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Skookum Robotics Skookum Robotics SK-360 SK-540 & SK-720 Digital Flybar


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Old 12-16-2012, 07:11 PM   #1
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Default Can't get it quite right

My 540 has been good for me so far, however I feel like I can't get it the way I want it. I've learned alot about setting it up, and have gotten a few other machines with an sk540 set up perfectly. I can't get my ENV as good though.
It's always a bit "squirly." I flew a buddy's ENV the other day, with pretty much all the same electronics, except a beastx. Now don't get me wrong, I still think my SK flies better than a beastx, even if mine isn't set up right, however I was shocked how much more stable his was than mine.

I do have FB Mavrikks on it, and he was flying Radix 710s, so I am inclined to think that's the problem.

"Squirley" is the best way I can describe it. I've gotten the tail locked in, however the cyclic just doesn't really feel locked. I've tried changing every setting I can think of, and it just doesn't get where I want it. Does anybody know what I mean, as vague as I have been? It's getting pretty frustrating. It's gotta be the blades....
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Old 12-16-2012, 11:57 PM   #2
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Have you read the latest sticky by one of the sponsored pilots. Can't remember the title but it lists their take on all settings. Read that and see if it takes you anywhere. Hiller decay at 75 is quite stable. Over 100 I think it gets squrilly if that's what you're talking about. Is your cyclic gain too low?

Luck mate and be sure to report any findings.
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Old 12-17-2012, 08:11 AM   #3
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=] fill your boots!! http://www.helifreak.com/showthread.php?t=478561
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Old 12-17-2012, 04:01 PM   #4
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It's tough, you have to look at everything. I have the 720 on white 2mm? foam with the plate inbetween. It's fairly rigid and the wires going to the bus box aren't too long and somewhat supported. So as things get pushed and pulled around it won't pull on the gyro.
Try reverting back to the sport cyclic settings, up the hiller gain by about 5, set the hiller decay to around 85-90, roll and pitch rates to 270 ish? Overall gain 50, acceleration 1 or what ever the lowest is. From there if it seems too slow turn up the acceleration. I notice that the stock numbers in the hiller and bell gain work pretty well but to get the feel I like, I work the hiller decay and acceleration. Also turn down the bell gain in elevator a little if you get the bobble with quick elevator movement.

What is your servo travel set at? 100-125ish? If it's below 100 you should move the ball in a hole.
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Old 12-17-2012, 04:37 PM   #5
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A guys know had a dodgy cyclic feel on his Rave with an SK540. Ended up being the geometry - too much travel on the cyclics. He moved the balls in one hole on the servo arm and it was sorted.
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Old 12-17-2012, 05:50 PM   #6
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Interesting on the geometry. I use round servo horns, i think I punched holes at 12mm. 12-14, somewhere around there. Sounds like it could make a difference.
It's strange though, it's not so much a dodgy cyclic feel, as it is just overall stability. One maneuver I can always make it squirrel on is coming out of a hard vertical drop, then grabbing hard positive. The heli just kinda lurches in a strange matter, always ends up tilted in an angle other than horizntal.

Servo travel I believe is at 125% off the top of my head. I'm not home right now at my computer, later when I get home I could screenshot and see if any keen eye notices anything off.
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Old 12-17-2012, 09:29 PM   #7
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Hard to say, my servo horn ball is in the outermost hole, same for the swash. Did you use a swash leveler, set zero, and check full collective + and -? maybe a little interaction there.
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Old 12-18-2012, 02:22 AM   #8
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To the OP - another thing to check is the swash - the Rave I referred to also had the swash start coming apart - the upper and lower portion split I think. This happened within the first few flights (pretty hard 3D).
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Old 12-18-2012, 09:31 PM   #9
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Swashplate is fine, that was one of my thoughts too. Nice and tight all around with nice smooth bearings. I'll go over my geometry again, It's due for a tear down maintanence pretty soon anyways. Guess I could either no-bar it or turn the hiller decay to 200 to see if the geometry is off. I'm gonna go over it again though.

I'm still leaning towards the FB blades. They have 200+ flights on them, they "could" be wearing out. It kinda feels "mushy" on the collective a little, too. Just not as sharp as it should be. It's probly all related, though. This weekend seems like a good time for a tear down and reset on the head.
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Old 12-19-2012, 08:49 PM   #10
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Here is my setup. Can anybody see anything here in the settings that would cause problems? I've gotten pretty good at setting the 540 up, but i'm still no expert.
Tx is off, bank 2 is the main bank.

