Setup - Pitch varies blade to blade / fore and aft

[franklin_m]

Finalizing a TRex-500 ESP (flybar) in prep for first flight. Set mechanical linkages per directions, put the electronic pitch gauge on it and set for -2 to +12 (scale type flight) w/ blade parallel to boom. When I rotate the blade 180 degrees, it changes to maybe a degree to at most two in either direction. When I change gauge to other blade, get a similar differences.

Took it outdoors for a ground runup to get the blade tracking close, saw a pretty big difference. Brought high blade down to within a blade thickness. Will adjust again after first flight.

My question is, could the slight variation I'm seeing blade to blade etc. just be a consequence of slight variations of gauge, blade grip tightness, etc.? It seems to me that if I can get blade tracking spot on after first flight, that's the best adjustment to pursue.

[Gladius]

Did you ensure that your flybar was perfectly level? If it wasn't, that will easily give you the results you are seeing.

[fuggetaboutit]

Did you balance your blades? As you turn the rotor head you will see minor variances in pitch because of imperfections and slop in the head. Was the head assembled correctly? Adjust both links (blades) until your tracking is correct. Then you should be Ok enough to try a hover to see how it responds. If they are way out of track, do not attempt to hover.

[mlp3028]

Are you certain the swashplate is absolutely level?

[franklin_m]

Thanks to all three of you...

(1) I used a flybar lock, so I'm pretty sure it was level, but it's good to confirm again.

(2) I feel confident the head, blade grips etc. were assembled correctly. That said, they are plastic blade grips, so that could account for a bit of the slop (I also used the softer dampeners).

(3) I did it on my table, which may not be precisely level (which could account for <2 degree change).

Lastly, on runup to about 2000rpm but keeping it on the ground, I'd say that the tracking is within a blade thickness...and much quieter than my initial spoolup.

Any other ideas?

[Gladius]

You can put your pitch gauge on the table to check whether it's level. Also, try switching the pitch gauge between blades without rotating them to see if they are sitting at different angles.

[fuggetaboutit]

Is the main shaft straight? Is this a new bird or a rebuild? Soft dampers will contribute later as they become weaker. I would continue adjusting the swash/washout linkage as you are probably about a turn on each to be in track (don't run out of threads). After doing that, you should be close enough to bring it to a 3 to 4 foot hover and see how the blades are tracking.

[Lee777]

Got to be swash isnt level or something is bent

[franklin_m]

All...keep them coming. It's brand new. I forgot to say last time, but I have balanced the blades. There's a chance the swash may be slightly off. I'm gonna pull the head off and check again.