New Flybarless System

[hamslice]

anyone know for sure what is causing the sudden jerks to the ail or elev. i have it flying pretty good but at 1950 through 2050 on the head i get these jerks like the heli lunges back or to the right. i have tried three diff kinds of mounting foam and have the heli flying with absolutely very min vibes. i have it mounted on the back tray of my 600. i thought it might be getting interference from the bottom bearing on the torque tube but it is 2 inches away from that. i am lost. when i kick the headspeed up to 2150 i dont get the jerks. any ideas are welcome.

thanks,

heath

[Skookum]

Huh. Sounds like resonance of some kind to me. Something on the heli doesn't like 2000rpm, I'd bet it resonates in the roll axis, and the resonance probably transmits to the gyro. If you've tried different mounting tape that would seem the rule out the gyro itself resonating, because its own freq of resonance would be changed by that. You might also try upping the filter setting on the advanced tab.

[hamslice]

i will try that. the new gyro you guys sent me does the same thing so i think we can assume that the first one was not faulty. thanks for the good customer service.

[Skookum]

Looking at the photos, the frame-tab the SK360 and receiver are mounted on looks like its just plastic. Total wild-ass guess, but maybe 2000rpm hits its resonant freq with their mass out there. You could test the idea by just by moving the receiver in a half inch.

Does the jerking happen at any particular time? If it happens during fast collective changes or hard climbout, if the headspeed is low you might be running out of cyclic pitch, or even stalling the blades on one side.

[LITHIUMSTATIC]

Has this been tested on a Logo 6003D? I'm thinking about taking the plunge.

[int2str]

Alright, I'm ready for my maiden flight with the SK360 tomorrow!

Did a quick night-time hover in front of the house. It hovers, but it's wagging (shaking?) just like the tail shakes when the gain is too high. So I'll turn down the gain dials (which one?) tomorrow morning and will try to set it up at the field.

For all the T-Rex 450 owners out there, I've attached pictures on how I converted my head.

Of note is the fact that I used a "jesus bolt" and two additional nuts to move the upper mixing arm ball closer to the main shaft. This get's me exact phasing.

What I don't like is the washout block. Essentially it is now possible that the mixing arm and the part that attaches to the swash can "fold in" towards the swash on full negative pitch and then pop off when you give full positive pitch.

I'm still going to try to fabricate a custom phase-lock bracket and get rid of the washout base down the road.

Wish me luck for tomorrow :)

[SpeedVision]

For all the T-Rex 450 owners out there, I've attached pictures on how I converted my head.


Can you post another picture similar to #1, but with the head rotated 90 degrees. I'd like yo see how you did your reduction arms...

I've posted pictures of my Mini Titan and my setup doesn't seem to allow for enough servo travel because I can only get Hillier gain to 40 on the gyro pot before oscillation starts.

I've lowered my swash menu % from 65 to 50 and increased servo travel to get to the suggested SK360 pitch and cyclic...

Hopefully I'll be able to test today.

[int2str]

Not my picture, but my upper mixing arm setup is exactly like this:

http://digitalflybar.com/img/photos/trex450_head2.jpg

[Finless]

anyone know for sure what is causing the sudden jerks to the ail or elev. i have it flying pretty good but at 1950 through 2050 on the head i get these jerks like the heli lunges back or to the right. i have tried three diff kinds of mounting foam and have the heli flying with absolutely very min vibes. i have it mounted on the back tray of my 600. i thought it might be getting interference from the bottom bearing on the torque tube but it is 2 inches away from that. i am lost. when i kick the headspeed up to 2150 i dont get the jerks. any ideas are welcome.

thanks,

heath

Sounds like noise effecting the unit. When Kevin and I were testing it on the 500 we had the unit mounted on the top of the boom block and had it too close to the belt drive bearings. At certain RPM's it would jerk forward cyclic randomly. We had to move the unit back farther away from those bearings and that solved it.
I see yours is mounted on the mid tray. I would make sure NONE of the wires between the RX and SK360 are anywhere near the belt drive bearings. You might even swap the RX and the SK360 and put it on the bottom plate as a test. Bottom line I think you getting noise effecting it as your symptom is just what we were seeing.

