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HelicopterFlybarless Rotor Head SystemsAlign GPro › Gpro rudder issue
04-08-2015 06:57 PM  34 months agoPost 41
amastron

rrNovice

Goldsboro, MD. USA

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Much the same with mine, I bought two of the Gpro systems and both have the same issue with the right rudder. One is on my 500 and the other is on my 450. It doesn't seem to happen while in the software, only after you disconnect the connection cable does it show up. I don't have much experience with the system because I just got it so I'm not much help.
I would think if it is this big of an issue Align would address it in another update, if not soon I have two I will be selling cheap on eBay!
Many thanks for the reply, maybe Dave will come up with something soon as well.

Tom

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04-08-2015 10:29 PM  34 months agoPost 42
tvoth

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Albuquerque

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Note that I was able to get rid of the stutter by setting the rudder center to the point where the heli doesn't rotate in rate mode. Then switch back to hh and it's gone. This may get rid of the stutter as you've effectively reduced the rightward motion of the servo (?)
--Tom

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04-14-2015 11:04 PM  34 months agoPost 43
amastron

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Goldsboro, MD. USA

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Cool, I'll try that and maybe it will work for me as well.
I tried both the I and P settings with no better results. Tried all sorts of rudder gain settings but nothing helps. I wish Align would jump on this but it seem as if you and I are the only ones having this issue. I have the problem in two Gpro's.

Tom

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04-15-2015 12:11 AM  34 months agoPost 44
dkshema

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Cedar Rapids, IA

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So what exactly is the problem you are having with your GPros? Maybe I can help.

-----
Dave

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

Team Heliproz

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04-15-2015 10:47 PM  34 months agoPost 45
amastron

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Goldsboro, MD. USA

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Right rudder servo jumps back and forth in heading hold. When I give it right rudder it seems fine but when I release it slowly it wants to jump back and forth. Can't make it do the same thing with left rudder, only right. This happens on both my Align 450 and 500, the 450 has a Futaba S9650 servo and the 500 has a Align DS525M. Two different helis and two different Gpros two different servos.

Tom

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04-17-2015 01:47 AM  34 months agoPost 46
dkshema

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Cedar Rapids, IA

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I guess I'd like to get my hands on one of these errant GPros to see what the fuss is all about. I've got eight up and running so far, and nary a problem with any.

Would still be enlightening to have one in my hands and see if I can figure out what the problem is.

This isn't meant to be a smartA$$ reply, I'd really like to get hold of one of the "bad" ones, and see if there really IS a problem, and if so, if it can be sorted out.

-----
Dave

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

Team Heliproz

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04-17-2015 04:05 PM  34 months agoPost 47
amastron

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Goldsboro, MD. USA

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I know how you feel, I would like to get my hands on one or two that have no issues and work right!

Tom

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04-17-2015 04:17 PM  34 months agoPost 48
dkshema

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Cedar Rapids, IA

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As an engineer, some things tend to bother me when I think about them.

I've got eight of these babies, all purchased at random, different times, different places. They just install, program, and work. No weird behavior.

You have two in a row that seem to be "bad".

What makes yours different than mine?

Software is software, and should have predictable behavior. I don't see any external variables that would drive some units to act weird, and others to act OK.

The hardware, too, is fixed. Its behavior should also be predictable.

I experienced this same issue with the 3GX -- a dozen installations that just plain worked fine for me, and predictably the same for me, while others just seemingly have nothing but trouble.

If I ever get a chance to run across a "bad" GPro, I'll try to tackle it.

-----
Dave

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

Team Heliproz

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04-17-2015 04:41 PM  34 months agoPost 49
tvoth

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Albuquerque

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Software is software, and should have predictable behavior. I don't see any external variables that would drive some units to act weird, and others to act OK.

The hardware, too, is fixed. Its behavior should also be predictable.
Dave, this is true in theory but (small) variations in input can result in *huge* differences in output and/or may trigger a code path that has a bug you never otherwise see (I write software for computational mechanics and see kind of bifurcating behavior on occasion - contact mechanics is awful for this...). Hardware "bugs" can also do this. Your setup may never see this but change receiver/transmitter, gains, limits, etc. settings others may tickle that bug.

As noted above I'd like to get my hands on a "bug-less" unit --- actually I bought another recently (very cheap for some reason) and intend on testing it as well --- I'll reply with what I find...

Tom, did you try fixing the issue using the method of setting rudder center in rate mode?

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04-17-2015 09:24 PM  34 months agoPost 50
amastron

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Goldsboro, MD. USA

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I have not got to that fix just yet, maybe tonight I'll try it on the 450 and post what happens.

Tom

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04-19-2015 06:33 PM  34 months agoPost 51
amastron

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Goldsboro, MD. USA

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Tried today setting it up in Rate Mode, same ol same ol...

Tom

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04-20-2015 10:26 PM  34 months agoPost 52
tvoth

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Albuquerque

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by same ol' you mean that the tail servo shows the stutter on right stick?

