Trex 500 Build Videos

[Jasmine2501]

Originally Posted by Andre Melo

Then I saw the Trex 500 builder finless video at beggining of this topic. He says that tail slide center is tail pitch zero degree. Maybe this condition only verifies when using
a gyro with diferent limits for each side. In this video is used a Solid-G gyro that has different limit for each side.

I just took out my 500 and centered the pitch slider, and there is significant pitch in the blades at that point, like 5 degrees maybe more. It is possible that Finless Bob is working with a different tail unit, and this is also a possibility for your helicopter. We don't know what your heli looks like without pictures, and there is variation within the brand, as well as many possible upgrade parts you could be using.

Since we have a language difficulty, I will try to be clear. These are the conditions which should exist on your helicopter.

With the gyro in rate mode, or with the servo plugged directly in rudder channel, and with no trim or sub-trim entered for the rudder, you should set the following:
A. The servo arm should be aligned with the case of the servo itself - arm centered.
B. The pitch slider should be in the center of its travel

With the gyro in either mode, and the servo plugged normally into the gyro, and the rudder stick held all the way to either side - adjust the limit until you have the following.
A. There should be no binding of the pitch slider against the grips or the hub bearing
B. The pitch slider should move all the way to the edges on both sides.

Now, when you fly in heading hold mode, and you are having the rudder stick centered, you are requesting the gyro to give you no rotation, right? The job of the gyro is to figure out how to do that, and it will. It will put the tail pitch wherever it needs to be - this might not be center, but you don't care. As long as the helicopter is flying correctly, and the gyro is able to hold and move the tail on your command, then the actual location of the pitch slider doesn't matter, right? That is how the GY401 works - you set it up so it knows the center of travel, and it figures out everything else in flight. It's actually ridiculously simple.

[Andre Melo]

Originally Posted by Jasmine2501

I just took out my 500 and centered the pitch slider, and there is significant pitch in the blades at that point, like 5 degrees maybe more. It is possible that Finless Bob is working with a different tail unit, and this is also a possibility for your helicopter. We don't know what your heli looks like without pictures, and there is variation within the brand, as well as many possible upgrade parts you could be using.

Hi Jasmine.

Your text is clear. I agree with it. I will inspect better my heli tail setup.

I was using the same tail unit of finless video.It was a belt tail driven system. No upgrade has been done.It was the original align trex 500 kit with belt tail driver system; In fact, I remember there was not zero pitch degree at tail slider travel center.

Now I have upgraded for torque tube tail driven and I am using in heli a different tail unit. The torque tube tail unit.

Thank you again;

[Andre Melo]

I believe that question is when using a gyro with diferent limits for each side such as a Solid-G gyro shown in flinless video you can set a center at zero degree tail pitch.

[Andre Melo]

The Finless refferred video is http://video.helifreak.com/?subpath=...lidg_stick.wmv


In this video the trex 500 has a belt tail driven system. It is the original trex 500 kit without any upgrade.The tail pitch is zero when tail servo arm is at 90 degrees.

[Jasmine2501]

Originally Posted by Andre Melo

I believe that question is when using a gyro with diferent limits for each side such as a Solid-G gyro shown in flinless video you can set a center at zero degree tail pitch.

You could, but I'm not sure why you would want to. Zero pitch on the tail isn't anything special really - it's a medium speed left turn. If you were going to pick a center, you would want it to have a little left pitch in the tail - that's what we're doing when we say "rate mode setup" - centering the tail servo at the point where the tail holds against the main drive reaction force.

So, what would be the point of setting the center to be zero pitch?

[Jasmine2501]

Originally Posted by Andre Melo

In this video the trex 500 has a belt tail driven system. It is the original trex 500 kit without any upgrade.The tail pitch is zero when tail servo arm is at 90 degrees.

That is possible to happen, but the pitch slider won't be centered. The servo would be centered, and the pitch slider not - this tells you to adjust the linkage - for the GY401 anyway. For other gyros, this may be different.

[Andre Melo]

Originally Posted by Jasmine2501

That is possible to happen, but the pitch slider won't be centered. The servo would be centered, and the pitch slider not - this tells you to adjust the linkage - for the GY401 anyway. For other gyros, this may be different.

Thank you Jasmine. You have confirmed my understanding is correct. I suppose person built my heli did not do the correct setup for tail servo and tail slider. I am
sure that tail setup is poorly configurated.