Bob

[Ludde]

well tested again today and it still wana flip over to the right at takeoff, then if u yank it giving lots of left stick it will settle and then takeoff, the tendacy to tilt right when doing hard pitch increases with increased Hiller, was realy scary as it whent almost sideways after five meter max pitch climb....

also slowly drift to the right, trimed it out but still wanted to tilt right with hard pitch...

[SpeedVision]

well tested again today and it still wana flip over to the right at takeoff

Queston, how level is your takeoff spot?

My driveway has a bit of a slope to the street and I tried to takeoff left side facing the street ("down hill") and my heli tipped on it's left side.

No setting problems as it flew fine minutes before...

Normally I take off nose to the street and I did notice a tendency for the heli stand on it's vertical tail fin during take off's. Hmmmm

EDIT!!!! Increasing my head speed during spool didn't help...

[Skookum]

Hi Ludde,

"Going almost sideways" at hard pitch really sounds like it's running out of cyclic pitch. I've only seen that sort of behavior if I set a really low head speed, or not enough cyclic pitch. That may also be why it's connected to Hiller gain - more hiller uses up the cyclic pitch faster. Try setting it up for +-10 degrees of cyclic pitch range.

Consistent take off tilting may have something to do with your heli being a nitro. Is the gyro mounted near a heat source? If it inits at a low temperature and is then heated it will try to adjust, but if the warming happened quickly the adjustment won't be perfect.

[Skookum]

Hi int2str,

>It hovers, but it's wagging (shaking?) just like the tail shakes when the gain is too high. So I'll turn down the gain dials (which one?)...

If it oscillates in hover, turn down the Hiller gain. The bell gain is used to remove oscillations at the start and stop of fast cyclic stick changes.

[int2str]

I put up a more detailed post with my current findings here:
http://helifreak.com/showthread.php?t=71960

[hamslice]

Looking at the photos, the frame-tab the SK360 and receiver are mounted on looks like its just plastic. Total wild-ass guess, but maybe 2000rpm hits its resonant freq with their mass out there. You could test the idea by just by moving the receiver in a half inch.

Does the jerking happen at any particular time? If it happens during fast collective changes or hard climbout, if the headspeed is low you might be running out of cyclic pitch, or even stalling the blades on one side.


i moved it in more and stiffened the mounting plate up and i still will do it. i found that reducing the hiller the kick will go away. i have like almost 14 deg of cyclic available and it is 15, 15 on the collective so i wouldn't think i would be running out of pitch. i only have the hiller in the teens now and i would like to add more in but the heli will kick if i do. the kick will happen whenever it feels like it, but during just hovering mainly.

[hamslice]

Sounds like noise effecting the unit. When Kevin and I were testing it on the 500 we had the unit mounted on the top of the boom block and had it too close to the belt drive bearings. At certain RPM's it would jerk forward cyclic randomly. We had to move the unit back farther away from those bearings and that solved it.
I see yours is mounted on the mid tray. I would make sure NONE of the wires between the RX and SK360 are anywhere near the belt drive bearings. You might even swap the RX and the SK360 and put it on the bottom plate as a test. Bottom line I think you getting noise effecting it as your symptom is just what we were seeing.

Bob


bob,

i added a copper plate (that is grounded to everything) above the gyro it essentially covers everything to block the noise. it made no difference. i have the wires isolated also.

[Ludde]

Queston, how level is your takeoff spot?

EDIT!!!! Increasing my head speed during spool up seemed to help! I had a linear throttle curve vs. norm 0-35-65-85-100...

tried several spots and no difference, just rememberd im gona increase head speed also, just to check.. test will be this weekend..

[SpeedVision]

tried several spots and no difference, just rememberd im gona increase head speed also, just to check.. test will be this weekend..

Hello Ludde:

Sorry, I meant to edit my post and say that IT DIDN'T HELP. I have now corrected my previous post.

I can no longer takeoff, regardless of headspeed, without MAJOR cyclic adjusment, which isn't right. My current unit was affected by the cold test failure issue, so I am awaiting a replacement that has been flight tested. If the problem persists, then it might be setup related, not gyro related. Stay tuned.

