Logo 800 head bobble on elevator stops

Howdy. In flight at around 1650 rpm, I can't seem to get rid of small elevator bounces, either from cyclic stops (returning to level after a radius) or even very windy disturbances in forward flight. I've played with reducing gain to 45 and style to 50. Better but not gone. I'm running stock dampeners without the two 90 durometer ones.

Do you think the issue is with NEO settings or do I need the stiffer dampeners?

Sam

Hi Sam,

new 800 or XXtreme? NEO or older VBar? What servos? What blades? What about the values for collective and cyclic 8° (see setup)?
Sorry for the many questions

Usually, it should become better with higher Style/higher gain, until (with gain too high) you get an audible oscillation at hard stops.

If older VBar, it might require the XXtreme firmware (available for full size, black/blueline/silverline, not mini, which was never designed for big helis after all).
If NEO, the heli size parameter needs to be upped.
In both cases, did you do the optimizer flight? If so, as well as if not, try lowering the optimizer value a bit (like 5) and compare.

With lower head speeds, you usually need softer dampeners, or less compression.

Kind regards

Eddi

Born to fly ...
forced to work.

Thanks, I appreciate the help. I know I wasn't complete in my description, sorry. (I'll attach a csv file of values and a setup file zipped together)

This is a new Logo 800 with RT 810 blades, MKS HBL599 cyclic servos. Collective max 73, min -73, cyclic calibration 67. The heli size defaulted to 65, I did try changing it to 70 last flight, but didn't notice a change. I have done an optimizer flight, but been quite a while, the value is 45. I attached a spreadsheet of setup values. I normally just fly bank 1 (hover) and bank 2 aerobatics. I usually don't bother to use bank 3.

The bobble is just a small, noticeable thing primarily in forward flight, particularly when returning from a curved radius to level flight. Or when the wind is horribly gustly, I even see it when the wind displaces the machine a bit in straight and level flight. I get the feeling it's a bit of bounce back on elevator stops, but not sure. Oh yes, I still have the 6 x 80 shore dampers in the head.

Any suggestions to try next time I'm out would be appreciated. I have a friend flying a logo 700/neo combination, and I see a similar thing in his flying. He didn't notice it until I mentioned it, LOL. I don't see this in any of my other machines, and even in my Specter 700 the only other that has a NEO, I don't really notice it. Of course it's running 1950 rpm head speed with small 715mm blades.

Thanks for the time,
Sam

Hi Sam,

the optimizer works if it has something to compare, stick inputs (requested roll or pitch rate) vs. sensor feedback (what the model actually does).

It defaults to 1/2 agility. So in Bank 2, with agility 90, 45 would be default.
If it remains at that even if you do circuits or aerobatics for some time, the blades would be about perfectly neutral, which ... I doubt

If you feel comfortable with it, do some aileron rolls and flips (at 1/2 to 3/4 stick), to give it something to work on, then land, check, disable again.
Lower or increase manually by 5 or even 10, to see/feel a difference (in stops, or when entering an aileron or elevator maneuver ... in smooth flying, you hardly notice).

Heli size could be way higher I guess, the tool tip in the computer software says 100 for an 800 size, so try that (first or next, not two things at the same time, for sake of better comparability.

I'm not familiar with the 800 myself, or with MKS servos, but would it be possible to mount the ball links one hole in, on the servo arms, for a bit more air (collective min/max/cyclic)? Shouldn't do much, with today's servos, but still ...

So you say if you fly banked turn (slow/medium/fast / right or left or both the same?) and level out, the model bobbles (pitches up / up/down / what exactly?)? I can hardly imagine such an effect from my own experience, at least if I smoothly control the machine. Your Bank 2 is pretty much default, and that's what I flew and still fly, on my machines. Of course, if I let go of the sticks, or if I have the springs at the gimbals considerably tight, I might notice the jump when the stick snaps in. Despite it's size, this thing is very nimble and direct.

I see such effects if I do a big air looping, at the time I level out, that the model pitches up a bit and that I have to correct – but then, also, usually something is still a bit off in the parameters, or I fly considerably low rpm, or I have to do high stick inputs to 'fix it' because I did not fly the thing properly through the maneuver, would come out too high or too low/slow, and have to correct (or wind plays shenanigans, whatever).
But not leveling out from banked turns ...

So, two things to try and fly: adjust optimizer some up some down, compare, then back to what it was and adjust heli size, compare.
You could save your latest setup for backup, and copy Bank 2 to Bank 3 so you have two similar (known) banks, then compare two settings back to back with the same head speed and everything else unchanged.

Please also check the CoG (neutral or slightly front). Flybarless will fly considerably well even if the CoG is (way) off, but you might see artefacts/effects at (harder) stops or load changes, because the electronics have to compensate for the following-through in addition to the normal control inputs.

Kind regards

Eddi

Born to fly ...
forced to work.



Edited 2 time(s). Last edit at 04/07/2021 09:10AM by Eddi E. aus G..