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Old Jan 30, 2013, 02:03 PM
it WILL fly! someday....
Richard_s's Avatar
Slovakia
Joined Aug 2008
448 Posts
Seems like one bamboo stick is softer than second one. Guess which one wobbles.... Okay, new frame it is. But I still can't get that ceiling thing.... why the hell lowering throttle doesn't slow down motors? I can't see that relating to throttle curve. It goes like this: I VERY slowly add throttle, motors spin up. I'm adding throttle evenly. At one point, quad slowly lifts off. I STOP throttle stick. Quad still rises, doesn't matter if I lower throttle. It stops (and goes to flip & fall) only if I pull stick to zero. Confusing as hell
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Old Jan 30, 2013, 02:12 PM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
14,721 Posts
R,
How much stick does it take for lift off? You are using a Turnigy Tx with Radioclone firmware correct? Your Radioclone thread here Check that you used a new model during setup and that it does not have any kind of throttle or other mixing set. It also has a pretty advanced throttle curve adjustments possible, so lots to check and play with there too.

If the arm(s) wobbles and vibrates this could affect the PID response to motors and varying the throttle changes the amount of vibrations and so forth causing an increase in throttle as the board does its best to compensate.
Cheers,
Jim
Quadrocopter and Tricopter Info Mega Link Index
Quote:
Originally Posted by Richard_s View Post
Seems like one bamboo stick is softer than second one. Guess which one wobbles.... Okay, new frame it is. But I still can't get that ceiling thing.... why the hell lowering throttle doesn't slow down motors? I can't see that relating to throttle curve. It goes like this: I VERY slowly add throttle, motors spin up. I'm adding throttle evenly. At one point, quad slowly lifts off. I STOP throttle stick. Quad still rises, doesn't matter if I lower throttle. It stops (and goes to flip & fall) only if I pull stick to zero. Confusing as hell
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Last edited by jesolins; Jan 30, 2013 at 02:19 PM.
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Old Jan 30, 2013, 02:16 PM
RC beginner
New York
Joined Oct 2008
6,054 Posts
first offl i dont recommend slow throttling on takeoff. due to "bad air" and control dynamics its best to goose it and get up quickly where there are fewer hard objects to hit and interfere.

its strange that backing off on throttle has no effect. are you sure of this? is the throttle bar on your lcd moving down but motors dont respond? that might indicate a bad board. almost always an open pin or solder bridge. maybe try the hot air reflow trick.

also note that these direct drive quads are a lot more "frisky" than geared ones like v929 or those with accelleromters like the expensive walkera. some people like this because it alloews them to play tricks but it can work against you in the beginning.
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Old Jan 30, 2013, 02:36 PM
it WILL fly! someday....
Richard_s's Avatar
Slovakia
Joined Aug 2008
448 Posts
I did use blank model with no mixes. I'm quite familiar with mixing and curves on radioclone. I tried very soft throttle curve just now, to see if I can hit that spot where quad flings out of controll, no luck. With default, linear throttle, it took about 1/3rd of stick to get it up. Quite a lot, IMO.

I know slow start is bad, like with any heli or n-copter. Im looking for breaking point, where/why it stops responding to throttle. I'm really sure that it behaves just like that - only zero throttle stops motors, no slowdown. Exactly, throttle bar moves according to stick, but quad is just freaking out.

But why this changes as voltage drops? I can fly it normally then, throttle responds OK Either that tiny voltage regulator overheats if it has to drop from full 4.2V (to I guess 3.3V), MCU voltage drops and it locks up. Or board is toast.

I cannot tell if it is only throttle channel that is weird, or it is absolutely out of control. Because after it flings, I immediately pull throttle back, not to smash the thing into something
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Old Jan 30, 2013, 02:46 PM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
14,721 Posts
Hi R,
Since you are experienced in Tx and multicopter setup, it is beginning to sound like your flight controller is not working properly. I think at this point the only sure way to find out is to have another of the same fcb to compare and either prove or eliminate it as the problem. As Dave mentioned, a board solder reflow is worth considering too.
Cheers,
Jim
Quadrocopter and Tricopter Info Mega Link Index

Quote:
Originally Posted by Richard_s View Post
I did use blank model with no mixes. I'm quite familiar with mixing and curves on radioclone. I tried very soft throttle curve just now, to see if I can hit that spot where quad flings out of controll, no luck. With default, linear throttle, it took about 1/3rd of stick to get it up. Quite a lot, IMO.

I know slow start is bad, like with any heli or n-copter. Im looking for breaking point, where/why it stops responding to throttle. I'm really sure that it behaves just like that - only zero throttle stops motors, no slowdown. Exactly, throttle bar moves according to stick, but quad is just freaking out.

But why this changes as voltage drops? I can fly it normally then, throttle responds OK Either that tiny voltage regulator overheats if it has to drop from full 4.2V (to I guess 3.3V), MCU voltage drops and it locks up. Or board is toast.

I cannot tell if it is only throttle channel that is weird, or it is absolutely out of control. Because after it flings, I immediately pull throttle back, not to smash the thing into something
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Old Jan 30, 2013, 03:01 PM
it WILL fly! someday....
Richard_s's Avatar
Slovakia
Joined Aug 2008
448 Posts
I'll try new, stiffer frame to fix vibrations. Then heatgun reflow. Then trashbin. I checked fc board visually, it looks ok, no solder bridges or visible faults.

