Head Wobbles on Hard Collective Stops

[mahbouni]

I still haven't solved my problem. I did use a Trueblood swash leveler to level the swash plate at full +ve and -ve endpoints. I couldn;t really notice any difference and the disc still tilts to the right during elevator tictocs, on the -ve pitch pump. One of my friends, a Synergy team plot, said that the tail is slightly out on half elevator flips, suggesting a phasing error. As I already said, the gyro plate is only 0.1 degree out from the head block and motor. I used an RcLogger digital pitch gauge to check. The Vbar sensor is mounted square. If I put a metal ruler against its side, the ruler runs parallel to the boom.

My friend suggested that possibly the Vbar sensor is not square inside its casing. He suggested I try adjusting the phasing with the control panel. I tried +3 degrees but couldn't tell if it was better or not. I wanted to try -3 degrees to see if it was worse but when I went into the Control Panel setting, it was back to zero again . I tried inputting +3 again, confirming and entering again. Each time I did this it read zero again . At first I thought its not accepting my input but when I realized it was actually affecting the swash movement. What's really happening is the Control Panel does not show you what changes you've made . I hope I can reset this with the PC software . Thinking about it I think adjusting the phasing is only meant to solve mechanical phasing errors and not problems with the sensor.

I have borrowed a Silverline sensor from a friend and I hope this fixes because I don't know what else to try. The competition season is going to start soon and I wanted to use this heli but I might have to stick to my 600

[futurase]

Does the L700 piro perfectly flat?

[mahbouni]

Yes. It's only on elevator flips and tictocs that we see the problem

[mahbouni]

I managed to reset the swash rotation in the PC software. I haven't fitted the new sensor yet. While examining the head just now I noticed it does not have zero delta. The ball joints on the blade grip arms are not in line with the Jesus bolt. They are a little bit further out as if the standoff is too short. I thought delta offset is only for flybars. Is this supposed to be as such on the L700? Perhaps I built the head wrong. Maybe my blade grips are too far out? Can someone please confirm?

[futurase]

No you built it right. It has been a big discussion. It is there on all L700 and L800's. You can shim balls out with washers it etc but flys the same.

It is there on all XX series.

[mahbouni]

Thanks for confirming. I'm just wondering if weak tail authority would cause what I'm seeing. I can't notice it kick out on pitch pumps though. If its not that and not the sensor then I don't know, give up. Protos 700 is coming this year

[stocksy27]

Got the same on my l700 only during elevator tic tocs is pretty cold here so could be hard dampeners im going to try different head gains see if that solves it .

[mahbouni]

Does your disc tip to the right on the -ve side of the elevator tic toc? Are you going to Charmouth this month? i'll be there. Would be good to compare. I'm hoping some of the other guys there might be able to help me.

[stocksy27]

Cant remember if it tips to the right ill check over the weekend think mine was more a wobble but didn't pay much attention, not sure about charmouth its a bit of a trek 400 round trip mile trip :-(

[mahbouni]

OK well mine isn't actually a wobble so the title of this thread is wrong. It actually rolls right during the -ve part of a rainbow and not at the stops. Where about are you located? I'm in SW London bordering Surrey.

[stocksy27]

So its leaning right when in negative pitch as if your added right aileron? Im in Grimsby 198mile to SW London often there working but never room in van for the heli :-(

[mahbouni]

Yes but I think it's more a case of leaning right when I put forward elevator in because it doesn't do it on -ve climbs from a level inverted hover. I think it's just more noticeable on the -ve of a tictoc because I was cueing off from inverted.

Anyway keep us posted about your issue. It may or not be the same as mine.

[Mentalic]

Originally Posted by mahbouni

Yes but I think it's more a case of leaning right when I put forward elevator in because it doesn't do it on -ve climbs from a level inverted hover. I think it's just more noticeable on the -ve of a tictoc because I was cueing off from inverted.

Anyway keep us posted about your issue. It may or not be the same as mine.

You might want to check to see that your tail box/tail disk is perfectly strait with the main shaft. If its off a little you can get odd affects.

[mahbouni]

The tail shaft is inline with the main gear. I think that's what you meant.

