RCU Review: Empire RC Align T-Rex 450x


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    Contributed by: Eric Balay | Published: September 2005 | Views: 165995 | email icon Email this Article | PDFpdf icon
    Align T-Rex 450x

    Review by: Eric Balay & Michael Kranitz


    Empire Hobby

    *Available at you local or online retailer

    Website: www.empirerc.com



    T-Rex 450x Video
    CLICK to Watch


    Quality
    Performance
    Ease of Assembly
    Aerobatic ability
    Appearance
    Price
    Manual

    Quality & Value
    Good Manual
    3D Performance


    Stock Z-bend controls are sloppy

    Editors Note: New versions of the T-Rex come with all ball links. No Z-bends.

     


    Surf the Web or browse RC catalogs and you'll find numerous mini helicopter designs. So how is one to make an intelligent choice? Which copters suit your needs and which ones should you avoid?  All good questions.   Answers, however, are difficult to come by; unless you have had the pleasure of flying the TREX from Empire Hobby. This little mini, especially when dressed up in aluminum accents and powered by the new Warp 4 brushless power system, delivers stability, performance and 3D snap.

    Is the TREX right for you? That depends on what you seek. Suffice it to say that the TREX provides new mini pilots with a platform to become accustomed to the size and responsiveness of a mini. On the other hand, TREX roars to life with full 3D prowess when you are ready to handle the beast. 

    The TREX is not a “discount” mini by any stretch. The stock version bears a price higher than many competitors, but quality always comes at a premium.  We were delighted with the quality and value of this kit.




    Kit: Align RC T-Rex 450x
    Price: $159.99
    Rotor Diameter : 640mm
    Length: 630mm
    Flying Weight as tested: 645 grams


    Included in the kit:

    • Lightweight mainframes
    • Collective pitch rotor head
    • Belt driven tail rotor
    • Fully ball-raced mechanics
    • Autorotation unit with driven tail transmission
    • Built-in motor cooling fan
    • Gear ratio: 10:4.95:1 to 13.6:4.95:1
    • Main Drive Gear: 150T
    • Auto rotation tail drive gear: 109T
    • 3D style fin set
    • Bell-Hiller rotor head mixing
    • Aluminum tail boom & skids
    • Dual carbon tail boom supports
    • Plastic tail rotor blades (150mm diameter)
    • Tail boom mounted tail rotor servo
    • Pre-built wooden and fiber main blades
    • 1 piece vacuum formed canopy with tinted windshield
    • Multi-color stickers
    • Handy foam rotor blade holder
    • Instruction Manual

    Additional equipment & upgrades used in the review:

    • RCer Warp 4 Brushless motor, BL4-15-3
    • ThunderPower Lithium Polymer Battery, 1320mah, 3s
    • Hyperion Titan 30 amp motor controller
    • Hyperion E-Meter
    • Airtronics Stylus 8ch transmitter
    • JR 610UL micro 6ch FM receiver
    • Hitec HS-55 micro servos (cyclic & collective)
    • Futaba S3108 micro servo (tail rotor)
    • Futaba GY-240 heading hold gyro
    • Align 325mm carbon main blades HS1042
    • Align 3D carbon fins HS1064
    • Align 347mm carbon tail boom HZ018
    • Align stretch kit tail drive belt
    • Align aluminum main rotor hub HS1080
    • Align aluminum main rotor grips HS1065
    • Align aluminum swashplate HS1062
    • Align aluminum mixing arms HS1056
    • Align aluminum flybar holder HS1060
    • Align servo link rod retrofit HZ010
    • Align tail pitch control lever arm HS1078
    • Align aluminum tail rotor hub & grips HS1103
    • Flight Tech aluminum flybar control arms
    • Great Planes Triton battery charger
    Packaging
    Manual
    The Kit

    The kit box boasts vibrant multi-color images of the helicopter on the outside, and a security tape seal from the Align factory. The contents were in perfect condition and in labeled, individual plastic bags. All pieces were accounted for, and bagged according to assembly steps.

    The instruction manual is quite good. The illustrations are adequate for most steps and atop each page is a grid which displays the bag identification along with the parts used in each step. I really used this reference grid during the build process, especially when trying to ensure that the bolts I was using were the correct ones for the location I was working on.

