vibe 90 and dx7 swash leveling problem

[whittm]

About 8-9 degrees for aileron and about only 6 degrees for elevator. I tried adjusting the throws for these in the travel adjust screen but it didn't adjust sufficiently. ..I then realised the battery on the receiver was running out before I could go any further.

So, am I correct in adjusting the travel to get sufficient angle for the cyclic movements? I did notice that when I adjusted the elevator throw, that only the elevator servo moved. ..This made me think I was barking up the wrong tree. ...

[whittm]

I am thinking it has more to do with swash setup?

[whittm]

About 8-9 degrees for aileron and about only 6 degrees for elevator. I tried adjusting the throws for these in the travel adjust screen but it didn't adjust sufficiently. ..I then realised the battery on the receiver was running out before I could go any further.

So, am I correct in adjusting the travel to get sufficient angle for the cyclic movements? I did notice that when I adjusted the elevator throw, that only the elevator servo moved. ..This made me think I was barking up the wrong tree. ...

[trillian]

You need to be adjusting the cyclic throws in the Swash Mix screen. The servo travel adjusts are used when levelling the swash at the top and bottom, generally they will all be pretty much the same but sometimes one servo will move a little more or less than the others.

(I am assuming here that yours is using a 120 degree CCPM setup, if not then you won't have a swash mix screen)

[whittm]

Yes it is 120 ccpm and there is a swash mix screen. I used it to reverse setup the servos in the correct direction.

I haven't seen cyclic setup yet. ..must be an extra set of controls in that screen lower down. Just popped out. ..really want to get back and check now. ..Thanks!

[whittm]

Just re-read what you said. ..I see what you mean, r.e. travel, my servos are all travelling at the same speed and so the swash is level top and bottom.

[waveydavey]

What Sheryl is saying is that in your swash mix setup for the relevant control surface you adjust that particular percentage, so if you want more than 6 degrees elevator then you increase the swash mix value for ele and so on. Don't adjust your end points to do this, use them to level your swash at top and bottom stick although this isn't normally necessary if you're head is a good design and the mechanical geometry is good.

[whittm]

Yes my setup looks pretty good, I can't perceive any difference top and bottom. ..I Could check with the pitch gauge top and bottom...

I'll try adjusting the cyclic when I get back.

[trillian]

Yes my setup looks pretty good, I can't perceive any difference top and bottom. ..I Could check with the pitch gauge top and bottom...

I'll try adjusting the cyclic when I get back.

I always use a swash levelling tool and visually see that the swash is level.

I have one of these as it fits several different main shaft sizes:

With a flybarred rotorhead it's more difficult trying to check the level of the swash using blade pitch because you must first lock the flybar in place although I guess it can be done that way. With the leveling tool you can see even the slightest variation, without it I know I could not be nearly as accurate.

(just to add - even if the swash is not perfectly level it's not the end of the world :-) but the trim will be out and the heli will drift and not do exactly what you want, so the more accurate the better)

[whittm]

I used a swash leveling tool to get it smack on right after 90'ing the servo arms.
As I had moved the swash links to centre the swash, I needed to re-level the swash. ..I thought it would be bang on, but as I was checking the pitch, I thought I'd check the pitch all the way around.
I found the swash was two degrees out at one point. I was checking it with the fly bar locked.
I adjusted the sub trim to get it back within 0.3 degrees at all points around the swash.
The blades are also within 0 1 degrees of each other.

I'm now a little concerned. ..

In order to get the direction of the swash moving in unison, I did exactly as he said in the video I linked.
In the swash mix screen, I changed the tabs as follows, in order to get the swash moving as it should:
Aileron: -55%
Elevator: -55%
Pitch: +55%

How will this affect setting up 12 degrees for pitch and also the elevator and aileron to the correct parameters?

Was it ok to play with the swash mixing settings to get the servo directions to work correctly. ..that's the crux question I suppose.

[trillian]

Yeah with the swash mix it's the plus or minus settings that determine if the three servos are moving in the right direction. The number values can change as needed and they don't all have to be the same, so you may need more collective, and / or more elevator etc.

[whittm]

Thanks. As I was playing with that earlier, the pitch difference was increasing, but, unequally, the pitch was different high stick and low stick.

How do I get the pitches equal high stick and low stick, after altering the amount of change in pitch?

[trillian]

Thanks. As I was playing with that earlier, the pitch difference was increasing, but, unequally, the pitch was different high stick and low stick.

How do I get the pitches equal high stick and low stick, after altering the amount of change in pitch?

It's a matter of having everything really centred at mid-stick. I'm not familiar with the Airskipper but generally you have the servo wheels / arms and various linkage and try to get everything at 90 degrees, the bottom line being that the geometry is the same in both directions. If the swash is already level and stays level at top and bottom stick then at least all three servos have the same geometry, so then it's a matter of getting the rotorhead to zero degrees collective at the mid point of the swash travel. And again, it's not a tragedy if you have a bit more collective at the top vs the bottom, you can still 'cheat' and adjust one or the other a little using the pitch curves

[whittm]

So, there's no bomb proof way to get the same pitch at high stick and low stick? :'-(

[trillian]

So, there's no bomb proof way to get the same pitch at high stick and low stick? :'-(

Yes there is but as I am not familiar with the Airskipper I cannot give you specifics. If it was sitting here in front of me I'm sure I could do it (unless there is some kind of unequal geometry in the design on purpose).

Things to look at:
servo travels set the same in both directions
linkage is as level / 90 degrees as possible at mid stick, all the way from servos to mixer arms to the grips.
Mid stick is resulting in 0 degrees pitch.