Align Trex 600 Nitro Pro - Build

Reviewer: Rob Turnbull
Publication Date: 15th October 2007
Manufacturer: Align
Supplier: Align UK
Model: Trex 600 Nitro Pro
Unit Cost: £345

Equipment

The equipment that I will be using for the Trex 600 Nitro Pro build is as follows:

Kit: Trex 600 Nitro Pro
Engine: OS 50 Hyper Max
Exhaust / Muffler: Hatori 522
Receiver: Spektrum AR7000
Collective / Cyclics: 3x Hitec 6965 for eCCPM
Throttle Servo: Futaba S3152
Gyro: Futaba GY611 with 9256 Servo
Transmitter: Spektrum DX7
Regulator Align 2 in 1 regulator
LiPo pack Revolution 2S2P 3000 mAh
Extras: JR Macgregor Header Tank
  Sullivan crap trap inline fuel filter

Jump directly to a section of this article

First impressions

The box looks good with a picture of the Pro model in both of it's available canopies, a snazzy design and the obligatory sponsored pilot signatures. The contents of the box are quite carefully packaged and in fact don't entirely fill the box up. The helicopter does not come pre-built, which is my preference as I usually take a pre-built heli apart and rebuild it again to ensure it's done right.

  • The outer packagingThe outer packaging
  • Box contentsBox contents

The contents of the box are carefully packaged into number coded bags, which are opened as you progress through the manual when building the kit. Some other helicopter kits manage to get this type of staged assembly perfect using a single bag at a time in the build process and if you move on a step when building and have parts left over, you missed it in the previous stage. Align have not quite got it nailed, with some bags needing to be opened to retrieve parts (usually fixings) before completing a bag step, however it's certainly not a million miles away from being right and the process it takes you through is still very easy to follow and methodical. I found the built to be quite enjoyable, with just a couple of frustrating points which will be detailed as we go through it.

Head assembly

The first task is to assemble the head which is in multiple bags contained in the single bag numbered 600NH.

  • The head assembly bagThe head assembly bag
  • The contents of the head assembly bagThe contents of the head assembly bag

Starting with bag 600NH1A, we will first assemble the blade grips.

  • The blade grips plus thrust races and fixings bagThe blade grips plus thrust races and fixings bag
  • The blade grips and thrust races plus fixingsThe blade grips and thrust races plus fixings
  • Use CA glue to fix ball link to blade gripUse CA glue to fix ball link to blade grip
  • Completed blade gripsCompleted blade grips

The thrust races are assembled onto the ends of the feathering spindle and sit inside the blade grips behind the bearing visible in the images above. The two outer races of the thrust bearings have slightly different inner diameters and the positioning of these races on the feathering spindle is very important. The race with the largest inner diameter must go nearest the main head block. To size them up, you can use the feathering spindle from bag number 600NH2A - slotting the races onto the feathering spindle easily shows which is tighter and which is looser.

  • The head block bagThe head block bag
  • Contents of the head block bagContents of the head block bag
  • Blade grip assembly with thrust race and spacerBlade grip assembly with thrust race and spacer
  • Liberally greased thrust bearingLiberally greased thrust bearing

Fill the thrust bearing with grease to ensure proper operation in flight and when finally assembling the thrust races and bearing into the blade grips, I always insert them with the open side of the thrust bearing facing the head block.

Make sure you fit the supplied shim in-between the radial bearing and the thrust race assembly when fitting into the blade grips. See bottom left pic above for assembly order.

Use a plug spanner, or suitably sized nut driver to ease the thrust races into the grip if they are a tight fit.

The supplied head dampers will probably be fine for general sport flying, but as they are not a very high durometer, they are easily destroyed when used in 3D flight. Based on this knowledge, I decided to skip the supplied dampers altogether and instead fitted the Infinivation dampers made specifically for the Trex 600n.

  • The supplied dampers - grey and black versionsThe supplied dampers - grey and black versions
  • Infinivation dampersInfinivation dampers
  • Infinivation dampers ready to fit to the headblockInfinivation dampers ready to fit to the headblock
  • Infinivation dampers fittedInfinivation dampers fitted

Fitting these dampers can be a bit tricky as they are a very tight fit. What I did was to fit one side onto the feathering spindle a little further on than it needs to be and pushed it through the headblock, then I slid the other side on and into position. If you don't do it this way, it's quite difficult to get the feathering spindle through the dampers inside the head without pushing them out and disassembling them whilst trying.

With the dampers in place, fit the brass shim onto both sides of the head, on the feathering spindle, then attach the fully assembled blade grips and using blue threadlock, attach the feathering spindle bolts into both ends and do up very tightly. Make sure you do not use excess threadlock to ensure you get none into the bearings.

  • Fitted dampers onthe feathering spindleFitted dampers onthe feathering spindle
  • Fitted brass shimFitted brass shim
  • Blade grips attachedBlade grips attached
  • Bolt and washer done up tight in both endsBolt and washer done up tight in both ends

The next part of the head assembly to be built is the flybar seesaw and upper mixing arms - bag number 600NH3. This bag also includes the flybar paddles but we will be leaving them until much later on in the build process.

