Torque Tube Setup

[coptermanic]

Have just replace the belt system in my 600NP for a TT - thanks Lee - and this has been referred to before, but is there a rule of thumb for TT meshing? Have heard that if the meshing is too tight, it can induce a low freq shake at the tail. Is it just trial and error??

[Mart61]

Yeah - there is a rule. As I recall it's about a "fag papers" clearance. I'm sure there is Finless video on it - let me go see...

[Mart61]

Here ya go: http://video.helifreak.com/?subpath=...ame=step17.wmv

It's nothing more technical than pushing in it and then backing it off a fraction.

Hope it helps.

[coptermanic]

LOL. Yes, I have used the fag-paper method for pinion - main gear meshing, so this is very much the same then.

[joe.lel]

Used to use this method for RC cars also, passing a bit of paper between the gears, the end result being a crimpled piece of paper, but not torn.

[coptermanic]

Well, it still isn't correct. I am still getting a little tail shimmy, and I have been up and down the gyro gain and am convinced it is NOT the gyro. Just how much slack should the rod have between the umbrella gear mechanisms?

[Geek]

one of my 600's does it I have never sorted it think it's because I do my blades up to tight for blade stop Auto's
if you fine it please let us know
good luck

[Mart61]

On mine I've just gone with the "fraction" as stated by Finless. Whereabouts on the TT did you put the "centre" bearing?

[Tom Burgess]

Well, it still isn't correct. I am still getting a little tail shimmy, and I have been up and down the gyro gain and am convinced it is NOT the gyro. Just how much slack should the rod have between the umbrella gear mechanisms?

What gyro Mike? Not a 611 is it?

[coptermanic]

GY401/S9254. Has done a sterling job oh holding whilst the tail was belt-driven. This has started since the TT was fitted. I followed Lord Bob Whites advice and put the TT bearing 5cm or so forward of the midpoint.

[rapidgaz]

check the center bearing as above

[coptermanic]

Gareth, I read somewhere that there should be some play between the rod and the two "umbrella" gears, that it should not be tightly compressed into the two cross slots.
Just how much play should there be?

[Nick B]

I got about 1mm each end with no issues,Mike

[coptermanic]

Cheers Nick. Was a frustrating day up at BMAC yesterday, as the engine was misbehaving, and I got the TT wiggle!!

[coptermanic]

Just had the tail off, and measured where the middle bearing for the TT is positioned, and it's rearwards face is 46mm from the rod mid-point.