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HomeAircraftHelicopterBeginners Corner › GY401 gyro do not hold steady the tail
03-04-2008 07:34 AM  10 years agoPost 1
kobou

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Thessaloniki, Greece

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Hi guys,

I have just finish my TREX 450SE V2 and I'm trying to track the blades... but i have the following problem with my tail.

The tail as soon as i increase my left stick moves slowly to right (CCW). I am afraid to hover this way cause i'm a newbbie...

After reading alot i rebuilt all my connections to the tail, check my belt tension, check my radio settings...

Do you think that the tail slider do not have to be in the center of the movement????

I discover, when i search for the solution, that if i turn the tail slowly with my hand, servo does not move, to "hold" the tail steady... but if i turn the tail more quickly, the servo moves...

Is this the right way that the gyro have to operate or i have sth wrong?????

thx in advance for your replies...

TREX450sev2, DX7, GY401

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03-04-2008 10:27 AM  10 years agoPost 2
Markus87

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Melbourne, AU

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Try increasing the gain on the gyro. How much gain do you have set at the moment? Both on the Gyro and in your radio set up? it almost sounds like its in rate mode instead of Heading hold

"Takeoff is optional, landing is not"

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03-04-2008 01:26 PM  10 years agoPost 3
jester4

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Brampton, Ontario

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yasoo file

I would check the gain as well. Also, are you in HH mode? Sometimes if you check the tail by moving it by hand, it's hard to see a movement if you are in rate mote.

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03-04-2008 05:31 PM  10 years agoPost 4
idigrc2

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Chico, CA

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Sounds like it's in normal mode. It's best to trim the tail in normal mode so that the tail doesn't rotate then switch to heading hold

I once choked a smurf to see what color it would trun

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03-04-2008 06:16 PM  10 years agoPost 5
kcass518

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Manhasset, NY - USA

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Sounds like you're in rate mode to me. When you power up the receiver, do you have the gyro in Heading Hold mode? If so, the little red light will come on and stay red. If the light is off, you're not in heading hold. If the light is blinking, you've either moved your trim, or you turned on your receiver with the gyro switch in Rate mode.

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03-05-2008 07:14 AM  10 years agoPost 6
kobou

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Thessaloniki, Greece

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thx for your posts,

I will check again about gyro mode and i will answer you...

The gain of the gyro is 25% on HH mode.

is it correct that the tail slider has not to be at the center of tail movement???

Or with different words the pitch of tail blades have not to be at 0 degrees????

thx again for your help

TREX450sev2, DX7, GY401

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03-05-2008 01:58 PM  10 years agoPost 7
kcass518

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Manhasset, NY - USA

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25% sounds low to me. I would try moving the gain up to 35 or 40% at least, and maybe more depending on how far from center your tailrod balllink is mounted on the servo wheel.

No, the tail slider does not have to be in the center, but after initializing the gyro (turning on the transmitter, then the receiver in Heading Hold mode), it should be close. If you are in Heading Hold (solid red light on gyro), the tail should not swing no matter where the tail slider was set up to begin with. To get optimal performance from the tail you will want to set it up correctly (there are two theories on how to do this), but just to hover it in the air, it should keep still whether the tail slider is set up correctly or not (within reason, of course).

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03-08-2008 06:53 AM  10 years agoPost 8
BuckyBlade

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Pasco, Washington - USA

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Kobou -

I've struggled with this myself, and think I've found just about every solution to the problem. I'll list a few things to look at here, and hopefully it will make some sense. I've listed them in the most likely order, so the first checks hopefully solve the problem. The more unusual ones will be toward the bottom of my list.

1. The GY401 likes ~79% gain on my JR 9303 2.4ghz. Futaba says start at 70% and adjust from there.

I am not familiar with the DX7, but if it's like the JR, you have a range of 0 - 100% gain. In this case start at 70% and go up or down from there. If your range is -100% - +100% then start with your gain at +35%. In these cases, negative numbers usually mean "rate" mode, and positive means HH mode. Also look at your manual to see if there is a setting for gyro control (my Futaba 9C had AVCS GY mode, and Normal mode, both of which needed to be set independently, and if not set correctly the gyro didn't behave as expected. Also ensure your gain is not dependent on your flight mode, or set each flight mode to the same gain value for now.)

If you have too much gain, when you're at mid-stick on the throttle, the tail will rapidly move side to side, which is called "hunting". If you're not comfortable lifting off the ground, try to get right to the edge of lift off so the skids provide as little grip on the ground as possible. It's also helpful sometimes to remove the rubber skid nuts to decrease friction.

