Next is the insertion of the feathering spindle into the rotor hub, the dampers are then pushed into place
The picture to the left has the spacers inserted on the feathering spindle..

When installing the mixer arms to the flybar hub make sure that you do not overtighten.
The mixer arms must be able to rotate freely, I've highlighted the affected screws below in red.
The photo on the right shows the flybar hub screws inserted, just for illustrative purposes..

The mixer fits into a slot on the main rotor hub, located on the screws shown for illustrative purposes above.

Next the flybar can be inserted through the hub and the flybar control arm locked into place using the grub screw.
Be careful on tightening up the grub screw, it's very easy to strip the thread.
At this stage it probably isn't worth doing the final tightening of the grub screw as the flybar needs to be measured
either side of the hub to make sure it is exactly centered.

The washout mixer assembly is next, parts invoilved can be seen below left :

The washout arms are screwed to the washout hub and run on a brass bushing sandwiched between two washers.
Again do not overtighten, the arms should move freely.

Next is the swashplate assembly, whcih mainly consists of screwing all the balls onto the swashplate.
This is a good opportunity to lubricate the centre ball with some light teflon oil or WD40.
The outer balls have screws which are slightly too long, I just ground the ends down with a dremel so that
they don't stick through and bind the inner ball links.

Next task was to screw on the flybar paddles, these should have a gap of 62mm of flybar either side of the flybar
hub. Remeber to use R48 loctite to secure the paddles.

The following show the linkages being fitted to the main rotor controls and mixers.

Below is the main shaft. The shaft has a reemed section part way up which is where the mast collar goes
above the top mast bearing. I'll highlight this in a lter photograph but for now note that this reemed section
is where the collar goes.

The mast inserts only one way up into the rotor head. The instructions denote that the mast has two holes
drilled at either end, the 4mm hole (smaller one) should be at the bottom. The following show the mast inserted
and the swashplate linkages connected.

That completes the build of the rotor head as seen below :

Next is assembly of the two main gears, rotor head and tail. The one way bearing comes pre-assembled.
This step is oiling the one way bearing and using R48 loctite to fix the bearing in the main gear.

The one way bearing has a spacer that fits between the main gear and the lower mast bearing.
The tail drive gear simply presses onto the main gear to form the two as seen below.

Next job to build the undercart, remember when using CA to not glue your fingers to it !

OK, the next part is the main frames. So to start with here are the constituent parts.
Main frames and servo tray on the left, servo tray close up to the right.

Below left are the screws for joining the main frames, the mast bearings and the canopy mounting pins.
Also on the left is the frame spacer that goes at the front of the frames.
Below right is the pre-assembled tail drive gear.

I decided to build up one side of the frame, glue the bearings in place and position the tail drive gear.
Below you can see the mast bearings in place, elevator seesaw and tail drive gear.

The remaining frame I screwed the servo tray onto ready for marrying up to the first frame.

Having put the two frames together (don't forget the frame spacer at the front) the whole thing can
be tightened up with the supplied screws. Below is the finished bare frames.
The undercart can be fitted at this time.

Next job is to build the collective pitch rocker assembly :

First task is to build the aileron control pitch arms as shown below right. Below left shows the brass bushings of
the rocker assembly and the screws used to fit the aileron control arms.

The elevator control arm is built in a similar manner, mounting parts and completed control arm shown below.
The screws and washers shown bottom left are the motor mounting screws. The smaller ones are much easier to fit than the larger ones. Consequently I didn't use the larger ones.

Having built the rocker you should end up with something like the pictures below.
I have highlighted in red the screws that mount the rocker assembly to the elevator assembly.
These screws should not be overtightened or your elevator linkage will be very notchy and not move freely.

The collective rocker assembly is fitted to the mainframes as shown below.
The screw highlighted in red on the right hand picture should not be overtightened.
Overtightening this screw or it's counterpart on the opposite side will cause the elevator to be very stiff or notchy.