As you said, the center of tail slider travel is not zero degree pitch. Considerating the gyro GY401 has same limit for both directions left and right, the tail servo arm at 90 degrees should not correspond to zero tail pitch. Should be a some left pitch.

As I have not experience, I would like to get more information with someone expert before I raise this question to person built the heli in order to a setup review.

Thank you very much for helpfull support and attention.

Andre

[Jasmine2501]

The GY401 is pretty good at compensating for just about any setup you want to do, as long as it's pretty close to center. So, you could have a helicopter that is set up off center because they wanted to fly in rate mode, but it works in heading hold mode just fine, you just don't have equal travel in both directions.

[Andre Melo]

Thank you again

Considerating the configuration in which tail pitch is zero degree when tail servo is centered and gy401 has the same limit in both direction, this implies maximum left and maximum right tail pitch would be equal. Thus this configuration does not take account the presence of torque force induced by main rotor.

The correct would be maximum tail pitch left bigger than maximum tail pitch right. Such configuration can not be done with tail servo centered in zero tail pitch and one gyro with same limit for both directions.

The problem is not about center but right and left tail movements; Same tail pitch when rudder stick in full left and full right position due to gyro401 have same limit for both side. The limit gyro is setup at maximum value without servo buzzer in both edges. Once tail pitch is zero at center, left and right edges will have the same pitch degree in opposite direction. This configuration does not consider reaction force induced by main rotor and
the same maximum pitch result in both sides.

[Finless]

If you run the 401 in HH mode only it will not matter. The gyro will move the slider to the point where the tail will hold and compensate for torque. Yes that will be offset now but the 401 doesnt care nor does it really know. If you want ot use RATE mode of the gyro then you will have to offset the slider with servo 90.

Bob

[Andre Melo]

Hi Finless

Congratulations to videos!!!
Thank you for your help.

My doubt corcerns about tail pitch at edges. If tail pitch is zero degree when the tail servo is 90 degree and considerating that gyro 401 has the same limit for both sides left and right, it results the same tail pitch value at limit position in left and right. Is my understanding correct? In this case it is not considerated the presence of torque force that raise tail turn movement velocity in one side and counteracts in another side.

How could I to configure bigger tail pitch in left side than tail pitch in left side if at servo center (tail servo in 90 degree )is tail pitch is zero and this specific gyro has the same limit for both sides ?


X - correspond position where tail servo arm is 90 degree

|-----------------X-----------------| tail shaft
A___________________ B
-10º_______ 0º__________10º tail pitch degrees with zero tail pitch at tail servo center



|-----------------X-----------------| tail shaft
A___________________ B
-14º_______ -4º__________6º tail pitch degrees with non zero tail pitch at tail servo center


Consider the limit for both sides equal and no servo buzzer at A and B points.

[Finless]

I am not understanding what your trying to do. The Align helis when servo is 90 and slider control arm is 90 to the boom (slider about center) the tail will have little or no pitch in the blades. That is just the way the Align helis are designed and nothing you can do to change that.

To setup a Trex500 with 401 for RATE mode this is what you do:
1) Setup 90 servo arm and 90 for slider control arm.
2) Set the 401 limit pot so no bind on either side.
3) Set the gyro gain for RATE mode
4) Now TRIM the rudder trim until it hovers and holds the tail. Yes that is correct. You TRIM the 401 for rate mode hover.
Remember to ALWAYS power up the heli with the gyro in HH mode so it sees this rudder trim as center stick position. All gyros on power up look at the position of rudder to "set" as what it thinks center rudder stick is. Thus it will lock on the trimmed position you put in.
FYI these are the instructions for the 401 gyro per Futaba.
Now when your all done it still will be about the same. Both the servo arm and the slider control arm WILL NOT BE 90 in the hover. That's just the way it is.

Now there is also another way to do this to setup for rate mode as well. Some prefer this method but I don't agree it is correct.

1) Setup the servo at 90
2) Setup the slider control arm for 90.
3) Adjust the servo or servo control push rod so while servo is still at 90 the pitch slider is moved to an offset to allow rate mode hover e.g. enough pitch is in the blades to hold the tail at hover.
4) Now adjust the 401 limit pot so it does not bind. You will see you cannot get the slider to go all the way over on the with torque direction. Some people think it doesn't matter as you won't need the slider to move all the way over in that direction anyway. I disagree with this approach myself but that is just my opinion.

