3gx with a mind of its own.. any ideas

[helimadness]

Hi All.

So my 250 project to use my 3GX I had sitting around has been a little bit of a challenge to say the least.
What was a copter x 250 is now 90% Align, Head, tail, blades, Skids All the important stuff.
Had cheapo 3 quid servos. Upgraded the tail to a 95i to fix the wag. Got it almost flyable then just doing some nice gentle lazy 8's it rolled over to the left and planted into the ground.
So figure my other 3 quid servo wernt up to it got some MKS for the cyclic as well.

Got back in the air tonight. Maybe 15 knot gusts but not too bad. Tail was still drifting so managed to up the gain another 15 points or so. Was coming back to myself tail first and got a big puff from behind and the tail gave a very slight wag. So dropped the gain a few points and had another go.

All seemed good. Actually surprising good. Not much flying around as a little windy but some basic flips and things and it seemed to be perfect. Was amazed at how well it was flying. Finally got it sorted and a smile on my face.

Then.......

It rolls about 30 deg to the left and starts a massive wag. Managed to catch it a long way away and keep it off the ground. Flicked back to normal mode and came back closer. Flicked back into idle up and moving around a little and it did it again. Just managed to save it so landed and pulled the plug for the day..

Totally lost this time. Was flying so well just felt great.

Exactly the same problem as last time I crashed with the cheapo servos. I blamed them but looks like..... Yes once again the 3GX.

So unless anyone has any great ideas Im happy to try.

If not looks like the "Kbar" (vbar ripoff) might have to go on my shopping list.

The servo wires and things are all in a bundle to get rid of the excess. Could it be getting interference from somewhere?

Upgraded to Ver 3.1 Not sure if that makes any difference.


Cheers

[helimadness]

Anyone heard of this happening before???

[coolice]

Hey buddy.

Sounds like vibration to me, seeing as you're going into idle up and then getting a problem thats the first thing that pops into my head.
What is the head speed/throttle change value between normal and idle up?

You don't have any trim in idle up which shouldn't be there have you?

It's like comparing chalk and cheese I know, but I recently setup a vbar on a raptor 50 that had vibration issues. Needless to say one minute it was hovering nicely and the next.... I've never seen a model twitch so violantly.

Another thing, BEC what are you using to power the 3GX? If it's the stock ESC BEC that could be a cause of problems with V3.1 to.
.

[helimadness]

Hey buddy.

Sounds like vibration to me, seeing as you're going into idle up and then getting a problem thats the first thing that pops into my head.
What is the head speed/throttle change value between normal and idle up?

You don't have any trim in idle up which shouldn't be there have you?

It's like comparing chalk and cheese I know, but I recently setup a vbar on a raptor 50 that had vibration issues. Needless to say one minute it was hovering nicely and the next.... I've never seen a model twitch so violantly.

Another thing, BEC what are you using to power the 3GX? If it's the stock ESC BEC that could be a cause of problems with V3.1 to.
.

I have the 3GX on the bottom frame with 2 layers of foam from the Vbar left overs. A vibe does sounds like what could be messing with it.
I had been in idle up maybe 30 sec to a min before it went crazy.
Will go through and double check all settings in the TX as was messing around with it a bit when I was trying to sort other problems. Might actually even wipe it and start with a complete new setup.
I had 75% normal 85% idle one and 95% idle 2. Was in idle 2 when it happened.

Copterx 250 3400 KV motor (one of the few copter x bits left on it)
Skywalker 20a esc using the BEC off it. 2A 5v.... Is this enough?
Cyclic servos MKS DS92
Tail MKS DS95i

It did settle down when I got out of idle up. how soft a pad do you recommend for the 3GX. I also have some fairly soft double sided tape I could try.

Will have another go through it and see what I can find.

[GIXERMAN]

I always mounted a 3gx with the supplied align 3m pad, which is pretty hard mounted, if your running 4 digital servos on 2amp bec not enought. Also as posted on a few occasions 3gx is pretty power hungry.

[helimadness]

I always mounted a 3gx with the supplied align 3m pad, which is pretty hard mounted, if your running 4 digital servos on 2amp bec not enought. Also as posted on a few occasions 3gx is pretty power hungry.

Yeah 4 digital. Its only a 250 but. Is that little guy going to use that much?
Whats the best option to power a 3GX on a 250 then? more powerful ESC with stronger BEC or separate? Getting mighty complicated for a little guy. My fat fingers are having enough trouble trying to stuff it all in now.
What sort of max current you think I should be aiming at?

