T-Rex 600 Build

The following is a full build of the T-Rex 600. I will not be providing any setup information in this build document as this will be covered in a separate article.

First and foremost I would like to thank www.GrandRC.com for providing the T-Rex 600 kit and lithium polymer battery. Please check out their website for great deals on the T-Rex 600.

The items used in this build are as follows:

T-Rex 600 CF kit
Align 6S 4200 mAh lipo
Futaba 3050S servos
Futaba GY611 gyro
Align motor
Align ESC
Align voltage regulator and 7.4 V lipo
JR 770 PCM receiver

I will go through the build a step at a time following the manual. The manual is actually very good and each of the build steps follows a logical order. Before embarking upon the build I have included below some pictures of the kit and what you get in the box. I would also like to point out that building this helicopter was extremely easy and should be a relatively easy task even for a complete beginner. This build document is not meant to replace the manual but just act as a supplement to the existing documentation provided by Align.

 

Having had a good look through the box contents it was time to get on with the build itself. Before I move on to start talking about the build it is worth noting what tools and materials may be required in order to assemble the T-Rex 600 correctly. Firstly I would recommend having a very high quality set of Allen screwdrivers. There were a few points in the build where a pair of small or long nosed pliers were useful. Aside from these basic tools nothing else was required.

Supplied in the kit there are some fluids which are denoted as R48 and T43. These are two different types of thread lock. Personally I do not like any of the thread locks that Align choose to supply in their kits. Instead I have used blue loctite (243) wherever either of these fluids is mentioned. Align supply some grease which I also did not use but instead used a high quality silicone based grease. Align expect the purchaser to supply superglue (CA) and for this purpose I used "zap a gap CA+".

The manual for the T-Rex 600 is split up into several sections, each section having a code number which corresponds to a bag of bits. Everything required for that particular build step should be within the bag with the same name. I found throughout the build that this was the case and that Align have done a very good job of making sure that each build step was logical and contained. This way you do not end up with lots of bags opened and very little clue as to whether you have used all of the right bits for that particular build step.

So, it was time to open the first bag in the assembly of the T-Rex 600. I will title each section of the build with the corresponding bag number. So without further ado let's get on with it.

50HH0001

This is the assembly of the blade grips and involves inserting the thrust bearings into the blade grips. In my kit the standard bearings had already been installed into the blade grips. It is extremely important to make sure that the thrust bearing with the larger inner diameter goes into the blade grip first. It is relatively simple to identify which of the thrust bearings has a larger internal diameter. Place the bearing on to the feathering shaft and just move it around. One thrust bearing will be much looser than the other and this is the thrust bearing that goes closest to the rotor hub. My thrust bearings were quite a tight fit in the blade grip and I used a very large Allen key to push the thrust bearings into place without damaging them. Remember to add some silicone based grease to the thrust bearings before inserting them into the blade grip.

The only other item in this build step is to screw the linkage ball onto the blade grip with a little bit of CA to make sure it does not come undone.

 

50HH002

This step is the installation of the feathering spindle into the head block. The rubber dampeners and copper spacer are then inserted and this holds the feathering spindle in place ready for the blade grips to be bolted on.
The feathering spindle when it is inserted into the head block will be a very loose fit. The dampeners need to be inserted in order to make the feathering spindle a snug fit. The dampeners should be liberally coated in silicon grease before they are inserted into the head block. Take care not to get silicon grease into the thread on each end of the feathering spindle. Getting grease on the thread would have a detrimental effect on the loctite used to make sure that the blade grip bolts do not come undone. If you do get any grease in these threads then just clean it out with tissue paper.
The bolts through the blade grip should have some loctite on them but be careful not to use too much as it will get into the blade grip bearings and cause problems.

 

Having assembled the head block it is time to bolt on the flybar mixer arms (SF mixer arms) and flybar hub. The flybar hub is factory assembled and therefore no construction is required for this part. All that is required is to bolt the flybar hub onto the head block and then install the SF mixing arms.
When installing the mixer arms make sure that you do not forget to put the washer between the mixer arms and the flybar hub. Also do not to use loctite on the screws that bolt the mixer arms onto the flybar hub as this is a metal to plastic connection and loctite will attack the plastic.

