T-Rex 450 SE V2 clone scrap build

I crashed one of my trainers, a 450 clone, really badly and ordered a new kit before inspecting the damage in detail. Later I took the crashed machine apart completely and realized that with the spare parts I already have I only need to order additional parts for a few euros to get a "new" machine in the air. It won't be pretty but cheap and still functional. This time, I will try to document this build.

The salvage operation

Salvaged parts

This initial picture show some of the parts that I could save. These are only the body parts. Tail, rotor and electronics excluded at this time. The old body was mainly a CopterX 450, which has their blue metallic parts, main drive and shaft was Align. I had to order new parts for the motor mount, tail drive and battery mount, this time from hobbyking. During inspection I also realized that the main shaft bearing needed to be replaced. This should be enough to start putting the body together.   

Parts


Body build, the screws

Most cheap 450 clones use really crappy screws. For the SE V2, a combination of M2 socket button head phillips screws are used with the special cup-shaped washer. Two lengths are required, 6mm and 14mm. DO NOT use these screws! The phillips heads will break if you ever need to unscrew them, which you will when practicing. Replace them with any other hex screw of the same dimensions. For example the Align Sport uses socket button head hex screws of the same dimension and with a wider head. They are easier to screw and unscrew and the do not need the cup-shaped washer. Alternatively, and maybe even better, is the use of a socket head hex screw with the same dimensions together with the cup-shaped washer. I have a set those but cant figure out where I ordered the hardware bag with those fantastic screws.

Parts

  • H45094 Align T-Rex 450 Sport Frame Hardware Set

Body build, one side assembly

IMGP5045
I start by putting together as much as possible of one side of the body. I won't use thread locking at this point as this is party a step of inspection. It also helps align all the parts when you add the other side to the assembly. As you can see from the image there is already a nice mix of HobbyKing and CopterX parts. What you might not notice is that I have replaced the main shaft bearings, which I discovered to be completely worn out. I replaced them with stock Align bearings, as I had a few in the drawer.

If you plan on using the classic HexTronic 9g servos, this is the time to mount them. Many pilots have good experience from using them on flybar setups. I'll be running flybarless and won't be using the good old blue ones. More on that later. Anyways, the 9g servos are often a bit wider at the bottom, where the cable comes out, and won't fit well without sanding/violence once the body has been put together. Most other servos can be mounted at this point with easier access to screws, but they can also be mounter later without violence.

Top frame assembly

Upper half While working on a project like this I think loosing a little time on assembling and disassembling is alright. Here, I've completely mounted the top part of the frame, only to check that everything fits and that I have all parts. Earlier I noticed that the hobbyking tail drive did not fit very well, but when screwing together the body it fell into place. Additionally there are no canopy spinners in this picture, that's because the PRO spinners I intended to use are too short and does not screw well onto this body. I've ordered the correct ones already.

Parts


Bottom frame assembly

Bottom plate electronics For this particular build I decided to use a different mounting technique by separating the top and bottom part of the frame. This is not uncommon in any way, I just haven't done it this way before. This is one of the advantage of this frame model over the PRO frame, which is much more impractical to put together. Now, I mount the motor, ESC, reciever and FBL gyro on the bottom plate assembly. This way I can do away with the cables much easier.

I've used an old motor that seems OK for this build. It's marked with some chinese signs and is speced at 4000Kv. It's a bit high for a 450 so I will be using an 11T pinion gear.

The ESC is a brand new Turnigy Plush 40A. 40A is more than enough for my flying style and the Plush is reasonably priced and has a 12s slow start, which many other cheap ESC:s don't.

I'm using a Corona R6FA Fasst reciever, possibly the cheapest 6ch Fasst recievers out there. I haven't had any problems with them yet, thus I keep on using them.

The reciever and gyro setup comes from a CopterX 250 setup which will get a more compact receiver later on. The CopterX 3x1000 gyro has served well so far, they're very cheap, but most forum users tend to prefer the ZYX-S over the CopterX. The ZYX has the fantastic bluetooth programmer, which the CopterX does not. Anyway, this time it'll be the CopterX.

Parts


Swashplate and cyclic servos

Servos mounted
Before mounting the top frame onto the finished bottom frame it can be advantageous to mount servos, main shaft, main gear and the swashplate. It simply easier to swing around haft a body while trying to get everything in place. Especially the cables might get improved placement if it is easier to get those wire straps in place.

On the SE/V2 servos are mounted using self tapping screws and a special plastic part behind the servo horn. But I always seem to run out of those mounting parts when I need them. There are a few alternatives to those. The simplest way is to use a self tapping screw and screw it into the carbon fiber, this is probably a bad idea. You can also use socket button head screws and nuts. This will require a few washers as well since a M2 nut will pass throught the hole in the servo horn.

