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Old Jan 11, 2015, 08:45 PM
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T-Rex250 w/GY280

I've been planning this project for a while. Today it was a rainy day in SoCal-no flying, so I finally got after it:

I've had a T-Rex250 SE that hasn't seen the outdoors for ~1yr. The FBL birds get all the action these days. So, I obtained an Align DFC head ($25 on e-bay), a GY280 ($60 on e-bay), and a CC Talon 25 ($38 on-line). Also needed are some Walkera to 3-pin header connector adapters ($3.95 ea @ Wow).

I've previously installed a GY280 on a Walkera V120D02S, so I didn't expect many issues installing in the T-Rex 250. And, it actually went pretty well with the unit fitting nicely on the gyro shelf. The connector adapters bundle up nicely in the space between the gyro shelf and the bottom tray.

The ESC likewise, fit nicely in the bottom tray, motor wires can be routed under the motor out the front. Throttle cable and battery wires out the back, looped forward. Nice and tidy.

Set-up went well with all settings within the slider range, with the exception of cyclic 8 deg requiring a lower number (40-ish) to be typed in, as the slider values only go to 60. (I think I will need a DFC swash, which has the balls closer to the mainshaft, for optimum cyclic geometry).

I probably won't get a chance to maiden until next weekend. Excited to do so-it should be a nice flyer. I'll try to get it weighed to see how it compares to the old, FB configuration.

Sorry for the dark pics-couldn't get outside due to the rain...

bill
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Last edited by BillG1; Jan 15, 2015 at 07:52 PM. Reason: swash info.
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Old Jan 12, 2015, 03:51 AM
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Mexico, Tamaulipas, Tampico
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Very nice heli, and your pictures are fine...I have the 250 DFC Plus...bought it bnf and it is a dream to fly....
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Old Jan 12, 2015, 09:44 AM
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USA, California
Joined Oct 2010
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Thank you. I have had this heli since shortly after I got into the hobby. I used to fly it a lot, and enjoyed it.
I made the switch to FBL and then it didn't get much flight time. I considered selling it at one time, but you can't get much for these used.

I invested a little bit into it again, but hopefully with the now FBL set up, I will once again enjoy it. It was always a reliable heli before.
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Old Jan 13, 2015, 01:51 AM
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Tucson, Az
Joined Feb 2007
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My friend has 250 dfc he biult a couple years ago. Flown many times and still flys well. He got rid of Align fbl unit as had problems with it. I am not sure what he uses now but looks good. good luck with your upgrade.
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Old Jan 13, 2015, 09:46 AM
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USA, California
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Thanks dankar. Yeah, the Align 3G, 3GX, etc FBL unit are not well liked by most.

The T-Rex250 is too narrow to accept common FBL units like the K-Bar without de-casing them and/or modifying the frame to fit.
That's why I went with the GY280. Fits where the old tail gyro was mounted.

I've cleaned up the wiring a bit more than what's shown in the pics. It's pretty tidy now. May maiden it this weekend... It should fly better than before when it was FB.
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Old Jan 13, 2015, 12:29 PM
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I will be following this thread as I an curious how this unit will perform on a larger platform.
Good luck and keep us updated.
rotorist.
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Old Jan 13, 2015, 05:22 PM
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Maidened this afternoon...

Well, I had an opportunity to come home from work early today.
So I went out to my driveway and maidened it while everyone else was at school or work (no street traffic or neighbor kids about...).

All I can say is that I'm super-impressed with the GY280. Not a hint of tail wag from 4200rpm to 4600 rpm (a big feat with a T-Rex 250). Pitch pumps (13 deg pitch) had only a hint of tail stepping out; upped the gain in all three banks one point and rock solid!

Hover and piros (upright and inverted) are so flat that I won't even bother with a trim flight, as it may screw it up! (careful swash leveling and spot-on CG helped here).

Flips were a bit slower than I like, so upped the agility 2 points and it helped- I will likely go another couple points.
Need to test fast backwards flight to really dial in the tail, but that has to wait for the flying field to do so.

I have to say that this unit is looking quite suitable for a 250-size bird. I have a Gaui Hurricane 200 with a yellow K-Bar that I'm now thinking of replacing with a GY280, just for the smaller, tidier footprint. Plus, the GY280 is 7 grams lighter than the K-Bar, not even adding in the satellite Rx weight. The G200 really appreciates light weight as it's only a 2S system.

bill
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Last edited by BillG1; Jan 15, 2015 at 07:49 PM. Reason: weight.
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Old Jan 13, 2015, 06:09 PM
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Thanks for the update. I see the unit used in 130 and 180 helis and was wondering if it would work without major issues in the larger platforms.
I just might have to purchase a couple to play with.
rotorist.
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Old Jan 13, 2015, 06:24 PM
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USA, California
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Quote:
Originally Posted by rotorist View Post
Thanks for the update. I see the unit used in 130 and 180 helis and was wondering if it would work without major issues in the larger platforms.
I just might have to purchase a couple to play with.
rotorist.
Just be careful with the current draw of the larger bird's servos. The little Walkera plugs are only rated for 1A (continuous) each. With all four servos working, I'm pretty sure that's being exceeded somewhat at the ESC/BEC plug, but not continuously, so likely OK on a 250. I probably would not try it on anything larger, say a 450.

Just be sure to test thoroughly on the bench. I used a Talon ESC with a beefy BEC circuit, and no brown-outs....
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Old Jan 16, 2015, 01:57 PM
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Tucson, Az
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Ant link to GY 280 RX ? I have a V120D02s that may be needing upgraded unit. glad you 250 is doing well.
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Old Jan 16, 2015, 03:49 PM
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USA, California
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Quote:
Originally Posted by dankar04 View Post
Ant link to GY 280 RX ? I have a V120D02s that may be needing upgraded unit. glad you 250 is doing well.
Hi Dankar,

There's a few on e-bay. This link is but one example:
http://www.ebay.com/itm/Flybarless-S...item41895b6c1c
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Old Jan 17, 2015, 09:03 AM
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Thank you for link.
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Old Jan 18, 2015, 03:43 PM
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USA, California
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Well I finally had a chance to take my 250 to the regular flying field I use. Got the tail gain dialed in in fast reverse flight, and fast inverted flight (got a nasty tail wag 1st time I tried it inverted ). 3 points down on the tail gain fixed it right up. Dialed up the agility another 4 points and this thing flies like a dream; tic-tocs, funnels ( nose up/nose down), all are fun and locked in.

Time to look for some lighter servos to replace the heavy-ish Align DS410's.
It's a tad heavy, requiring generous collective to arrest drop during pitch changes.
(well known issue with the T-Rex 250). Other than that, it's really nice. The GY280 is soooo worth it on this bird.
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Old Jan 18, 2015, 03:50 PM
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Thanks for the update. sounds like a winner to me!
rotorist.
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Old Jan 19, 2015, 12:42 PM
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I will get GY 280 for my V120D02s soon. I want to make one a 2 cell bird a little lader. No rush as have another plan under way and see how that goes.
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