 

50HT001

Having completed the install of the flybar seesaw and mixer arms the outer flybar cradle can now be installed. Make sure you put the ball links onto the flybar control rods before assembling the flybar cradle. Also make sure that loctite is used on all four screws used to bolt the flybar cradle together. The flybar cradle should be installed so that the grub screws for locking it in place are on the top.
Once the flybar cradle is bolted together the flybar can be inserted through the cradle, through the flybar hub and back through the cradle. I had to apply a certain amount of force to make the flybar travel through the cradle and the flybar hub as there were some small burs on the flybar which caused it to stick a little when being pushed through the flybar cradle and hub. If you also need to do this then be careful not to apply too much pressure on the flybar cradle and hub bearings, my flybar required some light sanding to get it to go through smoothly after the intial attempts.

Once the flybar is in position now is the best time to centralise the flybar before installing the paddles. Once you have the flybar centralised such that the same amount of rod is sticking out of each side of the flybar cradle, you can tighten up the grub screws on the flybar cradle to lock the flybar in place.
Don't forget to put loctite on the grub screws in the flybar cradle as you definitely do not want these to come undone in flight.

Next the paddles require the stickers putting over the holes in the paddles to make a nice aerofoil. Once this is done they can be screwed onto the flybar. The paddles have to be screwed in quite a long way until there is 130 mm between the flybar cradle and the paddle. The paddle should then be lined up so that it is parallel to the flybar cradle and then the grub screw on the paddle can be tightened to lock it in place. Do not use loctite on the grub screws that insert into the paddles.

 

50HH005

The swashplate just requires the linkage balls installing. Again remember to use loctite on all of the balls.

Once the swashplate is complete the head block, washout base, washout arms, swashplate and main shaft locking collar can be installed onto the main shaft. The washout base comes pre-assembled by the factory and does not require anything but the linkage balls installing onto the washout arms. The main mast locking collar has two grub screws within it, do not apply loctite to these just yet. These grub screws should just be lightly tightened to make sure that everything stays on the main shaft for now. This step also includes fitting the Jesus bolt through the headblock to hold it onto the main shaft. This bolt has a nyloc nut and therefore no loctite is required.

50HZ001

This step is just fitting the linkage rods to the completed rotor head, I found that all of the linkage rod lengths in the manual are correct and did not require adjustment.

 

 

50HB001

There is no assembly required for this step as the main gear and tail drive gear come pre-assembled by the factory.

 

50HB002

This step is where the main frames are bolted together. The diagram in the manual shows the main frames being bolted together with the three main shaft bearing blocks between the frames. In order to make sure that the main frames and bearing blocks are aligned correctly it is a good idea once the main frames are together to insert the main shaft before tightening up the screws on all three of the bearing blocks. This ensures that you have good alignment of the bearings. This is explained at the top of page 9 in the manual rather than on the preceding page where it shows the assembly of the main frames.

It is a good idea to install the canopy mounting bolts before putting the main frames together as it is very difficult to tighten the canopy mounting bolts screws after the main frames have been bolted together. The diagram on page 8 also does not show the use of loctite on some of the screws. Remember that whenever you are putting a screw into a metal thread loctite should be used, this is noted in the bottom corner of page 8 of the manual and is easily missed.

Remember to install the speciality washers on all of the screws on the outside of the main frames.

 

50HB003

The next job is to build the tail boom case which encloses the tail drive gear assembly. The manual shows bearing 684ZZ being glued to the tail drive gear assembly using R48, do not do this as the bearings will be extremely difficult to remove if they require replacing in the future. The bearings are quite a good fit on the tail drive gear assembly and I did not feel it was necessary to secure them with bearing weld (R48). Aside from this the assembly of the tail boom case is very straightforward, just don't forget to put the tail drive belt around the pulley before you bolt it all together.

Care does need to be taken to make sure that the tail drive gear assembly is put into the tail boom case the correct way up. The gear that drives the belt should be at the top where there is a large flat area for mounting a gyro once the tail boom case is bolted together.

Take care when tightening the bolts that go through the main frames into the tail boom case as if you overtighten these the plastic does strip quite easily.

 

50HB004

This step is just finishing off the main frames by installing the battery mount, motor mount, gyro mount, anti rotation bracket and the aileron and elevator levers.

