RunRyder RC Helicopter Topic - gyro mount location

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Bergen R/C Helicopters > gyro mount location

main rotor
Heliman
Location: Pomona NY USA

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bought my bird used and the gyro (gy501) is mounted just on top of the collective servo. The directions for the gyro say it should be as close to the center of the rotation axis as possible. what do you think??

03-28-2009 04:14 AM

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MAXHSHV
Veteran
Location: deerriver,mn usa

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true that it should be close to mainshaft, but not directly on servo,need to atleast space it up a bit . some servos will m ess up the gyros.

To much power is never enough.

03-28-2009 04:41 AM

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main rotor
Heliman
Location: Pomona NY USA

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its not attached to the servo but on the frame above it

03-28-2009 12:09 PM

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Chris Bergen
Elite Veteran
Location: location

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Gyros sense rotational movement. My opinion is that it does not matter if the gyro is directly under the mainshaft or on the end of the boom, it STILL sense a rotational movment.

45 degrees is 45 degrees, no matter how far out it is from the point of rotation.

More importantly, is the gyro mounted with some green 1/4" thick tape? This is Zeal tape, and HIGHLY recommended for use on Gassers.

Chris Bergen

03-28-2009 03:27 PM

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Pinecone
Key Veteran
Location: Maryalnd

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Unless you heli is flexible, it doesn't matter where the gyro is mounted, it will work fine. You can put it on the tail case if you want. Or a on a pole 10 feet out in front.

All parts of the heli frame rotate the same amount at the same time.

Terry
Blade CP Trex 450 SE
QJ EP8v2 EX Gaui Hurricane 550
Vibe 50 Bergen Intrepid Gasser

03-28-2009 04:02 PM

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Aaron29
Key Veteran
Location: Bossier City, LA

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Does not need to be near mainshaft. But it DOES need to be on a surface which is perpendicular to the mainshaft and level. I think where you have it above the collective servo will be fine.

In fact, right next to the mainshaft may not be as good because of some vibration it'll pick up there.

-Aaron

03-28-2009 11:49 PM

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main rotor
Heliman
Location: Pomona NY USA

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Im certainly no physics expert but I think there is only one place on the heli that pivots on the axis of rotation and thats right under (or above) the main shaft.After all any other point is just moving in an arc around that point. The further out you go the more the movements resemble liner motion?? In other words the outer edge of a circle starts to become straight as it gets larger and larger so with that in mind If the gyro was mounted out in front on a 10 foot pole than i bet it would respond to aileron inputs as well?? It obviously is not going to be out that far but just wondering if it is true? if it is true than even the small distance from center would effect its sensing by some amount. What do you think??? By the way the gyro is mounted with the tape that came with it from futaba

03-29-2009 04:19 AM

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Aaron29
Key Veteran
Location: Bossier City, LA

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It's impossible to turn any part of the heli without all parts of the heli (below the swashplate) turning the same. Any attempt to do so will bend the airframe, and is probably due to a crash.

Say you put your gyro right next to the mainshaft. A 30 degree heading change will be a 30 degree heading change. That we agree on.

Now, consider another gyro up front on the nose. Again, turn the heli 30 degrees. The gyro is now pointing 30 degrees off from where it was.

The front mounted gyro cannot sense the fact that, while rotating, it also moved to a different location. All it senses is rotational movement.

Both gyros sensed a 30 degree heading change.

A gyro doesn't need to swivel as though centered on a shaft. Yes, the gyro up front also had some side to side positional movement, but it didn't sense this. And the side to side movement doesn't take away the fact that it just turned. You can put it as far out as you want from the mainshaft and it turns that same 30 degrees and will notice it.

As long as it is mounted on a plane perfectly perpendicular to the mainshaft it should NEVER pick up on either elevator or aileron no matter how far from the mainshaft it is.

Imagine sitting in the front of a bus. Just because you aren't right in the middle of it doesn't mean you can't tell when it's turning. Or how about the instruments in an airplane? The gyros are all up front in the cockpit and still work fine.

The argument you are trying to make is akin to saying that an aircraft gyroscopic heading indicator cannot work well, because the airplane pivots around a point a mile off of one wing. (Think about it. An airplane with a one mile turn radius is a MILE away from its own pivotal center, yet the directional gyro still works.)

-Aaron

03-29-2009 06:15 AM

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Pinecone
Key Veteran
Location: Maryalnd

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Think of mounting a series of compasses on the heli. One on the tail, one under the mainshaft, one at the nose.

If we start with the heli pointed due north, all the compasses show North. Turn the heli 90 degrees clockwise and all the compasses show East.

Same with the gyro. It only senses rotation.

Terry
Blade CP Trex 450 SE
QJ EP8v2 EX Gaui Hurricane 550
Vibe 50 Bergen Intrepid Gasser

03-29-2009 01:06 PM

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main rotor
Heliman
Location: Pomona NY USA

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Sorry i dont know anything about real aircraft instruments but still have a hard time understanding how a gyro can tell the difference between rotational and liner movement?? I believe it can only tell the difference if the rotational movement is on its own axis. That way it has something to reference it self to.(like the other half of the gyro moving in the opposite direction) How can it not respond to a movement say 6" liner and respond to the same movement if it were rotational and not from its own axis?? Hope im somewhat clear on my question? Maybe the gyro in my brain is off axis and this is my problem?? LOL

03-29-2009 02:58 PM

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Aaron29
Key Veteran
Location: Bossier City, LA

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Quote
but still have a hard time understanding how a gyro can tell the difference between rotational and liner movement

It sounds like you're almost there, but you aren't putting 2 and 2 together...

