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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › Century Flybarless N640 w/ Gpro
11-07-2015 10:48 PM  4 years ago
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nrad2000

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Century Flybarless N640 w/ Gpro
I'm having trouble with the Gpro. I spool up the helicopter and I see the Swashplat moving slowly to the right. Head speed was fast enough where the helicopter began to tilt over. I punched the throttle and got her airborne. The settings on the Gpro is default. Had to start somewhere. The tail is hunting and the cyclic is twitchy. I'm ok with the twitches and hunting - I figure I can tweak that later. My problem is the takeoff. I tried it a few more time and every time it tips over Right and maybe even left. Once it even tilted backwards. I'm taking off from a hard asphalt runway. I have 2 double sided servo tapes holding the Gpro. No one at the club has a Gpro so, I need help.

Jim.
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11-08-2015 12:14 AM  4 years ago
dkshema

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Cedar Rapids, IA

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First things first, how certain are you that you have the GPro and your transmitter properly set up?

I have eight up and running, on nitro and electric helis, all are well behaved. The GPro is quite well-behaved.

Twitches and hunting tell me you don't have the basics set right.

What color is the status light?

What transmitter, what kind of receiver, what are you using to supply power to the GPro?

Pictures would help, too, of the installation.
-----
Dave

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

Team Heliproz
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11-08-2015 02:08 AM  4 years ago
jason46

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just tossing this out there..
I had the problem you're describing with a 3gx, the issue turned out to be a bad bind. Each time I powered up the centers could be on or slightly off, when the aileron center was off it creates a small amount of drift in the swash. Rebinding solved the issue.

I don't know what radio you're using but it might help.
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11-08-2015 08:37 AM  4 years ago
nrad2000

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My radio is a JR 9503. Running 2 satellite spektrum DSMX's. Running a Turnigy RotorStar Dual Power Regulator: 5.2v to receiver and 6v to Turnigy 1268HV servo's. I do not have a governor sensor hooked up. I followed the YouTube video instructions down to the word. Does the helicopter need to be on a level surface when powering up? Our runway has a slight slope.
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11-09-2015 04:03 AM  4 years ago
jason46

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Runnimg sats off the gyro at 5.2v may cause brown outs.
I would suggest raising it if you can, and rebinding if you haven't.
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11-09-2015 02:37 PM  4 years ago
wc_wickedclown (RIP)

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swashplate drift most of the time is caused by vibrationInsha Allah made in america
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11-10-2015 02:39 AM  4 years ago
dkshema

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Cedar Rapids, IA

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I'd have to agree that you're seeing excessive vibration at the GPro. I took a look at the N640 build manual, I didn't see a lot of great choices for where to nail the FBL controller down. It appears the only good spot is that flat spot, up front, just ahead of the hex start cup and start shaft.

I would guess that is one of the more active vibration spots in the whole heli.

OK, so how to tame the vibration monster? I'll assume you were able to get the clutch installed on the motor so it and the start shaft have as little runout as possible.

Beyond that, you're going to want some kind of vibration damper between the heli and the GPro.

In my NX4, the heli shipped with a rectangular steel plate about 3/32 inch thick and just a bit larger than the GPro base. I used two layers of 3M gray double-sided tape on the heli mounting spot, stuck the plate on top of the tape, added one more layer of the gray 3M double sided tape on the steel plate, then stuck the GPro on top of that.

The steel plate provided adequate vibration damping, and the unit behaves very well.

On my Trex 700N, I scrounged up a metal mounting plate from one of my old tail gyros. Again, it's a steel plate, it's square, and just a tad bit larger than the base of an old GY401 gyro.

On the 700N, I used a couple of layers of 3M clear VHB tape on the heli frame, added the steel plate, then used one more layer of 3M double sided gray mounting tape, and stuck the GPro on top of that stackup.

It's kind of hard to see, but that's my 700N installation. You can see the shiny steel plate.

You may have to resort to the use of a metal vibration damper to get the FBL controller to settle down.

