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HelicopterMain Discussion › Couple Additional 3GX with DX8 Setup Questions
01-01-2013 04:45 PM  5 years agoPost 1
jimmyG

rrNovice

Wisconsin

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I have the mechanical setup complete with 0 pitch at half stick and approximately +- 12 degrees on the top and bottom.

I have gone through the setup om the 3gx but things don't seem right yet. I'm not sure that the changes I'm making are saving. Anyone else have this problem?

I ran the head up a bit and the pitch seems way off, as do the cyclic movements. Again, I did the mechanical setup in DIR move. All servos are moving properly together.

As it stands, both my throttle and pitch curves are linear for all flight modes. I would like Normal to be -2 to +10. Is this obtained by adjusting the pitch curve, or, a different setting in the radio?

I'm still having problems assigning the gyro to a channel. I'm using a Spektrum DX8 with one satellite receiver. If I understand correctly, the gyro needs to be assigned to Aux 2 in switch select. Problem is that the tx will not allow me to do this. Gyro is currently assigned to gear and I can only change it to Inh, not Aux 2. In the gyro menu, the Sw does say Aux2 on rud. I thought at one time I had I had the gyro assigned to aux2 but something changed and I can't get it back. I have the gain at -30 for position 1 and 30 for positions 2 and 3. What am I doing wrong here.

Lastly, does anyone else have an issue with the battery meter on their dx8? Mine is never at 100%. The instructions say to charge no more than 12 hours. I can charge 24 hours and the indicator is still only about 2/3 full. I have the most up to date software.

I will try to run through the setup again this morning.

Thanks for any additional direction you can give!

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01-01-2013 05:10 PM  5 years agoPost 2
jschenck

rrProfessor

La Vista, NE.

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On the charging of the DX8, what is the voltage shown on your DX8? 5.4V is fully charged with the stock battery. If the pack got warm then it's definitely fully charged.

I have setup several heli's with a 3GX using sat. RX and the DX8. All flew great on first spoolup. You should be able to get the same.

I do NOT plug in the ESC for setup, I use a separate battery pack with a switch, no danger of the motor firing off while I'm setting up then.

Gyro setup - In the GYRO menu change the Ch: to Aux2 Sw: F Mode
The you can adjust gyro gain to flight mode. I start off with about 40% and adjust from there after flying.

Throttle curve and pitch curve - setup both straight linear for the setup. 0-50-100. In the DIR mode, make sure that 0 pitch as seen in the monitor function on the DX8 = 0 pitch on both blades all the way around. Then I use a swash leveler to make sure it's level at the top and bottom of the pitch throws, subtrim to straighten out small discrpenecies. I never need more than 3-5 points, if I did I'd look for something wrong.

make sure all the limit's and directions are correct. Make sure the swash is moving the correct direction after the setup. I don't vary the setup too far from stock settings.

If it doesn't seem right, don't try and fly it. Go through the setup again and post back here if it still doesn't look right.

btw - are you using 2.1 or 3.0 3GX software?

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01-01-2013 05:11 PM  5 years agoPost 3
dkshema

rrMaster

Cedar Rapids, IA

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Use pitch curves to set your desired pitch range.

If your DX8 won't let you assign AUX 2 to run the gyro, it's because AUX 2 is already assigned to something else, most likely governor, which is the DX8 default. You'll need to find where AUX 2 is already assigned, change THAT assignment to something else, to free up AUX 2 so it shows up in the list of available functions.

Did you do a model reset, or change to a new model memory at any time during your setup?

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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01-01-2013 05:57 PM  5 years agoPost 4
jimmyG

rrNovice

Wisconsin

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I went through the radio again and just can't see what is assigned to aux. see pictures.

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01-01-2013 06:39 PM  5 years agoPost 5
dkshema

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Cedar Rapids, IA

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Looks like you have the gyro gain set to be controlled by AUX 2, a good start. The glare from the camera flash makes it impossible to see which switch you have assigned to control the gyro, however. Is it set to "RUDD D/R"?

You also have it set so that one position of the controlling switch puts you in Normal/Rate mode operation (that negative number, -30). The other two flight modes are set for Heading Hold operation (+30, and +31). Is that what you intended?

With your radio set up as it currently is, go to your transmitter Monitor window and look at the position of the Channel 7/Aux2 slider as you flip the switch you have chosen to control the gyro gain. You should see the slider to the left of center with the controlling switch in Position 0, and with that switch in Position 1 and 2, you should see the slider move to the right of center, to the same distance as in Position 0.

