T-Rex 500 Build

 

The following is a full build of the T-Rex 500. I will not be providing any setup information in this build document as this will be covered in a separate article.

Bold titled pictures can be clicked on for a hi-res version to be displayed.

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 below included 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.

Also included in this build are small videos of each completed build step plus links to a full build video for each section of the build. For ease of reference I've included all of the build video links in the table below. As well as a download link for the T-Rex 500 Manual.

Additionally I've included a couple of 3D flight video links.

 

Introduction

Well once again I find myself on the receiving end of the eagerly awaited T-Rex 500. The kit I'm building in this review is the 500 CF. This is the carbon fibre framed version of the kit.

The kit used for this review is the 500CF version of the kit. This is the carbon fibre version with the carbon fibre 425 mm blades. Align also do a G10 version of the kit which comes with fibre reinforced plastic blades. Included in the kit is the new 500 class motor and this comes with the new Align 60 amp ESC. This new speed controller has governor mode and also has a switchable BEC which can provide 5.5 V or 6 V to the receiver.

This model will be kitted out with Futaba 9650 digital servos supplied courtesy of Grandrc.com

The manual provided in the kit is some 42 pages in length and is extremely comprehensive in describing both how to build the kit and also how to set it up. There are numerous exploded diagrams and parts diagrams with part numbers to aid with ordering spares.

Much like the T-Rex SE V2 the kit comes with a pre-painted fiberglass canopy. This is very nicely finished and gives the helicopter a very professional look once completed.

Each part of the build uses parts that are conveniently gathered together into numbered bags. For the most part you only need to open one bag at a time and it contains all of the required components to complete that particular build step. The exception to this is when you need something like ball links which are all together in one bag.

 

Rotor Head

In all the build pictures I have highlighted where loctite must be applied with red markers. Usually to highlight the particular screw or thread where the loctite should be applied.

The rotorhead is the most complicated part of the build. Fortunately this is split down into several steps which make it a little simpler to follow. The first step is installing the flybar seesaw. This part comes loosely pre assembled and all that is required is to remove the two screws add some Loctite and then put them back. This then completes the very first build step.

Following the assembly of the flybar seesaw we have another relatively straightforward build step. This time we are assembling the flybar cage and this consists of installing two push rod's onto the flybar cage and then inserting the four screws with Loctite and tightening it all up. The manual shows that the push rod is tightened until the ball links are touching. The two ball links should be orientated such that the 'A's on them are facing opposite directions. When installing these onto the cage make sure that one is installed from one end and the opposite one is installed from the other end. This is shown in the video of this build step and is quite difficult to explain in text. The reason for doing this is because if you install both push rods onto the cage from the same end then one of the push rods will need a half turn when you come to attach it to the washout arms.

 

Next the upper mixer arms are assembled as shown below. Once the balls are installed onto the mixer arms they can be attached to the flybar seesaw using self tapping screws. Make sure that you have a washer underneath the head of the self tapping screws as well as between the mixer arm and the flybar seesaw. Be careful not to over tighten the self tapping screws as it is quite easy to strip the threads.

 

Next we have the washout assembly. All that is required for this build step is to remove the two screws securing the washout arms to the washout hub. Apply Loctite, and then replace the arms and tighten.

Take note that these washout arms are very similar to the new upgrade washout arms that have just been announced for the T-Rex 600. So here we have some product improvements from the T-Rex 600 available as standard on the T-Rex 500.

 

Swashplate

Building the swashplate is another very straightforward part of the build. All that is required is to apply Loctite to all the balls on the swashplate. Once this is done all of the previously built head components can be installed onto the main shaft.