The installation of the various battery, motor and gyro mounts is very straightforward and does not require any further explanation.

Some care does need to be taken when assembling the elevator lever and aileron lever so that the linkage balls are in the correct places. As can be seen from the pictures below I initially installed one of the linkage balls incorrectly on the elevator lever. When installing the aileron levers do not forget to include the small washer that goes between the control shaft and the bearing in the aileron lever.

The control shaft is asymmetrical and should be installed such that the groove in this shaft is closest to the left-hand side of the frames. As usual remember to use loctite on all screws that are threading into metal parts.

The elevator lever has a set screw (grub screw) which also needs to be tightened onto the control shaft. It does not matter how you position the elevator lever as long as the grub screw is locating into the groove in the control shaft.

 

Below is the incorrectly assembled elevator lever.

 

Below are some further pictures of the installed aileron and elevator levers, note I still haven't noticed my error on the elevator linkage ball! This was corrected shortly after these photos and fortunately was easily accessible with a screwdriver.

 

50HB005

The next job was to install the undercarriage. In the kit there are two sets of cross struts for the undercarriage. The white set is lower profile and is for 3-D flight, the black set is the standard undercarriage which provides a little more spring for those heavy landings that sometimes occur when learning to fly. This part of the assembly is extremely straightforward and does not require further explanation.

 

50HT002

This step is installing the tail rotor servo bracket and the tail control guides. Pictures of which can be seen below. I wasn't very keen on using tie wraps to hold the tail control guides in place (as in the manual), so after some careful positioning I used a very small drop of CA to hold mine in place.

This step also includes inserting the tail boom into the tail boom case at the back of the main frames. The tail boom cannot be inserted incorrectly as it is keyed with a slot which lines up with a pin inside the tail boom case. The manual shows a 90° rotation in the belt in order to fit it onto the tail drive pulley and care should be taken to make sure that this is done exactly as shown in the manual. If the 90° rotation is made the wrong direction then your tail rotor will turn backwards.

 

50HT003

This step is bolting the tail case onto the tail boom. The tail case comes with the bearings preinstalled and so these do not need to be inserted. The tail boom has a small hole in it which locates with a pin moulded into the left-hand side of the tail case. Again be careful to make sure when installing the tail case that there is only one 90° rotation in the tail belt as shown on page 13 of the manual. The M3 nuts on the tail case are nyloc and do not require loctite.

 

50HT004

The tail rotor blade grips come with the bearings preinstalled and so these do not need to be fitted manually. The tail blade grip bolts go through the blade grips into the tail rotor hub and should have a very small amount of loctite applied to them.

Note: do not use too much loctite on the tail rotor blade grip bolts. If you get loctite into the tail blade grip bearings the tail rotor will lock up under load and cause a crash. This is extremely important and therefore I have highlighted this in red.

50HT005

This step is the completion of the tail rotor control mechanism, including the tail pitch assembly and the tail rotor control arm. The tail rotor control arm comes factory assembled and it just needs to be slid onto the tail rotor shaft and then attached to the tail rotor blade grips using the supplied collar screws. Do not forget to install the brass bushings into the tail pitch slider before inserting the collar screw.

The tail rotor control arm screws directly onto the tail gearbox. Install the tail pitch assembly first before fitting the tail rotor control arm. Once you have located the screw through the tail rotor control arm make sure that the tail pitch assembly linkage ball is inserted into the cup on the tail rotor control arm, then tighten it all up.

I've also added a little silicon grease to the cup in the tail rotor control arm so that is this item does not wear with use and become sloppy.

Note: the ball linkage on the tail rotor blade grips leads the tail blades and does not follow the tail blades.

 

50HT007 & 50HT008

This step is the installation of the tail boom braces and the horizontal and vertical stabiliser fins. The installation of the horizontal and vertical fins is extremely straightforward and does not require any further explanation. When installing the tail boom braces it is best to fit the braces first before applying CA to hold the cap ends onto the tail boom brace rods. The reason for this is you want to make sure that the cap ends are aligned correctly before gluing them to the tail boom brace rods. I just installed everything so that it was nice and tightly held together and then trickled some CA onto each cap end to glue it in place. Be careful when tightening up the horizontal stabiliser fin as the self tapping screws are going into plastic and it is easily stripped.

