mCX Toilet Bowl Symptom?

[Pipemajor]

Alex and I each have our own Blade mCX micro heli. The first one we broke the top hub which secures the upper set of blades. Took a week or so of searching but found a replacement part locally.

Now this mCX exhibits the "toilet bowl" effect where it no longer hovers in the rock-steady fashion these micro coaxial helis do out of the box.

I've heard this isn't uncommon with most coaxial helis but the only thing we changed was the inner shaft which certainly doesn't look like it's bent. I've swapped out the old and new set of upper blades but seems to have no effect.

Ideas?

[Ken]

I was reading a recent article at King Kong in an issue of Rc Heli mag that tackled this very problem. They mentioned a few things but I only remember 2 causes from their list.

1. Out of balance/bent rotating parts.
2. One of the motors is dying.

There were more causes but I don't remember them. Maybe someone with a 1-2 month old issue of Rc Heli Magazine can take a look.

[Doug]

Check that the screw in the top of the head that holds the flybar in isn't too tight. If the slot isn't symetrical the flybar won't be able to tilt evenly. The "toilet bowl" effect can also happen with a tight ball link or other hinge point.

[Pipemajor]

I already checked for that. In fact, I made one flight without the screw. No difference.

[Heli Fragmentus]

I just got through fixing the same problem with my CX3; I found out that one of the (very) small pins on the lower rotor head had broken off. It was pretty difficult to tell since the rotor blade would respond to control inputs, but when the rotors are spinning, the response it not reliable. To prevent the problem in the future (short of a major crack-up), I replaced the plastic part with the aluminum upgrade.