Setup with digi pitch gauge, 13.5 collective, 11 cyclic, zero on both blades at midstick.
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Old 12-19-2012, 10:06 PM   #11
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gitbse,
Your cyclic mixing should be higher. If you are getting that much collective and cyclic blade angle at 41% and 32% swash mixing, you need to either decrease swash servo values and increase cyclic mixing or move the ball in a hole on the servo horns and increase cyclic mixing and leave swash travels alone.

It's a trade off. You should be up in the low 60's for cyclic and around 45 or so for collective. Set those numbers into the mixing, and drop the travels until you hit your 13.5 and 11 degrees. I bet you drop to around 100% on the travels.

BUT, if you move the ball in a hole, turn up the mixing, I bet you will stay somewhere right around the 125% servo travel which is good. You need to improve the resolution between the throws and the mixing. Longer smoother throws is the best way I can explain it.

I'm at 63 Elev, 62 Ail, 42 coll, and a little over 125 on the servo travels and 50 on the overall gain. If I go to 60 on the gain, I start to get wobbles. Elevator I think was what initiated it. Around 50 it's great.

Play with the numbers and see. Also look at Alvin Chai's settings on the Skookum website. His are in the low 60's and 45 on collective.
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Old 12-20-2012, 11:09 AM   #12
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Makes sense. I definitely understand the benefits of having more resolution within servo throws. When I was setting it up, I was curious why most posts I read said set mixing around 50-60%, and to keep it underneath 60 if you can. Then I saw how mine was, and at 60% mix I was getting something like 38 degrees collective.
I'll go mechanical first, I'll drop the servo arm radius, and play with the throw values top see if I can get around 50-60% mix.
The ENV uses bellcranks too, so I may be able to play with those a bit to get a bit more.

I'll give it a shot. Thanks. Any other info is appreciated.

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Old 12-21-2012, 12:09 PM   #13
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I noticed something last night while I was going over the heli. The elevator swash link was on the outside hole while the other 2 were on the inner hole. Small error, but I guess it could contribute. I moved it in, and moved all the servo horns in a hole as well. Going to set up this weekend, aiming for the same 13.5 and 11 and see how the numbers and flying change

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Old 12-21-2012, 12:59 PM   #14
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=] herein lies the prob, I would say??!
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Old 12-21-2012, 03:32 PM   #15
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If nothing else that should even things out!
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Old 12-21-2012, 04:50 PM   #16
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Georgi, what's your opinion on the mixing being so low. Could that small a travel resolution be an issue? Reason I ask is because when it was set up like that, servo arms and bellcranks were set up at the same diameter, they rotated on a 1:1 ratio. Moving the balls in one hole screws with the links a little bit.
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Old 12-22-2012, 07:19 PM   #17
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Ok here's a question I'm not sure of. I redid my links, and it provides alot more resolution for given throw rates. However, I'm not sure about what is the best way to adjust control rates within the software.
If you have too much or too little pitch on any given control, is it better to aim for the mixing % to be a certain number and change the servo travel%'s? Or is it better to set the travel % for a certain number and adjust the mixing to get the right blade pitches?

Is there a benefit or negative to doing either one? Or does it not really matter?
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Old 12-22-2012, 10:43 PM   #18
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I set all the servo travels to 125%. Then I checked the max +- collective with the swash leveler. I wound up with one at 138. Must not have set one horn exactly 90 deg or one link is slightly shorter, not sure but I really should go back and re rig it. I know it's really good when I come within 3 or 4 points on each servo travel. But it flies fine. Then I set the collective to +- 12 deg in the mixing window and wound up at 42.

On to cyclic. Adjusted for +-10 deg. Wound up at 63/62.

So to answer your question, I think the servo travel adjust is a finer adjustment where the mixing may be a little larger coarser increment. I guess you could set in 60/60/45 and tweak all the servo travels down until you hit your numbers but you need a little room to play with the mixing numbers. I think at one point I had 115% in for travels but it wasn't enough. So I'm pretty close to using all the travel I have set in for good resolution AT the numbers I have set in for mixing.

Make sense?
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Old 12-23-2012, 09:50 AM   #19
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Quote:
Originally Posted by gitbse View Post
Georgi, what's your opinion on the mixing being so low. Could that small a travel resolution be an issue? Reason I ask is because when it was set up like that, servo arms and bellcranks were set up at the same diameter, they rotated on a 1:1 ratio. Moving the balls in one hole screws with the links a little bit.
=] yes the servo balls will need coming in, forget the 1 to1 servo / bell-crank ratio, I normally drop the default servo travels to 100% using the 60/60 swash mix to find the correct servo ball distance,

then use the servo trims to level the swash at mid-stick, followed by servo travels to level at top & bottom collective, using 100% stick movement.
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Old 12-23-2012, 11:20 AM   #20
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georgi, in the end stick scaling gives the 1:1 stick to servo match anyway correct?
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