    There are certain points during the build when you may wish to refer forward in the manual for an illustration of how servos are oriented or where pushrods connect.  The instructions do not overtly walk you through this process, but connections and servo orientations are not too difficult to ascertain from the diagrams.
    Warp 4 motor
    Aluminum swashplate

    3D fins

    The kit includes every thing you need to build the helicopter airframe. All other items (e.g. electronics, power system) must be purchased separately. To quench our thirst for all-out 3D performance, we purchased all of the Align upgrade parts, including aluminum main rotor head and tail rotor heads, swashplate and mixing arms, 3D extended tail boom kit, composite 3D style tail fins, 325mm carbon fiber blades, and a 30 amp Titan electronic speed control (ESC) for the Warp 4 brushless motor. Add a Thunderpower 1320mah Li-Po battery to the mix, and be prepared to slice and dice the air with this mini 3D monster!

    This is a full kit with good, quality materials. The parts fit together well, although we did have a tough time with two parts.  The landing skid tubes did not fit well into the skid legs. We broke a skid leg while attempting assembly. Empire addressed this issue immediately and indicated that it would be corrected in future packages.  The only other issue we encountered was a cross bolt that was too thick for the hole at the bottom of the main shaft (the one that secures the main gear assembly). Again, Empire addressed the issue immediately and recognized that our unit had been shipped with too large a bolt.  In my view, the important part of this experience is not that there were minor errors, but that Empire addressed them immediately. In any new product, there are bound to be minor glitches. I judge the company on their responses to these issues and Empire was extremely responsive.

    Parts list in the manual
    Main frame assembly
    Rotor head assembly

    Rather than reprint the instruction manual here, I have included photographs and commentary in connection with selected steps in the build process. The process of building is typical of a helicopter, but even someone who has never built a helicopter could handle the build steps.

    The plastic frame assembly is rigid enough to handle the rigors of 3D flight. It is lightweight and fits together well.  Screws bite into the plastic where the sides mate and the material seems to hold up well even after repeated insertion of the screws.  This is important in maintaining strength during rebuilds.
    Tail rotor assembly
    Grind a flat on the shaft
    Don't tighten these screws too much
     We replaced the stock tail rotor pitch control arm with the newly redesigned part from the Align T-Rex 450xl (part #HS-1078), which increased the rigidity of the pitch slider. Also, we found that the pitch range could be widened by grinding a flat on the tail rotor shaft and securing the tail rotor hub farther out on the shaft. The stock tail rotor shaft has a groove that anchors the hub set screw, but mounts the hub flush with the end of the shaft. By grinding a flat on the shaft, I was able to affix the tail hub a bit farther outboard (by about 1/16") which allows for a bit more tail pitch slider travel without fear of jeopardizing the security of the tail hub.

    It also helps to loosen the pitch control link screws a bit to allow them to flex outwards during travel of the pitch slider. Make sure that you have used lock tite to prevent the screws from coming out!

    Futaba GY-240
    Futaba S3108 servo
    Secure gyro with foam tape

    Don't chase your tail!

    We used the Futaba GY-240 Heading Hold Gyro to tame our TREX's tail. The gain can be modified with the potentiometer on the gyro unit.  Our gain setting is approximately 80% when using an 8mm servo arm. When coupled with the Futaba 3108 micro servo, this little gyro put a hold on our tail like a pro wrestler wielding a full nelson!

    The tail rotor assembly and boom setup are standard, except for the tail servo, which intelligently mounts on the tail boom, providing a direct path for the control rod between the servo and the tail rotor pitch control arm.  This setup is slop free, which is absolutely critical in providing 3D worthy tail performance. 

    The tail rotor is belt driven. When adjusting the tail belt tension, don't tighten it as much as you might a .50 sized nitro heli. Even though the tension on the belt is critical, if you over-tighten the belt, you will create too much friction on the gears and reduce overall performance. I played around with the tension until I got a nice balance of free movement and belt security around the gears.  Too much tail belt slop can cause the tail transmission to slip under power.

