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550 Class Electric Helicopters 550 Class Electric Helicopters manufactured by Align, Tarot, SYMA, Airhog, Chaos, HK and similar.


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Old 03-06-2012, 11:17 AM   #21 (permalink)
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i have five 3GXs...and i've built a few 550s.

not sure if i am missing something:

travel does not increase exponentially as the servo arms move off center. they come closest to approximating linear reaction close to center and begin to decay in linear motion as they move off center. helis are designed to use only a fraction of a servos total travel.

1. clear everything out to 0

2. go into set up and set arms at 90 degrees. use subtrim if necessary.

3. forget measuring the links - for now. position the phasing arms so they are dead even with the swash attached. THEN measure the distance from the swash to the servo arm balls and adjust your links accordingly. That ensures that the swash will be properly placed.

there are no tricks or mods required beyond what is stated in the manual.
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Old 03-06-2012, 12:00 PM   #22 (permalink)
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I don't think you read my last post. The problem lies within the servo travel at the servo itself. At 90 degrees setup perfectly (used subtrim) I get decent amount more up throw than down throw on the servo arm. So much that I can see it without measuring it even...

I'm setting this up with the old version of the DX7.

All endpoint adjustments are at 100 percent (haven't messed with them).
Revo mixing is all at 0. Rest of the mixes that I could disable ARE disabled.
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Old 03-06-2012, 12:04 PM   #23 (permalink)
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Have you confirmed that there's no "Hover Pitch Trim" ?

Sometimes it best just to create a new model and start from scratch.
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Old 03-06-2012, 12:42 PM   #24 (permalink)
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Positive. I just found out something that may be the cause of this. When I put my stick at dead center it is actually not registering dead center in the radio. I was fiddling with the screen that shows the sliding bars and when I have the stick at mid stick the slider bar is slightly off. I actually have to move the throttle stick up probably 2-3mm for the radio to have the slider bar in the dead center. This seems like it could def be the issue right?

Any way to adjust this if I open up the radio? I guess the temporary fix is to reset everything from scratch with the stick slightly off center (the radio's center).

Thoughts?
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Old 03-06-2012, 01:26 PM   #25 (permalink)
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3din,

What are your pitch curves for Normal, Stunt, and Hold in the radio.

I would change your Hold curve to 0, 50, 50, 50, 0 and then put the helicopter into TH. Now once the throttle stick is past the 25% stick posistion it will jump to give the servo a dead middle 50% pulse. At this point I would go into the monitor page as you have described and report back what you are seeing on this page. If it's still off from center then you may have an issue with the pots in the radio and it might need to be serviced.

Hope this helps....
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Old 03-06-2012, 01:54 PM   #26 (permalink)
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in that case, there are three possible problems with your setup

1. your travel adjustments are less than 100%

2. your pitch curves to do not go to 0 to 100%

3. your swash is not in the correct position

it has nothing to do with your 3gx or subtrims. iit's normal for the radio not to be at exact 0 at mid stick and there are some articles floating around on how the radio can be adjusted to find exact center. it's not a big deal if it is a little off.
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Old 03-06-2012, 01:59 PM   #27 (permalink)
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Turns out that the radio itself was messed up. The mechanical zero wasn't what the signal was putting out as zero....

Quick question for you guys. I'm trying to solder a 6S battery and I have solder in front of me that is "light duty solder" it is fairly thin 60/40. Does this mean that I shouldn't use it for the deans connector on the battery?
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Old 03-06-2012, 02:52 PM   #28 (permalink)
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Go into your Tx setup and recalibrate your throws for all axis making sure that when you finish with your pitch/throttle stick that you return it to exactly middle. I had the same problem with my DX8 and this is how I fixed mine. It's dead on now.
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Old 03-06-2012, 07:08 PM   #29 (permalink)
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Quote:
Originally Posted by mtuccio View Post
3din,

What are your pitch curves for Normal, Stunt, and Hold in the radio.

I would change your Hold curve to 0, 50, 50, 50, 0 and then put the helicopter into TH.
This is the best advice yet. This is how I have always setup my helis. It assures center stick to servos anywhere near center on the radio stick. You may just find that you put your horns on high. Also go through all three horns and try each combination on each servo. You'll find that you reach a very good middle ground. I would just start from scratch now. Now that you know your radio was off. It's worth it to be sure of a good mechanical setup. And after doing it a couple times you'll understand the whole process a little better. I have gone through and redid my beast x setup several times and found each time I get a little closer to perfect mechanical setup. At no point should you feel like you just want to hurry up so you can fly. That may just cost you some serious bench time. (way more than doing setup two or three times)
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Old 03-06-2012, 07:23 PM   #30 (permalink)
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set your radio up with linear pitch curves and in hold set the middle 3 to 50% makes it easier to center things.