 

50HZ002

Before fitting the motor the pinion should be installed. The pinion is secured onto the motor shaft using a set screw. The set screw should locate against the flat on the motor shaft. Make sure plenty of loctite is applied to the set screw so that it does not come undone.

The motor can then be bolted to the motor mount using the supplied M3 screws. Before tightening up the motor screws make sure that the pinion is meshing nicely with the main gear. A very thin piece of paper can be placed between the pinion and the gear order to set the mesh correctly. When the paper is removed it should be corrugated to the shape of the pinion and the main gear but it should not have been cut, if there are cuts in the paper then the pinion mesh is too tight. Personally I do not use the paper method myself, I setup the gear mesh so that there is a little tiny bit of play between the pinion and the main gear. However, for the inexperienced the paper method is best to use.

 

Below are some pictures of the Align 6S 4200mAh pack that I will be using for the flight testing.

 

Whilst we are looking at electronics below are some pictures of the regulator that comes in the kit as well as the 7.4 V lipo which is supplied to power the radio gear. The regulator steps down the voltage from 7.4 V to 5.8V. Also included is a further regulator which is used to step the voltage down again from 5.8 V to 5.1 V as many tail servos do not like or work on 6 V. This second regulator is placed between the gyro and the tail servo.

Pictured below I have also included the Align 75A ESC and a picture of where I mounted it.

As can be seen I used the rear gyro platform as the mounting place for the radio lipo and the regulator.

 

50HZ007 & 50HB001

The last step of the build is to install the main shaft and main gear. Following this is the installation of the servos and radio equipment.

The main shaft is inserted down through the three sets of bearings, through the main gear and then a bolt and nut is put through the main gear and the hole at the bottom of the main shaft to secure it all in place.

The helicopter should then be suspended from his rotor head so that the main gear is pulled up against the bottom main shaft bearing. With the helicopter still suspended the main mast collar should be pushed down onto the top of the upper main shaft bearing and secured in place by tightening the set screws in the main mast collar. This is the point where loctite can be applied to the set screws in the main shaft collar. The point of suspending the helicopter by its head whilst you do this is to make sure that there is no vertical play in the main shaft.

Following this the servos can be installed into the main frames using the supplied servo plates and self tapping screws. This is shown on page 17 of the manual in a little window labelled 50HZ007.

I found that the frames are not very deep and that to install the front two aileron servos it was best to put both servos in loosely initially and then tighten them up together. When they are tighten up it pushes the bottom of each aileron servo against each other. If you tighten up one servo before the other a problem occurs because the servos are essentially too deep for the frames you end up with one servo sticking out more than the other. The picture below shows how the aileron servos butt up against each other.

Depending on the make of your servos and how deep they are you may need to play with whether the servos are mounted to the outside of the frames or mounted to the inside of the frames. Mine had to be mounted to the outside as they are quite deep.

Once the servos are installed the linkage rods can be built to the specified sizes in the manual and installed. Depending on make of servo you may have to adjust the rod lengths accordingly.

One thing I have noticed is that my aileron servos control horns are rubbing very slightly on the canopy. At this point I cannot see an easy resolution to this problem but the rubbing is very minor so I have let it be for the moment. I did try mounting the linkage balls on the underside of the servo control horns but this caused binding elsewhere.

 

 

 

Aileron servos pictures

 

Completion

Essentially that is the completion of the build. Obviously the helicopter now needs to be set up and I will cover this in a separate article. Below are some further pictures that I took having completed the build.

 

 

Final Thoughts

Building the T-Rex 600 was in fact a pleasure. It is not a complicated build, the manual is very thorough and clearly set out. The packaging of the various parts is superb and the quality of the parts is also very good. None of the build steps were frustrating or fiddly and it was always very clear what needed to be done and how to do it. For these reasons I would have no hesitation in recommending to a beginner that they could build the T-Rex 600 without much assistance.

Overall I was very impressed with the kit and how well it all went together. Align have done a very good job with the T-Rex 600 and hopefully it will be as nice to fly as it was to build.

Finally some pictures of the finished article :)