Review: Trex 250 Super Combo
As soon as Align released the Trex 250 I wanted one, such a fun practical size, however like most other new releases there are always teething problems so I thought I’d hold off. Eventually I got around to getting one the other week as the super combo deals were just getting too good to ignore. The Trex 250 Super Combo comes with everything you need except the transmitter, receiver and batteries which is quite impressive.
The first thing you notice is the box is just so dam small, it is quite literally a work of art how they manage to fit an entire model plus electronics into a box less than 30cm wide.
In the box
- pre-assembled head
- pre-assembled tail unit
- pre-assembled main frame with the motor loosely attached for packing
- 1x Align GP750 Gyro
- 3x DS410 cyclic servos
- 1x DS420 tail servo
- 1x RCE-BL15X 15A Brushless ESC (Build-in 5~6V adjustable BEC)
- 1x RCM-BL250 Brushless motor(3400KV)
- 1x Motor pinion gear 15T
- 1x 205mm Main blades (plastic)
- 1x 200mm Main blades (plastic)
- 1x40mm Tail blades (plastic)
- 1x42mm Tail blades (plastic)
- 1x #00 Phillips screw driver
- 1x #0.9 Hexagon screw driver
- 1x Tweasers
Pre-Assembly
The pre-assembled head and swash was completely lock-tightened everywhere as was the tail unit, of course the only way I could know that was by taking it all apart first (which I recommend you do). The main frame was mostly lock-tightened, in my case the worst that would have happen was I would have probably just lost a couple of bolts, of course this is down to how much care is taken with pre-assembly in the factory, you may not be so lucky.
The Build
The upper head links are one piece which makes final assembly of the head a lot easier as there are less links to measure and get wrong. The link coming up from the swash needs to be made, which is a simple process of making too links the same length according to the manual (something we all should be used too).
The frame is pre-assembled and only really needs a quick check over, it is a good idea to think about how you will route the servo wiring and sand the appropriate carbon edges to avoid wires being cut in flight by the frame (remember there really is limited space on this heli). The power cables coming from the motor will either sit left or right hand side of the frame and depending on your setup may come close or touch the frame. The motor comes with a small amount of heat shrink pre-installed where the 3 wires exit the motor, I decided in the interest of preserving my motor wires to add more heat shrink to avoid any direct wear.
Main gear vertical alignment was another consideration I had during the install. Because this is one of the later kits with various different upgrades etc to address and improve performance I have one of the new main gears which actually has a one-way bearing hub. Unlike the older version which has the one-way bearing seated directly into the maingear itself. The advantage of seating the one-way bearing directly into the maingear is that you are able to get the vertical alignment of the maingear to tail gear perfect. In my case I had to re-shim the main gear to get the vertical alignment to the tail gear perfect. Luckly the motor pinon wasn’t a problem as it’s quite tall and allowed for up and down adjustment of the maingear which was helpful. All that said I probably could have left the vertical maingear alignment as it was but hey I’m picky and it’s worth doing right in my opinion.
The tail setup as per manual was straight forward enough, the first main issue is servo horn length which is very important. Too long and you have too much mechanical gain, too short and the tail is not fast enough or has low mechanical gain. What works well and is stated in my version of the manual is the inner most hole on the round servo horn (servo horn that comes with DS420). After adjusting the push rod length so that the tail slider was centered the GP750 with no setting changes had almost perfect limits, which I increased slightly to get maximum throw.
The DS410 servos dropped straight in the frame no problems, the 2 front aileron servos are stacked hence the push-rod lengths are different, so care must be taken with push-rod length, subtrims and ATV’s. The DS410 servo horns holes are small and are incredibly difficult to get the “long ball ends” to self-tap without stripping the plastic holes (ask me how I know). I managed to get them to self tap by putting the horn on the bench and applying massive pressure to the hex driver with one hand (almost with my chest on top of my hand) while turning with the other. The good thing is because you have 4 Align servos, you have 4 servo horns which means you can practice on one to get your technique right, and still have 3 good ones for the cyclic. I also recommend using a drop of CA on the threads to fix them snug in place.
The canopy is a tight fit or at least mine was so a little trimming was needed but otherwise no problems there.
Accesories
- Battery: Outrage 3s 860mAh 30c which fit and work great.
- Receiver: Spektrum 6100
- Transmitter: DX7
Flight Test
I have only had a couple of flights on it and it seems pretty sweet, the tail feels locked in with basic stuff like circuits and piros. Flying sideways fast the tail starts to jitter a bit, also with large gusts of wind but it certainly hasn’t let go (inverted fast backwards would be interesting). I have the gain at about 50% on my DX7 which feels good any more than that an it starts to oscillate in hover.
The tail in general probably needs a little work, even with a considered build there is a bit too much slop for my liking. There are a couple of options, Align have released a second version of their “Chinese Weight” tail hub and grips part number: H25095A. Also Micro Heli has a full CNC tail unit upgrade which looks “the nuts”. There are also custom Chinese weight mods and tail bearing/spacer improvements that can be made see here:
http://www.helifreak.com/showthread.php?t=107276
Collective punches seem overly soft but I believe that maybe due to the plastic blades… I’ll be upgrading to carbon blades. Flipping and rolling the the heli seems slow and hence takes up more space. The manual states 40-45% swash mixing for both elevator and aileron, I might increase that a fraction and with harder dampers and carbon blades I should be in business.
Summary
All things considered it is an amazing heli for it’s size no question. The head quality is great (yes I know it’s Align), all carbon and the kit contains a decent gyro. The only thing that lets it down is a lack of attention with respect to the tail, probably due to rushing it to market, one thing that is certain is Align will fix the tail, however we the public are the beta testers.
Rating: 7/10 (would be more with an improved tail)
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