Head Wobbles on Hard Collective Stops

[mahbouni]

Flies beautifully but as the title says, I'm getting head wobbles on hard collective stops. Its more noticeable during elevator tictocs than aileron ones. I tried lowering the head gain but didn't make a lot of difference and made the heli feel loose at the center.

I'm running Edge SE 713's @ 2100rpm and 2200rpm. Futaba BLS 255HV servos @ 8V, powered off a Kosmik 200. Fullsize Vbar Silverline using bank switching. Head gains for each bank are 102, 104 and 106. The optimizer is currently on.

Any ideas what I can change?

[Mentalic]

Originally Posted by mahbouni

Flies beautifully but as the title says, I'm getting head wobbles on hard collective stops. Its more noticeable during elevator tictocs than aileron ones. I tried lowering the head gain but didn't make a lot of difference and made the heli feel loose at the center.

I'm running Edge SE 713's @ 2100rpm and 2200rpm. Futaba BLS 255HV servos @ 8V, powered off a Kosmik 200. Fullsize Vbar Silverline using bank switching. Head gains for each bank are 102, 104 and 106. The optimizer is currently on.

Any ideas what I can change?

Cold weather makes the dampeners a bit harder which can lead to bounce, but those are high head gains for this heli. Flying my head gains in the 80's.

[OICU812]

WAAAAAAY too high gains, heck I am at 60. I actually have no idea how Wayne is so high? lol

ALSO....why such high headspeed??? 2000-2050 is fine???

[mahbouni]

I tried lower head speeds and didn't like it. Felt very soft and docile. Also with the gains lower than 90 it feels soft in the middle and doesn't hold true. A bit like a flybar. Also there's lag. If I try a 4 point kaos its very hard to time it when the cyclic response is half a second behind my input. I can't fly like that.

My L600 head gain is at around 102 and its locked. Flies just like the simulator. Hopefully warmer weather will fix it for my L700.

[dahld]

I noted that you have the optimizer "currently on".

If you have been running the heli and flying it all the way through your normal flight routines with the optimizer on, the stop behavior is surely all screwed-up.

I won't go through the procedure for doing an "optimizer flight", as this info is detailed I believe on Mikado's site. Too long to go into detail here about how to accomplish a optimizer flight, but suffice it to say, leaving it on all the time is NOT good for making the V-Bar fly right. It largely effects stop behavior, and thus if you've had on continuously, it doesn't surprise me the heli stops badly.

Turn off the optimizer, reset the cyclic in the V-Bar's menu, and start over...leaving the optimize off...and leave it off. Frankly, Kyle never uses it, and makes the heli fly like he wants just by adjusting style, gains and agility etc. If you want to use it after you've made the heli fly as well as you can without it, and if you want to try it after checking-out how to use it, then give it a try.

Hope this helps.

(-: Dave

[futurase]

As it has been said I can't image how you have the gain that high. I fly at 64 and the Logo is VERY locked in. Going on up it starts to bump and odd things start to happen.
As Dave said leaving the optimizer on is your problem. Clear it out and watch Fredrik's video on how to properly do a optimizer flight.

I never do a optimizer flight and I learned that from Dave Dahl. He told me that a couple of years back and it was great advice. I never liked what it did and when we went from 4.0 to 5 on vbar we can independently tune the aileron axis from the elevator so NO NEED IMO.

Norman Ross Jr.

[mahbouni]

OK I will try resetting the optimizer but the heli has had only 9 flights. It's been out of action for a couple of weeks while my Kosmik went back to Germany. I will also try some lower gains before I do that.

The thing that's got me though is I have 11 other Vbars on different machines, some of which are listed in my signature. This is the first time I have ever had this problem. One of the things I've always loved about Vbar was that it was so systematic to setup. Up until now the same procedure has given me the same great results on every machine.

Anways I'll try your advice and maybe I'll be a little wiser at the end of the day

[mahbouni]

Today I tried all of the above. I cleared the optimizer settings and I tried head gains of 60, 70, 80, 90 and 100. None of it cured the problem but I've now realized its not actually a head wobble. A friend that was with me on Sunday asked "what is that head wobble", which set me down the wrong track. What is really happening is the heli is rolling to the right when I pitch forward and rolling to the left when I pitch backwards. Its hard to notice in gentle flips but in elevator tic tocs you can see the disc has changed axis at the stop points.

On my maiden flights I had the same problem but much worse. I thought I had fixed it but obviously not properly. When I built the heli the gyro plate was very loose in the frame sides. I could lift it up and down in the slots. I had put some CA in there to stop it moving it ended up sloping to the right and when I did flips the heli rolled to the right. When I got home I remounted it and thought it was level at the time. I did a few test flights and it seemed OK. Then I had to send my Kosmik back to Germany and I didn't fly the heli for a couple of weeks. I only noticed there's still a problem this Sunday just gone. So now when I look down the boom I can see the gyro plate is still not parallel to the boom blocks. Its not loose because the CA is still holding it. I need to take it out and remount it level again.

[Mentalic]

Originally Posted by OICU812

WAAAAAAY too high gains, heck I am at 60. I actually have no idea how Wayne is so high? lol

Lol, it was 80F sunday!

[mahbouni]

Has anyone else had this issue with the gyro plate being loose or is it just mine? What did you do to level it correctly?

[futurase]

Level it no, but glue it in place yes everyone has had to. Mine is level but I added a silicon glue that doesn't crack over time.

[mahbouni]

How did you level it? Eyeball or with a tool?

[acrow]

Originally Posted by mahbouni

Head Wobbles on Hard Collective Stops

Maybe try a kneck brace

Regards

Acrow

[futurase]

Bubble level.

[mahbouni]

You're lucky that your heli was sitting on a level surface. When I tried to do it I used an RCLogger digital pitch gauge. I zeroed it on top of the head block and then measured on the gyro plate. All seemed good at the time (it was like 0.1 deg out) but now it looks off again. I haven't had time to measure it again yet.

[futurase]

My bench not necessarily on perfectly flat ground. I took reading off of motor for left-right and than main mast collar and then tray and then I took same reading for front-back.

All you need is a frame of reference to work off of.

[mahbouni]

I'll try the same then

[OICU812]

If you really want it
is easy enough to dremel yourself a small piece of CF and put on bottom in back, just another option for remote location of sensor if you want to do away with the top portion. I've suggested they make that part solid for future but hey I am just a guy suggesting is all not much stroke lol.

[mahbouni]

I actually thought of doing that too but then again maybe that plate isn't level either. I'll try to level the top plate first and if no luck I'll try the bottom plate

[mahbouni]

It turns out that the gyro plate is level after all. When I eyeball it down the boom it looks at an angle to the boom block but that is just an illusion because there is light visible on the left side but the elevator servo blocks light on the right side. I measured everything again with my RCLogger digital pitch gauge. I zeroed it on top of the motor and then measured in other places. Top of rotor head and blade grips have zero error. On gyro plate has 0.1 degree error. I think that is insignificant. The bottom plate has 0.3 degree error.

So it seems my problem is elsewhere. I was just now having a chat with a friend who flies for TT and HH. He told me I should check my swash is level at the pitch end points as one of my servos could be moving more or faster then the others. So that's my next thing to check. It seems like it could be the cause because the last time I flew it I noticed the disc did roll slightly to the right at the knifedge part of a half flip but it seemed to correct itself once the half flip was completed. Other things he mentioned to check were thrust bearings and spacers. I'll check those too.