The gyro DOESN'T know or care that it moved linearly. It only senses the rotation.

Realize no matter where it is on the heli it rotates the same amount.

Imagine 2 gyros on the heli and turn the heli 90 degrees. They BOTH turned that same 90 degrees. It matters not that one is displaced from it's original position while making that same rotation.

It was once thought you needed it near the mainshaft and that myth has been busted in books like Curtis Youngblood Q and A and Ray's Authoritative Manual. (Plus a little analysis)

-Aaron

03-29-2009 03:59 PM

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Aaron29
Key Veteran
Location: Bossier City, LA

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Put another way...

The only time the ROTATIONAL AXIS is on the MAINSHAFT is when you are hovering.

Say you go through all the trouble of making the gyro as close as possible to the mainshaft. Now take your helicopter into forward flight. And make a turn. Say it's a 300 foot radius turn.

Your carefully mounted gyro on the mainshaft would be flying a giant circle in the sky. But it still wouldn't have a clue that that turn was in FF vs. a hover.

In this big turn, the actual ROTATIONAL PIVOT POINT is not even on the helicopter!!! Read that twice.

It's inside the turn basically on the ground somewhere a few hundred feet away. Your argument would have us moving the gyro there now.

The gyro doesn't care where it is, it cares about it's heading.

-Aaron

03-29-2009 04:08 PM

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main rotor
Heliman
Location: Pomona NY USA

My Posts This: Topic Forum

I think your misunderstanding my point. Im not saying that the gyro has to be at the pivot point of any imaginary flight circle but must be on the pivot point of the heli which is under /over the main shaft and NEVER changes. I totally agree that the pivot point of a 300 foot circle is not on the heli. I dont believe that the pivot point of reference for the gyro is that point though. The action of making a turn from foward flight among other things (ie aileron)is to pivot the bird about its mainshaft and force the nose to point in the direction you want to go.During that instance the gyro wants to oppose that movement and as long as the rudder input is there the gyro dont do anything to the nose but the heli is still in a circle correct??

03-29-2009 05:26 PM

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Aaron29
Key Veteran
Location: Bossier City, LA

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Well.

You need to understand the fact that 2 gyros mounted on a heli, one in the nose and one on the mainshaft, make the same rotational changes.

I understand what you're trying to say, but the fact that I'm not nodding my head is because you're wrong. Not because I don't understand.

Even in your 10 foot long pole example. If you turn the heli 90 degrees it turns the gyro on the front of the pole 90 too. THAT is what you need to wrap your head around.

In any case, this argument is moot. No gyro has ever been mounted below the mainshaft, and many people are using gyros well away from the mainshaft with no ill effect.

Theorize all you want. Your mental model is not shared by the real world. Logic tells us that if we think one thing and reality presents us another, that we might be wrong, but you're hanging onto your idea.

Until you can at least accept the two gyros turning the same rotational movement we cannot move further.

-Aaron

03-29-2009 05:38 PM

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main rotor
Heliman
Location: Pomona NY USA

My Posts This: Topic Forum

(quote) You need to understand the fact that 2 gyros mounted on a heli, one in the nose and one on the mainshaft, make the same rotational changes (quote) same rotational changes with respect to what point?

03-29-2009 05:52 PM

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Aaron29
Key Veteran
Location: Bossier City, LA

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The North Star for all we care. It doesn't matter!

But I'll play your game, the mainshaft.

This reminds me a lot of the frame of reference arguments in the off topics forum.

-Aaron

03-29-2009 05:56 PM

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Aaron29
Key Veteran
Location: Bossier City, LA

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You need to understand what a gyro does.

It isn't a little person in there. It can only sense change in heading. It cannot sense the linear or arcing movements that you seem hung up on.

And I'll add...

In any case, this argument is moot. No gyro has ever been mounted below the mainshaft, and many people are using gyros well away from the mainshaft with no ill effect.

I'm going flying...

-Aaron

03-29-2009 05:59 PM

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main rotor
Heliman
Location: Pomona NY USA

My Posts This: Topic Forum

if it can only sense a change in heading (which i totaly agree) than wouldn't the "RATE" of change be greater further from the main shaft?

03-29-2009 06:29 PM

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Aaron29
Key Veteran
Location: Bossier City, LA

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I can't believe I'm still here.

No.

90 degrees is 90 degrees. If the nose got there first you'd be bending the fuselage like a banana!

Edit: If you were to pirouette at 360 degrees per second, every part of the heli would pirouette at that rate.

-Aaron

03-29-2009 06:35 PM

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main rotor
Heliman
Location: Pomona NY USA

My Posts This: Topic Forum

So what your saying is the RATE of change from the tip if the tail to the main shaft is the same in a 360 pirouette?

03-29-2009 06:43 PM

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Bergen R/C Helicopters > gyro mount location

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