General New Trex 450 Setup

[mooserider]

Hi! This is my first helicopter build and I have a few newbie questions. I watched the youtube series on going through the 3GX configuration, which helped a lot! But a few things don't seem to be set up right on the heli still and I had another question about the rudder push rod.

This is for a Trex 450 pro dfc, spektrum dx7 (airplane version), using the receiver as a receiver with one satellite. I'm using a receiver battery pack w/o the lipo so the motor doesn't work during setup.

* Main rotor blades - When the throttle is completely off (all the way down) in normal flight mode, are the rotor blades supposed to be pointing down (neg pitch)? I kind of assumed that they should be level until 50% throttle, and after that they would increase (start pointing up). In other words, no downward pitch unless you're using idle-up. Not sure if this is normal or if I am missing something in setup.

* Anti-torque rotor? When I increase the throttle (without the motor battery plugged in), the tail rotor pitch doesnt' change at all. Another assumption here, but I thought that it would change in pitch along with the throttle increase to compensate for the torque. Not to be confused with when the tail is moved left and right (yaw), and the gyro auto-compensates and changes the pitch. Will this only work if the motor is spooling up or is this something I'm just confused about?

* Tail rotor throw range - even after going through the tail rotor 3GX setup, the throw on the tail servo is still going to its maxes, causing binding in the rod. Not sure what I'm missing. The step in setup to do this has you move the left stick left until the blades are at their limit, wait for the status to start flashing red, then you do the right too. Then you press the button on the 3gx and do the delay. One weird thing is that you barely need to move the rudder stick left/right at all, as just a little stick movement will cause the rudder blade pitch to keep changing until it reaches its limit.

* Tail rotor push rod - This little thin metal wire is way too flexible. There are only two of those push rod guides, and they also move around. I'd like more like 4 of those things and lock them all down somehow, but they only gave me 2. I can't imagine actually flying it like that. Any suggestions?

I can't seem to find a way to export all of the settings from the 3gx. You can 'save', but the txt file it creates doesn't have all the same numbers I see in the UI. Below is a copy of the settings from the saved file though. I have some screen shots of the other stuff, so I'll try attaching it.

Thanks for any help you can provide! It's taken quite a time to get this far, but I'm almost there.

Settings file from 3gx:
0;
1;
0;
50;
0;
0;
0;
20;
20;
20;
1;
0;
20;
70;
70;
0;
80;
70;
70;
70;
50;
60;
50;
;
20;
;

- - - Updated - - -

Added attachments with settings parameters.

View attachment SettingDisplay.txt

 

[Tony]

* Main rotor blades - When the throttle is completely off (all the way down) in normal flight mode, are the rotor blades supposed to be pointing down (neg pitch)? I kind of assumed that they should be level until 50% throttle, and after that they would increase (start pointing up). In other words, no downward pitch unless you're using idle-up. Not sure if this is normal or if I am missing something in setup.

Yes, you are supposed to have some negative pitch when you are at low stick. This is set up in your pitch curve menu on your Tx. My suggested pitch curve for Normal mode is 46 48 50 75 100. Then IU1 set to linear.

* Anti-torque rotor? When I increase the throttle (without the motor battery plugged in), the tail rotor pitch doesnt' change at all. Another assumption here, but I thought that it would change in pitch along with the throttle increase to compensate for the torque. Not to be confused with when the tail is moved left and right (yaw), and the gyro auto-compensates and changes the pitch. Will this only work if the motor is spooling up or is this something I'm just confused about?

What you are thinking about is called Revo Mix, and you do NOT want to use it. Revo is for rate mode gyros only. As you apply throttle, you won't see the rudder blades move at all. This is all corrected by the gyro while you are flying. The other way I adjust for the torque of the motor is to fly with a flat throttle curve. If you fly with a linear throttle curve, the tail is going to blow out on pitch pumps. But if you fly with a throttle curve of 0 65 65 65 65, the tail will not blow out as the only thing changing is the pitch on the blades.

* Tail rotor throw range - even after going through the tail rotor 3GX setup, the throw on the tail servo is still going to its maxes, causing binding in the rod. Not sure what I'm missing. The step in setup to do this has you move the left stick left until the blades are at their limit, wait for the status to start flashing red, then you do the right too. Then you press the button on the 3gx and do the delay. One weird thing is that you barely need to move the rudder stick left/right at all, as just a little stick movement will cause the rudder blade pitch to keep changing until it reaches its limit.

In some cases, you will have to do the tail setup many times. this is one of the bad parts of the 3GX (along with others). There are times that I Had to do the pitch setup on the tail about a dozen times before I got it set where I wanted it. For some reason, the 3GX just doesn't remember the settings.


In Flight Parameter 1, set all of those back to default. You will make adjustments to that menu after you learn how the helicopter is going to react in teh air.

 

[mooserider]

Thanks Tony. I reset param 1 like you said. So far I have only default throttle and pitch curves... just linear. I don't yet understand it enough to tweak it, but I'll read up on it soon. At 0% stick, it's -50% pitch, and at 100% stick, it's +50% pitch on the blades. Thank you for the help!

 

[Tony]

what do you mean +50% and -50%? What is the actual degrees?

 

[mooserider]

[just posted this in the wrong thread, arg]

I was testing things out a little this morning after making all the changes and setting up the 3GX and noticed two things... there's a good deal of vibration and shaking at certain RPMs, around 30 or 40% throttle. At 50% it goes away. It could just be that I had it clamped down so it wouldn't go anywhere. But also, some of the teeth on the large main gear are chewed up a little. About a week ago, I had a the blades come off because I had forgotten to tighten them down properly. I think that stripped some of the teeth up. I'm guessing I should replace that now, even though it's spinning up fine?

I took a video to upload, but it's too big (even though it was like 8 seconds).

Thanks

 

[Tony]

The vibration is normal as long as it all goes away. Every helicopter has a resonant vibration at a certain RPM, even full scale helicopters. But they hate being clamped down.

As for uploading a video, you should upload it to youtube and then post the link here. Unfortunately, we just dont' have the server space to allow video uploads on here.

And yes, I would replace the main gear. Cheap insurance.

 

[mooserider]

what do you mean +50% and -50%? What is the actual degrees?

No, sorry, that wasn't very accurate. I just meant 50% of the throw range... i.e., it's split in half for up or down. The pitch is around 10% positive and negative, each way. Actually, it's off by 1% between the two and I need to re level the swash I think.

 

[Tony]

Right on, 10º is a good place to start. If you find that you have to put in a lot of collective pitch, raise your collective pitch up to about 12º+-

 

[mooserider]

Here's the video, I uploaded it to youtube: https://www.youtube.com/watch?v=PxPeowid_-o

I'll make some tweaks and unclamp it and see how it behaves. Thanks again.

 

[trainrider06]

Hey I like that makeshift test stand!