  • Flybar seesaw bag of partsFlybar seesaw bag of parts
  • Seesaw and fittings bagSeesaw and fittings bag
  • Fitting seesaw to head blockFitting seesaw to head block
  • Seesaw fitted - using special shouldered boltsSeesaw fitted - using special shouldered bolts

The seesaw block is fitted to the headblock such that the square corners of the outside shape of the block are leading when the head turns. To fit the seesaw, you must slide it up to the base of the headblock (where it cannot go any further) then rotate it 90° there (the headblock has a round portion for just this purpose) and drop it back down and into position inline with the mounting holes. Apply blue threadlock to the special shouldered mounting bolts and fix into position. The bolts should be done up tight to avoid slop, while still having completely free movement between the seesaw and the headblock.

Next we will assemble and fit the upper mixing arms to the flybar seesaw. Use CA glue again on the mixing arm balls. Take not of the different sized balls that will be attached to the mixing arms. Each mixing arm has a long ball and a short ball - with the short ball being attached to the short side of the mixing arm (relative to the arms pivot point). If in doubt, refer to the top right picture below.

  • Flybar mixing arms and fixingsFlybar mixing arms and fixings
  • Assembled mixing armsAssembled mixing arms
  • Mixing arms fitted to seesawMixing arms fitted to seesaw
  • The head assembly so farThe head assembly so far

Make sure that when you put the screws through the mixing arms (to fix them to the flybar seesaw) that you have the two washers installed, one on either side of the arm - these are here to ensure the mixing arm bearings run freely. Do not use glue on this particular fixing.

I wanted to set this heli up with lively cyclics, so I attached the mixing arms to the outer hole of the two available mounting points on the seesaw (you can just see this in the picture below right). The one furthest in will soften the cyclics if thats what you prefer - this would be more suited to beginners who neither want or need lively cyclics.

Next we will build and fit the flybar cradle and the two rod links that fit onto it.

  • Flybar cradle partsFlybar cradle parts
  • Assembled and fitted flybar cradleAssembled and fitted flybar cradle

This is quite straight-forward. Make up the two rod links as per the manual (38mm from centre to centre of ball links) and fit them to the balls making sure that the A's on the links are opposite to each other - this is so the lower links will fit on the lower mixing arms the right way around (Align ball links are sided so one side is slightly larger than the other - the smaller side is marked with an 'A' so it faces 'out'). Loosly attach the two flybar cradle ends to the rods with the extended collar on the outside. Hold the loosely assembled cradle in place while you slide the flybar through the entire head assembly, then use threadlock and tighten the bolts into the ends of the flybar cradle while ensuring the cradle is pulled tightly together. I did not complete this part of the assembly at this stage - instead choosing to do this at the end when fitting the flybar paddles. Doing this allows me to get everything else completed without the fully assembled flybar getting in the way so much. I will later be centering the flybar and tightening everything down.

The washout base, lower mixing arms and swash are next on the assembly list. Slide the main shaft into the bottom of the head assembly and lock in place using the main shaft bolt and nyloc nut.

Fit the balls to the mixing arms using CA glue again. Remove and threadlock the mixing arm bolts before tightening them up firmly. Ensure they move freely once tight. Slide the washout base and mixing arms assembly up the main shaft and into the guide pins. The short side of the lower mixin arms will be leading when the head turns. Finally, clip the rod links from the flybar cradle onto the long end of the lower mixing arms.

  • Main shaft and washout assemblyMain shaft and washout assembly
  • Fitted main shaft and washout assemblyFitted main shaft and washout assembly

The swashplate requires a small bit of assembly in the shape of attaching the ball links to it. Make sure you threadlock them all in place and do them up tight.

  • Swashplate with threadlocked balls fittedSwashplate with threadlocked balls fitted
  • Fitted swashplate and mast locking collarFitted swashplate and mast locking collar

Slide the assembled swashplate onto the main shaft and attach the short arms from the lower mixers to the inner balls of the swashplate. Push the mast locking collar up the shaft and lock everything in place temporarily by nipping up a grub screw on the collar. This keeps it all in place while we continue with the rest of the build.

Main gears

This is a quick and easy step, but necessary to try and ensure longevity of the parts.

Open the bag numbered 600NB3 which contains the main gears and split them apart. Remove the one-way bearing housing screws one by one and re-fit them using a dab of CA glue.

  • Main gears, sleeve and mast locking boltMain gears, sleeve and mast locking bolt

Push lots of grease into the one-way bearing and then use the sleeve to work it into the bearings, and also to remove the excess, by pushing it through and spinning it around. Clean up the parts when done. Finally, fit the nyloc nut into the moulded nut housing in the tail drive gear, while it's handy.

  • Use the one-way sleeve to work the grease inUse the one-way sleeve to work the grease in
  • Completed gear assemblyCompleted gear assembly
  • Completed gear assemblyCompleted gear assembly
  • Nyloc nut fitted into moulded housingNyloc nut fitted into moulded housing

The clutch stack

Next we come to bag number 600NB4, which contains the clutch stack and the fan shroud. We can put the fan shroud to one side for now.

  • The clutch stack and fan assemblyThe clutch stack and fan assembly
  • Clutch and fanClutch and fan
  • Clutch bell, pinion and starter couplingClutch bell, pinion and starter coupling
  • Component parts disassembledComponent parts disassembled

The clutch and fan assembly needs to be taken apart to that we can threadlock the relevant parts. Remove the grub screw from the starter coupling, pull the coupling off the shaft and then drop the shaft out through the bottom of the clutch bell. Remove the smaller bearing, then the nut, then the larger bearing from above the pinion, then carefully remove the pinion from the bell. Use a thick cloth and some grip pliers or similar to remove the pinion without damaging it.