 

This next step is just assembling all over the previously built components onto the main shaft and then connecting all of the various push rods onto those components. The push rods should be built exactly to the specifications in the manual and a vernia scale should ideally be used to make sure that the push rods are exactly the right length. First install the main shaft into the head block and security using the Jesus bought and it's nyloc nut. Next put the washout arms onto the main shaft followed by the swashplate. Lastly put the mast locking collar onto the main shaft and very likely tighten the set screws to make sure that all of your components don't fall straight back off the shaft. With all the components on the main shaft you can now go about installing all of the push rods. The manual shows the installation of the flybar at this point. I would advise leaving the flybar until the very last thing in the build. The reason for this is that you have a lot more building to do and the flybar typically gets in the way, pokes you in the eye and is generally a nuisance as it sticks out so much. It does not need to be assembled at this point and therefore can be left until the end of the build. Make sure you put the two grub screws that up are part of the build step to one side for safekeeping as they will be needed when you come to install the flybar paddles right at the end.

 

Blade Grips

Installing the blade grips is another area where there are mistakes that can be made. In particular great care should be taken to make sure that the thrust races are installed correctly into the blade grips. I recommend watching the build videos for a detailed description of how this should be done. However, in brief the thrust races should be assembled such that the race with the larger inner diameter is closest to the head block and the race with the smaller inner diameter is furthest away from the head block.

Before we get to that point we need to install the dampers and feathering spindle into the head block. The dampers should be lubricated with a Teflon grease before they are installed. You now have to push the feathering spindle through these greased dampers. There is a risk that you will get grease in the threads of the feathering spindle at this point. In order to stop this happening insert the two screws into the feathering spindle before you push it through and then remove them. Once the feathering spindle is in place the two brass spacers can be inserted onto the feathering spindle and pushed up against the dampers. We are now ready to install the blade grips.

Follow the manual very carefully or watch my build video to see how to install the thrust races into the blade grips. Thing is to make sure that you have a space washer between the thrust race and the radial bearing in the blade grip. Also make sure that once the thrust race is installed into the blade grip that you can see the word "out" on the thrust race when you look into the blade grip from the blade socket end.

Make sure you have Loctite on your feathering spindle bolt, insert the blade grip onto the feathering spindle and then put the feathering spindle bolt into the end of the feathering spindle and tighten. Repeat this for the second blade grip and then use to hex drivers to tighten both of the feathering spindle bolt simultaneously.

Lastly we install the head button. Put some Loctite on the screw and screw the head button down tightly into the head block.

 

Rotorhead Video

The following video has no sound, it just shows what the finished rotorhead should look like.

 

 

Main Frames

The next thing to build is the main frames and undercarriage. Let us start with the main frames. The first thing to do is to screw the bottom tray to the two carbon side frames. Take note that there are various different length screws in the hardware bag for this build step. Be careful to select the correct screws for mounting the bottom tray.

Once the bottom tray is secure we can install the gyro mount. Again this is secured by self tapping screws, in this instance the shortest ones in the hardware bag.

With the gyro mount in place the motor mount should be secured into the side frames. The motor mount comes with the screws already in it and they need to be removed have Loctite applied and then replaced to screw the motor mount into the side frames.

Having installed the motor mount the bearing blocks can now be installed. Take care to use the metal screws for this and not the self tapping screws. Again Loctite should be used to secure the bearing blocks in place. It can be a good idea at this point to insert the main shaft into the bearing blocks before you tighten them up. This helps to align the bearing blocks before they are secured in place.

After installing the bearing blocks the upper battery tray and the anti-rotation slider can be screwed into the frames. The anti-rotation slider has some very long set screw style mounting screws. These are screwed in halfway and then the set screw thread that is left sticking out is used to screw the canopy mounting posts onto.

 

Having assembled the main frames the undercarriage can now be assembled and bolted to the main frames using the supplied bolts and nuts. Note how I have installed the rubber anti-vibration tubes onto the skids, this makes it impossible for them to come off and get lost.

 

Mainframes Video

There is no sound in the following video it just gives an overview of the built main frames and undercarriage.