Bob

[Andre Melo]

Originally Posted by Finless

I am not understanding what your trying to do. The Align helis when servo is 90 and slider control arm is 90 to the boom (slider about center) the tail will have little or no pitch in the blades. That is just the way the Align helis are designed and nothing you can do to change that.

I think I have understood now. This is a geometry issue that Align has setup the tail shaft, tail slider and tail slider control arm. At center the tail pitch is zero degree, This position allows maximum distance to edges in both sides left and right. Thus slider is able to move all the way over tail shaft atchieving both edges in left and right side. All tail shaft way can be reached by slider once this is middle position.

In this case, could you confirm if the maximum tail pitch degree when slider is positioned in left edge and right edge are equal or almost equal? The align design does not give more tail pitch in left side than right side considerating torque force?
A full right stick input and full left stick give the same tail pitch value (or almost same) in opposite direction.

Originally Posted by Finless

Now there is also another way to do this to setup for rate mode as well. Some prefer this method but I don't agree it is correct.

1) Setup the servo at 90
2) Setup the slider control arm for 90.
3) Adjust the servo or servo control push rod so while servo is still at 90 the pitch slider is moved to an offset to allow rate mode hover e.g. enough pitch is in the blades to hold the tail at hover.
4) Now adjust the 401 limit pot so it does not bind. You will see you cannot get the slider to go all the way over on the with torque direction. Some people think it doesn't matter as you won't need the slider to move all the way over in that direction anyway. I disagree with this approach myself but that is just my opinion.

Bob

I agree with you concerning on second method as explained for you.

[Finless]

Correct it is a property of how Align designed the tail assembly. Many other helis when slider is center or close to it, there is close to enough pitch to fight torque. Align didnt do it this way.

Bob

[Andre Melo]

Originally Posted by Finless

Correct it is a property of how Align designed the tail assembly. Many other helis when slider is center or close to it, there is close to enough pitch to fight torque. Align didnt do it this way.

Bob

Great. You have addressed my question exactly.

Thank you very much.

[Jasmine2501]

Originally Posted by Finless

Correct it is a property of how Align designed the tail assembly. Many other helis when slider is center or close to it, there is close to enough pitch to fight torque. Align didnt do it this way.

Bob

My heli seems to have some pitch in the blades with the slider centered. It's not just a little bit either... however, when I move to the max it looks like about 22-23 degrees on both sides? Maybe I have some slop in the linkage.

Point is, regardless of this it doesn't really matter. The 401 figures out what to do, and if you want max throws, you center the slider like I said, right? Are we making it too complicated? On 4 helis with 401s, I've done it this way and it works... is there something wrong in my description before?

Also BTW - if you're using Spektrum/DSM stuff, it's a good idea to re-bind after you set up everything. Spek mentions this in the manuals - always re-bind after completing your setup and first flight that you are happy with the setup. Goes for planks too.

[Finless]

Jasmine, I think your not understanding what he was really after. We both told him to do center, 90, etc and forget about it. He was asking really why and how could he fix that. E.g. he did not want it that way. I think he is use to helis that are not 90/90 center and no pitch. So I explained why due to Align tail design. He was looking for a way to correct that. I think he realized at that point there is nothing he could do and how to setup just like you told him Maybe the language barrier, but I think that is what he was looking for. Again, as to "why that way" and not just do it "this way".

Hey... maybe I am worng... Just how I am reading what he was after for answers.

Bob

[Jasmine2501]

Oh yeah, I didn't follow that. Usually if I have really different max piro rates on each side, I'll just reduce the travel on the rudder channel in the radio, or increase the other side, or both, till I get what I like... but I haven't really had that problem except on the 250, where I have a GP750 not a 401. To be honest though, it's been a while since I actually set up a 401 - I re-did all my helis earlier this year, but I haven't changed anything since, and all the folks around here are using GP780s and GY520s now.

[Finless]

I have had many different gyros on Align helis and for me setting up HH only with 90 and center works the best for me. So I agree. FYI even the Align manual says to setup that way! Not saying the manual is correct but hell.... They designed the heli, had many good pilots test it, and so who am I to argue

Bob

[Jasmine2501]

Yeah if you ask me, I will usually say my design is correct. Engineering types are like that. Just wish I could fix the phasing problem. Mixing helps, but it's still weird. On the 9503 I can do a curve mix, might try that.