Next we can threadlock and rebuild the parts, starting with the pinion gear into the clutch bell. Make sure it is done up tight and use threadlock!

Add the larger bearing to the top of the pinion - it sits on the smooth space above the pinions teeth - use a smear of threadlock on the smooth space and be careful to not let any get in the bearing when fitting it.

  • The clutch bell with pinion re-fittedThe clutch bell with pinion re-fitted
  • Larger bearing re-fittedLarger bearing re-fitted (threadlocked)
  • Nut re-fitted - ensure it's tight and use threadlockNut re-fitted - ensure it's tight - use threadlock
  • Rebuilt clutch bell, pinion and starter couplingRebuilt clutch bell, pinion and starter coupling

The starter coupling is only loosley fitted at this point, as the upper plastic bearing housing needs to be fitted which will position the top bearing correctly. Once that is in place (next), you can threadlock the grub screws into the starter coupling, ensuring they sit into the cut-aways in the shaft, and are nice and tight.

  • The upper clutch bearing housingThe upper clutch bearing housing
  • Upper clutch bearing housing assembledUpper clutch bearing housing assembled

The plastic housing has mouldings for the nyloc nuts to sit in, one one each side of the housing.

With that done, we can put it to one side for a minute (we'll be using it in the next step) and get on with building the body of the heli, starting with the sideframes.

Sideframes

  • The sideframes are carefully bagged - separatelyThe sideframes are carefully bagged - separately
  • Frame and nose fittingsFrame and nose fittings

We need the metal frame and engine mounts out of bag 600NB1 for this next step, along with the actual side frames from bag 600NB.

  • The metal baseplate and engine mountingsThe metal baseplate and engine mountings
  • The bag of fixingsThe bag of fixings

Before we fit the engine mounts and frame mounts we need to build the intermediate tail lever which sits inside the back of the right side frame. There is a long ball and a short ball, which must be glued into the lever and this then attached to the mounting plate. The shorter ball goes to the outside of the frames when fully assembled.

  • The intermediate tail lever and fixingsThe intermediate tail lever and fixings
  • Completed intermediate tail lever and fixingsCompleted intermediate tail lever assembly
  • Fitted intermediate tail lever (right sideframe)Fitted intermediate tail lever (right sideframe)

Remember to put the supplied washers above and below the bearing to keep it protected from the bolt and the mounting plate and to ensure smooth operation of the bearing. The build order is bolt then washer, through the bearing, then washer, then into mounting plate - and use threadlock into the mounting plate too!

The intermediate arm should be able to freely pivot on the plate when everything is tightened up.

Next we can mount the baseplate fixings and the engine mount fixings to the sideframes. Make sure that the engine mounts are tightened up square on the heli by standing the sideframe on a flat surface. Also make sure you use threadlock and take note of the orientation of each piece when fitting.

  • The front baseplate fixingThe front baseplate fixing
  • The rear baseplate fixingThe rear baseplate fixing
  • The engine mountThe engine mount
  • The engine mountThe engine mount

Now we can attach the three main mast mearing blocks and the clutch bell and starter assembly to the left sideframe. There are two large and one smaller bearing blocks to fit to the heli, the small bearing block goes at the bottom of the main shaft.

  • Bearing blocks and clutch bell fittedBearing blocks and clutch bell fitted
  • Bearing blocks and clutch bell fittedBearing blocks and clutch bell fitted

We only want to fit the bearing bloocks loosely for now as we will be making sure they are correctly positioned before tightening them up by using the main mast. The second side-frame will be in place before this happens.

Next we can fit the canopy mounting posts and stand-offs.

I've been told by another 600n builder that the little bits of metal that are on the screws in the photo below left, which go through the rubber mounts, were screwed onto the aluminium spacer so they couldn't find them to start with. If yours appear to be missing, it would be worth checking this. Mine were easily located.

  • The front canopy mount/stand-offThe front canopy mount/stand-off
  • The front canopy mount/stand-off fittedThe front canopy mount/stand-off fitted
  • The rear canopy mounting postThe rear canopy mounting post
  • The rear canopy mounting post fittedThe rear canopy mounting post fitted

Now the second sideframe, complete with its baseplate fittings, engine mount and canopy mounting post and stand off, can be fitted. Line up and slot the bearing blocks into position, get the mounting bolts loosely in place, then stand the heli body up on a flat surface to ensure it sits straight while you tighten the bolts up one by one using threadlock.

Check that everything is square by fitting the main shaft through all three bearing blocks - it should slide in quite freely. If it doesn't, loosen the bolts off a little and do it again with the main shaft still in the bearing blocks as this will help to ensure the frames are tightened up straight.

Fuel tank

Bag number 600NB2 contains the fuel tank and fittings, which we will build and add to the heli next. First, we can assemble the fuel tank and clunk line to go inside it.

There are four pieces to the clunk line; the clunk weight, a short length of fuel tube, the fitting and the tank rubber. The short side of the black plasic fitting goes on the outside of the fuel tank, with the long flat portion of the fitting sat inside the rubber ring.

