3G flybarless kit on T-Rex 250 -- a mini-review

[Jotto]

There hasn't been much info here about 3G on T-Rex 250. It appears to be a somewhat rare combo, so I thought I'd share my experiences with you. You might call it a mini-review! I'm not a 3D pilot, but I'm doing sports flying (flips, loops, stall turns, eights, inverted, etc).

Some time ago I installed a 3G kit on my 250. Most people make comments like "Huh? Flybarless on that little thing?". So why did I invest in FBL on this bird instead of my bigger birds? Well, I happen to fly my 250 more often than the other birds. I can fly my 250 at the local soccer field. If I want to fly my 600 or 700, I need to go by car somewhere else. My incentive to install fbl on the 250 was to make it more stable and more tolerant to wind.

The stock 250 is a funny bird, but it's not very stable. For example, it's hard to maintain orientation in a loop or a flip. The bird tends to "tip over" or twist around in the top of the loop. Wind makes things even worse.

Results:

My experience with 3G after some tweaking are

• The FBL heli is somewhat more stable during hovering. It doesn't require as much correction as with a flybarred one.
• It maintains orientations FAR bettery in flips and loops. It behaves much more like the bigger birds -- it behaves like I expect instead of tipping over or twisting. It's flies more "on rails" than my Blade 400, which is same size as a T-Rex 450.
• It is MUCH more tolerant to wind. The flybarred version used to be tossed around in moderate wind gusts. I have flown in 3-4 m/s with fbl and hardly noticed the wind. I can even loop in sideways wind without corkscrewing.
• There is much more punch. Based on the sound of the blades, I am pretty sure that the headspeed is significantly higher with the same throttle curve. I had to reduce the throttle curve from 100% to 80% because the bird flew to fast for me! Flip rate is also way higher than before.
• It's easier to hover inverted. I need to make fewer corrections than before. The difference here is more noticeable than upright hovering.
• Still, there are some problems. I'm sometimes getting slight oscillation in all three axes -- especially after a stall turn or after inverted flight. It's not really a problem, but it looks a little stupid. I'm getting the impression that the system is not 100% mature. I have tried to reduce gain, but I haven't been able to eliminate the oscillation.

Tweaking:

The first flight was miserable. I thought I had wasted money on a crappy system. Fortunately, it turned out to be a question about tuning and tweaking.

A few hints and tips:

• The aleron and elevator gain factory setting is 50%. That's too much! My current setting, which seems to be the sweet spot for me, is 45% aileron and 10% elevator gain. Your mileage may vary, but it seems like most people need to decrease the factory setting.
• It seems to me like you can increase the gain if you increase headspeed.
• The gyro works better if you strap it tightly to the gyro tray. It seems like the align gyro tape is too soft. I'm using one of the align gyro tape pieces and an Align velcro strap tightly around the gyro and gyro tray. That helped a lot!
• With flybar, I had 0% cyclic expo. With fbl, the heli has a MUCH quicker cyclic response, making it hard to control. I have increased expo to 40% on aileron and elevator, and it's still more agile than before!

One more tip: the other day, the bird suddently got violent spasms. I couldn't find any loose links or things like that, but I eventually realized that the gyro connector had worked itself loose. I've read about that before on the 3G, so be aware of this!

Conclusion:

A flybarless on a 250-size helicopter is well worth the money! No doubt! Now I have a small helicopter that can be flown on windy days. It behaves more like my bigger birds. Given the price, the 3G is a good choice. You're getting a nice fbl setup that is less pricey than V-bar.

I will most likely convert to FBL on my bigger birds as well. However, I don't know if I will choose the 3G system or another system. The fact that this seems like a somewhat immature system makes me a little sceptical. Loosing control of a 700 because of a disconnected plug is a little bit more tragic than loosing control of a 250... ;-)

[jwtje]

sounds like we both have the same problem oscillation. I have around the same gain settings as you.
I always had problems with inverted flight with this little monster but now with fbl it goes so much iesier, just with the oscillation it takes me a sec longer to get a good inverted hover compared to my 500fbl and 700fbl.
hope the update will come soon and solve this a bit.

