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T-Rex 700E — Review 19Aug10

Posted by tanker in Advanced, Beginner, Products, Reviews, TRex.
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T-Rex 700E 3G Combo

T-Rex 700E 3G Combo

The T-Rex 700E is Align’s long awaited 700-class electric helicopter. Currently you can buy the heli in two forms. First is the traditional 700E flybar version that also includes the 700M motor and 105mm carbon fiber tail blades. The other option is the 700E 3G combo kit that includes not just the 700M motor and 105mm carbon fiber tail blades but also 690mm carbon fiber main blades, 3xDS610 servos, 1xDS650 tail servo, flybarless head and the Align 3G flybarless system. Both kits include both an aluminum tail boom and a carbon fiber tail boom. There are reports of a new 3G package that includes a Castle Creations ICE 120 ESC as well as the new 700MX motor and CNC main gear.

Assembly/Build

We picked up the 3G kit. The build was as straightforward as a heli build gets. If this is your first heli you should not have any trouble. The large size makes everything easy to work on. The only issues confronted were that both the main head and tail assemblies were pre-built. We wanted to check them for grease so we had to disassemble them. Unfortunately this was easier said than done. We had to put the main head assembly into a vice with a wrench on the hex driver to get the dang bolts out of the grips. After all that work we discovered that the assembly was well greased but it is still probably better to get these things off now rather than later once everything is together. We do wish Align would just not pre-assemble these things.

Align recommends you place a line of CA against the top of the battery rails where the rails meet the side frames. There have been a few reports of the rails separating from the frames if this is not done.

If you have never assembled an Align Torque Tube before carefully note the position of the bearings on the shaft. Position them and give them just a little CA. Make sure not to CA the bearing internals; you just want to CA the bearing to the Torque Tube itself. After the CA has set put on the rubber guides and give them a little bit of synthetic lubricant. Inserting this assembly into the boom will be a bit tricky as it creates a weird suction effect. Apply a small amount of synthetic lubricant to the inside end of the boom and then carefully push and pull and twist the Torque Tube assembly and you will eventually get it into place.

Note: Bert Kammerer and others have reported problems with the tail blade grip bolts snapping off (the bolts that hold the grips onto the shaft) resulting in total loss of tail control. He recommends replacing the stock Align tail blade grip bolts with any quality bolt (M3x8mm).

When placing the tail assembly onto the tail boom make sure it is straight up and down. You may need to increase the size of the guide hole in the tail boom on one edge to get the assembly straight.

When mounting the motor and pinion be sure to get the pinion set screw on the flat spot of the motor shaft. It is up towards the motor stator and easy to miss.

The 3G combo kit comes with everything you need except a receiver and an ESC. An 80-120amp ESC is all you need for the 700E. There is a nice mounting plate for the ESC back behind the main shaft where you would traditionally put the gyro. The 3G unit (which includes the gyro unit) goes in the nose.

This was the first time we had used the Align 3G and flybarless systems in general so it took us awhile to go through the setup but once you do it a few times it really is not a big deal. Simply follow the instructions and you will be fine. The manual does a good job of explaining the steps. Bert Kammerer also has a short video that explains the 3G setup. We setup our servos and swash directly off the receiver first as you traditionally would and then went through the 3G setup. We do not think this is actually necessary but it was a process with which we were more comfortable.

Main battery installation is a bit of a pain. Getting the packs in and out and secured is just annoying to say the least. It is hard not to get your balance tabs and misc things stuck when putting the packs in/out. It is easier to do this from the front if you kept the area free of straps. Align does not provide enough velcro straps so you will want to have some additional 12″ straps on hand. We had to put our packs all the way to the nose to get proper CG and none of the remaining Align straps were long enough to go around the front of the packs (after using the two longer ones on the pack racks themselves) on the nose.

The canopy fit just fine (we have read others saying they had trouble with it) but the little cotter pins will most certainly be a pain. We do not think the cotter pins are probably necessary because the canopy fits on snugly but we went with the RCBooya 700 E Rear Quick Release Canopy Mounts. These work very well and we recommend them for that extra piece of mind and easier canopy installation/removal.

Flight

The first thing you will need to do with the 700E when you first fly it is to adjust the 3G unit. On our first two flights we had a fair amount of wobble in Normal mode (set to defaults listed in the manual). It almost disappeared in Stunt1. At first we tried cranking up the power on the Normal curve a bit but that only helped a little. We do think the manual’s normal throttle curve is a bit low as the 3G seems to be more sensitive to lower headspeeds than a flybar. We went with 0-60-70-inh-100. We ended up turning down the gain and by the third flight it was almost perfect, just a tiny bit of wobble on occasion. We turned the gain down a smidgen more and all has been well. Of our two helis one is at 9 o’clock on gain and the other 9:30 (both pots). If you have no wobble but the heli drifts then you will need to increase your gain settings for the appropriate drift correction.

Tail control seems excellent with a good pirouette rate and it stops on a dime. We did not need to adjust our gyro gain but if you need to do this it is done on your transmitter as you would with any tail gyro. We, and others, have noticed some occasional tail wagging in gusty conditions. See below. The 700M motor provides plenty of power except for those doing hard 3D flying. Full power climbout is slightly weak with the 700M. We do 6:30min flights of hard sport flying/light 3D (at ~2,100rpm headspeed) and probably have another 30secs of time left. With the headspeed turned down a bit you can easily get 8:00min of hover or light flying.