Fit the clunk weight to one end of the short length of fuel tube, slide the tank rubber over the tube and then attach the black fitting to the other end of the tube. Feed the clunk into the fuel tank, fit the tank rubber and then gently push the black plastic fitting into the rubber.

Add a length of fuel tube to the outside part of the black plastic fitting to give yourself an easier retrieval option in case it all pushes through into the fuel tank when fitting. (See bottom right picture below)

  • The fuel tank, mounting rubbers, tube and fittingsThe fuel tank, mounting rubbers, tube and fittings
  • The fuel tank clunk line componentsThe fuel tank clunk line components
  • The assembled fuel tank clunk lineThe assembled fuel tank clunk line
  • The fuel tank clunk line assemblyThe fuel tank clunk line almost fitted

Once the black plastic fitting of the clunk line is seated in place securely, we can prepare the frames and then fit the tank. Slide the black rubber tank dampers into place, one on each sideframe where the fuel tank sits. Then fit the rubber O rings into the holes above and slightly forward of the fuel tank - these are used to ensure the exhaust back pressure pipe doesn't get eaten by the frames when in flight. If you run an engine that doesn't require exhaust back pressure to run, you can skip this part if you like.

  • The fuel tank clunk line fittedThe fuel tank clunk line fitted
  • The fuel tank clunk line componentsThe fuel tank frame rubbers fitted
  • The assembled fuel tank clunk lineBack pressure pipe frame rubbers
  • The fuel tank clunk line assemblyBack pressure pipe frame rubbers fitted

Now to fit the fuel tank into the frames. Gently, but with sufficient force, squeeze the top of the tank enough to allow it to pass through the hole in the sideframe, and ease the tank into place. You may need to work the damping rubbers back in place after fitting the tank as they can be dragged out during this step. Finally, feed the back pressure pipe through the rubbers fitted in the side frames to get it across to the exhaust side of the heli.

  • The fuel tank fittedThe fuel tank fitted
  • Back pressure pipe fittedBack pressure pipe fitted

Next we can fit the carbon baseplate, which was in with the sideframes in bag number 600NB, and assemble and fit the skids and struts from bag number 600NG.

Fix the carbon baseplate to the heli using the supplied bolts and washers - and use threadlock too. At this stage just fit the bolts through the baseplate to attach it to the bottom of the engine mounts with the large baseplate hole to the front of the heli.

Slide the skid tubes through the struts and position them roughly where you want them. Fix the struts to the to the baseplate and use threadlock to tighten them into the baseplate aluminium fixiings that were previously attached to the sideframes. Finally, with the skids in the position you want them to be in, lock them in place by tightening the grub screws down through the skid struts. They will bite onto the skid tubes and lock them in place.

  • Carbon baseplate, skid struts and fixingsCarbon baseplate, skid struts and fixings
  • Grub screws used to lock the skids in the strutsGrub screws used to lock the skids in the struts
  • CA glue the skid tube caps into the skid endsCA glue the skid tube caps into the skid ends
  • Tighten down the grub screws to secure the skidsTighten the grub screws through the struts

Nose piece

This is a nicely designed part of the heli giving you lots of mounting points to put a modern electric setup onto a heli. The receiver, gyro amplifier (if using a GY611, like I am in this build) LiPo battery and regulator all fit comfortably onto this piece. Notice the slots in the nose-piece which allow you to strap items securely to it. Align even supply several hook and loop straps for just this purpose.

  • The nose piece fittedThe nose piece fitted
  • The nose piece fittedThe nose piece fitted

Engine fitting

Next, we can fit the engine to the heli, however, before we get to that final part of this step, we need to fit the fan and clutch assembly to the engine, and then fit the fan shroud.

Fit the fan, upside-down, to the silver fan hub. Then place the engine washer onto the crack shaft thread and then fit the fan assembly to the top of the engine, followed by the locking nut (supplied with the engine). Use threadlock on the engine locking bolt and tighten down securely. Lock the fan mount in place with the two bolts provided.

Next, fit the clutch to the top of the fan mount, again, threadlock the bolts and tighten them down securely.

  • Fan and clutch fitted to engineFan and clutch fitted to engine
  • Threadlock the clutch boltsThreadlock the clutch bolts

Now we can fit the fan shroud around the fan and the engine. Notice I have cut a portion of the fan shroud away to allow a governor sensor to poke through in order to pick up a sensor magnet which will be glued to the fan. The stock fan in these early kits is known to be flexible which results in the magnets comeing out of the fan, so this did not get fitted to the stock plastic fan (as you can see in the pictures). Instead, I used a G-Force aluminium fan, and a review article of that wil be available soon.

The fan shroud doesn't need to be split completely apart, but just enough to get the fan through the gap. Once the fan is inside the shroud, press the shroud tightly together, ensuring no gaps are present. Tilt the carb to one side on the engine to enagle it to be fitted into the heli body.

  • Engine, fan shroud and fixingsEngine, fan shroud and fixings
  • Fan shroud fitted to the engineFan shroud fitted to the engine

The engine is fitted through the large hole in the carbon baseplate. The fan shroud is the guiding factor in this part of the job. It will push in between the frames on a 45° angle and slide up into position with a little effort. You will probably need to pull the side frames apart slightly to get the fan shroud mounting screw points to slot in - then slide it into place. Push the engine up against the engine mounts and threadlock the four engine mounting bolts in.

