How-To: Easy setup for perfect (bail-out) self-level

[jamesg53]

Just curious Does the trim affect inverted self level ? Just fitted sk720 to my 450 and I'll set up the normal self level tonight. Currently when I switch self level on it drifts left and back.

[soko]

Hhmm...

Good question. I'm not able to fly stable inverted yet so I haven't given it a thought.

But I think you should NOT use inverted SL, just the normal one.
I think the trim you do to get a stable normal-SL-hover will counteract in inverted mode => make it worse!!

Here's a how-to to find out:
- have SL+Inverted active in your SL-bank but haven't done SL-trim yet
- bring your heli in normal-hover with no SL active
- switch to selflevel
- the heli drifts in one direction
- now you can hold your right Tx stick (mode 2 Tx) in one direction to correct that drift (thats is essentially what the trim does). lets for instance that your heli drifts to the front-left, so you have to hold your stick to the lower-right.
- switch back to normal-mode (no SL)
- now bring you heli in inverted-hover
- switch to selflevel
- the heli drifts in one direction
- now you can counteract this drift with a Tx-stick-movement to bring the heli back into hover.

if you have to move your stick to the same direction as for normal-hover (lower-right in our example) it is safe to use this how-to trim-method with SL+inverted active.
otherwise you must use normal-SL (no invertion)

let me know! I'm curious

Soko

[georgi UK]

=] feeling a bit lost here as to what is being discussed?

a trimmed SL upright hovering heli will equally hover inverted at 180 degrees to that using inverted SL, no differences.....

[soko]

Geori!
That's exactly what I/we needed to know.

In conclusion: If you SL trim your heli according this how-to in normal hover and than use the inverted-SL function everythings works OK. The heli doesn't start to drift realy bad in one direction (as if the trims will add to the drift instead of counteract to it).

Great
Soko

[neavissa]

Originally Posted by soko

AND (of course) make sure the SK720 is mounted in level (all 3 axis) with the heli as stated in the SK720 manual.

This is the point where I am about to loose my mind! What exactly is "level with the heli" I see how it is done in the manual but it does not work on my heli like that! I have a Protos 500 and mount it under the main shaft. Unfortunately that part of the frame, right under the main shaft, is not level to the rest of the heli?! Funny enough, in all Skookum videos, the use the same heli and have it mounted at the same spot I do?! That being said, their SK cannot be level with the rest of the Heli either?! I don't get it?! Please take a look at my pictures, or even better, at my thread...

thanks,

G

http://helifreak.com/showthread.php?t=451957&page=5

[dpelletier]

Level to the heli means level to the main shaft.

[neavissa]

Originally Posted by dpelletier

Level to the heli means level to the main shaft.

OK. Thanks for the fast reply...

G

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[Thunder Fighter]

If you have a plastic frame 500 Protos and you want to mount there you need to make up a wedge to go under the Skookum. I used 2 peices of plaster scraper from the hardware store, cost about $5 and 1/2 hour. You just need to grab a couple of ones with different angles and work out where to cut them. Then just use thin double sided tape to keep the layers together. I still have this setup on my night flyer Protos.

If you have the carbon frame there is an upgrade lower tray available that has a 90 degree setup ready to go.

//Dennis.

[soko]

Hi,

I'm not quite sure (please Georgi or others correct me!) but I don't think the SK720 needs to be level with the main shaft.
All it needs is a calibration with the main-shaft in level. So you tell the SK720 that this "out-of-level" position should be its new 0,0,0.

After that the heli SL should work great.

Soko

[neavissa]

Originally Posted by Thunder Fighter

If you have a plastic frame 500 Protos and you want to mount there you need to make up a wedge to go under the Skookum. I used 2 peices of plaster scraper from the hardware store, cost about $5 and 1/2 hour. You just need to grab a couple of ones with different angles and work out where to cut them. Then just use thin double sided tape to keep the layers together. I still have this setup on my night flyer Protos.

If you have the carbon frame there is an upgrade lower tray available that has a 90 degree setup ready to go.

//Dennis.

I thought about building something as well. However, I have the carbon version, so I might as well get the tray...Thanks for the great info!

G

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[neavissa]

Originally Posted by soko

Hi,

I'm not quite sure (please Georgi or others correct me!) but I don't think the SK720 needs to be level with the main shaft.
All it needs is a calibration with the main-shaft in level. So you tell the SK720 that this "out-of-level" position should be its new 0,0,0.

After that the heli SL should work great.

Soko

That's exactly what I thought should be possible... that's what I thought the reset-level function was for... anyhow, I might drop Art an email as well as see what he says...

