Ball tightness

[Chigoe]

Hi, has any one experimented with the tightness of the ball end (stiction, drag, ) in regards to a Flybarless setup. Seems a flybar set up would require the elusive "loosely tight" and friction free ball action, due to the sensitivity of the flybar itself.
Wouldn't, in a FBL setup, the controller want a firmer and direct control to apply its commands, as its "sensitivity" is digital and not requiring a sensitive feedback thru the control rods and flybar?

[deebee]

Since noone has replied on this one. I wiĺl give it a shot.
Reguardless of the system FB/FBL the ideal ball joint would have 0 drag and 0 play (slop). Overall FBL can tolerate varied link tightness better than FB, so much so that those who started on FBL, dont seem to concern themselves with it unless there is a problem.


With a FB system it is better to err on the side of slightly loose b/c we want as little drag as possible, otherwise we lose sensitivity and accuracy of the FB and get some quite undesirable effects.
On a FBL system play or slop is the enemy and it is better to err on the side of a slightly firm joint . The control loops that FBL controllers use are sensitive to slop. It adds error that is hard to compensate for . I really not qualified to explain why this is, I only have a basic understanding myself.

With my little FBL 450, I had a link that was tight on both ends it was tight enough to cause a bit of drag on that particular servo, seen on the bench when going from max negative to max positive collective. I set my links in the same manner I set my main blade tension, tight enough to hold themselves up and level when everything is still, loose enough to fall some if I hold the heli and give a firm bump.

Hopefully someone else will reply that can better explain how the FBL control loop works, and to verify and coŕrect this info.

[R_Lefebvre]

With FBL, a tight pitch link will probably not cause control problems, but it will cause a vibration. This is because the swash always has some slop in it, and the tight link will cause the swash to wobble as it goes around. It would basically make it impossible to get the tracking perfect.

However, tight servo-swash linkages would probably not cause much trouble unless it was fairly tight, because this will make servo output deadband worse.