  • Engine fitted to heli bodyEngine fitted to heli body
  • Engine fitted to heli bodyEngine fitted to heli body

Next, fit the four fan shroud mounting screws (with supplied sunken washers) to hold the fan to the frames.

At this stage, using a starter wand is advisable to ensure that the fan is not catching on the fan shroud. Turn the starter wand to check that it runs freely and doesn't catch. Move the fan shroud until it runs freely.

  • Engine fitted to heli bodyFan shroud fixings
  • Engine fitted to heli bodyThe upper rear fan shroud fixing fitted

Bell cranks

The next stage is to assemble and fit the CCPM bell cranks to the heli. All three levers need the balls CA glueing to them.

  • Bell crank and ballsBell crank and balls
  • Bell crank with balls fitted - use CA glueBell crank with balls fitted - use CA glue

Once all three bell cranks have been fitted with balls, fit one of the outside bell cranks to one end of the shaft (the two that are the same are the outside bell cranks), ensuring the balls will be innermost to the helicopter when the shaft is fitted.

Slide one standard metal shim and one brass shim onto the shaft and then feed it through the bearings in the sideframes - once halfway through, fit the centre bell crank onto the shaft, ensuring correct orientation (see pictures below) and then finish sliding the shaft through the other sideframe. Slide the other brass shim, and then the other standard metal shim onto the shaft and fit the other outside bell crank. Make sure you use the small shims with the bolts to tighten into the ends of the shaft - these prevent binding of the bearings in the bell cranks, allowing smooth operation.

Take note of the cutaway on the shaft - this is where the elevator bell-crank will be fitted, inside the frames, and it needs to be over to the left side of the helicopter.

  • Bell cranks, shaft, shims and fixingsBell cranks, shaft, shims and fixings
  • Bell cranks and shaft fitted to the heliBell cranks and shaft fitted to the heli

With the shaft fitted securely, position the central bell crank so that the grub screw hole is over the cutaway on the shaft (towards the left side of the helicopter). Correct alignment will result in the ball on the long arm being in the centre of the helicopter, which you can check by lining it up with the mainshaft bearings. See the picture above for further clarification. Tighten up the grub screw onto the shaft (in the cut away) and use threadlock.

Fitting the servos

Next I fitted the servos. The servo fixings bag is number 600NZ4, and contains carbon servo mounting plates, screws and plastic nuts (as they call them!), along with balls and nuts to fit to the servo arms.

  • Servo fixings bagServo fixings bag
  • Servo fixings bag contentsServo fixings bag contents

Making life a little easier, I fitted the rudder servo first as it sits below the front two cyclic servos, so there's plenty of access while they are not fitted. Following the rudder servo, I fitted the throttle servo on the other side of the heli. Following that was the front left cyclic servo, then the front right cyclic servo and finally the rear right cyclic servo.

All the servos have their output shafts closest to the main shaft when fitted to the heli.

All of the front (four) servos are fitted to the frames using the carbon mouting plates between the bolts and the servo lugs - the servo lugs are fitted with servo rubbers, but not the brass ferrules as the servos won't tighten down properly with the mounting plates in use. Finally, the bolts are screwed into the plastic nuts nice and tight. Don't over tighten them though as you could strip the plastic nut.

  • Rudder servo fittedRudder servo fitted
  • Throttle servo fittedThrottle servo fitted
  • Front left cyclic servo fittedFront left cyclic servo fitted
  • Front right cyclic servo fittedFront right cyclic servo fitted
  • Rear right cyclic servo fittedRear right cyclic servo fitted
  • Rear right cyclic servo fittedRear right cyclic servo fitted

The rear cyclic servo is mounted slightly differently to all the others, in that the screw goes through the mounting plate, then through the frame, through the servo lugs (fitted with rubbers) and then into the servo nut).

Being a push-pull system, the cyclic servo horns in the pictures will be swapped out for circular discs, supplied with the servos.

At this stage, the rod links can be made up and put to one side for fitting later, once the servo horns have been changed.

  • Front cyclic servo rod links (51.00mm)Front cyclic servo rod links (51.00mm)
  • Rear cyclic servo rod links (21.00mm)Rear cyclic servo rod links (21.00mm)
  • Swashplate rod links (31.50mm)Swashplate rod links (31.50mm)

The measurements shown in the pictures on the digital verniers are close to what will be finally required, but may not be exact - small adjustments can be made later, if necessary, to get them exactly right.

Shaft drive tail assembly

The Trex 600 nitro pro comes with a shaft driven tail, as opposed to the sport version which comes with a belt driven tail. The front end of the tail assembly is a pretty clever piece of design, allowing you to completely build the tail without getting anywhere near the rest of the helicopter. The complete tail unit can then be slotted straight into the back of the helicopter body and fixed in place with 6 screws and two boom stay bolts.

The first job, as noted in the manual, is to remove the screws holding the umbrella gear box together and replace them using CA glue.

  • Front tail gearbox and tail assembly fixingsFront tail gearbox and tail assembly fixings
  • Shaft drive front umbrella gearShaft drive front umbrella gear

We start the assembly from the back end of the boom - the tail output gearbox and shaft assembly. The first job here is to fit the the vertical carbon fin - use threadlock.