Tipping tendency has started to become somewhat if a trend and Skookum is working to address it...

Take a look at the last few posts in this related thread: http://helifreak.com/showthread.php?t=71960

[Skookum]

Hamslice> have like almost 14 deg of cyclic available...

The actual pitch from the Hiller gain is gain x pitch range, so if you have 14 degrees of cyclic pitch, I'd expect the max hiller gain on a working-well machine would be around 30%.

It sounds like you've eliminated vibration/electrical as the kicking issue. Yours is the first hurricane conversion I've read about so I'm starting to think this is a mechanical setup issue, that the servos are constantly fighting to control the swash, and sometimes just lose the fight. It may help to try firmer teeter damping. Are you using leading or trailing grips?

Re: tipping at takeoff in general, tipping at takeoff is sort of the generic symptom for flybarless conversions. If something isn't right, it will show up at take off. So there is not one cause out there, there are maybe 10. Possible causes for tipping:

* reversed/rotated mounting settings
* reversed swash mixing
* reversed cyclic input + reversed mounting setting (swash still moves right, but compensation doesn't)
* Spektrum failed to bind before the gyro initialized
* leaned on the cyclic stick during initialization
* applied cyclic before heli was light on the skids
* unstable mechanics, servos cannot control swash
* servos don't hold well enough to control swash directly
* teeter damping is too soft
* heavy vibration, particularly high frequency vibs
* resonance at a certain frequency (still investigating this one)
* faulty gyro (shouldn't be any more out there, and it would fail a preflight check for swash-fights-tilt)

If the heli kicks in cyclic 30 degrees its much worse than if the tail kicks 30 degrees or spins around. So if it does anything weirder than tipping 5-10 degrees at take off, please shut er down, check it over, and/or ask for help.

[hamslice]

skookum,

i am flying the trex600 with the rotorworkz hfx frame. radix 600mm blades. i have the hardest k&b dampeners in the head. i am running 8717's at 6volts. my hiller is 13 for the elev and 10 for the ail. my swash settings are at 55% and servo travel is at 110%. maybe i need to add in more servo travel. oh and i have the bell gain at 40 for both


let me know if that sounds right or not.

heath

[Skookum]

Hamslice:

Ok, somehow I had the idea yours was a Hurricane 550.

That all sounds good, except that 14 degrees is a lot of cyclic pitch range, you must be using direct control? Those are serious servos, so with low slop it should be ok anyways, but I could be wrong. I'd consider trying reducer arms.

As it is, because the gyro compensation is gain x pitch range, 40% bell and 13 hiller for your heli is equivalent to 70% Bell and 23% Hiller for an +-8 degree range. So the bell is way too high, that would be twitchy. For +-14 deg cyclic pitch, closer to 25% bell, 30 hiller is closer to normal. So your still low in hiller. I'll do some testing here and see if I can come up with some ideas.

[hamslice]

i am using reducer arms. i just rechecked the cyclic range and it is more like 11 to 12 deg. i think i was a little excited when i typed 14. anyways the heli is not twitchy at all. it is actually way slower than when i had a flybar on it.

[Skookum]

There is so much variation of helis and mechanical setups going on, I may not be able to solve every problem based just on what I know from local testing. The best I can do is eliminate firmware and hardware issues, and offer what's been learned here to date.

There are at least 3 smaller manufacturers working on flybarless helis and conversion parts, I think the situation will improve quite a bit when those come out. As it is, unless you follow a well-worn path every conversion is an experiment.

[hamslice]

i understand i have a feeling it will work. i just want it to work now :OK

[Skookum]

Ya. The day before we had a beam working fairly well in about 30 minutes. But then I was humbled yesterday by a lowly blade 400, even with direct access to data logs I couldn't get it working. No problem with that gyro either, I could see directly what was happening with each command cycle. It did it all: tipped at takeoff, couldn't get the hiller high enough, wandered & kicked. Seemed that its head + blades just wasn't suitable. One guy has one working though - but with a conversion using trex head parts and blades. There are a lot of variables.