The end goal here is to have your gain set so that the heli *just* barely stops hunting when you yaw right or left. As high as possible, without hunting.

2. Some folks may disagree, but when I setup my 450v2 I centered my servo, set my sub-trim to zero (0), and then carefully adjusted my linkage (tail push rod) so that the blades were 0-deg pitch.

To determine this, I fold my blades up so both blade ends point at the ceiling, and then from directly behind the tail, I watch the blades as I move the rudder to ensure when they return to the center position there is no "V", or spread between the blades. When you move the rudder stick, the blades should make a "V". When you release it, they should be almost exactly in-line with each other. Try to adjust your pushrod so that they're almost perfectly inline.

I'm certain some may think this is overkill, but I have 5 helis that have zero trim and zero sub-trim on the tail, and my gyros (4x401, 1x611) all hold just fine.

3. In some very rare cases, the motor can cause this issue. If your headspeed is low, when you're up to lift-off speed sometimes the tail is not being driven fast enough to counteract the torque from the blades. This is really unusual, but it's happened to me. If you are running the stock Align motor, this is very very unlikely unless the motor is damaged or defective. If you're using a different motor, this is a whole separate topic.

To check this, look at your throttle-curve in the radio. My personal opinion is that when my throttle is at center stick my throttle percentage is at 70%. There are tons of opinions on this, and I can't say mine is the right one, but I've personally found that this works well for me. This is the "normal" curve by the way, and not the idle-up settings. That's another conversation entirely.

4. It's also pretty unlikely, but if your tail-belt is very loose, it could possibly cause this problem. If the belt is too loose, you will notice sudden movements of the heli as if you were quickly pressing and then releasing left rudder (heli's nose rotates counter clockwise.) This would be very quick, unpredictable, and may even be heard if you're close enough to the heli and the belt is slipping. If you can easily press one side of the belt against the other (just inside the body-frame, behind the pulley and in front of the tail boom) with a screwdriver or something, this may be an issue. The belt tension I like is keeping it tight enough not to allow one side to touch the other side, but loose enough to *almost* touch (within 2mm).

Also, if you suspect any belt damage at all, be sure to replace it. You'll know it's damaged if some of the belt-teeth are missing, or if they look smaller than other teeth, or if the edge of the belt looks like someone ran a yellow marker over it (showing the belt fibers). Again, this is unlikely.

5. I'm not certain this could cause such a drastic problem, but it's worth checking. In throttle-hold mode, set your throttle at center-stick and check your main-blade pitch. If you just look with your eyes, try to see that each blade is flat (or at 0 degrees pitch). If you're a newbie you may not have a pitch gauge, or you may not be entirely certain how to measure this, so here's an example of how to check:

a. Put the heli in front of you, pointing directly to your right.
b. Turn on your radio, and enable throttle hold (if you don't know how to do this do NOT attempt this without help).
c. Ensure your throttle is at zero, and then plug in your battery on the heli.
d. STEP AWAY from the heli, and move the throttle stick up just a little bit; ensure your throttle hold is actually working (the swashplate should rise, but the rotor will NOT spin).
e. Rotate the rotor blades until the flybar is parallel to the tail-boom (pointing the same direction the nose of the heli is pointing).
f. Try and adjust the flybar so it is level. I use a small level that I actually attach to the flybar with two-sided tape.
g. Look at the blades and try to determine if the blade is level with the flybar. I use another small level that's attached to my pitch-gauge to get an accurate measurement, but we're looking for gross mis-alignment here).
h. If both rotor blades look relatively level, this is definitely not your problem. If they are not both close to level, it could potentially create enough drag that it would slow your tail and cause counter-clockwise rotation. Again this is a very unlikely cause.

6. This is a newbie mistake I made a few times, but it's worth mentioning. Ensure your gyro direction is set correctly. There's a small dip-switch on the top that will let you set "Normal" or "Reverse". Ensure this is set right.

If you have it set wrong, as soon as you approach lift-off speed, the heli will rotate very fast on the ground (as if you had no gyro at all or were doing a rapid pirouette) and you will be unable to control it at all. It can rotate both ways, so it's not always counter-clockwise.

If this is the case, try changing that setting to the opposite value. Generally, if the gyro is mounted on top of the tail, and you can read the words on the top when the heli's tail points toward you, you should be in normal mode. If you have it mounted under the tail (and the gyro is upside down) then it needs to be in reverse mode. Again, this particular symptom is drastic, so you'll likely know right away if this is a potential issue.