I have heard of 3GX being power hungry but thought only on the bigger birds.

Cheers

[helimadness]

Is just downgrading to V2.1 the easiest way to test maybe??

also just reading about it I see people were having trouble with twitching. I noticed on my tail when it got near the limits it did a twitch. I reduced the travel slightly as was close to the end (but not touching) but still did it.

I might have a look tonight and if its still doing it go back to 2.1 and see if it goes away. If the tail glitch goes away maybe the cyclic one will as well.

Cheers

[coolice]

Hey buddy.

As above single foam pad is normally enough. The raptor problems I had showed that softer pads and even the addition of a metal plate didn't help if the vibration was that severe, in fact harder mounting was better surprisingly.

With the addition of V3/3.1 the power requirements for the 3GX have increased and 2amps isn't enough, you'll find if you read most ESC manuals the stock BEC is only rated to run 2-3 servos max and we have 4 high power ones being driven harder by gyros.Tell-tale signs are fflashing spektrum lights signalling a brownout in most cases. But if the voltage fluctuates then the servos loose their performance and could no longer hold the model so well.
.

[coolice]

Ooops double.
.

[helimadness]

Hey buddy.

As above single foam pad is normally enough. The raptor problems I had showed that softer pads and even the addition of a metal plate didn't help if the vibration was that severe, in fact harder mounting was better surprisingly.

With the addition of V3/3.1 the power requirements for the 3GX have increased and 2amps isn't enough, you'll find if you read most ESC manuals the stock BEC is only rated to run 2-3 servos max and we have 4 high power ones being driven harder by gyros.Tell-tale signs are fflashing spektrum lights signalling a brownout in most cases. But if the voltage fluctuates then the servos loose their performance and could no longer hold the model so well.
.

Ok so maybe first point of call is more power. Reading the specs on the Align ESC that comes with the 250 they don't mention how much current it draws. On the 450 one it says 3a 5 peak. So the ESC they are supplying with the kits on the small models are not up to the job also?
If I want to stay with 3.1 what would you recommend for a ESC with BEC powerful enough. Surly on a 250 adding a separate flight pack would be over kill? end up caring a flight pack the size of the main one :-)
It was flying very well for a short time. Would be nice to stick to 3.1 if I can. Would like to give it an honest run.

Would be interesting to see what happens to the flight times going from 3.1 to 2.1 if that is the case.
the 250 is my test heli maybe Ill try it.

[GIXERMAN]

Have a look at this as a example will give 10amps and seems compact without using a extra battery

Gryphon Polaris 30V 10A Mini BEC GSR-3030

[helimadness]

Have a look at this as a example will give 10amps and seems compact without using a extra battery

Gryphon Polaris 30V 10A Mini BEC GSR-3030

Thanks might just go that road. Only 7g so I guess not too bad. Should be big enough to cover any scenario. Just need to find some room now.

Cheers

[sp4rky-m4rky]

I have had similar issues to what you have described but with a tarot zxy flybarless unit. Interesting most are saying vibes are the issue. I still havnt built mine up since the crash, I was going to swap out the electronics but perhaps I will look more for vibes and better mounting. I have had 100s of flights unchanged before an issue but will check everything over for wear that may cause vibes. Will keep following your thread and will let you know the outcome of my heli if I get it sorted.

[helimadness]

I have had similar issues to what you have described but with a tarot zxy flybarless unit. Interesting most are saying vibes are the issue. I still havnt built mine up since the crash, I was going to swap out the electronics but perhaps I will look more for vibes and better mounting. I have had 100s of flights unchanged before an issue but will check everything over for wear that may cause vibes. Will keep following your thread and will let you know the outcome of my heli if I get it sorted.

Like most things its best guess. I am thinking now It is more a power problem. Going to try a separate BEC and if it does the same thing then it must be vibes :-)
Will check for vibes as well. Guess with a 250 can just hang on to it and spool up.

Let us know if you have any breakthroughs. Where do you have your ZXY mounted? I took mine off the supplied gyro plate as it was so thin and light figured it would be attracting vibes. Have on the bottom frame now.

[sp4rky-m4rky]

Its mounted on the top side of the base of the frame inside the frame of my 450 pro. I have flown it this way for ages though with no issues (although have fitted a larger tail servo recently). I am going to look into a separate bec too (running a 3A one currently). Also will be checking all bearings and gear meshing and shafts and making sure everything is running smooth with no chance of producing vibes. Cant face it causing a crash for a third time, so frustrating.