilizes after 10-20s but if I make a significant adjustment while hovering it will start doing it again.
Could this be linkage related? My CG is set slightly forward..

Shard

coltech

It sounds a bit like a "death wobble", but that normally ends in a crash.
How tight are your blades? Are they the same?
Does it happen when you put in a sudden burst of throttle?

I need more info to make a judgement.

jbalat

Also check that your tail rotor is balanced... But yeh it sounds like either your main blades and/or rotor head dont have enough slop.

Shard

Hmm.. I loosened my main blades (stock) and it seemed to work. I still saw some wobbling but not really bad, unfortunately my trusty tail motor has finaly gone to tail motor heaven so more testing to be done shortly!... I don't think that this would matter but I have a head stiffener installed plus all the other "necessary" mods and my tail rotor is missing a small chunk after it was attacked by my damn furniture.
I'll let you know how it goes after my soldering iron heats up

Shard

Hmm.. I was wrong. I'm still getting the "bobbing" effect.. it's weird cause while in air it only happens from time to time. While flight level I tried doing some sharp movements to determine what induces the wobble and it seems to me that going from hover-forwards-backwards-hover is what is causing the bobbing (but not always which is very strange).
Anyone experienced that? Very intriguing..

Hangerbearing

Hv u got Head stiffners on?

justin_92_92

My Feedback: (2)

cause if you dont have a head stiffener I can get you one for $5.00 shipped to you.

Shard

Yes I do have head stiffner installed and the shaft colar, swashball mod, Johnson 250 w/ 9T pinion gear and couple of heat sinks.. besides that it's pretty much stock.

meb48

I had this problem on an Aerohawk that I customizeda bit... I found I could lessen the effect almost to vanishing by moving the CG aft a bit more than usual. The battery I was using was big & boxy, and I attached it pretty low under the frame... this set up a swinging effect that quickly got out of hand. Changing the CG helped a lot, also making sure the VERTICAL cg isn't too low (ie too far below the plane of the main blades; heli becomes a pendulum).

jbalat

Setting the cg too high has a nose down pendulum effect resulting in a nose dive that is irrecoverable. Yes, Vertical cg is just as important as forward and aft.

If you have never flown or just installed a new rotor head or head stiffener then you need to create some slop in the head. Un-click the head and sand out some of the inside so that it clicks on and off with only a little bit of effort.