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T-REX 250 › Trex 250 -- 3GX -- Settings sanity check
02-06-2012 05:05 AM  6 years agoPost 1
dkshema

rrMaster

Cedar Rapids, IA

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I just converted one of my 250s to FBL using the Align head and a 3GX controller.

When going through the software (V1.2) setup stuff, they recommend +/- 12 degrees pitch, and +/- 12 degrees elevator and aileron cyclic.

Is that for real? Seems like an awful lot of cyclic AND collective for the 250.

-----

I got a few minutes of hovering in the driveway under the porch lights and cold. Sure is a responsive heli right now.

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Dave

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

Team Heliproz

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02-06-2012 12:38 PM  6 years agoPost 2
jsenicka

rrProfessor

Eagle River, WI

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The amount of cyclic tells the FBL unit how far it can move the blades to stabilize the heli. So 12 degrees is not just to move it, it is also to stop movement. But that can leave it a little fast.
You can address 1 of 2 ways.
1. Reduce swash settings for cyclic about 25% after you finish setup

2. Use the programming dongle and lower control rates. You can lower aileron and elevator control rates from from default of 70 to maybe 55. Write the settings. Then go to the movement speed screen and move cyclic stick to full in each direction. You would want about 240 degrees per second at full deflection. If still too high, go lower the control rate sliders a bit more, write settings again, and try again

Jim Senicka
Team Manager, GrandRC Flight Team

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02-06-2012 01:13 PM  6 years agoPost 3
dkshema

rrMaster

Cedar Rapids, IA

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Thanks for the great info.

-----
Dave

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

Team Heliproz

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02-06-2012 09:45 PM  6 years agoPost 4
Richardmid1

rrProfessor

Leeds, England

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Yeah its like tail gyros, you have set maximum tail pitch but it doesn't use it all to do a piroette however it may need to use all of it to keep the tail in line during hard manuevers or strong cross wind or simply to stop the tail as quickly as possible when stopping a piroette.

You are telling the 3GX how fast to rotate the heli, your not telling the servos to put 12 degrees cyclic on the blades.

60% of the time, it works every time!

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02-07-2012 12:13 AM  6 years agoPost 5
dkshema

rrMaster

Cedar Rapids, IA

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D'oh!

Makes perfect sense.

Too bad you can't set the roll/pitch rates by adjusting the aileron and elevator endpoints like you do with the rudder gyro. That would be too easy!

I'm relatively new to flybarless stuff although I've been flying my 3G 550 for a couple of years. It set up relatively easily and I never got the USB dongle or updated the software.

The 3GX comes with the USB stuff, software, and I've upgraded to V1.2 and set the response to "normal", but haven't yet gone in and taken a long look at the settings and what I can to to really get myself in trouble!

Back in October, for Black Friday, I bought a couple of 3GX controllers from Grand RC's Black Friday sale for $129. I've got a 700N set up now for FBL and a 600 Nitro Pro, but since the weather STILL sucks here in Iowa, I've not had a chance to try them out.

I got my 250 up and running and it's quiet enough and small enough to fire up in my driveway at 10:30 PM without rousting the neighbors!

-----
Dave

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

Team Heliproz

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02-07-2012 04:58 AM  6 years agoPost 6
dkshema

rrMaster

Cedar Rapids, IA

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Richard -- I spent some time playing with the 3GX box and its software tonight.

Your post and Jim's have both been helpful.

On a gross setup scale, I believe I need to adjust the length of the three servo arms to allow me to get the overall stated travel (+/- 12 degrees collective and +/- 12 degrees cyclic) while the Swash Mix numbers for Aileron, Elevator, and Pitch are all greater than 50 (the 3GX software indicates that the Swash Mix numbers must be greater than 50 for the thing to work correctly). This happens in DIR mode. The rest of the initial setting sequence sets the Aileron and Elevator travel limits and direction similar to what you'd do for a TR gyro.

Gains for elevator and pitch are set by the two pots on the 3GX body, and are adjusted until the unwanted oscillations just disappear -- like setting maximum usable gain in a rudder gyro.

With that mechanical setup out of the way, and the direction and limits calibrated, the actual maximum roll and pitch rate are selected by the Elevator and Aileron numbers in the swash mix menu. Numbers headed towards 50 decrease the maximum rates, numbers headed toward 100 increase the maximum rates, similar to that of a standard gyro setting sequence. This is similar to setting the allowable yaw rate for a standard rudder gyro.

-----
Dave

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

Team Heliproz

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02-08-2012 03:45 AM  6 years agoPost 7
jschenck

rrProfessor

La Vista, NE.

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I'll be very interested to see how your 250 3GX turns out. I shelved mine about 2 months ago primarily because I don't have time to really figure it out. My main issue was the elevator was way over gained. With a fast forward flight it'd go into a severe elevator porpoising, nearly lost it a few times but I had the elevator gain pot turned down to the point of utter mush in a hover. It wasn't fun to fly or hover. I figured too much mechanical gain but I moved the ball links in on the servo horns and that didn't help. Also my swash mixes were at like 30% which told me it's mechanically setup wrong. This is using all Align head components.

Also getting to the gyro setup components is a major pain with it mounted on the base plate. I moved the gyro to the gyro shelf which I don't think is quite as solid as the base plate. I have seen the gyro being mounted upside down on the baseplate with holes drilled to allow access to the gyro. Might try that next time I have a day to tackle hobby projects.