 

 

Servo Installation

The manual shows servo installation at this point. This includes setting up the servo horns. Whilst installing the servos now is no big deal I would personally not install horns until the heli is fully built and I'm doing my radio setup. However, the problem is that the rear servo is very hard to access once the tail clamp is installed into the frames. Therefore, I would recommend just fitting the servos at this point, without servo horns. Later (during setup) install the horns on the front servos and just remove the rear servo from the frames to do it's servo horn.

The servos are installed using the supplied self tapping screws. These screw into small plastic retainers that go on the opposite side of the frames forming a nice clamping effect of the servo to the frame.

Tail Boom Clamp

Installing the tail boom clamp is a relatively straightforward affair. The front pulley should be installed into the bearing recesses molded into the clamp. Don't forget to thread the belt around the pulley before fitting it into the clamp, it is not possible to fit the belt once you have closed the tail boom clamp around the front pulley. Once the front pulley is installed the belt can be threaded through the hole where the tail boom will insert. You can now screw the tail clamp into place between the side frames. Check the pictures below to make sure you install the pulley the right way up as there is nothing to stop it being installed upside down.

Main Gear

The manual shows the main gear assembly but in reality it comes pre-assembled by the factory. All that is required is to slot it into the main frames and then push the previously assembled rotorhead down through the bearing blocks and through the hole in the center of the main gear. Then it is a simple case of lining up the holes in the main shaft and main gear and installing the supplied bolt and nyloc nut. Do not over tighten the nut as it will warp the main gear.

Now is also the time to set the mast locking collar correctly. The rotor head and gear should be pulled upwards and the mast locking collar pushed down onto the top bearing block and the set screw tightened. This then removes any vertical movement in the main shaft and keeps the main gear in the correct position.

 

Tail Boom & Tail Gearbox

Installing the tail boom is a simple matter of pushing it into the tail boom clamp, it has a slot to locate it correctly. However, before this can happen the belt must be threaded through the boom. I usually tie a bit of string to the belt, thread through the boom and then pull the belt through.

With the boom in place thread the tail servo mount and the two tail push rod guides onto the boom.

Now we can build the tail gearbox. This requires the two tail cases and the tail output shaft and pulley. In order to install the tail output shaft the belt must be given a quarter twist as shown in the manual and then the pulley and output shaft placed onto the belt. The two tail cases can then be closed around the tail output shaft and the three bolts and nuts installed and tightened. Check the output shaft direction, it should rotate anti-clockwise when you rotate the rotorhead clockwise. Now is also a good time to set the belt tension and do up the two screws securing the boom into the clamp.

 

Tail Rotor & Fins

Installation of the tail rotor involves installing the tail pitch slider and it's control horn as well as the tail rotor hub and blades. Fitting the fins comes after this.

First the tail pitch slider should be slid onto the tail output shaft followed by the tail hub. This can be secured in place by the set screw in the tail hub. Don't forget to loctite this set screw. Also, remove the tail blade bolts and loctite them so the blade grips don't come off of the hub.

With the tail rotor in place orientate the blade grips so that the hexagonal nut retainer on the blade grips is to the rear (facing the tail gearbox). The pitch slider can now be secured to the grips using the brass bush and small cross head screws provided.

Lastly the control horn can be secured into place. This has a washer under the screw head as well as between the control horn and the plastic gearbox mount point. Align the pitch slider ball with the horns hole and then screw it tightly into place. Make sure you don't over tighten and that it all moves freely.

Lastly bolt the horizontal and vertical fins into place and fit the tail boom supports.

 

Motor, ESC & Paddles

The kit comes with two pinions for the motor. 12T is for sport fliers and beginners, 13T for 3D fliers. Push the pinion fully down onto the motor shaft, apply loctite to set screw and secure against the flat in the motor shaft.

Now bolt the motor into it's mount and set the gear mesh such that the gear can just rock in it's mesh with a slight clicking noise. That's the motor done.

I left the paddles from early on in the build, now is the time to slide the flybar into place, making sure equal amounts protrude from each end of the flybar cage. Secure the flybar in place with loctite on the two set screws in the flybar cage.