  • Rear metal tail gearbox - comes pre-assembledRear metal tail gearbox - comes pre-assembled
  • Rear metal tail gearbox with vertical fin fittedRear metal tail gearbox with vertical fin fitted

Next, we assemble the tail hub, which involves attaching the tail pitch slider to it. The hub comes in bag number 600NT2B with a pretty decent set of carbon tail blades. The blade grips are already fitted to the hub. There are also two blade grip bolts, nyloc nuts and a grub screw which is used to lock the hub onto the output shaft all in the same bag. The next few steps will use parts from this bag, and also bags numbered 600NT2C and 600NT2D.

  • Rear metal tail gearbox - comes pre-assembledRear metal tail gearbox - comes pre-assembled

At this point, we only need the hub and blade grips assembly, so put the other items safely to one side for now.

We will first assemble the tail pitch slider. Use CA glue and screw the ball into the step on the tail pitch slider's collar. Then insert the brass sleeves into the blade grip levers, insert the bolts through them and then attach each lever to the arm of the blade grip.

  • Tail pitch slider assembly and fixingsTail pitch slider assembly and fixings
  • Tail pitch slider assembly fitted to tail blade gripsTail pitch slider assembly fitted to tail blade grips

Next we need to fit the tail pitch slider lever to the underside of the metal tail gearbox housing. Fix the ball into the arm using CA glue again, then fit the bolt through the bearing, making sure to use the two shims, one above and one below the bearing, and threadlock it into the mounting point on the underside of the metal tail gearbox housing.

  • Tail pitch slider lever and fixingsTail pitch slider lever and fixings
  • Tail pitch slider lever fitted to tail gearbox housingTail pitch slider lever fitted to tail gearbox housing

With that done we can fit the tail hub assembly onto the output shaft and connect everything together. As you move the slider onto the shaft, line it up so that the ball drops into the hole of the slider lever. This can usually be rolled around the shaft and into the hole. With the hub and slider fitted onto the output shaft, line up the grub screw hole over the flat near the end of the output shaft and then fit and tighten down the grub screw using threadlock. The very end of the output shaft should be pretty much flush with the outside edge of the hub, as you can see in the pictures.

  • Tail hub and slider assembly fittedTail hub and slider assembly fitted
  • Tail hub grub screw fitted with threadlockTail hub grub screw fitted with threadlock

Next we can fit the tail blades, noting the correct (anti-clockwise) rotation to get the leading edge of the blade mounted the right way around.

  • Tail bladesTail blades
  • Tail blades fittedTail blades fitted

Next we need to CA glue the shaft drive bearing in place. Take the shaft drive and find it's centre point by balancing it on a hex driver or similar. When you find the centre point, place the bearing between 5cm and 7cm (I went for 6cm) towards the front end of the shaft and using a small amount of CA glue, fix it in place there. Be careful to not get any glue in the bearing!

  • Glue the bearing 6cm from the centre of the shaftGlue the bearing 6cm from the centre of the shaft

Now we can fit the tail pushrod guides and the horizontal fin mount onto the boom. Bag number 600NT3BA contains the tail pushrod guides and also the four rocket links to go on the ends of both the intermediate and the rear tail pushrod pieces. Slide the tail pushrod guides onto the boom, one towards either end of the boom - we will glue them in place later, but for now, just leave them roughly in place. Connect one rod link to the long tail pushrod as per the instruction manual and slide it through the guides on the boom - then connect the second rod link to the other end and make the length approximately right. This will need adjusting (in all likelihood) once the heli is flying to ensure the correct length is set.

Bag number 600NT2EA contains the horizontal fin mount fixings needed to mount the flat plate on the underside of the tiny horizontal fin. Attach the boomstay clamp to the underside of the horizontal fin mount and fit the boom stays to it. Leave the horizontal fin mounting bolts a little loose for now - they can be tightened up in the right place once the boom is fitted to the heli body and the boom stays are fixed in place.

  • Tail pushrod guides and rocket links for both rodsTail pushrod guides and rocket links for both rods
  • Horizontal fin mount assembly parts and fixingsHorizontal fin mount assembly parts and fixings
  • Horizontal fin and mount ready to be fittedHorizontal fin and mount ready to be fitted
  • Horizontal fin and mount fitted to the boomHorizontal fin and mount fitted to the boom

Apply some grease to the rubber housing on the outside of the shaft drive bearing to help it slide smoothly into the tailboom. Then with gentle force, push the shaft into the boom, being careful to position the bearing closer to the heli body (remember it is offset from the centre approx 6cm towards the helicopter body).

  • Grease the shaft drive bearing rubber housingGrease the shaft drive bearing rubber housing

All that remains to complete the tail assembly is to fit the now assembled tail parts together. Push the boom into the front housing. The shaft drive shoudl click into place, but if it doesn't, turn the other end of the shaft and push it in at the same time - it will find it's way in and seat properly. Once the boom is fitted, tighten up the four boom clamp bolts into the nyloc nuts.

  • Assembled front end tail partsAssembled front end tail parts
  • Assembled rear end tail partsTail front end assembled
  • Assembled front end tail partsAssembled rear end tail parts
  • Assembled rear end tail partsTail rear end assembled

Tighten up the pinchbolt on the underside of the tail gearbox using threadlock. Connect the tail pushrod link to the ball on the rear lever.