This test will tell you if the switch you THINK is controlling the gain actually IS. I believe the Status LED on the 3GX will change color from Green (HH) to Red (normal) mode as you flip the switch you have controlling the gain.

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I also second Jschenck's recommendation to set the gyro control to the Flight Mode Switch instead of using what appears to be the Rudder Dual Rate switch.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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01-01-2013 07:10 PM  5 years agoPost 6
jimmyG

rrNovice

Wisconsin

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Hi Dave, happy new year.

Firstly there is really no reference to Aux2 except in the gyro menu. In the monitor, swash and switch menu that channel is called "gyro". I think this is how we want it? All references to aux2 seem to change once the gyro is uninhibited.

On the monitor screen the indicator is just left of center in norm and to right of center for the next two positions. However, they are not equidistant from the center point. The indicator is just a hair from center in norm but several clicks in the other two positions.

Is there a reason that I wouldn't want to be in rate more in norm?

Yes, the gyro was set to rud d/r, I switched to f mode

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01-01-2013 08:02 PM  5 years agoPost 7
jimmyG

rrNovice

Wisconsin

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Also, why the led on the sat receiver blink at times and is solid lit at other times?

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01-01-2013 08:20 PM  5 years agoPost 8
jschenck

rrProfessor

La Vista, NE.

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every time you turn off the RX you have to turn off the DX8 and turn it back on. If you don't the RX will blink, showing that it lost power since the last time it "talked" to the DX8.

For setup, I don't worry about it. The RX blinking doesn't hurt anything or affect anything. It's meant to show you if you lost power during flight.

Your gyro looks to be setup correctly on the DX8 to Aux2 which is needed for the 3GX with sat. configuration. I would change the Sw: to F-mode, but it doesn't have to be there, it's my preference.

and yes, after you are all setup then I would change your pitch curves and throttle curves to what you are looking for. But for the initial setup I would do that with 0-50-100 on the radio for both and +/-12 pitch measured. Once you are satisfied that is right, then adjust throttle and pitch curves to what you are looking for.

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01-01-2013 08:39 PM  5 years agoPost 9
dkshema

rrMaster

Cedar Rapids, IA

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Looking at page 33 of the DX8 manual, you would go to the Function List menu and select GYRO. You would initially see "INHIBIT" in the screen. Ignore the note that says the DX8 will show an "N" for Normal mode and "T" for tail lock mode, I think that's one place where the manual doesn't match the real world.

Anyhow after you turn the gyro on, the next menu ought to say FM Gyro, there should be entries for Normal, Stunt 1, Stunt 2, and Hold. I believe they all default to zero.

The bottom left corner should say "CH:" and most likely "Gear". The bottom right corner would probably say "SW:" and most likely "F.Mode". Regardless of what is selected in those two corner options, set the bottom left "CH:" to say "AUX 2" if it isn't already set that way. This assigns gyro control to channel 7 where it needs to be for the 3GX when using Satellites as your main receivers.

In the bottom right corner, set "SW:" to "F.Mode" if it isn't already set that way. This assigns the Flight Mode Switch to control the gain for each of the flight modes.

In the center of the screen where you have the four possible values, numbers less than 0 (negative) will select Normal Mode operation, numbers greater than 0 (positive) will select Heading Hold operation.

You can double-check that last paragraph about normal/heading hold mode by watching the 3GX status LED color as you adjust the number for the particular flight mode you have selected, by the way. You can also see the result of your numbers by looking at the Channel 7 slider in the Monitor window as you set a value and change the Flight Mode switch position.

Also, note that when the gyro is operating in Normal mode, the servo will follow the rudder stick and return to neutral when you let go. When the gyro is in Heading Hold mode, the servo may not seem to faithfully follow the rudder stick, and usually won't return to neutral when you let go of the stick.

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As for the Switch Select menu, I believe that will reflect what your current switch assignments are for the various switches, knobs, and levers on the DX8. In the example on page 16 of the DX8 menu, it appears that they have the Gyro set to be controlled by the Gear channel (channel 5) and the Governor set to be controlled by Channel 7/Aux 2. Page 16 also seems to show you how to set the Flight Mode and Throttle HOLD switches properly.

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Gains of 30 as you're trying to run, are considerably low. If you're flying a Trex 250, a gain of 30 would be considered monstrously large. For larger helis, a gain of 30 is very low, to the point where the gyro may not really be doing much for you to begin with. Unless you are flying a 250, consider a starting gain number on the order of 60-65%. Fly some very fast forward flight and watch the tail of the heli. Increase the gain until the tail begins to oscillate quickly, then decrease it just to the point where the oscillation ceases in fast forward flight.

