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HelicopterFlybarless Rotor Head SystemsFutaba CGY › Rudder Starting to Kick and Not Hold
02-22-2017 01:07 PM  7 months agoPost 1
Ironside

rrApprentice

Baltimore, MD

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So I've been flying my Trex 600E with a CGY750 and a BLS251 servo for quite a while now with no issues. However as of late, the rudder is starting to get what I can only describe as a twitch in both normal and idle up mode and is starting to float and not hold a heading. It doesn't seem to be as bad at lower headspeeds but it is still there. Its not the normal gain being too high (constantly hunting for center) type of motion but more of a slight kick every 2-3 seconds. I thought it might be the tail servo going bad so I replaced it but that didn't fix the problem. I also tried lowering and raising the gain to no avail either. I don't know why I would need to but my next step is to replace the tape on the sensor to see if that helps. Like I said, its been running fine for well over a year and nothing has changed. Anyone have an ideas I can try?

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02-22-2017 01:47 PM  7 months agoPost 2
JuanRodriguez

rrProfessor

The Villages, Florida

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Replacing the tape is a good and cheap start.....

Also make sure that ALL your connections are sound.....

Are you running a separate BEC ?

Been there, done that and old enough to know better.....

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02-22-2017 01:59 PM  7 months agoPost 3
Ironside

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Baltimore, MD

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I am. I'm using a CC BEC Pro. Is there something I should check with that other than the connection?

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02-22-2017 02:05 PM  7 months agoPost 4
JuanRodriguez

rrProfessor

The Villages, Florida

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What's the output voltage ? Just make sure you're getting the right voltage from it....

The other thing to check is to make sure nothing has gotten "loose" all the way from the servo to the tail and pitch slider assembly which may cause the pitch to the t/r blades to creep....

Been there, done that and old enough to know better.....

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02-22-2017 02:27 PM  7 months agoPost 5
Tool Man Vegas

rrApprentice

Las Vegas, Nevada, U.S.A

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If you have guides for tail control rod, make sure there is no binding.

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02-22-2017 02:28 PM  7 months agoPost 6
Flyin for Jesus

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Dana Point, Ca. 92629

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Check that the tail is moving smoothly through its full range. .

EDIT - ^^^ beat me by a minute.

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02-22-2017 04:31 PM  7 months agoPost 7
don s

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Chesapeake, VA

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Could be motor related...

E820, Raptor G4N, X50F/E, E620, Forza 450, and some planks.

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02-22-2017 06:46 PM  7 months agoPost 8
Ironside

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Baltimore, MD

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I will definitely check these out. I'm not using any pushrod guides. I'm using a Sullivan Gold-n-Rod setup. The rod is taped and CA'd to the boom except for a small bend at the back to engage with the ball-link, so its pretty straight. It's in a fuselage. Don S, I considered the motor as well so I changed it out going from a Scorpion to a KDE motor. This however gave me the same symptoms. I haven't looked at the voltage on 750. I will check that when I get a chance (hopefully this weekend). I will also double check the solder connection of the BEC. I haven't looked that in a while. Thanks for the help fellas. I appreciate it. If anyone else has any ideas, please share those as well.

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02-22-2017 11:38 PM  7 months agoPost 9
don s

rrElite Veteran

Chesapeake, VA

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in a fuselage
Are the mechanics still mounted to the fuselage securely?

E820, Raptor G4N, X50F/E, E620, Forza 450, and some planks.

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02-22-2017 11:54 PM  7 months agoPost 10
daggit

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Claremont, MN

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I don't know electrics but on my big gasser helis tail hits was an indicator of a bearing going out somewhere.

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02-27-2017 01:29 PM  6 months agoPost 11
Ironside

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Baltimore, MD

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don s, I took the mechanics out of the fuselage until I can figure out the tail issue. It's in a pod-n-boom mode now.

daggit I think that's probably the next thing to check. I had a chance this weekend to try and track down the problem but couldn't find it. I checked all solder joints and even replaced a few just to be safe. I also ensured that the tail was getting the proper voltage which it was.

However in my search for a solution to the tail kicking problem, I did find that the pin that came pre-installed in the torque tube had come out some kind of way and appears that the engagement tooth of the torque tube may have started to spin. When I pulled the boom off, the first picture is what I saw with the torque tube. As you can see the pin hole had turned and wasn't lined up.

I should've known better because I thought damn what are the chances I'd immediately find the problem? Well it wasn't. After re-pinning the torque tube and putting it back together, I figured I'd try and see if that fixed the problem but it didn't. The helicopter it still kicking. I even went as far as resetting the CGY750's rudder section and set it up again but that didn't work either.

It's hit or miss in normal rpm mode. Sometime the tail will kick and sometime it won't. However once I switch to idle up 1 & 2 it really starts to kick (tail kicking to the left). The funny thing is it only does it in heading hold (AVCS) mode. In normal rate mode it's rock solid. This fact alone is starting to make me think it may be something wrong with either the control unit of the CGY750 or the gyro sensor itself, but that's just a guess. The next opportunity I get, I will check the bearings but in the meantime if anyone has any other suggestions I'm all ears.