There are a few even more obscure issues, but I don't think they're worth mentioning unless you try everything here and still have the problem. If so, send me a private message, and we'll see if we can get it sorted.

Hope this helps, and Cheers!
BuckyBlade

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03-08-2008 07:00 AM  10 years agoPost 9
BuckyBlade

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Pasco, Washington - USA

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Man - I forgot a very important step for point 5, between "d" and "e".

Move your throttle stick to center, or as close to 50% throttle as you can manage. This should put your swashplate at 50% travel, and your rotor blades should be level (or at zero degrees pitch).

Sorry I missed this. Hopefully you solved this before you got to this point.

/Bucky

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03-08-2008 04:03 PM  10 years agoPost 10
kobou

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Thessaloniki, Greece

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I try all these...

I increase the gain from 72% to 79%.

I move the tail servo servo about 2mm backwards so tail blades have a little pitch.

I try to hover in normal mode... the heli i think was more stable but it the tail turns to right less than before...

The problem was when i pull my left stick backwards to stop, the heli turns like a crazy machine, i think cw, and i brake one tail blade.
I replace it and try again but the same happens without any breaks this time.

I don´t know if this rapid turn take plase because of the pitch that the tail blades have or from the gain or from another reason...

Also i notice that if the throtle was about at the middle of zero pitch and full down the heli has more vibration that if i increase the throttle...

PS: I check my belt and i see the yellow line that Bucky said. Is it possible to destroy the belt with just 1 or 2 minutes of working????

kobou

TREX450sev2, DX7, GY401

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03-08-2008 04:06 PM  10 years agoPost 11
kobou

rrNovice

Thessaloniki, Greece

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2. Some folks may disagree, but when I setup my 450v2 I centered my servo, set my sub-trim to zero (0), and then carefully adjusted my linkage (tail push rod) so that the blades were 0-deg pitch.

To determine this, I fold my blades up so both blade ends point at the ceiling, and then from directly behind the tail, I watch the blades as I move the rudder to ensure when they return to the center position there is no "V", or spread between the blades. When you move the rudder stick, the blades should make a "V". When you release it, they should be almost exactly in-line with each other. Try to adjust your pushrod so that they're almost perfectly inline.

I'm certain some may think this is overkill, but I have 5 helis that have zero trim and zero sub-trim on the tail, and my gyros (4x401, 1x611) all hold just fine.
So you tell me to have slider in the middle of the movement and no pitch to tail blades...

TREX450sev2, DX7, GY401

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03-08-2008 04:26 PM  10 years agoPost 12
kobou

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Thessaloniki, Greece

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PS: I check my belt and i see the yellow line that Bucky said. Is it possible to destroy the belt with just 1 or 2 minutes of working????
i will post a photo of my belt in order to tell me if has a problem...

the yellow line is barely visible...

TREX450sev2, DX7, GY401

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03-08-2008 04:37 PM  10 years agoPost 13
kobou

rrNovice

Thessaloniki, Greece

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1. The GY401 likes ~79% gain on my JR 9303 2.4ghz. Futaba says start at 70% and adjust from there.

I am not familiar with the DX7, but if it's like the JR, you have a range of 0 - 100% gain. In this case start at 70% and go up or down from there. If your range is -100% - +100% then start with your gain at +35%. In these cases, negative numbers usually mean "rate" mode, and positive means HH mode. Also look at your manual to see if there is a setting for gyro control (my Futaba 9C had AVCS GY mode, and Normal mode, both of which needed to be set independently, and if not set correctly the gyro didn't behave as expected. Also ensure your gain is not dependent on your flight mode, or set each flight mode to the same gain value for now.)

If you have too much gain, when you're at mid-stick on the throttle, the tail will rapidly move side to side, which is called "hunting". If you're not comfortable lifting off the ground, try to get right to the edge of lift off so the skids provide as little grip on the ground as possible. It's also helpful sometimes to remove the rubber skid nuts to decrease friction.

The end goal here is to have your gain set so that the heli *just* barely stops hunting when you yaw right or left. As high as possible, without hunting.
75% at dx7 means 50% in HH mode

TREX450sev2, DX7, GY401

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03-08-2008 04:45 PM  10 years agoPost 14
kcass518

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Manhasset, NY - USA

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Are you saying that you can keep it still when in a hover with the rudder stick in the middle? And then when you lower your throttle it starts to rotate? Before you lift off, is the red light on solid on the GY401? Have you checked all your programming on the transmitter? Is there any trim in the rudder? Is anything input in the REVO? REVO should be disabled or zeroed. Subtrim should be zero on the rudder.