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04-20-2015 10:49 PM  34 months agoPost 53
amastron

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Goldsboro, MD. USA

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Yep, still doing the same thing it was. I think both of mine will get replaced with iKON's over the next few weeks. Weather is warming up and I can't see wasting any more time on these. Thanks for all the help!

Tom

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04-22-2015 01:40 PM  34 months agoPost 54
tvoth

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Albuquerque

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Sorry it didn't work for you.

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04-26-2015 10:45 AM  34 months agoPost 55
gonehelimad

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Melbourne, Australia

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This is a wide spreadissue.
I currently experience the bounce back issue on right rudder to at present having just rebuilt my trex 500L using stock GPRO 1.2 and DS525M servo.

Prior to crash, heli was working fine, no tail wag and no bounce back tail twitch on right rudder tx input.

Post rebuild, starting seeing the same issue slight tail twitch on right rudder (Slow). REversed rudder on tx and in gpro software and twitch is replicated on left rudder.

Switched cyclic servo for rudder servo and twitch seen on one end of servo operation for cyclic.

Less concerned with tail wag as was able to get most if not all of tail wag under control by running gov with head speed min 2500 (idle up / 2700rpm idle up 2) and playing around with p gains.

Am about to try out the idea which has been covered in previous comments in this thread and also as described in the second link below.

Ie adjusting nuetral tail position based on hovering heli in rate mode. and then switching to hh mode.

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04-28-2015 02:51 AM  34 months agoPost 56
dkshema

rrMaster

Cedar Rapids, IA

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Not sure how "widespread" this issue really is. Yes, a few people have written about it on HeliFreak, a few people here on RunRyder.

I've got eight of these up and running, and you'd think I would have at least one of them acting up, but no, they all work fine.

From what I gather, there are two things that the people who have problems, report.

1. Servo movement that's not smooth from end to end while sitting still on the bench or ground. Some call it a twitch, others, a stutter.

2. "Bounce back". Presumably when you let go of the stick in a pirouette maneuver, the rudder will overshoot and the tail will bounce, or perhaps you point the nose in a given direction, and when you let go of the stick, the nose may seem to want to go back where it was.

I don't know for sure what to tell you about the first problem, as I have not seen it. If I ever get my hands on one of these with that problem, I'll see what I can do to figure it out.

The second problem should be more easily dealt with.

Back in the days of flybarred helis, when tail rotor gyros were King, for many it was established practice to put the gyro in rate/normal mode, hover, then adjust the tail linkage to get rid of any tendency for the nose to yaw left or right on its own. Then recheck/reset travel limits, go back to heading hold mode and enjoy.

Near the end of the reign of the Tail Rotor gyro, people were beginning to argue that this particular setup step wasn't necessary, as the heading hold gyro would take care of it.

Frankly, the only real substitute for a proper setup is a proper setup.

Many FBL controllers these days just say center the tail rotor pitch slider and move one. But those same helis don't have the correct tail rotor control geometry to actually get away with that.

So -- for GPro bounce back. Take the extra time needed to get the heli linkage set up so the heli won't yaw left or right in rate/normal mode. Recheck/reset your travel limits to prevent servo/slider binding, and go back to Heading Hold mode.

Adjust your Gyro gain from the TX as needed, and don't be afraid to work on the software settings for the P and I gain for the tail. Don't forget that you also can tweak the rudder left and right stops. One other thing to keep in mind is that the software default setting for rudder expo is 50%. That's a lot of servo deadband -- move the stick a bunch and you get very little response from the gyro.

-----
Dave

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

Team Heliproz

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04-28-2015 01:32 PM  34 months agoPost 57
gonehelimad

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Melbourne, Australia

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GPRO TAIL RUDDER BOUNCE - PARTIALLY SOLVED
Thanks for your response dkshema,

Im an engineer by profession just wanted to make it clear that i have tried to be systematic in my approach to resolving.

I should have been a little more specific in my first post. For clarity i have not been plagued with any ongoing tail wag issues. I learnt a while ago that if tail gain / P or I gain dont make significant improvements with regards to tail wag, then its something mechanical.

With regards to the twitch which i was experiencing / described in my last, i took your advice and decided to do a quick bench experiment prior to mechanically setting up the tail to be hands free hover in rate mode. Ive outlined starting and finishing outcomes to assist others and for clarity.

Heres what i did and my findings.

Current situation,
---------------------------------
a) when i apply right rudder manually from my 14sg slowly in heading hold mode, the tail slider moves all the way closest to the gears (towards boom). But when i appply rudder further via tx, the slider jumps back a little and then returns to the closest point near the gears again (the bounce back), not so much a jitter as it only does it once each time.

b) my gpro setup was setup with tail blades lining up at nuetral.

c) my servo horn /arm / tail control rod was setup so that in the gpro rudder setup screen my nuetral point is as close to being 0 (ie mechanically trimmed out to provide centre balanced blades.

d) right and left stop in parameter kept at 20 each.

e) stock P and tail gains (80) and stock I gain 60.

f) before this test, rechecked for binding in tail assembly, which was completely non existent. I already knew this, but did at one stage have binding due to locktite within the screw collars. Only through careful disassembly and reconnecting each arm / screw collar / rechecking for smooth rotation after each connection (had to do some over a couple of times to get right) did i get rid of complete binding.