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02-27-2017 04:12 PM  6 months agoPost 12
Dr.Ben

rrMaster

Richmond, VA, USA

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I would look outside the 750 itself as a cause right now. The fact it does it in AVCS but not rate mode is not necessarily unusual. You have to start at the ball link on the rudder servo and work you way back to the pitch arms on the tail rotor grips looking for binding. Then you have to look at the thrust races recognizing that if the tail was working ok and now isn't BUT nothing has been replaced, then the usual suggestion about making sure the thrust races are in there correctly carries less weight. They and the radial can go bad over time, though.

If you have ruled out every single mechanical issue with the tail, you can play around with thicker gyro tape. Understand though that if that helps the issue, you need to be looking for vibration on the model. In the rare cases of sensor failure with a 750, a hunting tail is not the normal presentation for that. They drift badly.

Ben Minor

Team Synergy Team Futaba Team Kontronik USA
Progressive RC

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02-27-2017 04:50 PM  6 months agoPost 13
don s

rrElite Veteran

Chesapeake, VA

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Problem with the one-way bearing?

E820, Raptor G4N, X50F/E, E620, Forza 450, and some planks.

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02-27-2017 05:02 PM  6 months agoPost 14
Ironside

rrApprentice

Baltimore, MD

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Thanks guys. I'll look into it and report back.

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03-13-2017 02:00 PM  6 months agoPost 15
Ironside

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Baltimore, MD

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I had a chance to mess around with the heli this weekend to try and figure out the kicking problem. My first initial thought was that maybe the OWB was bad or slipping as was previously mentioned. So I replaced the one way bearing with a brand new one (2nd) and tried a hover. Same kicking result. Next I swapped out the entire gear train from the upgraded KDE M1 version to the stock MOD.7 (3rd) and tried a hover. Same results. I then pulled the entire boom section off to make sure the bearings were good on the torque tube, looked at all the bevel gears to make sure no teeth were missing, look at the thrust bearings in the tail rotor, and checked to make sure there was no binding between the tail servo and the control arm which there wasn't. As mentioned I've already replaced the tail servo from a Futaba 9254 to a Futaba BLS251. After all of that I still have the kicking problem and it doesn't hold a steady heading. The next thing I will try which I literally just realized I never did was to replace the tape. I looked at it before and it felt fine. the stock CGY750 tape is really thin but I will replace it nonetheless. However as Dr. Ben said, if that ends up being the problem, there is a bigger issue with vibrations somewhere. I will also try a different motor as well. I'm currently using a recently purchased used KDE 530Kv motor. I will try my Scorpion motor and see if that makes a difference as well. If not, I think the first thing I will do is try a complete reset of the CGY750. If that doesn't work, I have a GY401 that I will put on and see if the same problems show. If none of these work I will completely take the helicopter apart and rebuild it. At this point I'm starting to get a little irritated. I only get to touch my helis a few hours on the weekends because of kids sports and family duties. I hate having to diagnose problems when I should be flying lol. The next time I can I will also get a video of the heli that way you guys can see what I'm talking about.

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03-15-2017 08:03 PM  6 months agoPost 16
nickmaxwell

rrApprentice

Huntsville, AL

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What ESC? And using internal governor or CGY750 gov?

This sounds more like an ESC kick due to GOV GAIN or PWM rate... or possibly noise.

I fought this a bit with Castle ESCs in my F3C models + Scorpion motors. Matching the timing to the motor specs, and then increasing the PWM frequency cured the problem.

If you are using a Castle ESC try increasing the PWM rate from default (I think 8khz, so increase first to 16khz). If that makes the kick worse, leave the frequency the same but lower the gain 5-10 points (default I think is 15).

Also, do you have the Ferrite Ring on the ESC lead? If not a RadioShack choke will work.

Edit: Regarding gain, I am referring to the GOV gain in Castle Link. From what it sounds like the PWM is off (low RPM tail kick), and maybe the gain is too high too, which is why it is worse at HIGHER RPM in a hover.

Nick

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03-15-2017 09:28 PM  6 months agoPost 17
Ironside

rrApprentice

Baltimore, MD

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I'm currently running a KDE 530kv motor with a CC Phoenix Edge 120HV with a CC BEC Pro and the ESC does have the Ferrite ring installed. I will try increasing the PWM rate and see what happens. The timing specs of the KDE motor say 5-15 so we'll see how it goes. Thanks for the advice Nick. Probably won't get to it until the weekend but I will report back.

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03-27-2017 03:22 PM  6 months agoPost 18
Ironside

rrApprentice

Baltimore, MD

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***Problem Solved***

Well I finally got a chance to play around with my helicopter this weekend and got the problem worked out. It turns out Nick was spot on. I first looked at the PWM rate and that was at the top range of what the motor specs suggested, so I left that one as it was. So taking into account what Nick suggested, I then looked at the gain settings on the ESC and figured I'd try lowering the ESC gain by 2pts. Sure enough after that the tail kick stopped and the helicopter is rock solid on the tail and as smoothed as can be. It's crazy though because I've been flying helicopters for a little more than 8yrs and I've never once messed around with the ESC gain or the PWM rate. Goes to show you never stop learning. Thanks for the knowledge Nick and also a big shout out to everyone for your suggestions. Hopefully this will help someone else down the road somewhere.

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