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HelicopterFlybarless Rotor Head SystemsAlign 3G › UPDATE 3GX Gremlin Help
11-16-2015 04:53 PM  22 months agoPost 1
Dee Flies 3D

rrApprentice

Farmington Hls, Mich - USA

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For the life of me I can't get this 'bobble' out of this machine... V1 TREX500, non DFC FBL head, Torque Tube tail drive, Futaba FASST radio, controller thru the Rx, 90AMP ESC, DS515M servos on cyclic.
When doing hard collective moves, and getting near '0'deg pitch (MID stick) the body of the heli 'wobbles'. Swirls like it can't hold the '0' center point.. I call it 'toilet-bowling'. Not violent, but does it all the time. Kinda like the controller is 'overshooting' & re-correcting a little around the center '0'??
Tried lowering gains a bit, added more EXPO, & still there. Went thru the whole head & replaced some worn ball links, but no help.
The older 500's did have a swash that was a bit weak, & there is a bit of play in the bearing, but this is a NEW part, less that 10-15 flites on it & no crashes. AND I can feel a bit of gear play in the servos, but again only 1 year old & no crashes.
Need some suggestions on what I might be able to tweak to get rid of this... No other probs with controller.
A bit strange to have Tic-Toks all wobbly just after changing directions..

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11-18-2015 01:15 PM  22 months agoPost 2
dkshema

rrMaster

Cedar Rapids, IA

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This happens after "hard collective moves ." Are you just maybe bleeding off too much head speed with sudden collective changes and this has nothing to do at all with the 3GX?

What motor are you using?

-----
Dave

* Making the World Better -- One Helicopter at a time! *

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11-18-2015 05:27 PM  22 months agoPost 3
Dee Flies 3D

rrApprentice

Farmington Hls, Mich - USA

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Got MX500 motor -1600kv. It's not lugging when doing this, and if I slow down the movement, make it more like a 'rainbow' it's not as noticeable. BUT still there.
I can get a similar event by just doing pitch-pumps, but once again, not as noticeable, but still there.
Seems to be something with the combination of collective AND cyclic..
Even moved the 3GX unit to different location, no noticeable change..
ALSO - the 3GX is ver 5.1.

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11-19-2015 04:19 AM  22 months agoPost 4
dkshema

rrMaster

Cedar Rapids, IA

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You mean V5.0, right?

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Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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11-19-2015 04:22 AM  22 months agoPost 5
dkshema

rrMaster

Cedar Rapids, IA

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I flew the same setup for quite awhile on a 3GX -- same motor, DFC head -- worked just fine. FBL unit mounted up on top of the tail boom mount, behind the main shaft stuff. It got updated to a GPro this summer, same old heli, still flies great.

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Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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11-19-2015 12:00 PM  22 months agoPost 6
jason46

rrVeteran

MI

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Are the servos sloppy? How much free-play can you see at the servo arm, and check for any sloppy ball links.

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11-19-2015 05:04 PM  22 months agoPost 7
Dee Flies 3D

rrApprentice

Farmington Hls, Mich - USA

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Yes- 5.0.. typing fast on number pad..
My unit is also on TBoom mount.
There is a bit of play in the servo gears, (less than 0.5mm total @ the ball, didn't try & measure) and that combined with the swash play might be enough to make the controller 'hunt' a little as I go thru '0' deg on collective. Standard style swashes are known to get loose over time- I'm original owner, so I've replaced swash a few times..
Are there adjustments for the center stick 'deadband' area, and cyclic OR collective boost?

I only have this one 3GX, my other controllers are Beast X, so kinda referencing the adjustments they have.

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11-19-2015 08:13 PM  22 months agoPost 8
jason46

rrVeteran

MI

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Where is the gain pot? Although if it were set too high I'm not sure that would give TBE. I believe there is a collective dampening adjustment in the software...

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11-19-2015 11:21 PM  22 months agoPost 9
Dee Flies 3D

rrApprentice

Farmington Hls, Mich - USA

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Gain pots - Ele around 10:30, Ail around 11 o'clock. Elevator always felt 'twichy', so usually dialed it down. Going to find the PC interface dongle & see what settings are in the software...
Do you think the sensors are sensitive enough to try & dampen-out a little play in the mechanics? Local flyer here had a 3GX on a Trex550 & a little linkage play never bothered it, & he beat it up HARD

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11-20-2015 04:03 AM  22 months agoPost 10
dkshema

rrMaster

Cedar Rapids, IA

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Elevator and aileron gain pots are located on the top of the unit. The factory setting is with the slot at 12 o'clock. Mine usually ended up being set somewhere between 10 and 11 o'clock.

Chances are that's all you really need to do, to fix the problem.

While you're at it, hover your heli with the gyro in normal/rate mode. Adjust the tail rotor linkage so your heli doesn't yaw nose left or right on its own. Land, re-set the left and right rudder travel limits since you adjusted the tail linkage. Go back to HH mode and enjoy. If you don't do this, the tail will behave really weird. Set the tail for a no yaw hover in rate mode, the tail will behave very well.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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11-20-2015 12:07 PM  22 months agoPost 11
jason46

rrVeteran

MI

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That is what I was thinking on the gain pots, probably too low causing it to hunt. Assuming there isn't something else wrong, the gain pots should be turned up, then if it is too twitchy decrease roll/flip rates and there is also cyclic/collective dampening that you can increase. For the gain pots you can see the actual values on the Setting Display tab under Aileron Sensitivity and Elevator Gain(if I remember right). While turning the pots and watching the values on screen, try setting both around 110-120ish...

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11-20-2015 08:34 PM  22 months agoPost 12
Dee Flies 3D

rrApprentice

Farmington Hls, Mich - USA

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Just to clarify - I adjusted the pots DOWN to the above positions to correct flight issue SEPARATE from the 'bobble' Im trying to eliminate.

@ Dave - do you think the tail is affecting this ? Because tail is setup rite & is locked...

I will be out of town over wknd, so can't mess with it, but will get bask to it next week...

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11-21-2015 12:28 AM  22 months agoPost 13
dkshema

rrMaster

Cedar Rapids, IA

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Turn the pots down (counter clockwise, from center).

The tail info was something I wanted to pass along about how to get the tail control to work properly.

How many layers of mounting tape did you use to stick the 3GX down to the boom mount?

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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11-25-2015 04:29 PM  22 months agoPost 14
Dee Flies 3D

rrApprentice

Farmington Hls, Mich - USA

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3M grey - 2 layers. I usually fold it onto itself & use that thickness to attach. Works good even on my Nitro birds, so not concerned with mounting.
Since I should have good weather, will be able to do sum 'tweaking' next few days...

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11-28-2015 07:13 PM  22 months agoPost 15
Dee Flies 3D

rrApprentice

Farmington Hls, Mich - USA

My Posts: All  Forum  Topic

After looking into both the Mech & Elect sides of this, I think I got this 'dialed-out' as much as possible..
The swash bearing play is the main culprit. There is 3/4 of a deg actual blade angle 'play' measured with a pitch gage & only around .2 deg is from the servo gears.
Using the Collective & Cyclic Dampening, I was able to get the 'stopping bobble' down to a slight wiggle. Went from '0' to 20, then 25 and settled at 28 on both.
The only way I believe I can totally eliminate it, is to put on a DFC head for a better swash (PRESUMING that the bearing is a bit beefier)and then better servos.
SO until a BIG crash happens, I just fly & ignore as best I can..

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