Set the servo arms on as close to center (90) as you can get and follow the manual for the 3G to set your subtrim to finish them off. as far as travel you will need to lengthen the servo links and shorten the grip links from what you said prior, this may be a mute point if the radio was giving you issues.

If your positive pitch is high versus the negative then lengthen the servo links as I mentioned and if it is opposite then shorten them, the grip links should be adjusted at mid stick to zero out you blades pitch.

Now be aware that if you use too much sub-trim you may need to adjust your travel adjust limits (ATV's) to get you more travel .

If I recall the 3Gx uses standard swash mixing in the radio (i.e.120) versus a 1 servo setup like the beast or vbar units.

You want to make sure the swash is in the middle of its travel to get symmetrical collective pitch ranges.
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Old 03-06-2012, 07:27 PM   #31 (permalink)
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Oops I missed I quoted 0,50,50,50,0
Should've read 0,50,50,50,100
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Old 03-06-2012, 09:29 PM   #32 (permalink)
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Quote:
Originally Posted by 3din View Post
Turns out that the radio itself was messed up. The mechanical zero wasn't what the signal was putting out as zero....

Quick question for you guys. I'm trying to solder a 6S battery and I have solder in front of me that is "light duty solder" it is fairly thin 60/40. Does this mean that I shouldn't use it for the deans connector on the battery?
Are you using TH for setup by chance? Because TH by default is -5 and then is sets the mid stick point off. If your using TH reset it to 0
That 60/40 works fine but I use lower lead content, it provides better continuity but requires higher temps just above 200 vers the 60/40 around 175. Lead is a poor conductor but 60/40 does work.
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Old 03-06-2012, 09:48 PM   #33 (permalink)
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3din

Start over.

If I am reading your earlier post correct you used the trim tabs on the face of the radio to set the servos to 90 degrees.

MISTAKE!!!

Set all the trim tabs on the face of the radio to 'zero' or middle.

Now go into the set-up in your radio and find your servo set-up (DX7s) and use this function to:
1) check that all of your servos have 100% travel
2) use sub trim here to set your servo arms to 90

If you have a different radio you still will have a sub trim travel and sub trim menu.

Hope I was reading your post correctly and I have given you the correct advice.
Cliff
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Old 03-06-2012, 10:13 PM   #34 (permalink)
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Quote:
Originally Posted by LowSpark View Post
3din

Start over.

If I am reading your earlier post correct you used the trim tabs on the face of the radio to set the servos to 90 degrees.

MISTAKE!!!

Set all the trim tabs on the face of the radio to 'zero' or middle.

Now go into the set-up in your radio and find your servo set-up (DX7s) and use this function to:
1) check that all of your servos have 100% travel
2) use sub trim here to set your servo arms to 90

If you have a different radio you still will have a sub trim travel and sub trim menu.

Hope I was reading your post correctly and I have given you the correct advice.
Cliff
You may have found the problem.

Quote:
Originally Posted by 1004ron View Post
Make 100% certain that there's no trim, hover-trim, ATV's at 100, and the pitch curve is 0 25 50 75 100


Edit: Deleted the word "subtrim".
The advice to start over with a new model in the TX would ensure that most of the inadvertant settings would be removed, but if you are using the "trim" buttons on the front of the TX instead of the "subtrim" in the menus, then that would most certainly be the cause of your problems.
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Old 03-06-2012, 10:47 PM   #35 (permalink)
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I never use trim for anything. I found that my radio is messed up from the factory and the center point mechanically isn't the same as what the radio outputs to the servo.

Quote:
Originally Posted by LowSpark View Post
3din

Start over.

If I am reading your earlier post correct you used the trim tabs on the face of the radio to set the servos to 90 degrees.

MISTAKE!!!

Set all the trim tabs on the face of the radio to 'zero' or middle.

Now go into the set-up in your radio and find your servo set-up (DX7s) and use this function to:
1) check that all of your servos have 100% travel
2) use sub trim here to set your servo arms to 90

If you have a different radio you still will have a sub trim travel and sub trim menu.

Hope I was reading your post correctly and I have given you the correct advice.
Cliff
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Old 03-07-2012, 08:58 AM   #36 (permalink)
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Quote:
Originally Posted by 3din View Post
I never use trim for anything. I found that my radio is messed up from the factory and the center point mechanically isn't the same as what the radio outputs to the servo.
3din
I read this and assumed you were using the trim tabs on the face of the radio?

"There is subtrim.... there has to be. I'm at 20 clicks or so for all 3 servos to get it at 90."

If you do use the trim it would explain why your servos are not centered up to match the output from the radio to the reciever and the difference in travel you are experiencing.
My mistake if I misread your post.
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