Bearing Blocks and Wobble

[rjg]

Guys,

Tuesday we attempted to do some test flights with my new 600. It had a horrible wobble in the frame. Basically the top of the frame was moving one direction while the bottom was moving in the other.

We tried new blades, new tail unit, changed dampeners, changed paddles, and I can't remember what else to no avail.

We decided to replace the bearing blocks so I ordered a new set. I just installed them and also used a new main shaft while snugging down the bearing blocks to keep it all aligned.

My concern is that the mainshaft is crazy tight in the bearings, I have to put one of my hex drivers in the top bolt hole to pull it out.

How tight do the mainshafts fit in your machines?

In addition, any other suggestions if this doesn't work?

[Ticidytoc]

As far as the wobble goes, sounds like a low headspeed and tight main blades.

The main shaft should slip in and out with minimal effort. sounds like you have an alignment problem. You may have to play with screw tension until you get it right.

How tight to you have the screws ?

[rjg]

I have the screws as tight as I could get them, which is pretty darn tight. The main blades are pretty tight too...

The problem actually got worse with higher headspeed...

[Ticidytoc]

Then your wobble is from the main blades. They should be snug, to the point if you turn your heli on its side they will not fall. If you shake it then they should move. Some do like them a little tighter than that. Overy tight blades will induce a shake as your describing.

Also, if something on the head is out of balance. i.e. flybar & paddles.

[Mercuriell]

You put the frames on a glass surface before tightening up the side frames to ensure aligned bearings - also you checked main blade CG and balance ? Also wildly mistracked blades could cause this.

PS You aren't using the SAB blades with 10mm roots and spacers ate you ? - I just put some on my Sceadu and even doing them up real tight they are quite mobile causing some alarming spool up wobble.

[OICU812]

My bet is on what Ticidy has mentioned according to everything you describe.

[rjg]

Alright guys, thanks for the suggestions.. I will let you all know how it goes...

[rjg]

Well, it is much better now...

I hovered 4 packs over the past 2 days just to get a feel for it and did some FFF today. I still notice a tiny wobble while landing, but this is probably just low headspeed...

Thanks everyone!

[Phil.L]

Lots of people including me have had this vib even when replacing just about everything head upwards including main shaft, and it was cured when replacing the main shaft bearing blocks and bearings. But first check everything else, main shaft, spindle, flybar distances etc.

[rjg]

Yeah, it seems good now.. I replaced the mainshaft when I did the work. It seems that tightening the screws going into the bearing holders in the right order is of extreme importance or the bearing blocks don't align right...