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HelicopterMain Discussion › Tail Question
05-04-2005 05:16 PM  12 years agoPost 1
Chris Lupa

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Lancaster, UK

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Hi,

I use Futaba GY401+S9253 on all my machines but I was wondering about one thing.
I have always set my servos MECHANICALLY so that in centre position, the rudder is slightly ofset(to the right), in order to conter-act the torque of the engine/blades. I know that in heading lock mode, the gyro will naturally find its own neutral point, but it does not in normal mode.
So my question is, do I need to mechanically set the servo so that my tail blades are slightly ofset (like I have been doing), or shall I just make sure that the tail is dead straight (no pitch) when the servo, stick is neutral?

Many Thanks.

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05-04-2005 05:22 PM  12 years agoPost 2
C-DOG

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SunShineState

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yes the tail blades
need to be set with a certain degree of pitch in them,Al Magaloff sent me a set up technique,I will search for and post it for you if, It has'nt been deleted

Good Luck Corey I PAY-PAL

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05-04-2005 06:02 PM  12 years agoPost 3
Drunk Monk

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Preston, UK

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You certainly need to setup the offset with a 401 but you don't need to on the 601. I've never understood why you need to set the 401 up like that since the idea behind HH is that with no rudder stick input the tail should stay where it is. However if you don't set it in normal mode and adjust the rod length so there is no drift the tail will just drift in HH. I've not heard anyone give a decent explaination why this happens.


Stephen

I only open my mouth to change feet.....

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05-04-2005 06:10 PM  12 years agoPost 4
Leif

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USA

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The more important questions are:

Do you FLY in normal mode?
and
Where is the MECHANICAL CENTER of the tail pitch slider?

For those flying exclusively HH, it's better to set the mechanical center to match that of the tail pitch slider. This is especially true when using gyros such as the GY401 that only offer ONE endpoint adjustment.

The whole purpose of the mechanical/endpoint adjustment is to allow the mechanics full travel movement without binding. All of the rest of the configuration can be done with radio/gyro settings.

If you DO fly in normal mode, you can set the mechanical centerpoint to more closely match the rudder neutral at hover when in normal mode, but you'll then need to set the gyro limits so that you don't bind at EITHER limit. This will often result in a setup where the slider will reach one mechanical limit, but fall short of the other due to the off-center neutral point.

Strengthening the tail rotor system (either by speeding it up or using larger tail blades) will move the neutral point closer to center as well.

I fly HH only, so I've set my heli up with the servo centered on the mechanical midpoint of the tail slider. I don't even care what this corresponds to for tail pitch, as the gyro corrects the neutral point as soon as I lift off.

Leif

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05-04-2005 06:15 PM  12 years agoPost 5
Leif

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USA

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However if you don't set it in normal mode and adjust the rod length so there is no drift the tail will just drift in HH
I've never seen this on my GY401s. I can initialize the gyro with a zero-pitch tail and the gyro doesn't drift once I lift off.

Leif

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05-04-2005 06:27 PM  12 years agoPost 6
Drunk Monk

rrProfessor

Preston, UK

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I find it won't hold very well either, speacially backwards inverted


Stephen

I only open my mouth to change feet.....

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05-04-2005 06:29 PM  12 years agoPost 7
Chris Lupa

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Lancaster, UK

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Cheers guys, here's my second question:

I run the GY401 with a Futaba FF9 Radio. I have set the end point of the servo on the tail AND set the LIMIT function on the GY401 so that there is a correct amount of movement both ways. BUT why is it that (only) in HH mode, my tail will tend to slow down as it gets to the end of its travel???????????? In order to eliminate this, I have to set the end point of the servo much higher than what is required. Only then does it stop it slowing down near the ends. The only problem is that now I get full rudder movement at about half stick movement

Why does this happen? I want to get fast (no slow-down) responce that reaches the full travel when my stick is at full.

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05-04-2005 07:04 PM  12 years agoPost 8
BarracudaHockey

rrMaster

Jacksonville FL

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End points on a 401 only set the piro rate and have nothing to do with where the servo stops. The stops are set (as you did) on the gyro itself.

