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A Main Hobbies . Boca Bearings . Modefo's RC Helicopters

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Flybarless Rotor Head Systems > New Flybarless System
 
 
Bruce2.5D
Heliman
Location: Vancouver, Canada

Hi Frittslogic,

As unnatural as it sounds, you should almost never apply wind correction cyclic with the SK360 gyro. The gyro will do it for you. The one exception might be if your Hiller Decay value is set fairly high.

Did the helicopter roll in the direction you had been applying correction?

[later edit: not that familiar with the v-bar, but if it has a something like high hiller-decay as a default, then the behavior would be different]
04-16-2008 09:27 PM
 
 
FrittsLogic
Senior Heliman
Location: Honolulu, Hawaii

I gave it slight forward and slight right during the liftoff. I was consciously trying to keep it small based on the warnings posted on this forum, and only fed it in at the last moment. The wind was causing some disc bobble while on the ground. I never knew about this concern with gyro assisted digital flybars and typically take off with stronger wind corrections on my Vbar birds without issues.

Menehune Rotorworks Inc.
04-16-2008 09:33 PM
HOMEPAGE  
 
 
Bruce2.5D
Heliman
Location: Vancouver, Canada

Hi FrittsLogic,

The slight right you applied may well have been the issue. Before the heli is light on the skids, it cannot physically respond well to cyclic commands.

If Hiller Decay is set to a low value, as it is in the default setup file I assume most people use as a starting point, then any such cyclic command "builds up". Let's say you use just 10% of right cyclic for just 2 seconds before liftoff, and hiller decay were near zero. This will result in about 30 degrees of "frustration", ie the gyro believes it has been told to roll right by 30 degrees, and so it will dutifully do so as soon as it has the chance.

The wobbles you saw on the ground were probably not a problem, possibly just that the gyro had not been tuned up yet. It should lift off in wind hands-off with very little disk tilt before it compensates.

I'm starting to think the low default value of hiller decay makes for take off behavior that is too unnatural for new users, but which myself and local beta testers have simply become used to.

I'd like to recommend that all users start with a Hiller Decay value of 100%, and only lower it after some flight experience. It will make the system a little less locked-in but generally more forgiving.
04-16-2008 09:54 PM
 
 
flying glass
Heliman
Location: Rockford, IL. U.S.

it almost sounds like the phasing issue I was having when setting up. I have a quad head so I am unsure if the same rules on phasing apply.
What you describe is exactly what I saw after spool up, the rotor would dip left and back as I was attempting to lift off.
A few degrees of adjustment and I was fine.
I have flown mine 3 or 4 times now and it is working great. I can even take my hands off of the sticks for a few seconds in a hover.
What I have to get used to is how different the heli responds without a flybar.
I will try to post some video footage this weekend.
04-16-2008 09:57 PM
 
 
fly boy 1
Senior Heliman
Location: Milwaukee,WI

Why would you turn gyros off for lift off vs speeding up the decay so it looks more like rate mode for lift off? It really sounds like a vibration issue.
Eric

Probar Flybarless
Aerospire MultiGov
Thunder Power RC
04-16-2008 10:52 PM
 
 
jyzoom
Senior Heliman
Location: Singapore - jyhelistore

Frittslogic,

Your earlier post said you were testing some theory. May I know and better still see a picture of you mechanic setup you just for the bad maiden flight?

" I flipped my grips, and just for fun I will start with the stock Trex blade grip balls. I'm toying with a little theory that delta will not have as noticeable an effect on flybarless helis, where the gyros should be in firmer control of head response than a mechanical flybar"

EDIT: I see the pic from your Gallery. Just wonder would it make a difference if the grip is extended a bit to have the balls all line up to the center of the main shaft like the way the VBAR heads is on Logo.


Jonathan

MSHELI Protos with Gyrobot - Jazz80,cc bec@6V,9650s,9257,15T, Lipo2600-6S
04-16-2008 11:08 PM
HOMEPAGE  
 
 
Eury
rrProfessor
Location: Ankeny, IA, USA.

Where the balls are in relation to the center of the head wouldn't cause that. It'll throw the phasing off, but that's adjustable in the software.

To be honest, Fritts' issue sounds more like the system drove it into the ground because he bumped the cyclic before takeoff. Not defending the system, it is WRONG that touching the cyclic before takeoff can kill the heli, and the manufacturer NEEDS to address that in a software update. I may end up sending the SK360 that I have on the way back to the manufacturer, if I don't, I'll be waiting until we get to the bottom of the issues everyone seems to be having with this.


Nick Crego
Still wanted by the government, I survive as a soldier of fortune.
04-16-2008 11:18 PM
 
 
jyzoom
Senior Heliman
Location: Singapore - jyhelistore

from experience

From my personal experience with VBAR, CSM, it does make a difference. It make it a lot easier if it was done.

Here is what VBAR stuff said : http://vstabi.de/wiki/index.php?tit..._of_other_helis

Jonathan

MSHELI Protos with Gyrobot - Jazz80,cc bec@6V,9650s,9257,15T, Lipo2600-6S
04-16-2008 11:49 PM
HOMEPAGE  
 
 
Bruce2.5D
Heliman
Location: Vancouver, Canada

>it is WRONG that touching the cyclic before takeoff can kill the heli...

Well...let's just call it a values conflict then :-). If you find you really like maximum rigidity it has to be accepted. As mentioned up thread, the Vbar can behave similarly, although perhaps not as harshly, my guess is due to higher decay.

For most people, it does seem to be too weird. The "software fix" would be to simply increase Hiller Decay, which existing users can do themselves. At a value of 100% (it can go to 200), most of the "heading hold" action will still be there, but it will "forgive" within around 1 second rather than "hold grudges".

