XXtreme 700 head bobble

[snafu9241]

Hello everyone,

I can not get the elevator bobble tuned out of my 700 I have tried raising the head gain very high and had it as low as 60. Has anyone else had this problem? BTW Mini VBar torque servos 8.4 volts. I have about 25 flights on it now. I have gone through my setup several times and cannot find anything mechanically wrong. This is not my first heli to build and setup so I feel pretty confident that I'm not missing something but who knows!

Thanks

[mat081278]

60 seems to be a "standard" value for 700 xxtreme head gain.
Have a look à Kyle vbar settings ....

[helicraze]

try different blades and also i gain increase for head

Also check dampers are stiff

[rcmarty]

Is this a wobble on a hard stop ( like tick tocs ? )

There have been a few post about a few possible answers.

- Very hard stop causing a slight wobble/cavitation at the point where one direction stops and the other starts. Thread went on to think that it might be a phasing issue, noting the vertical links to the grips are a slightest bit out of phase.

- receiver plate where sensor is mounted. The plate needs some extra glue to secure to the side frames. On my first 700 (2mm frame) I put some epoxy on the side frame where the receiver plate keys into the side frame. On my recent 700 (1mm stacked frames ) I found the receiver plate very loose and it would even slide back and forth a bit. (substantially more movement in the stacked frame - personally prefer the 2mm 1pc ) . I have some hotglue in there in hopes it will do the job.

- Vibes and the mini V . The mini v (blue I assume ) is less resistant to vibes than the later generation silver sensor. Silver sensor is intended for the high vibe turbine guys but I can still pull several extreme vibes per flight on my 700 and 800.

- another possibility is that there were a certain run of mini V blues that had the case to board fit a bit off. Board wasn't tight to the case and wiggled a bit. In flight causing small issues naturally. Check to see if board moves inside the case (typically with nothing plugged in) , some dabs of silicone (not sure if silicone is 100% ok - will need to find a thread discussing it) out servo tape to fasten board down.

- I'm assuming the leads aren't fastened to close to the mini v as not to induce errors due to there mass and strapping.

Worth noting that the XX series of heads has a bit unique damper setup that will use a lower gain than a typical head. Credits to dave dahl on the head info.



Hope this helps some

Martin

[snafu9241]

My plate is glued and have the newest blue mini v. I do have a silver line I can try though. I have read that some people are running one hard shore on the outside of the 3 O rings. I have tried a Bavarian Demon and had the same problem. It is on hard stops like tic tocs. I have checked all linkages to make sure they are all the same length.

[rcmarty]

No experience with the 90 shore dampers.

On my 770 build I put them in but haven't flown heli yet.

IMO it seems like the blades are cavitating right at the stopping point. Stock edge 713 I assume.
Also assuming at a cavitated state there not producing any lift and the machine is free to wiggle. Once they start to bite again the vbar makes the correction (as seen as a wobble) and gets back on track.

I mentioned the phasing in the last post and the guy that found it put some extra washers under the mixing arms - to the headblock to change the phasing. Said it was better.

Not sure on what theory to go with. If phasing is off (id have to say unlikely for Mikado) then shim it out , or if the blades cavitate then a different blade could be the solution.

I have edge blades on my 700 and 800 , the 770 is sporting sab blackline 770 3d blades. When I get it up in the air and tuned a bit i'll have to see if the bobble is still there.

Hard to believe what kyle can do to a 700 and not have a bobble. Could be because it happens so fast or he just that good that he auto corrects without even knowing it.

Let me know if you find a solution. Would be interested to see what it would be.
You've subbed in a demond so the vbar is good.

Martin

[Alignment]

Been having the same issue with mine and havent figured it out yet.

[snafu9241]

Replaced with shore 90 dampers and a new set of cyclone 715's. Just flying or hovering in the front yard it does seem better.