Andy
AMA 77227
http://www.jaxrc.com

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05-04-2005 07:09 PM  12 years agoPost 9
Chris Lupa

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Lancaster, UK

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Yes, but on the FF9, you have 2 different end point selections. One which is for the Rudder end point and the other is the Gyro end point.
So by increasing the Gyro end point will result in me having a faster piro rate???????

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05-04-2005 08:27 PM  12 years agoPost 10
Leif

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USA

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What the RADIO presents as features and what you need are two different things.

When using the GY401, first reset all rudder trims, subtrims and revo mixing to zero; reset all rudder ATVs and Rates to 100%. THEN, set the endpoint limits using the adjustment on the 401 to match your physical endpoints on the tail slider.

At that point, ATV adjustments will work similar rate or expo (they'll slow down or speed up the tail). For a faster tail, set the ATV to something higher than 100%.

Also, what the tail slider is doing while the heli is sitting still is NOT a good way to diagnose a HH gyro. The gyro logic controlling the rudder servo expects the heli to yaw when rudder inputs are received. Forcing the heli to remain static when on a bench means the gyro logic will think something is wrong and won't necessarily produce the control movement you expect. For this kind of observation/diagnosis, you should switch the gyro to normal mode.

Leif

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05-04-2005 08:44 PM  12 years agoPost 11
JerryLu

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Gretton, Northants - England

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Does that address the requirment for full rudder movement to correspond to full stick movement. Possibly not and I think this can be set only with the giro in normal mode. In HH mode if you just move the stick a little off-centre, (without moving the heli) you can see the rudder blades slowly turn for full throw.

If the mechanical setting is initially done with rudder ATV at 100% to give full rudder throw then adjusting the rudder ATV above 100% will result in full rudder at less than full stick. If you want to increase the piro rate by increasing the rudder ATV above 100% then you will need to adjust the mechanical linkage to give 100% throw at 100% stick movement. (I'm not sure this won't then just negate the attempt to increase the piro rate.)

The giro ATV (channel 5) only sets the gain and whether you are in normal or HH modes.

Jerry

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05-05-2005 02:12 AM  12 years agoPost 12
Leif

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USA

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If the mechanical setting is initially done with rudder ATV at 100% to give full rudder throw then adjusting the rudder ATV above 100% will result in full rudder at less than full stick. If you want to increase the piro rate by increasing the rudder ATV above 100% then you will need to adjust the mechanical linkage to give 100% throw at 100% stick movement. (I'm not sure this won't then just negate the attempt to increase the piro rate.)
What you're missing is that with a HH gyro the GYRO settings are used to define the mechanical endpoints. Once that's done, there is NO WAY at the radio to place the tail slider further than the endpoint. The reason is that the GYRO is the unit that is sending the rudder control commands to the servo, and you've already told it to never go past the set mechanical limits.

When you subsequently change your ATVs, you are then changing the INPUT signal to the gyro, asking it for more or less piro rate. In HH mode, a larger rudder input command is interpreted as "spin faster". That's why setting the rudder ATVs to more than 100% will not only result in a full-deflection sooner, but will also cause the heli to spin faster (as long as the tail is strong enough). Also note that the full deflection you see when the heli is on the bench is only because the heli refuses to obey the tail command to piro. In the air, you would very rarely get full deflection unless you put in full rudder offset at maximum ATVs. Changing the ATVs after you've got the gyro set up will have NO INFLUENCE on the mechanical endpoints.

This is a common misconception that comes from outdated information from older generations of gyros (where the rudder ATVs were used to set the endpoints).

Leif

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05-05-2005 09:12 AM  12 years agoPost 13
JerryLu

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Gretton, Northants - England

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Thanks Leif, that has cleared up a matter that's been causing me a little confusion of late.

Cheers.

Jerry

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05-05-2005 02:59 PM  12 years agoPost 14
smity777

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California

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I always set things up as mechancially as possible, let the radio take up little stuff

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05-06-2005 02:56 PM  12 years agoPost 15
flybarless

rrKey Veteran

Torrington, CT

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set up
I agree, back in the days before gyro's, we had to do it all with mechanical adjustments, I belive that a "good" mechanical set up is always the best way to start.

Just remember -- if the world didn't suck, we would fall off.

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