We have not had any issues with the main gear stripping after over two dozen flights but we are using the KDE Adjustable Motor Mount and are not doing hard 3D. We are also running traditional V curves on throttle (86%-100% Stunt1 and 91%-100% Stunt2) and not governor mode.

We have flown in up to 25mph gusts and the T-Rex 700E does just fine in the wind. The only issue is when you get the blades perpendicular to the wind  the large blade area will allow the wind to really grab and throw the heli so you will have to compensate with collective. Another issue we have noticed in gusty conditions (and has been reported by many folks online) is an occasional tendency for the tail to wag especially when perpendicular to the wind. This can sometimes be cured with simple gyro gain settings but for many, including us, it actually came down to tail blades. We replaced our Edge 105mm blades with the larger 115mm tail blades and so far all has been well. We should also note we have been running the JR 8900G tail servo all along. The stock Align DS650 servo has been blamed for causing wag as well. It seems to possibly be a quality control issue but since we never used it we cannot say. Persistent wagging is probably due to the mounting of the 3G gyro unit (and/or the DS650). [Note: The new V3.0 of the 3G firmware probably eliminates any tail wag issues. Even better move to the 3GX.]

Flying flybarless for the first time was certainly different for us. It is hard to describe but it just feels a bit odd if you are used to a flybar. After about a dozen flights you grow accustom to it and it now feels normal again. Overall the T-Rex 700E is our favorite heli ever. Certainly some of that enthusiasm comes from the .90 size — but this alone is a big deal for electric fliers — and the 700E delivers a solid experience.

Also see Bert Kammerer’s T-Rex 700E ESC Setup and Data Graphs.

Upgrades

The 700E 3G combo flies great in its stock configuration but there are a number of changes you may wish to make.

Align 3G Link: Flybarless fliers will want to pick up the USB 3G Link that allows you to upgrade the firmware as new updates come out and tweak the 3G unit settings to your heart’s content.

Adjustable Motor Mount: The stock mount is fixed and thus does not allow you to adjust gear mesh. The KDE Universal Motor Mount allows this and works great. Note, you will need to grind down your motor mount screws to 8mm total length for the mount to work properly.

Blades: The Align main and tail blades seem just fine but there are plenty of choices in blades including new blades design specifically for flybarless. We have been using the new Edge 693mm flybarless main and 105mm tail blades and they seem fine as well. Align is also releasing new 3G blades as well. There are of course larger 710mm main blades and 115mm tail blades that some folks prefer. See main text above about wag issues.

Landing Gear: Some folks have reported problems with the landing gear breaking on hard landings. We have not had any problems with doing autos but the gear does seem a tad small. The Align T-Rex 600/700 Nitro gear is stronger and fits just fine.

Main Gear: If you are stripping main gears or are worried about doing so KDE makes an upgraded Main Drive Gear. Align has also released an upgraded CNC cut main gear that should be available any time now and folks who have used it report it works very well. If you are using anything other than the stock motor you probably want to upgrade the main gear just to be safe.

Motor: Those wanting more power, or who just do not like the stock Align 700M motor, may wish to upgrade. There are a number of different options available. Scorpion 4035-500/510 motors (Scorpion also makes a non-adjustable motor mount for the 700E that fits its motors) are a popular choice. If you do not get the optional longer shaft then the stock Scorpion shaft will only extend about halfway into the lower support bearing (there is the new Scorpion 4035-500 XL that has the longer shaft as stock). The KDE Neu motor is another popular option and Align also released a more powerful 700MX motor.

Receiver Mount: We also went with the KDE Receiver Mount. This replaces the stock plastic mount. Its big advantage is that it has rails that allow the battery packs to slide all the way forward. This is nice but is probably not really necessary. As long as you put a strap around the nose on the stock mount you will be just fine. But if you want some extra security the KDE mount is very well done. Note: Folks are reporting that the latest 700E kits are shipping with longer rails that would need to be cut for the KDE Rx Mount to fit (and probably eliminates any need for it entirely anyway).

Servos: Most folks are reporting that the stock Align servos do a very good job overall. But others are also reporting the Align 650 tail servo as the cause of tail wag issues. We went with our standard JR 8717s and 8900G on the tail. But on our T-Rex 500 the Align servos have been just fine. If you go with JR/Hitec servos get the Align red aluminum servo wheel set (a blue Align/Futaba set is included in the 700E 3G kit).

Servo Mounts: Align and KDE also make aluminum elevator and tail servo mounts to replace the plastic. We used the KDE Elevator Servo Mount. The rear side hole was not large enough for our ESC wires so be sure to check that before installation and be prepared to grind a couple millimeters away [Note: KDE has since redesigned the mount to eliminate this problem]. A better option is probably the Align aluminum mount that has a much larger opening.

Tail Upgrade: Many folks complain of the slop in the Align metal tail on the T-Rex 600E/N, 700N and now the 700E. If the play in the tail grips bothers you then you can use the KDE Performance Tail Upgrade that will get rid of almost all of the slop or replace the tail unit entirely with a third party unit such as the Quick UK Tail Grip Assembly (the 600 and 700 are the same).

Also see our Hughes 500D scale build for the 700E.

[Updated: 8AUG12]

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