Tuning help/question

[Hopester]

I've have used the spartan exclusively for 4 years now.

The issue I'm having is I'm becoming aware of little bobbles that happen when I do hard stops. They don't have any effect on flying, but I would like to try and eliminate them as much as I can. I have replaced dampeners, changed thrust bearings, lowered the head gain to the point the helicopter feels mushy. I have increased head speed, lowered head speed, and played with blade tightness, but the bobbles are still present.

I have discovered that this condition changes a little with different brands of blades. So, is it correct to assuming this is a tuning issue?

I have never really gotten hung up on tuning. I have always been able to fly through or use the basic gain settings to correct anything that caught my eye. I'm going to dedicate a day at the field for tuning, and wanted to get some ideas from folks that know more than I do. I think I might start playing with the PID side of the advanced menu.

Any thoughts or comments are going to be absorbed.

Thanks,

Dave

[crashcopterman]

Your diligence with all the mechanical tells me that maybe an ‘I’ gain tweak is in order. Do yourself a favor and move about 5 (or more) points at a time so you can definitively see the difference instead of creeping up up on your desired tune, that can be a tedious task.

Steve

[myxiplx]

Agreed, I gain and D gain may need a little tweak. However, the challenge with little bobbles is that they're not necessarily caused by the main rotor gain.

Very often the root cause is a tail shake, which twists the Heli slightly, and causes the main rotor corrections to be a little off axis.

And the fun with a tail shake is that it may be caused by either tail or governor settings :-D

What kind of bobbles are you seeing, and what move are you using to get them to show up?

[Hopester]

When I do rainbows or tic toc’s with any hard jabbing stop. If I Slow the stop down, the bobble is almost imperceptible. Best description I can think of is a slow wave of the disk. It’s not stopping flat. Hell, maybe it is a tail issue.

How would a guy go about isolating a head bobble caused by a tail shake?

[myxiplx]

A slow wave of the disc could easily be tail related.

Check your tail tune first:

- disable any governors
- watch the tail in a pitch pump, check that it's holding well and not shaking from side to side on stops

If you need to tune the tail I don't have time to write the whole process right now I'm afraid, but it's been mentioned several times. It's basically:

- tune main tail gain in fast flight, when you hear chatter, lower it a little

- use pitch pumps to tune I gain, usually needs raising

- add collective to tail mix at the end to fine tune in pitch pumps

If you can't get pitch pumps to totally lock in, up your rpm a little and decrease your collective pitch a fraction (200 rpm and half a degree steps is what I'd suggest).

Once you know the tail is solid, turn the governor on again and check it hasn't caused any problems such as tail chatter under load, or shakes on a pitch pump.

[Hopester]

Thank you.