Living with a Trex 250 DFC

[KevG]

Well guys as you know I have been living with the 250 for a good few months now, love this helicopter and tbh it's all I have been flying, but it's biggest Achilles heal out of the box is it's got a big belly, well it's heavy, that and it likes to be a dog and wag it's butt off,

Firstly the wag, as I think this is the killer to the deal,

This is down to bad design on Align's behalf, theyhave to much play in the bearing supporting the tail hubs, these twist in flight and cause binding, as well as the fact they have scaled down the pro double arm tail slider, these two things mean the stock servo, while it is reasonably quick does not have quite what it takes to get the job done, coupled with the 3gx it results in wag and when you dial the gain down to stop the wag you get next to nowt tail authority,

How did you get around this you ask, well a couple of things can be done,

1. Remove the stock tail blade grip bearing and washer, then replace these with two 861xx bearings and no washer
2. Remove the stock tail push rod and guide, and replace with a carbon fibre one I manufactured mine from a piece of 3mm carbon tube with a 1.5mm inside diameter same length as none threaded part of original rod, and epoxied some 450 fly bar head control rods in each end,
3. The last item is to change to a faster servo, now I have got at the moment the MKS DS95i servo on the heli, it is nothing short of amazing, but it's heavy, I mean heavy, I will be trying the DS76t Blade servo next week and I will report how this compares,

All this mind is hard to get the best out of when using the 3gx but I learnt the hard way till I swapped mine out,

After sorting the issue of the tail, I have got to say this little bird flew pretty good, even on my meagre ability, but I wanted to make it better,

Controller and weight, the main problem with the weight is disc loading, it's HIGH

A stock 250 dfc weighs in approx 360grams give or take, depending on cells used, mine was 257g I think,

Now I heard and read about people having brown outs so at the same time as switching the tail servo I swapped the ESC for a Talon 15 as it has a much better bec and as a bonus is about half the weight of the stock Esc, this meaner I only gained 5 grams when I done these mods

My weight now 362g

My next change though was my FBL controller, out came the 3gx and in went a Beastx V3 and holy s**t it transformed the heli, it felt loads more locked in and really stable, but that came at a price, yes you guessed it, weight,

Now she's 370g

Now it's time for slimming world, the fat bird needed a diet,

First I got rid of some excess wiring from esc and sat cables and ties,
Then I swapped the fibreglass canopy for a plastic canopy,
And finally the tail boom was swapped to a carbon fibre item,

The diet is working the bird was down to 348g

This is where in the story I was lucky enough to get hold of a pair of pre production Zeal 210mm blades to try, you can see my write up on these in the heli blades section,

Next diet tip,

My heavy ass beastx, now although this controller was nice and stable it is realy portly, at 20g it's prob the heaviest nearly, I had been hearing good stories and feedback of the Spartan Vortex Vx1e and was close to giving it a go, but managed to get a great deal on a used Vx1n, again I have a short write up in the controllers section, with this swap I managed to lose a nice 11g because of the sat adaptor as well,

Her weight now stands at 337g

But it's not over yet, swapping this week was the place of the servos cyclic to be exact, out came the DS415mg's and in went DS76 servos, not flown this setup yet I will report back when I do, but this was a good slimming and the girls is getting a bit more thin,

Her weight now stands at 320g

With what I have left, the tail servo swap, if the DS76t works out well and stays on the bird she will weigh between 305g and 308g, my batteries are too heavy and I have new ones on the way so potentially the bird could weigh 295-298g,

All this weight reduction should really help this bird with its disc loading and make it so much more fun to fly, we will see, more reports will follow.......

[Tony]

Wow, Kev, that's a lot of work and effort, not to say extra cash to get your 250 up to scratch.. It will be interesting to see how she performs now after her major diet..

[Lee]

You have really gone all out with that little bird.
I gave up on mine, and sold it

[KevG]

Yeah lads it's been a trip alright. But unlike the trip I done with my 130x this has been a pleasure and leaves me with three cyclic servos, and a great quality tail servo and a spare FBL controller,

Mmmh I wonder what they would fit nice into, I would only need a kit, quantum motor and hobbywing 50a v3 esc,

Yeah Lee I have flown so many packs through this bird this year, and done virtually no maintenance to it appart from oiling bearings, and all the parts I have changed will be crash repairs sometime in the future,

[KevG]

Or been impressed with the Oxy 3 for a while now

[murankar]

The Oxy seems to be getting some talk. I cant wait to see the release version. Right now team pilots have beta versions.

[KevG]

Well she is finished, everything that is going to get replaced has been replaced,

I tidied the wiring as I wanted, although once I have flown it a few times I might end up shortening the servo wires so they are as neat as possible inside the frame,

I wanted the servo wires to come into the frame above the gyro not past the motor and the only way was to run along the outside the frame, did not like that idea, but it was the only way, so I decided to run the wiring in some heat shrink so it would be hidden a little and I think I nailed it,

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Here's some more shots of the sides

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Here's the tail servo area

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And the finished weight

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And the finished article, I even put some bright yellow fins for the bling factor,

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[Graham Lawrie]

The battery looks huge?:)

[murankar]

Looking good. I hope all this weight cutting proves to beneficial for flight.

[KevG]

Lol Graham yes it does look big, but the heli is small,

Uri, even just after a hover it feels lighter on the collective , and you can hear less effort on pitch pumps,

Did have a little issue and a word of warning, I went through my setup and got all the servos lined up and moving in the right directions but forgot the correction direction so tipped it over on the first spool up, luckily for me I was quick to cut the throttle so it only done one chicken dance flip, one slight Nick out of a gear was all the damage,

Lesson learned!

[Tony]

Nice looking bird Kev... You've done a good job there..

[KevG]

New batteries a arrived today, nice quick turnaround for HK RMA process, and straight off the bat they feel smaller, well thinner anyway,

The office scale for postage says 66g so that's like 9g lighter than the ones I had first, I will do a comparison later but I think the original ones were miss labeled and they should have been 35c cells not the 25c that's on the label

[KevG]

Well I got to do the wire tidy up that I wanted to do, as I had my crimpers before Xmas but not got around to doing much hobby wise over the holidays as I loved having the family time,

Shortened two servo leads and the esc battery and Rx wires, all in all I think I took out about 6" of wire in all

Now my bird with the lighter batteries is 293 grams, and feels a lot better for it,

Now the wait for the new Lynx servos, BK speed but the package for the 180 cfx and trex 150 size, but with adaptors will work on the 250, mmmh

[KevG]

Well I have had a lot of fun with this little bird without putting bling on it, but I secumbed as I needed a bit of help with the COG, I needed to move the battery forward slightly (5mm) and the original tray did not leave a lot of support then, after a bit of looking I decided I needed the KDE battery tray, it gave a good bit extra size and lots more support and the battery strap goes through slots in it,

The old one,

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The new and old side by side mounting holes lined up, the new weighs 1.8g more but that was a gain I was willing to accept for better COG

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And the new one fitted,

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Hopefully I will be able to get the Cog perfect now,