The default decay is set to only 25% because, well, I personally like the rigidity when it's that low, and have habits now around the take off behavior that results. Obviously the default is mistaken there :-P

The problems I've seen feedback on so far appear to be, with one exception, setup and mechanical/mounting problems. I admit that as of this posting w/r to MrMel's, I don't yet know what is going on, and if I still don't tomorrow will offer to ship an immediate replacement or give a refund.
04-16-2008 11:51 PM
 
 
Eury
rrProfessor
Location: Ankeny, IA, USA.

I think it's safe to say that the majority of people out there would be used to using the cyclic on takeoff. With that being the case, then setting the defaults so that the habit patterns we've all developed over the years will kill the heli within seconds of liftoff is a version 1.0 mistake. I'd think the goal of the default setup should be to create a relatively conventional feeling heli, and allow the user to crank up the settings as they get used to the differences in handling. It may very well fly better the way it comes setup now, but you need to dumb it down for those of us new to a flybarless setup.


Nick Crego
Still wanted by the government, I survive as a soldier of fortune.
04-17-2008 12:03 AM
 
 
FrittsLogic
Senior Heliman
Location: Honolulu, Hawaii

I will test again once my new parts arrive. I do think this is going to be a great little system. I like the setup procedures, they seem a bit more intuitive than Vbar's. I do agree that these should be set up for boring default settings, like they do with Vbar. As to the question of phasing, the ball location wrt centerline does not determine that. The location of the swash ball wrt to centerline does. The phasing checked out perfect on this heli during setup (as it should with the old washout used as a swash driver locked into synch by the head pins). The blade grip ball location determines whether you have positive/negative/neutral delta. My experiment is to see if the delta effect is reduced when the flybar is replaced by gyros. As I have it currently configured, it should add some stability.

Menehune Rotorworks Inc.
04-17-2008 01:34 AM
HOMEPAGE  
 
 
Clearance
Veteran
Location: Left Coast Canada

I sorta agree with Eury. Having flown for several decades, I couldn't get my head around the "unusual" behaviour of the flybarless system when it was on the bench. It seemed to me as an accident just waiting to happen to my precious Evo 50. That's why I tended to lift off quickly, knowing that I can fly anything as long as it was in the air.

Now that I am becoming more familiar with the SK-360, I am becoming more comfortable with it and have realized that it does do what it is suppose to do, and does it extremely well. And I haven't changed my flying style, perhaps I am just more cautious and attentive

Ken
04-17-2008 03:17 AM
 
 
MrMel
Elite Veteran
Location: Lidingo, Sweden

My issue is solved.


It was a temperature sensitive component in some of the gyros. (we have around 40F here)

they was amazing fast on the support, I tell you.


He has hold all shipments of gyro's now and will fix this asap.

If your in doubt about your own already purchased, I suggest that you contact their support, he has a simple test to show if there is an issue with the gyro regards to temp or not.

Ive been told my will be replaced asap with a new tested one.


- Fredrik
04-17-2008 02:27 PM
 
 
Eury
rrProfessor
Location: Ankeny, IA, USA.

Great to hear. Why don't you post the test here so we can all try it.


Nick Crego
Still wanted by the government, I survive as a soldier of fortune.
04-17-2008 02:51 PM
 
 
JKos
Elite Veteran
Location: City of California in the state of Maryland

MrMel,
> (we have around 40F here)

Do you really mean positive 40 deg F?

Really glad to hear you got it figured out. I plan to maiden mine this weekend in my Logo 14 with the Mikado head.

- John

MSH Protos
04-17-2008 02:54 PM
 
 
Eury
rrProfessor
Location: Ankeny, IA, USA.

Dear God, I hope they don't have -40F in April!


Nick Crego
Still wanted by the government, I survive as a soldier of fortune.
04-17-2008 02:57 PM
 
 
JKos
Elite Veteran
Location: City of California in the state of Maryland

I ask simply because +40F seems a bit high for an electrical componenet to have issues. Since it has been below +40F here the last several mornings, I would just like to know if I need to worry about it.

> Dear God, I hope they don't have -40F in April!

No, they're not; I did just check.

- John

MSH Protos
04-17-2008 03:01 PM
 
 
Eury
rrProfessor
Location: Ankeny, IA, USA.

I agree, +40F is an amazingly high temp for a component to fail at. Certainly wouldn't cut it here, I fly all winter long.


Nick Crego
Still wanted by the government, I survive as a soldier of fortune.
04-17-2008 03:05 PM
 
 
MrMel
Elite Veteran
Location: Lidingo, Sweden

Yup, +40F.

As for posting the test, its files & instruction, so send a PM with email and I can forward it, or email them directly and they can send it to you.
04-17-2008 03:21 PM
 
 
Bruce2.5D
Heliman
Location: Vancouver, Canada

Hi All,

Yes, as MrMel has said a small number of gyros sent out in the first week will sometimes not initialize to a stable zero in cold temperatures. Each gyro is given a burn-in, vibration tested, and run through a test plan that includes down to -10c, some are also even test hovered, but the issue wasn't that easy to detect at first (not a lot of sleep at this end isolating it).

I have modified a version of the setup GUI to detect these gyros as they init, and will email it today to everyone in that batch. If you don't get an email, then don't worry about it. The test may be a bit over-sensitive, but better safe than sorry, and this will avoid the delays of a recall/test/replace process. If the software claims yours has a problem, a replacement will be sent out immediately and compensation given for return postage for the faulty one.

Note: If you're having problems with flybarless take off behavior, or with tuning, this is probably not the issue :-) That's just general tech support, please don't hesitate to contact us directly.
04-17-2008 05:14 PM
 
 
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