I'd be curious to see pictures of your mechanical setup. I can post them of my 250 3GX though right now it's not much to see.

For now I built my other 250 with my FB head and fly that when I can.

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02-08-2012 05:56 AM  6 years agoPost 8
dkshema

rrMaster

Cedar Rapids, IA

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The 250 has that gyro mounting plate between the frames at the rear. On top of the frame is my trusty AR6100E receiver, plugs facing forward, antenna whiskers out the rear.

The 3GX controller is mounted upside down, on the bottom of that plate, its plugs facing forward. That puts the pushbutton, LEDs, and the two gain pots out in plain sight and fully accessible.

I custom made some short cables between the RX and the 3GX (mainly because the "NIB" bargain 3GX controller I got from Hobby Hut didn't come with cables) using my crimper so I wouldn't have a lot of extra wire to stuff in between the frames.

After I got done setting the controller up the first time, I had +/-12 degrees of collective, +/-12 degrees of cyclic, and used the 3GX dongle to select "normal" parameters for a 250.

My PITCH number in the SWASH menu was something like -36, the Aileron and elevator numbers came out to about 45 each. That seemed low (I had to decrease them from the flybarred values).

I went out to my front drive and found I had a really wild and crazy 250. I added 30% expo into aileron and elevator on the TX, that seemed to tame it down a bit.

I had to turn down both gain pots from the 12 o'clock position to about the 10 o'clock position to stop the shakes in hover.

Next, I moved all three balls in one hole on the servo arm. (Using the long, straight two-armed output wheels that came with the DS410s). This allowed me to get the same collective and cylic movement range, but I was able to bump that 36 number up to something like 40 and the elevator and aileron numbers also moved about 5 points.

Then, I got to looking at the actual rate numbers in the 3GX setup windows and based on stick position. I found that I had rate values in the neighborhood of 300 deg/sec. Based on Jsenicka's comments, I adjusted the elevator and aileron numbers in the swash menu until the displayed rate numbers were in the 240 range as he suggested.

Another flight test, the heli was still pretty darn squirrely, I experimented with the aileron and elevator numbers in the swash mix menu again, making them smaller yet -- in the upper 30's. This time the heli was just plain weird, would lift off rolling right, I'd correct, it would tip over full left. I managed to ding up the tips of both blade bottoms on the concrete, but got it shut down before I broke something.

The 3GX software says you really don't want to get the aileron and elevator numbers in the swash mix menu below 50. I found out if you do, things go bad in a hurry.

Bumped the numbers back up to the 50 range, the heli flew again, but is still a handful.

So next step is to figure out how to get the desired pitch values while maintaining swash mix values greater than 50, and still being able to turn down the rate numbers. I think that's the key.

If I figure out the 3GX tweaking stuff, I'll write it up here somewhere for others to use and understand.

Meanwhile, the darn thing shows enough promise that if I get it figured out, the 250 is going to be a blast to fly.

One other observation, as I was able to maintain a somewhat decent hover, the nose wanted to slowly drift to the right as if the rudder gyro was wanting me to pay attention to it, too!

One thing at a time. FBL gyros first, rudder last!

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I'll try to post some pics tomorrow night. I ended up bringing work home with me tonight, so I didn't get a chance to play.

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Jim Senicka PM'ed me earlier today saying I should call him to get some help. I may end up doing that. Just gotta get his number and arrange a time to call.

-----
Dave

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

Team Heliproz

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02-08-2012 10:15 AM  6 years agoPost 9
Richardmid1

rrProfessor

Leeds, England

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Have you tried Aligns all white 205D blades? They are slightly heavier than the standard 205D's with the black on them.

Also I found the 250 has really soft damping in the head, maybe you could try stiffening it up?

Both of these things should allow you to run higher gains.

60% of the time, it works every time!

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02-08-2012 02:14 PM  6 years agoPost 10
dkshema

rrMaster

Cedar Rapids, IA

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Since I got the stuff installed, I've not had a lot of time to sit down and mess with it. Just enough to know I need to understand the software a bit more.

Perhaps this weekend I can get some quality time with my 250.

-----
Dave

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

Team Heliproz

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02-08-2012 06:26 PM  6 years agoPost 11
jschenck

rrProfessor

La Vista, NE.

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Sounds like you are in about the same place I was when I shelved the project because of lack of time.

One thing I did note and others that saw mine fly. The tail was locked in very solid. I'm running a Futaba 9257 on the tail with a CF rod instead of the wire pushrod. But cyclic 'felt' wierd, hard to describe. I didn't trust it. I did manage to flip it a few times and discovered that in addition to too much cyclic I have way too much collective. so I run down the swash mix values but that makes it "weirder"

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02-09-2012 12:46 AM  6 years agoPost 12
dkshema

rrMaster

Cedar Rapids, IA

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I did put a DS520 on the tail, I wasn't sure a DS420 would really have done a good job.

-----
Dave

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

Team Heliproz

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02-09-2012 04:41 AM  6 years agoPost 13
dkshema

rrMaster

Cedar Rapids, IA

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Jschenk -- pitcures:

Jim Senicka's posts and a little time to figure out the 3GX GUI on my PC and I'm finally on my way to understanding how to set up the controller. I now need to go back through the mechanics and shorten up those servo arms to get my swash mix numbers back up into numbers greater than 50...then I can start down the tedious path of value tweaking.

-----
Dave

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

Team Heliproz

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