    Don't forget to tape your receiver crystal
    Rotor Head
    Keep power wiring away from the receiver
     The control layout on the TREX is quite clever.  The roll cyclic is controlled by a single servo using push-pull linkages (above). This servo sits in the collective lever housing and actually rises and falls as collective is changed. The relative position of its pushrods to the roll cyclic, however, never varies so it makes for a very efficient way to control roll while taking up little space.  This machine has a 90º mechanical swashplate setup so efficiency is critical. Make sure that all of the linkages are adjusted to provide smooth movement without slop. The collective and pitch cyclic servos are tucked neatly up front, above the battery tray.

    With any electric powered model, it is important to keep all of the power wiring and components (motor, battery, speed controller) routed as far from the radio electronics (servos, receiver, gyro) as possible. This will help prevent any RF noise related glitches that could cause your model to skitter across the sky like a spasmodic lawn dart.

    I always apply tape to my receiver crystals so that they won't come out of the receiver socket. Also, don't forget to add a bit of lock tite or super glue to each servo horn screw.

    Leveling the linkages
    No more Z-bends
    Included blade holder
     

    The key to superior 3D performance lies in the setup. Careful measurement of the linkages, and alignment of control arms is critical! 

    Begin by assembling your helicopter with the recommended linkage sizes specified in the instruction manual.  If any adjustments are needed later, you will at least have a baseline against which to measure the significance of your changes. If you find yourself deviating too much from the recommended linkages or pitch values, reexamine your entire setup because you may have overlooked something. Be careful to not thread the linkage rods too far into the plastic ball links, or you might crack the link.

    The stock T-Rex 450x kit utilizes z-bends at all of the servo arm connections. This proved to be the root of most all of our slop in the control system. By adding the Align upgrade set HZ010 (control rod link retrofit kit), we replaced all of the z-bend elements with ball link ends. If you plan to make any upgrade to your T-Rex, this $4 set should be at the top of your list!

    Initially, most all of the Align links fit well, but a few fit too tightly on the control balls. At best, the helicopter will be very hard to control if flown with tight fitting links. In extreme cases, the copter might crash due to the ball link friction overpowering the servos. Careful fitting of each ball link to each control ball will ensure that your TREX will fly smoothly. I use a JR Ball Link Sizing Tool, JR part #960219, to adjust the fit of each link. The link fit needs to be secure to minimize slop, and should also be loose enough on the ball to allow easy movement.

    We flew our T-Rex using an Airtronics Stylus transmitter, with the following settings:

    Normal Mode - Hovering and take off
    >> Throttle curve 0%, 23.7%, 50%, 80%, 100% at low, 1/4, 1/2, 3/4, high stick positions
    >> Pitch, linear from -4 to +10.
    >> Expo on cyclic controls.

    Idle up 1 - I use this mode for mild forward flight, sometimes if flying backwards circuits in strong wind.
    >> Same pitch curve as normal mode (-4 to +10).
    >> Raised throttle at the lower two points to maintain blade rpm during descents.
    >> Gyro in heading hold mode.
    >> Expo on cyclic controls.

    Idle up 2 - Aerobatic mode, inverted flight, 3D, etc.
    >> Pitch from -10 to +10.
    >> Throttle set at 100% at every stick position (ESC governor mode)
    >> Expo on cyclic controls.

    Idle up 3 - This is my 'piroflip' mode. I set up a separate idle-up for piroflips so I can set the tail rotation rate independently of my other modes.
    >> Pitch from -10 to +10.
    >> Throttle set at 100% at every stick position (ESC governor mode)
    >> Linear travel on cyclic controls.
    >> Tail rotor travel rate cut to about 65%.

    Idle up 4 - Throttle hold - autorotation mode.
    >> Pitch from -4 to +10.
    >> Expo on cyclic controls.

    The gyro is set in heading hold mode (what Futaba calls AVCS mode) for all flight modes.

    Notice that I have at least enough negative pitch in all modes to autorotate. All of these mode changes are ganged to my idle up switches. I don't have additional switches to flip to change gyro modes, travel rate or endpoint changes, or time delays functions. I just remember which switches activate which mode, and all of the other changes -in addition to the throttle and pitch changes- automatically switch too.