This is the plate from the Gaui NX4 -- a couple of bucks plus shipping from EmpireRC:

http://www.gaui.com.tw/product/nx4-...ibration-plate/
-----
Dave

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

Team Heliproz
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11-11-2015 06:40 AM  4 years ago
nrad2000

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I'll try rebinding the Gpro. Is there something I can do in the parameter setting to stop slow down the tilting? Cyclic Swashplate gain? It's set at 80. Agility 80. And the other one 80 also.

can I just add more double sided servo tape (3 high) or is servo tape to spongy? I don't want to quit just yet on my first flybarless system.
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11-11-2015 12:34 PM  4 years ago
jason46

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Does the swash tilt while it is sitting or only after spool up?

If you set flight agility and flight response to 70 that will slow things down.

Was the nitro engine new or used when you got it?
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11-11-2015 01:04 PM  4 years ago
dkshema

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Cedar Rapids, IA

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If the problem is due to vibrations, you will have to fix that.

1 Find the source and correct it.

2 Move the GPro to a different part of the chassis

3 Use a steel gyro mount plate as described above to change the mass and associated resonances at the gyro due to the vibrations.

4 Make sure the wires plugged into the GPro have some slack and aren't drawn tight or flopping around.

5 Make sure your canopy isn't resting on top of or one or more corners of the GPro.

It may require a combination of the above to cure the problem.

As the whole setup appears to behave without the motor running, rebinding won't hurt but it won't help. The radio link appears good.
-----
Dave

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

Team Heliproz
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11-11-2015 03:21 PM  4 years ago
nrad2000

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The engine is my trusty OS 55hz. Just replaced the bearings before installing the engine into this century frame. I have 4 other engines to swap out with but they all run the same. One thing I haven't checked is the clutch/clutch housing balance. Gpro is clear from the canopy by a centimeter. I think there is enough slack from the servo wires (the bundles of servo wire attached to the Gpro is thick).

While engine is idling I can see the swashplate jittering. When I slowly spool up I can see the swashplate slowly pitching either left or right. Can't tell if it's pitching back or forwards but I'm sure it does. I'm guessing because the blades are not perfectly stretched out that the copter slightly shackes until center is found. My blades are not tight nor loose on the grips. I think it's just right. I'll try to mount the Gpro differently. Maybe use 3M double sided (instead of the servo tape from dubro) and go quadruple stack high.

I had a blade strike the ground the other day. Tried to spool up really fast to get her off the ground quickly. The helicopter pitched forward/left on its front skids - tipped backwards - hit the tail fin on the ground - while punching collective up the copter tilted more back/right - blades struck ground - got her hovering 10 feet. Rock solid once in the air. The tail is hunting but I can adjust the parameters later on that.

The helicopter is balanced.
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11-11-2015 03:26 PM  4 years ago
nrad2000

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Forgot to say, while spooling up I can see the swashplate plate slowly going towards one side (it can be left, right, maybe forward or back) so as spooling up I'm countering it with my right stick.
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11-11-2015 04:18 PM  4 years ago
jason46

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The engine bearings is what I was getting at, but if you replaced them shouldn't be an issue.

If the swash isn't tilting at idle it's not the radio/bind centering issue.

The engine isn't super rich is it?

It is possible to have too much sponge effect in the gyro pad and you get a rebound kick, but adding another layer of gyro tape sounds like a good thing to try.

Are the blades snug?
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11-11-2015 07:05 PM  4 years ago
don s

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Chesapeake, VA

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Maybe the unit is one the way out?E820, Raptor G4N, X50F/E, E620, Forza 450, and some planks.
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11-11-2015 07:18 PM  4 years ago
nrad2000

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Engine is towards the rich side. But not lean. It idles nice but gurggles a little as the engine ramps up RPM. I'll try remounting the Gpro. 1) add a metal plate, 2) add a couple more layers of 3M tape, 3) changing parameters for the swash to 70, 4) if that fails I'll get another Gpro and see if that makes a difference.
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11-12-2015 02:16 AM  4 years ago
dkshema

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Cedar Rapids, IA

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Forgot to say, while spooling up I can see the swashplate plate slowly going towards one side (it can be left, right, maybe forward or back) so as spooling up I'm countering it with my right stick.
That sounds like a classic vibration-related problem. I seriously doubt the GPro is "going out."

You may want to look for the source of the vibration in the meantime.
-----
Dave

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

Team Heliproz
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