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For the gyro, it has two operating modes. Rate (or Normal), and Heading Hold (or tail lock).

When operating in Rate mode, the gyro will attempt to stop any left/right yaw motion of the nose, and that's about it. It will NOT keep the nose pointing in the same place.

When operating in Heading Hold mode, the gyro will not only stop the nose from yawing left or right, but it will also do what it can to maintain the direction that the heli's nose is pointing.

Most people will set their gyros to run in Heading Hold mode and just go out and have a great time flying. Many people who fly scale helis may prefer to fly in rate mode, as this seems to offer more "scale like" flying. It's not common for a scaler to take his heli out and fly wild and crazy 3D with it...so Heading Hold may be a secondary option for him.

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The blinking light thing on the satellites. From the 3GX installation instructions:
Should both satellite receivers lose connectivity during flight, LED1~LED5 will flash continuously as a warning.

A single power cycle of the system will NOT clear this error.

The system needs to be power cycled a second time to reset.
You'll see this if you turn the transmitter off first.

If you cycle power on the receivers and leave the TX on, you'll also see the satellite LEDs flash.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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01-01-2013 09:31 PM  5 years agoPost 10
jimmyG

rrNovice

Wisconsin

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This is so great, thanks!

I'm getting it.

If the gyro gain is controlled by the f mode switch then I can only use rate OR HH mode in Norm, correct? Not that I have a problem with that as I will probably only use HH but I thought the system wanted to be "booted" up in rate mode. Is this true? If not then that is how I will set it up.

I now have norm set at -2 to +12 and will probably not be switching to a different mode for quite a while as I'm still only capable of light forward flight. If I do this I will not be able to switch between rate and HH (not that I would really need to).

Am I on the right track?

Thank you both so much.

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01-01-2013 10:12 PM  5 years agoPost 11
dkshema

rrMaster

Cedar Rapids, IA

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If you use the Flight mode switch, you have your choice of Normal OR Heading Hold in EACH of the different flight mode settings.

You are NOT locked into one operational mode for all flight settings.

It's uncommon to be switching between gyro modes in flight, especially as doing so can confuse the gyro.

The 3GX does NOT need to be started in rate mode, nor does it require to be started in HH mode.

Is this your first ever heli, and do you understand the difference between operating in rate and HH mode?

With a heading hold gyro, when you apply power in HH mode, the gyro looks at the width of the rudder channel pulse during its initialization sequence. In doing so, it "learns" what the rudder "neutral" pulse width is. During the ensuing flight, the gyro will always want to use that initial pulse width as its reference of where rudder neutral is.

If you then for whatever reason, change the learned neutral point (use the transmitter rudder trim tab, or have different neutral points in each flight mode for example) the gyro no longer knows the proper width of the neutral pulse, and becomes confused. It may drift, may drive the servo to one endpoint, or just plain act weird. So when operating in HH mode, you should NEVER use rudder trim, and should always have the SAME trim in all flight modes.

In Heading Hold mode, the rudder neutral position is learned each time power is applied to the system. That is why you don't move the heli until initialization is complete.

As a matter of fact, once you get the 3GX set up, you NEVER use ANY of the trim tabs -- elevator, rudder, or aileron. If you can, in your DX8 set the TRIM STEP setting to zero for all flight control surfaces.

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I guess when you say you have Norm set at -2 and +12, that would be in your original setup where you used the RUDD D/R switch. At that, -2 and +12, you might as well just not use the gyro anyway, as it is essentially so dumbed down it will never react when you need it to.

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Unless you have a burning desire to run your gyro in Normal mode, it's a mode that is rarely, if ever used by most flyers. About the only time it gets used is during initial heli trimming. After doing all your mechanical setup, you'd put the gyro in Normal mode, and bring the heli to a hover. You would then adjust the tail rotor linkage to stop any tendency to yaw left or right in a hover. After doing that step, recheck your travel endpoints to make sure you're not mechanically binding the servo, then go back and fly in Heading Hold mode forever.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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01-01-2013 10:52 PM  5 years agoPost 12
jimmyG

rrNovice

Wisconsin

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The -2 to +12 was the pitch curve in norm, not the gyro gain. I will set the gyro gain to 60 as you suggested to start with.

He he, based on my questions I can see why you ask if this is my first ever heli

It isn't. I was in the hobby for a short time about 11 years ago with a raptor that I eventually converted to electric. I left off with slow figure 8s and an occasional sloppy loop.

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