Thanks,

G

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[dpelletier]

Originally Posted by soko

Hi,

I'm not quite sure (please Georgi or others correct me!) but I don't think the SK720 needs to be level with the main shaft.
All it needs is a calibration with the main-shaft in level. So you tell the SK720 that this "out-of-level" position should be its new 0,0,0.

After that the heli SL should work great.

Soko

I don't think so... imagine the helicopter hanging suspended by the head, which is what is happening when hovering. (assuming CG is correct)

If you level the SK off of that axis, the SK will think that the helicopter is not level when hovering.

[neavissa]

I mean, think about it. They sell the SK calibrated or level or whatever you wanna call it. Most spots the SK is being mounted on, are in a 90° angle to the main shaft, thus when hovering, the heli is in a somewhat level position. Right?! Why shouldn't you be able to tell the sk720 hey, this is the new level?! Isn't that the reason why I have to wait a few seconds after plugging the battery into my nano cpx?! So it can initialize AND know what level is... at least that's what I thought this whole time...ha ha.

G


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[dpelletier]

Originally Posted by neavissa

Isn't that the reason why I have to wait a few seconds after plugging the battery into my nano cpx?! So it can initialize AND know what level is... at least that's what I thought this whole time...ha ha.

Nope... while sitting on the deck the heli is not necessarily level.
Like my Beam E4, it has a forward lean.
In fact, I remember instructions on a particular FBL unit that said, if the heli is not still during the initialization process due to wind, lay the helicopter on its side for the initialization.

[soko]

Yeah,

I think during the init of all helis (mcpx as well) its just about not moving it. it has nothing to do with "what is level".

Originally Posted by dpelletier

If you level the SK off of that axis, the SK will think that the helicopter is not level when hovering.

Thats why I said you have to calibrate "level" on the SK720 when the main-shaft is in level AND it does not matter in which relation/angle the SK720 is relation to the main shaft. i.e: if your SK720 is mounted leaning forward due to a tilted mounting platform you have to recalibrate the SK720 when the main-shaft is in level (SK720 not in level).
Then everything should be fine

Soko

[neavissa]

Originally Posted by dpelletier

Nope... while sitting on the deck the heli is not necessarily level.
Like my Beam E4, it has a forward lean.
In fact, I remember instructions on a particular FBL unit that said, if the heli is not still during the initialization process due to wind, lay the helicopter on its side for the initialization.

LOL, I actually just tested it with my nano cpx... I really tilted it forward and then plugged the battery in... Guess what?! Nothing! No problem at all, the heli flew normal!

Thanks,
G

[neavissa]

Originally Posted by soko

Yeah,

I think during the init of all helis (mcpx as well) its just about not moving it. it has nothing to do with "what is level".


Thats why I said you have to calibrate "level" on the SK720 when the main-shaft is in level AND it does not matter in which relation/angle the SK720 is relation to the main shaft. i.e: if your SK720 is mounted leaning forward due to a tilted mounting platform you have to recalibrate the SK720 when the main-shaft is in level (SK720 not in level).
Then everything should be fine

Soko

This is the point where it sucks, English not being your native language! (talking about me! ) What is it now?! I didn't get that?! Are you saying that if, lets say the main shaft is leaning 5 deg forward and my SK is leaning 3 deg backwards, that all I have to worry about is tilting the heli back, till the main shaft is level, 90 deg to the ground, 0 deg or how ever you wanna put it, then re-level the SK?! sorry for being such a bonehead but I am not getting it!

thanks,

G

[georgi UK]

Originally Posted by soko

Hi,

I'm not quite sure (please Georgi or others correct me!) but I don't think the SK720 needs to be level with the main shaft.
All it needs is a calibration with the main-shaft in level. So you tell the SK720 that this "out-of-level" position should be its new 0,0,0.

After that the heli SL should work great.

Soko

=] Soko, the problem here is, the SK lower case is it's datum, the main gyro's are calibrated to this, as are the accelerometers,

the unit must be mounted perpendicular to the mast, and re-calibrated off the model on a level surface, we must keep the main gyro's and accelerometers in sync with each other, no exceptions here!

[soko]

Thanks Georgi

Everybody: forget what Ive said its "wrong" when it comes to the whole SK720 setup. As georgi said: the level of the main sensors must be "the same" (at least just fractions of degree) level as the accelerometers. at SL recal you just acc-levels my theory wont work in practice.

In other words: the SL would work but the would fly like crap, or even not at all, in normal mode.

Soko

PS: yeah sorry bout that: english isnt my first language. im still not getting how you english guys differentiate between relative angle/level and absolute/spirit angle/level

[georgi UK]

Originally Posted by soko

im still not getting how you english guys differentiate between relative angle/level and absolute/spirit angle/level

=] I like it!