[Jotto]

Interesting. I never get oscillation when I flip into inverted, but I sometimes get it when I flip back.

[elkmaster01]

GREAT write up Jotto,,,,I'm sure that will help guys contemplating the 3G on a small bird.

I just put the 3G on my 500,,waiting for weather to test fly. If all goes well,,,my 250 will be the next victum!!

THX!!

Randy

[CaseyDDR]

Link to where you purchased it?

[HiroboFreak]

Great write up.

I will most likely convert to FBL on my bigger birds as well. However, I don't know if I will choose the 3G system or another system. The fact that this seems like a somewhat immature system makes me a little sceptical. Loosing control of a 700 because of a disconnected plug is a little bit more tragic than loosing control of a 250... ;-)

The 3G seems to work much better on the larger birds at the moment.
I'm sure the imminent firmware update will address some of the issues with the smaller models as well as other minor bug-fixes.

Don't be sceptical, my 3G 700 is absolutely rock-solid!
A bit of shoe-goo or hot-glue on the connectors will help with your insecurities.

[Jotto]

Originally Posted by CaseyDDR

Link to where you purchased it?

www.elefun.com (norwegian retailer)

[Jotto]

Originally Posted by HiroboFreak

.

Don't be sceptical, my 3G 700 is absolutely rock-solid!
A bit of shoe-goo or hot-glue on the connectors will help with your insecurities.

Won't that make it impossible to disconnect the cable to do firmware upgrades?

[HiroboFreak]

Not at all.

I use hot-glue & it comes off easily in one piece.

[SidewaysLS4]

Nice review. I took my pod/boom 3G 250 out yesterday with the gains turned up where the oscillation is apparent. Other than that issue, I was amazed how well it handled heavier wind. I'm getting the feeling that if you turn up the gain so wind becomes a non-issue, the thing bobbs, but if you turn down the gain so the bobbing is gone, wind handling isnt as good.

Hopefully that upcoming software update/usb cable will address this or the unit can be tuned via PC with that cable interface like a SK360 to get enough gain on the unit without bobbing.

[agha_kevin]

Thanks Jotto.
can you share a video of your fly with Trex 250 FBL ?

[TBK]

Does a flybarless system eliminate all tracking issues?
I mean: in a flybarred 250 there are a lot of mixing arms, rods, and a lot of slope and almost impossible to get tracking well.
With a flybarless heli, most of these parts are not present anymore, but there will always remain a slope in the swash plate. My question is: does this still cause inextricable tracking probls?

[Jotto]

Originally Posted by agha_kevin

Thanks Jotto.
can you share a video of your fly with Trex 250 FBL ?

I haven't taped my flights, but I will share a video whenever I get
someone to record it!

[Jotto]

Originally Posted by TBK

Does a flybarless system eliminate all tracking issues?
I mean: in a flybarred 250 there are a lot of mixing arms, rods, and a lot of slope and almost impossible to get tracking well.
With a flybarless heli, most of these parts are not present anymore, but there will always remain a slope in the swash plate. My question is: does this still cause inextricable tracking probls?

You still need to make sure that your blades have the same pitch. It should be easier, however, as the mechanic setup is simpler.

That having said, I have never had any issues with tracking.

[Silverexpress01]

Jotto great review. What type of esc, and batteries are you using, and did you see an increase in flight time?

I'm currently considering this 3g system or the mini Vbar for my 250....decisions, decisions.....

[Jotto]

I have the stock ESC and 1000 mAh Turnigy batteries.

Flight time is still the same, but I'm charging just 650 mAh now (as opposed to 750-ish earlier), so I can safely increase it.

[Heechee]

[freewheel510]

Thanks for the review!!

Am hoping you get a VBar system next, put it on the 250, and move the 3G to your bigger birds. Then you can give a really good comparison report!!.

[llbr22]

Originally Posted by Heechee

Far from worthless.. this was a great read.

Thanks for posting!

[Heechee]

Originally Posted by llbr22

Far from worthless.. this was a great read.

Thanks for posting!

We still want pictures!