T-Rex 450 sport head wobble

[hallstu]

Hi to all, i have just purchased & built a trex 450 sport & i'm getting really bad head wobble.
I have balanced the blade.
I have checked main shaft & thats ok.
I have check the flybar & thats ok.
I have weighted the paddles & they are the same.

I was wondering if anyone know what it could be.

[michael503]

We need some more info.
when does it wobble? all the time? just at spool up?
does the nose bob up and down?

??

[jonnyk]

That leaves either the feathering shaft or headblock. If it is a vibration and not a wobble there are a million more possibilities including bearings, motor, belt, tail.

[Buffaloirish]

After my most recent 450 pro/street in front of my house conference I replaced feathering shaft, flybar, blades, boom, TT, TT gears front/back, tail rotor shaft, and main rotor shaft. Balanced everything out and got her up only se see a tail vibration and a head wobble. My two main gears had that goofy Align wobble from day one so I didn't think anything of it but I had some fresh ones in the tool box so I swapped them and tail vibe was gone as well as a reduced head wobble but it was still there. Upon further investigation I found a bent/dented lower bearing in the main shaft/servo block trying to hide on me. That was the head wobble. Inspect those things good.

[Finless]

Probably too low a head speed. The 450 Pro really likes higher head speed. What is your throttle curve? If you left in linear then you head speed is probably too low.

Bob

[xf100t]

Originally Posted by Finless

Probably too low a head speed. The 450 Pro really likes higher head speed. What is your throttle curve? If you left in linear then you head speed is probably too low.

Bob

It's a sport, not a pro. I don't know if that makes a difference though, I only have the pro. Does a belt make a higher headspeed more unstable? That doesn't seem like a rational theory...

[Finless]

A wobble of the heli is usually caused by tight dampening and low head speed. The sport has the same head as the Pro. Head speed needs to be up there or you will get a wobble. Not a shake like something is bent, a wobble.

Bob

[Buffaloirish]

Any wobble that isn't actually a mechanical problem should be experienced at headspeeds to low to take off. If your in the air and you have a wobble something mechanical is going on any electric CP heli. I'm telling you, check those bearings in the main shaft block... It took me days to figure that one out. You are talking about a head wobble, not the whole heli right?

[Slyster]

what are your radio settings for P and T curves?