Okay so with the above clear and with my issue in a) present heres what i did as a mock up test based on replicating mechanical nuetral setpoint (Rate mode- handsfree hover).

1. connected heli to gpro,
2. parameter screen already defaults so no change.
3. returned to setup menus and went to tail adjustment screen.
4. made sure i had 1520ms setting for rudder servo. (Which was already set).
5. trimmed the current neutral rudder position to the right ie +20 (previously it was 0 as described in b) and c) above previously. This would simulate a rough position of the rudder similiar to where hands free rate mode hover is achieved. The actual position would only be verifiable as part of an iteration of mechanical setup adjustmentsand test hovering. This initial approach was to verify if the bounce back issue does improve with an adjustment of the rudder nuetral position.
6. checked for binding adjusted right and left travels.
7. exited the setup screen unpowred and repowered gpro (to ensure new settings take effect).
8. kept gyro in hh mode and did the rudder test with the tx (With throttle hold on!),

Can confirm that based on the mock up above, the bounce back issue has completely gone. (no stop adjustment required and stock settings).

Based on this, i will go ahead and do the mechanical setup tomorrow which in principle should replicate the final tail slider position albeit specifically to provide a hands free rate mode hover.

I have a video illustrating before and after which i plan to post to Youtube and link to assist others with my actual experiment and hopefully real world success.

Thanks for your advice. Seems setting up the gyro correctly (hands free rate mode) is all it takes.

One thing bugs me though. First time i ever built this bird, i swore i followed the manual to the letter, nuetral tail blade positions trimmed out to 0 and did not have a tail bounce issue. Don't know why this would have changed.

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04-29-2015 02:35 AM  34 months agoPost 58
tvoth

rrNovice

Albuquerque

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gonemad. though you've outlined this much better than i, i also found that setting the tail for hands free rate mode fixes the bounce-back, jitter, stutter problem (think these terms are all describing the same issue).
I'd like to see align address this issue. it's apparently rare but does happen.

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04-29-2015 03:33 AM  34 months agoPost 59
dkshema

rrMaster

Cedar Rapids, IA

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I, too, am an engineer. That is why my posts generally try to describe the problem, and systematically try to eliminate the possibilities. I got a lot of experience troubleshooting problems via telephone early in my career supporting some of the products the small company I worked for designed, built, and sold.

OK -- as I understand it, the only real problem you seem to have is that odd rudder servo movement when you're slowly moving the stick. I suspect the rudder reaches its travel limit with only a small amount of stick movement, as that's the way a heading hold gyro should behave on the ground, as there is no movement detected, and therefore, no rudder correction needed. The odd jump in the servo seems to be the real issue, and what you're calling "bounce back".

My advice on the rudder left and right stops was given to correct any uver/undershoot of the rudder when you let go of the rudder stick after a pirouette maneuver.

Perhaps I've been fortunate enough with eight of these units, to not have seen the rudder servo behavior. I was tempted to purchase a GPro here from a fellow who had this problem, simply to experiment with it, to see if I could replicate the problem. As it turned out, I wasn't too thrilled with paying what I have been paying for NIB units, without an apparent "known" problem. I passed on the opportunity. The one I was interested in went to Ebay -- I hope the buyer has better luck with it, than the original owner.

-----

TVoth -- I emailed the folks at AlignRC USA last week, asking if they had seen the odd servo behavior. They told me they were aware of the few posts on various threads, but had not been able to replicate the problem. As I've not been able to replicate the problem with my random sample of 8 units, I'd have to agree that it is not common, and not necessarily easy to replicate.

-----

Goneheli's experience to date appears to indicate if there is an issue, it's somehow related to user setup as he seemingly made it disappear with simple setup steps.

I have to assume there are a lot of GPros in use, as Align has sold a lot of heli combos, and there are very few GPros, new OR used for sale anywhere. If that's the case, there are a very small number of people who have reported the problem.

-----
Dave

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

Team Heliproz

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04-29-2015 10:46 AM  34 months agoPost 60
Richardmid1

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Leeds, England

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I too tried to dial in a friends Trex 500L tail with the GPro to no avail.

The Trex 500 has always been a bitch when it comes to the tail so im not blaming the GPro. Although even with full tail pre comp the tail would still swing with fast collective inputs despite being run on a flat throttle curve. This was down to the low gain needed to fly without wagging, again, airframes fault not the GPro.

What used to improve the 500's tail was using a full size tail servo and beefier tail support rods with a better boom clamp (QuickUK) because in my opinion the tail boom is too skinny for its length on the Trex 500 and flexes too much.

60% of the time, it works every time!

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HelicopterFlybarless Rotor Head SystemsAlign GPro › Gpro rudder issue
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