Screw the paddles onto your newly fitted flybar until you can no longer see the thread on the flybar. Line the paddles up to be exactly horizontal to the flybar cage. Measure the gap from the flybar cage to each paddle and verify the distances are identical for each paddle, if not adjust. Once the paddles are in line with the flybar cage and the distances from cage to paddle are equal on both sides the set screw for the paddles can be installed and tightened. Remember this set screw is in plastic so don't over tighten and strip the threads.

Lastly use supplied tie wraps to secure the ESC to the side frames and push the motor wires into the corresponding colour coded wires on the ESC. I needed to squash the bullet connectors with pliers in order to get them in.

 

Odds & Ends

There are still a few items to tidy up. The tail push rod needs to be set to correct length and the control rod guides secured in place using the supplied small black tie wraps. All the servos need setting up, rx installing etc etc

Setup of the T-Rex 500 is covered in another article to be published shortly.

Blades should be fitted to the rotor head and the rest of the radio installation & setup completed. I used 9650 servos on my heli and found the servo wires not long enough. Therefore I had to solder some extensions. Some velcro needs installing onto the front battery tray to hold lipos in place.

Pictures below show the blades and completed model minus servos, which I had removed to set the horn positions accurately. Once done the various servo to swashplate push rods can be installed as well as gyro and tail servo.

 

Overall Build video

 

 

 

Canopy Video

 

 

Build Review

The T-Rex 500 has been one of the easiest helicopters I have ever had the pleasure of building. It has an excellent manual and all of the various build steps are logical and modular.

For the most part this helicopter is a scaled-down version of the T-Rex 600 and in this respect it gains many of the good characteristics and proven capabilities of that model. However, it also inherits some of the characteristics that may not be so desirable.

The things that I have been impressed with the overall quality of the kit as a whole. The ease with which the various components go together. The fact that it builds upon a proven design and inherits some of the upgrades from that proven design (such as the new washout just released for the T-Rex 600).

The things that I have been not so impressed with are the quality of the plastic for the frame components. It feels very soft and stripping threads is extremely easy. The canopy fits very nicely but the servo push rods rub against it meaning that the canopy has to be trimmed. The geometry of the servos and their push rods is such that with the servo horns at horizontal there is not a right angle between the servo horn and the push rod. This is apparently to account for the fact that servos move through an arc and that the swashplate ball is not directly above the ball on the servo horn. Most radio sets have options to account for this so I would have preferred a more traditional right angle between the servo horn and the push rod when the servo horn is at horizontal. This can be accounted for in the setup but without knowing about it you can end up with unequal throws on the collective pitch.

I do like that the kit comes with metal pulleys that the belt run on, both at the front and rear of the boom. However, Align are still using the two-stage belt drive system which although proven on the T-Rex line of helicopters is inefficient compared to a single stage belt drive system. I guess this is just a case of using proven mechanics. The helicopter has a metal head block and grips and these also incorporate thrust races as do the tail hub and grips. Which should give excellent flight characteristics.

The rotor head has plastic flybar mixer arms and these do introduce a very small amount of slop into the control system. I would have much preferred if the kit came with metal mixer arms to start with. Particularly as plastic components tend to get more sloppy with use.

The kit comes with the 500L motor and 60A ESC with a switchable BEC and governor mode options. How good these are will have to wait for the flight review.

Overall I think this is Align's best kit to date in terms of quality of components and including most of the upgrades you might want as standard within the kit. It is definitely a scaled-down T-Rex 600 rather than a scaled up T-Rex 450.

We now have to see if this translates into good flight characteristics.

Flight Review

I chose to fit the 13 tooth pinion on the 500L motor and also to use 9650 servos all-round including tail servo. The gyro is a CSM 720 and I set the BEC on the speed controller to 6V. I also turned off governor mode as this normally induces tail wag on the Align range of speed controllers (this was later proven to be the case).