    The pitch difference between the idle up 1 and 2 modes will normally make the helicopter jump when you switch modes. However, the Stylus has time delay functions which allow you to specify time delay movements between MODE changes. I set this to about 10 seconds, which means that it makes the move from the current servo mode/pitch position, to the new mode/pitch position (the pitch difference), over the time period specified (10 sec). I can switch between modes, at any time, and the heli never jumps. In a hover, the heli will very slowly start to descend when switching into idle-up 2 if you hold the stick still. These time delay functions make the transition between modes seamless.

    I also have lockouts on certain modes so that I can't accidentally enable throttle hold (idle-up 4) if I'm in idle-up 2 or 3(and inverted, for example). I have to be out of idle-up 2 to enable the throttle hold mode. Also, idle-up 3 cannot be switched ON unless idle-up 2 is also ON.

    I use linear rate travel on cyclic controls in my piroflip mode, idle-up 3, because otherwise the expo will make the cyclic movements uneven when using my cyclic limiter ring. I think that this ring makes a big difference - piroflip cyclic movements are now very smooth.

    Now that our blade setup is done, we can put the nifty foam rotor blade holder into service!

    Soldering the ESC leads
    Hyperion 30A ESC
    Hyperion E-Meter
     Be sure to solder the connectors carefully! Poor solding technique can lead to diminished performance at best, and at worst you might find yourself with a barbequed speed controller! Add heat shrink tubing over exposed terminals to prevent inadvertent battery shorting.

    We used the Hyperion E-Meter to assist in programming our Titan 30A speed controller. There are 10 different settings that can be adjusted. Using the E-Meter couldn't be easier - just plug it into the speed controller and power up the unit. The menu path scrolls through the various tuning options, as listed below. Unlike other brushless speed control programmers, the E-Meter does not need the motor to be connected, nor is an additional battery required. The instructions suggest that the power battery (in our case, the Thunderpower 1320mah 11.1v Li-Po) remain disconnected in the interest of safety during programming.

    We programmed our Titan ESC with the following settings:

    1. Brake (OFF)
    2. Battery Type (Li-Po 3s)
    3. NiCd/NiMH Auto-cut (0.6V)
    4. Li-Po Auto-cut (3.0V)
    5. Auto-cut Type (REDUCE)
    6. Soft Start (ON)
    7. Timing Mode (AUTO)
    8. Frequency Mode (8 Khz)
    9. Reverse Rotation (OFF)
    10. Governor Mode (RANGE 3)

    This handy device made quick work of programming the speed controller to meet our needs. The Hyperion E-Meter can also measure real-time voltage and current (with the included interface cables with Deans style power connectors), calculate power draw (wattage) and motor efficiency, and has a tachometer function to measure the rpm of 1 to 7 bladed props or rotor blades. All of the data can be saved for download to your PC with the available serial cable.

    Ready for flight
    Don't forget to charge the battery!
    Got Aluminum?

    Pictured is our completed T-Rex 450x. Ready to fly, the Rex weighs in at a scant 645 grams!


     

    One of the tasks on my first flight checklist is to track the rotor blades. If the blades are out of track, meaning that they are flying at two different levels, it will create vibration. Observe the edge of the blade disc when hovering, making note of the blade that appears to be flying higher than the other (you did remember to affix the tracking tape stickers, didn't you?). Adjust the linkage rod of that blade (connecting the swashplate to the upper mixer arm attached to the flybar assembly) until both blades are flying in the same plane.

    Adjust the throttle curves to achieve approximately 1700-1800 rpm rotor head speed for flying in normal mode. With experience you can judge this by sight and sound. Otherwise, use an optical tachometer, or someone else's more experienced eyes and ears. For 3D flying, set the throttle to give 1800-2200 rpm.

    Our heavily upgraded T-Rex flies smoothly and with authority. Loops, rolls, stall turns, backwards flight, pirouettes, inverted flight, tumbling maneuvers, funnels, piroflips - the little T-Rex can do it all!

    To maximize the 3D potential of the 'Rex, we chose the Thunderpower 1320mah battery for it's light weight. We were thrilled with the performance, with nearly 6 minutes of pulse pounding 3D moves!




    See the Align T-Rex 450x in action!
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