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03-08-2008 10:19 PM  10 years agoPost 15
kobou

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Thessaloniki, Greece

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Are you saying that you can keep it still when in a hover with the rudder stick in the middle? And then when you lower your throttle it starts to rotate?
i have never be in the air...heli is almost steady just before the lift...and when i lower the throttle it starts to rotate!!!!!
Before you lift off, is the red light on solid on the GY401?
When i try to setup gyro do i have it in normal or in HH mode??? cause i try to setup it in normal
Have you checked all your programming on the transmitter?
Yes
Is there any trim in the rudder?
No
Is anything input in the REVO? REVO should be disabled or zeroed. Subtrim should be zero on the rudder.
just as you said...

TREX450sev2, DX7, GY401

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03-08-2008 10:28 PM  10 years agoPost 16
allns47

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Richmond IN.

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It sounds like you need to get some help from someone to make sure everything is set-up right..

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03-09-2008 12:14 PM  10 years agoPost 17
kcass518

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Manhasset, NY - USA

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Two things that I think might be the problem.

1. You need to be sure that the gyro is in Heading Hold mode when you turn on your receiver. You should have a switch on your transmitter assigned for Heading Hold. Flipped one way, it is in heading hold, the other way, it is in Rate mode. It needs to be switched to Heading Hold before turning on the receiver. (Of course, you turn on your transmitter, and then your receiver) The little red light on the top of the gyro should glow solid RED. If it doesn't, you need to turn everything off, then flip the switch the other way, then turn on your transmitter and then your receiver. Make sure the red light stays on solid.

2. Your gyro might be REVERSED. After turning everything on in Heading Hold Mode as stated above, flip the switch back to Rate mode. The RED light will now be OFF. Make a mental note of which way your rudder moves when you move your rudder stick all the way to the left. (with the rudder straight up and down, looking at it from above, the top blade should rotate counter clockwise. Okay, now center your rudder stick. Pick up the heli. Rotate the whole heli clockwise (like a right turn). The top rudder blade should again turn counter clockwise as it did before. If it doesn't, find the switch on the gyro that says "Reverse" and flip it the other way. Test it again as above. This should fix your problem.

Let us know.

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03-09-2008 04:01 PM  10 years agoPost 18
kobou

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Thessaloniki, Greece

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kcass518 you are right...!!!
1. You need to be sure that the gyro is in Heading Hold mode when you turn on your receiver. You should have a switch on your transmitter assigned for Heading Hold. Flipped one way, it is in heading hold, the other way, it is in Rate mode. It needs to be switched to Heading Hold before turning on the receiver. (Of course, you turn on your transmitter, and then your receiver) The little red light on the top of the gyro should glow solid RED. If it doesn't, you need to turn everything off, then flip the switch the other way, then turn on your transmitter and then your receiver. Make sure the red light stays on solid.
This is ok... gyro is on HH mode when i turn on the receiver...
2. Your gyro might be REVERSED. After turning everything on in Heading Hold Mode as stated above, flip the switch back to Rate mode. The RED light will now be OFF. Make a mental note of which way your rudder moves when you move your rudder stick all the way to the left. (with the rudder straight up and down, looking at it from above, the top blade should rotate counter clockwise. Okay, now center your rudder stick. Pick up the heli. Rotate the whole heli clockwise (like a right turn). The top rudder blade should again turn counter clockwise as it did before. If it doesn't, find the switch on the gyro that says "Reverse" and flip it the other way. Test it again as above. This should fix your problem.
WRONG my gyro is REVERSED...

I will try this and i will let you know...

TREX450sev2, DX7, GY401

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03-09-2008 04:39 PM  10 years agoPost 19
kcass518

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Manhasset, NY - USA

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Good. Maybe we're getting somewhere.

Also, and forgive me if you know this, when the gyro is in Heading Hold mode, and you first turn on your receiver - THE HELI MUST BE KEPT ABSOLUTELY STILL UNTIL THE RED LIGHT COMES ON SOLID. If you move the heli when the gyro is initializing, it will confuse the gyro which will cause it to turn the heli on its own.

Hope this helps.

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03-13-2008 12:14 PM  10 years agoPost 20
JetFire

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The Golden STATE

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GY401 unresponsive..
Futaba radios with gyro functions… check your mode set to “GY”. I had the same problem and this did the trick.

Best of luck

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HomeAircraftHelicopterBeginners Corner › GY401 gyro do not hold steady the tail
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