Next task is to fit the main gear and the main mast with the rotor head attached.
The main gear is just pushed into the frames loose, the mast goes through the main gear.
Lastley the main gear is secured by a screw with nut through it and the main mast.

Next is the tail gearbox assembly. Shown below is the tail drive shaft and the tail gearbox housing.
The larger bearing shown mid picture is the belt tensioning bearing, the others have the tail shaft pass through them.

The Trex is a belt drive so below can be seen the belt, boom, boom braces and tail servo mounts.
Bottom right is the tail pitch control horn.

OK, so lets run through the tail build. The tail shaft bearings must be R48 loctited in place, so again caution required.
Apart from this it's a fairly simple case of just screwing the two halves of the gearbox together.
Below left the bearings loctited in place. Bottom right the belt drive gear in place.

Next job was bolting the housing around the boom with belt inserted.
The belt should only have a 90 degree twist which can be difficult to see later in assembly.
As a tip I tape my belt in place so that it can't rotate beyond the 90 degrees, I remove the tape just before
installing onto the tail drive gear in the main frames.

Next task is to build the tail rotor hub and blade grip assembly, including the pitch slider.

The important thing to remeber when building the tail pitch assembly is that the ball links must be able to rotate.
They must not be screwed down tight on the tail pitch slider hub.

So having built the tail gearbox and tail blade hub you should end up with something like the pictures below.

Check your tail is rotating correctly in that when you spin the main rotors clockwise the tail rotor should spin anti-clockwise when viewed from the right hand side of the helicopter. If it doesn't then loosen your boom and change the 90 degree rotation on the belt to the opposite of what you had before. The tail blades should be spinning such that the lower blade should be rotating forwards towards the nose of the heli and upwards towards the blades. Also make sure that your ball links on the tail blade holders are leading and not trailing the tail blades.

Next task is to mount the tail onto the main frames and for effect I also put on the main blades at this point.
Below left is the belt shown on the tail drive gear. Belt tension should be fairly loose.
Pinching the belt together it should be possible to make it nearly touch.
An over tight belt will sap performance.

It's starting to look like a proper heli now, just put on the blades to get an idea :)
Note the brass bushings in the blade holes.

At this point I decided to install the motor, on reflection it would have been far easier to have done this at the
time I assembled the basic main frames as there is a lot of stuff to get in the way now.
This wasn't really a problem, just more fiddly than it needed to be.
The motor here is the Align 400s 2800kv.

That completes the mechanical build, the following steps are all electronics installation.
Starting with the tail rotor servo mount and control rod.
My machine has four Align 9g servos.

Next task was the servo installations for cyclic and collective. Getting the servos into the trays provided
is quite a struggle. I had to unscrew the cases on my servos in order to get them into the trays.
The problem is getting the servo wire where it exits the servo case to go through the very narrow slot.
Also included below is a picture of the tail linkage where it fits onto the tail pitch control horn.

The next sequence of pictures show the installation of the control rods for the cyclic controls.
Note that the cyclic controls are on the inner most holes of the control horns.
The trex has VERY sensitive cyclic so this is the only option unless you want a hyper sensitive heli.

Having done the servo installation it's time to fit the electronic speed control (ESC) and Receiver.
I went for a side mounted ESC to get it away from the receiver as the BEC can cause interference.
I have a rear mounted receiver as it avoids the need for servo extension cables.
The items pictured here are the Align 35A ESC and Align single conversion 6ch receiver.

OK, almost done, the canopy now has to be cutout and assembled.
Lastly the gyro should be mounted as shown in the photo below. Also check my article on gyro mounting position and save yourself some money.
Warning : if you have the Align gyro do not mount it with the label facing skywards as in the instructions.
This is incorrect and WILL cause you to crash (don't ask how I know).

Last of all, charge the lipos, grab your transmitter and fly .......



- Article taken from trextuning