  • Threadlock the pinchbolt and clamp the boom tightThreadlock the pinchbolt and clamp the boom tight
  • Threadlock the pinchbolt and clamp the boom tightConnect the pushrod link

Fit the front end of the tail assembly into the rear of the heli body. There are a couple of slots in the carbon frames that the plastic housing will slot into. With the plastic housing slotted into place, tighten the screws into the plastic housing using a drop of CA glue on each one.

  • Tail boom mounting fixingsTail boom mounting fixings
  • Tailboom assembly fitted to the heli bodyTailboom assembly fitted to the heli body

Fix the boom stays to the lower rear frame mounts using the aluminium frame stiffener in-between the frames and threadlock on the bolts. Then tighten up the horizontal fin mount on the boom, ensuring that the fin is level.

  • Aluminium frame stiffener and fixingsAluminium frame stiffener and fixings
  • Aluminium frame stiffener and boom stays fittedAluminium frame stiffener and boom stays fitted

Carburettor arm

The carburettor arm can be a little awkward to fit, having to control a few moving parts while trying to get the arm locked tightly in the correct place. That correct place is exactly horizontal at the mid throttle position. The throttle servo horn centre will be set to exactly horizontal too and with the connecting rod set to the right length and the linkage balls set to the same distance out on the servo horn and the carburettor horn, the throttle will be pretty much set.

The OS50 Hyper engine has 5 markings around the edge of the carburettor casing. These markings show the fully closed and fully open points, along with three markings close to each other in the mid range. Set the carburettor arm such that the inner single mark lines up with the centre of the three mid range markings when it is horizontal.

  • Carburettor arm and ball with nutCarburettor arm and ball with nut
  • Aluminium frame stiffener and boom stays fittedCarburettor arm fitted with the carb centred

Flybar setup

With almost all of the helicopter built now, we can return to the head and complete the assembly of the flybar and then set the main shaft into it's correct position (so that there is no vertical play).

The stock paddles in the kit require stickers over the holes that have been cut out to remove some weight from them. Carefully apply the stickers to the paddles, trying to keep air bubbles to a minimum, and then screw the paddles on to the flybar until the thread of the flybar has passed the grub scrw hole, then use an M3 grub screw in each paddle to secure it to the flybar.

The long M2 grub screws supplied for this job did not actually fit (they are too small) so I substituted my own M3 grub screws in place.

  • Flybar paddles with stickers appliedFlybar paddles with stickers applied
  • Flybar paddles attached to the flybarFlybar paddles attached to the flybar

Use a vernier to set the flybar centrally in the head and then tighten down the flybar cradle grub screws to hold it in place. Use threadlock.

  • Flybar cradle grub screw threadlocked in placeFlybar cradle grub screw threadlocked in place

This is a good time, while the head is not on the helicopter, to fit the rod links to the elevator bell cranks as it is still fairly accessible at this point.

Fitting the main gears and rotor head

The main gears are easily fitted to the helicopter, they just slide in through the side frames, and the main mast is then lowered down through the centre of them (the one way bearing housing) which is then secured to the gears with the shanked jesus bolt which locks into the nyloc nut housed in the moulding of the gears.

Do not overtighten the main gear bolt or you can distort the one-way bearing sleeve, which will help to destroy the one-way bearing.

The next task is to tighten down the main mast locking collar. There needs to be no vertical play in the main mast so with the main gears secured in place, the head needs to be pulled up and the mast locking collar fixed down onto the upper bearing as tightly as it can be. There are two grub screws to hold the main mast locking collar in place, tighten one of them down to hold it in place, then threadlock and tighten the second one down, then undo, threadlock and tighten down the first one again.

  • Main gear jesus bolt fitted but not overtightenedMain gear jesus bolt fitted but not overtightened
  • Main mast locking collar threadlocked in placeMain mast locking collar threadlocked in place

Check there is no vertical play in the main shaft - if there is any play at all, redo this step until there is none.

Anti-rotation bracket

Before fitting the anti-rotation bracket, fit the rod links from the bell cranks to the swashplate.

Next, fit the anti-rotation bracket to the sideframes, ensuring the long ball link on the swashplate is being guided by it, and use a drop of CA glue on the screws.

  • Anti-rotation bracket and fixingsAnti-rotation bracket and fixings
  • Anti-rotation bracket fitted (use CA glue)Anti-rotation bracket fitted (use CA glue)

Outside of the engine muffler, that completes the helicopters mechanical build - now we need to finish installing the electronics and set it all up ready to fly.

Electrics installation

The nose piece is a useful addition to the helicopter layout as it offers a lot of surface area for mounting things to in a relatively small space.

Align put some very useful extras into the box which is a really nice touch. Along with the blade caddy, you get lots of hook and loop sticky pads and straps, which were used all over my electrics installation as it makes it easy to remove and re-attach these things as and when you need to, plus you also have the security of the hook and loop straps to ensure nothing will fall off in flight.

I placed the Align 2 in 1 regulator inside the right side of the nose piece, with the regulator switch positioned on the right sideframe for easy access with the canopy on. The earth lead comfortably reaches the lower right engine mounting bolt, which is where I connected it, and the remote glow clip reaches down to the glow plug. The main part of the Spektrum AR7000 dual receiver is fitted on top of the nose piece, the Futaba GY611 gyro amplifier is fitted inside the left side of the nose piece, with the gyro sensor fitted on top of the tail boom housing and my Revolution 2S2P LiPo pack sits underneath the nose piece.