I tried it with my friend's Silverline sensor but it made no difference. I also tried bank switching again, with head gains of 60, 80 and 100. It actually was worse with 60, slightly better with 80 and best with 100. Just rocking the elevator back and forward, you can see the disc bank to the right on forward rotation phase and come back level on the backward rotation. It's very pronounced. Several people have witnessed the same. Even my friend who is a Synergy team pilot had a go and it was the same, so not just me. I can't think what else to try.

[dahld]

Quote, "...just rocking the elevator back and forward, you can see the disc bank to the right..."

Since we're grasping at straws here, and since the elevator input uses all three servos to control the swash plate, maybe one of your roll servos is bad or weak, and can't keep-up with the other roll servo?

Sorry if the idea sounds lame, but after 35 years of playing with helis, I've been where you're at before (I hate it too)...and you start looking for really strange stuff out of desperation.

(-: Dave

[mahbouni]

At this stage any thing is better than nothing. My cyclic servos are Futaba BLS 255HV's running @ 8V off a Kosmik 200. Less than 50 flights on them. I had tested them previously on a Logo 600SE without issue but that is a much lighter machine. I would have thought they would be powerful enough for the Logo 700 so perhaps one of them is weaker. If it banks to the right on a forward elevator flip then that would suggest the left hand aileron servo moves less or slower that the right hand one. Does that make sense? Perhaps If I swap it with the elevator servo and see if it makes a difference to elevator flips?

[Mentalic]

Originally Posted by mahbouni

The tail shaft is inline with the main gear. I think that's what you meant.

I tried it with my friend's Silverline sensor but it made no difference. I also tried bank switching again, with head gains of 60, 80 and 100. It actually was worse with 60, slightly better with 80 and best with 100. Just rocking the elevator back and forward, you can see the disc bank to the right on forward rotation phase and come back level on the backward rotation. It's very pronounced. Several people have witnessed the same. Even my friend who is a Synergy team pilot had a go and it was the same, so not just me. I can't think what else to try.

Reason I mention the tail because I've had it happen, and it acted exactly as you describe. I figured it was close enough a little turned clockwise, no it needs to be perfect. I used a level to get it spot on, problem solved. Never noticed smaller machines being picky on the tail box but yea this one is.

Dave's idea of servos causing it is a good one. About the only other thing I can think of is you have some kind of mix active in the radio. May want to redo the setup.

[mahbouni]

The tail shaft is absolutely in line with the main gear so I believe it is good.

I just finished going over my setup yet again. There are no mixes. If I move the ailerons, only the aileron servos move. The elevator servo stays where it is. I put my finger on top of the elevator ball link and I can feel if it moves.

I'm now thinking that IF one of the aileron servos is weak then if I swap them round, it will roll to the left instead of right. If it doesn't make any difference then the servos are equal. Does that sound like a good test?

[rcmarty]

(been folwing this thread in the background as there's little action on the 7/800 forums)

My thought last night was to swap them side to side to see if there's a difference. Would take the servo's out of the mix.

Some other thoughts and thinking out loud...

Where is yuor sensor located. I have mine on the top plate and where it keys into the tab slots it's a bit loose.
It could be possible that the plate is moving a bit and causing an error to the helicopter. That sensor is small and the plate is larger so that could tally up to a few degrees roll.

Sensor may not be 100% true to the centerline. I used a piece of lego to the frame to place mine. But in reality that grey sensor is small and the smaller the harder to get bang on. I'll add IMO

transmitter.

Possible calibration issue ?
Or adding a bit of ail when moving stick ? I'm bad for adding rudder to my quick pitch shots.
I did tighten up the spring on just the rudder , helped alot, now i can feel the tension when tossing about with pitch, helps me to learn not to. (work in progress).
So you could try tighening up the spring on the ail and going for another test. Or possibly have someone video your servo monitor screen when doing tocs to see if there's any ail being sent out.


Hope you figure it out , hopefully my random thoughts might help.

I'm still low on the ladder for learning tic tocs , gettting there. So random thoughts based on how system works .

Martin

[rcmarty]

one more thought.

Where is your sensor ? off center on back plate ?

My canopy does clear the sensor by 3/16" but in a fast toc i'm sure the canopy does some moving about.

Possible the canopy is banging the sensor.

Of course this might be a more random.


martin