Buying each part twice gets quite expensive and pproaching chinese festival means no goodies until maybe easter . Okay guys, thanks for help and ideas. I'll chime in if I fix the damn thing.
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Old Jan 30, 2013, 03:54 PM
RC beginner
New York
Joined Oct 2008
6,054 Posts
too bad youre not local. id walk over and fish it out of the backyard bin. so far i been lucky to revive all the duds people have tossed. one way or another. make sure you slobber on lots of flux and its smokin' real good before shutting off the heat.

do they hit you with 2x vat or whatever tax/fees over there if you buy two at the same time?

you know what they say "buy cheap...buy twice". i agree with this. i get at least 2 at the same time and shelve the spare for backup. hardly ever need it though because ive had good luck w/cheapo chinese "junk". lol!
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Old Jan 30, 2013, 04:59 PM
it WILL fly! someday....
Richard_s's Avatar
Slovakia
Joined Aug 2008
448 Posts
Quote:
Originally Posted by dave1993 View Post
too bad youre not local. id walk over and fish it out of the backyard bin. so far i been lucky to revive all the duds people have tossed. one way or another. make sure you slobber on lots of flux and its smokin' real good before shutting off the heat.

do they hit you with 2x vat or whatever tax/fees over there if you buy two at the same time?

you know what they say "buy cheap...buy twice". i agree with this. i get at least 2 at the same time and shelve the spare for backup. hardly ever need it though because ive had good luck w/cheapo chinese "junk". lol!
Well, with tight budget, its more like "buy cheap, or don't buy!" It's not tax or fee, it is price itself .

I've built new solid frame, it still wobbles. Again, with fresh battery quad gets that ceiling syndrome for about a dozen of starts. Then normal liftoff and I can fly for about 3 ~ 5 mins. Wobbly, but flies. I observed that it's response to throttle decrease depends on battery voltage. It was in such state, that I was really wrestling with throttle stick up/down, trying to hover. As battery discharged, throttle response was more predictable. Tomorrow I'll try to swap motors, if problem moves or persists. Not giving up
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Old Jan 30, 2013, 05:13 PM
it WILL fly! someday....
Richard_s's Avatar
Slovakia
Joined Aug 2008
448 Posts
So, it is oscillation, as one of you said earlier!

If I disturb oscillations by working sticks immediately after liftoff, ceiling run won't happen. Then I tried to hover, it started wobbling, rising up and pretty much ignoring my throttling down. Now to get rid of wobbling and it *should* fly okay.
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Old Jan 30, 2013, 05:46 PM
KlonWarz
Joined Dec 2012
455 Posts
Hit the bin... lol

A friend once pulled up to make his deposit after a disgruntled divorced gal had just dumped her X's hobby room... Fortunately he was there in a pickup truck... took him a while!

I never saw much that was any better than what I was getting rid of!
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Old Jan 31, 2013, 02:59 AM
Registered User
Joined Apr 2012
6 Posts
Does anyone have both.....MJX 200 Quad & MJXf47 Heli ??

Is MJX 200 transmitter compatible with MJX F47 Helicopter???
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Old Jan 31, 2013, 05:58 AM
Registered User
Joined Jan 2012
1,594 Posts
Quote:
Originally Posted by rastsaurabh View Post
Does anyone have both.....MJX 200 Quad & MJXf47 Heli ??

Is MJX 200 transmitter compatible with MJX F47 Helicopter???
Wrong thread. Please, check topic.

This could be your right thread: http://www.rcgroups.com/forums/showthread.php?t=1775436
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Last edited by mystman; Jan 31, 2013 at 06:05 AM.
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Old Jan 31, 2013, 12:38 PM
it WILL fly! someday....
Richard_s's Avatar
Slovakia
Joined Aug 2008
448 Posts
Solved! Seems like motor angle is critical (prop discs exactly perpendicular with ground). I swapped two motors, moved props around, changed one rattly prop for balanced one, fixed some really small motor angle deviations, and it works! . Oscillations and ceiling run are gone. Sweeeeeeeet. Now to make a new, light frame, and some tool to align motors precisely.

I love how fast and agile this thing is. I flew friend's hubsan twice or so, and it was way too lazy. Too much inertia, no punch from battery... like driving a loaded truck. It is quite heavy for its size and such small battery, and maybe he had tx set up with training wheels or something
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Old Jan 31, 2013, 12:54 PM
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LittleMo's Avatar
United States, VA
Joined Dec 2006
1,497 Posts
Great!

Definitely not something I would have considered to be a problem because with as many times I have broken and re-glued arms on my quads the motors are not straight at all yet it flies fine. In fact I have flown with multiple broken arms hanging loose and crooked and it still worked fine.

I'll have to add this to my things to watch out for.
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Old Jan 31, 2013, 01:16 PM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
14,721 Posts
Hi R,
Hmmmm...maybe your friend's X4 lipo was in need of replacement, motors or props were damaged, or he needed to fly on expert mode?...

hubsan x4 in wind (2 min 8 sec)


--Micro quads comparisons 101

Glad you cured your BIY Flexing motor tilt as pertains to multicopter neutral stability and vibrations play havoc on flight controllers even more so when they are fitted with accelerometers, which the V939 does not have.

See --TIP 7 in the Project Quads/Hexas/Octos section of the Quadrocopter and Tricopter Info Mega Link Index for more info on multicopter dynamic mechanical neutral stability
Cheers,
Jim
Quadrocopter and Tricopter Info Mega Link Index
Quote:
Originally Posted by Richard_s View Post
Solved! Seems like motor angle is critical (prop discs exactly perpendicular with ground). I swapped two motors, moved props around, changed one rattly prop for balanced one, fixed some really small motor angle deviations, and it works! . Oscillations and ceiling run are gone. Sweeeeeeeet. Now to make a new, light frame, and some tool to align motors precisely.

I love how fast and agile this thing is. I flew friend's hubsan twice or so, and it was way too lazy. Too much inertia, no punch from battery... like driving a loaded truck. It is quite heavy for its size and such small battery, and maybe he had tx set up with training wheels or something
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