The following flight assessment is based on flying several different packs of differing sizes and voltages.

Firstly and as expected the T-Rex 500 flies much more like the T-Rex 600 than its smaller brother the T-Rex 450. It is very stable in the hover and copes with the wind far better than the T-Rex 450. Head speed is around 2600 rpm when utilising the 13 tooth pinion and a 6S pack. I have also flown 5S utilising a 16 tooth pinion which gave a slightly higher head speed.

Moving out of the hover the T-Rex 500 is again very stable and tracks very nicely in flight. The motor supplied with this model is surprisingly powerful and all but the most hardcore of 3-D flyers should be happy with the performance it delivers. It certainly has enough power to perform Big Ben's and any of the other more power orientated manoeuvres without dropping lots of head speed. However, you do need to use the correct pack in order to get the best out of the motor. In testing we have used packs ranging from 2100 mAh through to 4200 mAh in 6S configuration. Packs down at the 2100/2200 level give a lower head speed and a less powerful performance. They also run hot and from a balance perspective give a tail heavy model. Packs around 3000/3200 level give a balanced helicopter and also a very good head speed and flight time. The packs also do not run hot. The pack we tried at 4200 size gave the best head speed of all, the coolest running but also felt heavy in the air. This pack size was also nose heavy. The best compromise of power, head speed, weight and helicopter balance is around the 3000 mAh level in our opinion.

This is also where we ran into some problems as the most ideal pack size seems to have some problems in fitting inside the canopy. The 6S 3200 pack that we have been using only just fits but it does go in. A small modification to the location of the canopy mounting posts resolves this.

Moving on into more complex 3-D flying and our own experience was that the mini servo on the tail started to show the limit of its capabilities. When we swapped this for a standard tail servo the tail became much more locked in and very similar to the tail response on a 50 sized model. Pushing the model harder we found no lack of capability, this is an extremely agile and capable helicopter which can fly the entire book when it comes to 3-D manoeuvres. In many respects it is the perfect size for a 3-D practice machine both in terms of flight characteristics and the cost of spares should you be unfortunate enough to crash.

It was flying 3-D that we had our first problem when the model crashed due to what appeared to be a lockout or reset of the spektrum receiver. Having done a significant amount of research into this crash we believe that the speed controller internal BEC is not providing adequate voltage but more investigation is required in order to come to conclusive proof as to exactly what is happening to cause this failure. In the interim I have converted my machine to run on a separate BEC rather than have another failure. It should be noted that of the two models we have for flight testing only one of them has suffered this issue.

Aside from this one issue we have not had any other failures on the helicopter of any kind.

This unfortunately does not mean that all is well. Right from the initial flights we felt that the damping was too soft and in fact the dampers are wearing out very quickly in aggressive 3-D. Trevor in testing his T-Rex 500 also managed to destroy the thrust races in his rotor head due to this overly soft damping. We believe the T-Rex 500 requires the same modification as the T-Rex 600 had for its dampers in order to resolve this. We have improvised this solution by wrapping the center of the feathering spindle with electrical tape in order to make an emulation of the T-Rex 600 modification. And this has worked very well in hardening the damping and improving the damper lifetime.

 

 

Conclusion

Overall the T-Rex 500 is an extremely capable 3-D helicopter. It has very good power to weight ratio and also a very light disc loading. This makes it very agile but also capable of handling a variety of different pack sizes. The increase in size from the T-Rex 450 makes it much more stable than its smaller brother and its extra size makes it both easy to see and easier to fly in 3-D flight. It is not too big to park fly and the packs for it are not overly expensive. Add to this that it is quite possible to achieve flights of seven minutes or more of 3-D. The kit is of a good build quality apart from some of the plastics used and most of the items that you would normally look to upgrade have already been supplied as upgraded. The build itself is very logical and the model draws from already proven designs in the T-Rex 450 and T-Rex 600. All in all I believe Align have an excellent product which I am sure will take the market by storm and probably be their most successful model to date.