With the electrics fitted, I attached the Hatori 522 muffler to the engine. I do not use any sealant between the engine and the muffler manifold, it works fine when done up nice and tight, with no leakage.

  • Blade caddy, hook and loop straps and padsBlade caddy, hook and loop straps and pads
  • Electrics fitted - right sideElectrics fitted - right side
  • Electrics fitted - left sideElectrics fitted - left side
  • Fuel tube to protect wires from carbon sideframesFuel tube to protect wires from carbon sideframes
  • Fuel tube to protect wires from carbon sideframesFuel tube to protect wires from carbon sideframes
  • Hatori 522 muffler fittedHatori 522 muffler fitted

Make sure the top two cyclic servos at the front of the helicopter have their wires pulled away from the starter coupling, and ensure that you secure them so that they cannot wriggle their way back into it in flight. I made use of the front frame stiffener for this job, using a tie wrap (zip tie) to make sure they were secure.

Canopy

The Trex600n Pro comes with a painted fibreglass canopy, in a choice of two designs. The one I received was the red canopy version, the white version can be seen on the box picture. It is a well made and carefully painted canopy with a very nice finish, which makes the heli look great.

The fittings come in a separate bag, not fitted to the canopy, but that's a very easy job. Fit the rubbers into the canopy mounting holes. Fit the canopy mounting clip to the bottom of the canopy so that the pre-drilled holes in the canopy line up with the clip holes, and then fit the supplied screws through the clip and secure them fairly tightly - don't overtighten though otherwise the fibreglass, sandwiched inbetween the plastic clip, could crack.

  • Canopy and fittingsCanopy and fittings
  • Canopy rubber grommet fittedCanopy rubber grommet fitted
  • Canopy clip fittedCanopy clip fitted (screws not yet in)
  • Canopy complete and fitted to the heliCanopy complete and fitted to the heli
  • Canopy complete and fitted to the heliCanopy complete and fitted to the heli
  • Note the gap between canopy and exhaustNote the gap between canopy and exhaust

Another nice part about the 600n is the canopy being moulded in such as way as to not need cutting or trimming in order to fit the canopy and avoid fouling the exhaust, as can be seen above, in the bottom right picture.

Wrap up

With all of the mechanical building completed, all that remains is to setup the heli electrically. Switch the helicopter on and make sure the servos are centred before attaching the servo horns to them. Attach all rod links and make sure the eCCPM is correctly setup, and that there is no interaction on the swashplate through it's entire range of pitch movement. Make sure the swashplate moves in the correct direction for each cyclic input. If it does not, you may need to reverse a swash mix setting in your transmitter - i.e. if Aileron left to right input on the transmitter results in right to left swashplate movement, reversing the swashplate aileron mix from a positive to a negative number will fix the problem (or a negative to a positive number).

Set up the throttle linkage so that it reaches fully open and fully closed at each end of the throttle servos travel. You may need to adjust the throttle end points to achieve this, but try to get the end points even, and as close to 100% as possible.

Set up the rudder servo, attach all linkages and ensure the rudder is operating the right way. Then make sure the gyro sensing is working correctly. I usually input a right rudder feed and watch the tail rotor blade movement, then move the helicopters nose to the left which will make the tail rotor blades move in the same direction as the right rudder input from the transmitter.

Finally, fit the main rotor blades and check that the pitch range is set correctly and that you have the right amount set for your flying style. I fly 3D so my pitch is zero degrees at centre stick position, with 12.5 degrees at full positive and full negative, on a linear pitch curve. If you require more or less pitch, increase or decrease the pitch value in the swash menu on your transmitter.

Here's a few pictures of the Trex 600n Pro at the flying field.

  • Complete and ready to flyComplete and ready to fly
  • Complete and ready to flyComplete and ready to fly

Pros and Cons

Pros
Clear and easy to follow manual
Hex head fixings used throughout
Aluminium parts where they are needed
Supplied extras including blade caddy, hook and loop straps and pads
Painted fibreglass canopy which doesn't need cutting to avoid the engine muffler
Easily removed tailboom assembly
Generally very easy helicopter to work on
Lightweight helicopter
Nicely presented box
Cons
The supplied dampers don't last very long in 3D flight
The stock plastic fan is too flexible to hold a governor magnet - if you glue one to it, you will probably lose it in flight
Some fixing screws go into plastic and should not be overtightened as they can easily strip, ruining the fixing point
Small amounts of slop in some parts of the head - the flybar cradle and washout base particularly

Conclusion

Building the helicopter is pretty straight-forward. The manual is clear and easy to follow and the bagged parts are numbered to make it even easier. Occasionally you need more than one bag open at a time, but it's rare, so it's not really much of an issue.

The helicopter itself can be built in a day, depending on how quickly you go, and then the electrics installation and setup is done soon after that. The design of the nose piece is good, giving you plenty of mounting points on the heli where you need it most and it also keeps it all quite compact, and Align supply plenty of hook and loop tape and sticky pads to aid with mounting things to the helicopter if needed. The tail boom assembly is well thought out too, allowing you to remove it completely without touching the rest of the helicopter.

Overall, it's a pleasure to work on and feels robust and light when complete. I think this is money very well spent.