For this build I made my own mounting parts. Those plastic pieces are made from a broken landing skid. Landing skids seems is made out of stubborn plastic to handle all the beating of newbie fliers and are perfect for this. I used the screws that came with the servos.

I regret the wiring I did. I should have pulled all the wires on the inside of the frame. Both for good looks and because my tight placement of the servo may make the linkage ball to touch the wire strap holding the servo wire.

For this particular build I'm trying out a new servo, Corona DS-929MG. Any question on forums about cheap FBL servos are answered with expensive servos. I'm still looking for a potential favorite. This one is cheap and the spec should/could be good enough. Guess we'll see when/if it flies.

Main shaft and gear
As mentioned, I also mount the main gear and shaft it this point. I use the original main shaft, since it is the only one that is good enough. I usually choose original main gears as well, since all copies are junk. But this particular one is a RCX gear, which are surprisingly good. (edit: this shaft is a FBL shaft, later replaced by a DFC shaft, and even later replaced by a SPORT shaft.)

Parts



Frame assembly

Now is a good time to put the frame together. It can be quite fiddly to get the transversal shafts in place for the screws, especially the ones in the front, but it's not impossible. This is also the time to get the lock-tight out of the drawer and make sure the frame will hold together with the vibrations going through during flight.

Body finishedAfter putting the frame together I connect the electronics and go through the swashplate setup. Before mounting the swashplate, make sure the servo horns are properly centered to provide 90 deg at zero pitch. Mount the swashplate and put on the swashplate leveling tool. Just go through the setup of the transmitter and gyro. I use the CopterX 3x1000 for this build. I've used this gyro a lot and it performs well (not as well as a BeastX). I have the programming box available which makes the setup easy.

You can mount the rotorhead now or at a later time. If you mount it now you can adjust the pitch angles at this point, otherwise do it later. It was when adjusting the pitch angles I discovered that my choice of main shaft was faulty. I had accidentally used a FBL shaft which is longer than the DFC shaft. Unfortunately the PRO DFC shaft will not fit in the SE/V2 body. It is slightly shorter between the collar and lower bolt and the collar is fixed. Clone shafts have a non-fixed collar and a CopterX or similar DFC shaft will fit onto the SE V2, but make sure it has the correct length matching the length of your push-rods and desired swashplate position.

Parts


  • Hobby King 450 swash plate
  • Align 450 PRO landing gear (Align part: H45050)

Tail

Tail partsI had used a tail I intended to use for this build in the drawer but I finally got to using it I realized it was actually ready for the garbage bin. Most of components were alright but the aluminium around the bearings was worn out. This is something that is very common with the cheap clone tail assemblies. The aluminium alloy is not good enough. I had one such tail that broke off in-flight. For this build I ordered a new tail assembly from hobby king. I'd prefer a stock Align one but they are quite expensive and won't fit into this budget heli.

TailWhen buying this kind of cheap tail assembly you MUST take it apart to check it out, grease it and lock-tight it. In this particular assembly thread locker was randomly applied and seemed to be off lesser quality. I replaced the screws with hex screws, greased the bearings and applied thread locker before reassembly.

The boom is a no-name carbon boom straight from the drawer. Seems fine but it has a slightly larger radius than the original and does not fit without a fight. Non-carbon boom can be advantageous on belt driven tails to avoid static electricity buildup from the belt. Static discharge is know to disturb electronics (especially the 3GX gyro).

Servo mountI picked a new type of tail servo this time, Turnigy 212DMH. I usually use the RCX S9257 but read about this servo in a few forums and people have had great success. This surprises me to be honest, the torque spec is far to low. And to my surprise the servo is also quite small. The mounting holes does not fit for screwing onto the mount. Very well, I will still give it a try. 90 the servo before mounting and adjust the tail blades to give a few degrees on 90 degrees by sliding the servo and mount on the boom. Plug it in and check/adjust the transmitter and gyro settings.

Parts


Rotor head

DFC HeadI use a used, but never crashed, CopterX DFC rotor head. I've had good experience with the CopterX heads, no complete-junk heads to far. Before mounting the rotor head you MUST take it apart to grease bearings, thrust bearings and apply thread locker to the entire assembly. Doing this ensures it wont come apart in-flight and binding and bad bearings is much easier to detect when you can spin one part at the time.

Parts



Canopy, main blades and tail blades

FinishedNow for the last parts. The blades are important to consider. I will put on cheapish RCX main blades. RCX blades have served me well before and they seemed well matched in the package. But you won't know until you tried them. The tail blades are more sensitive. I've used clone tail blades, often yellow for visibility, on flybar helis before but never gotten them to work well on FBL helis. Simply because they are badly balanced and hard to balance properly. I only used Align tail blades now.

I didn't have a good canopy on the shelf, only a stylish shark one. The shark canopy looks cool but does not have the visibility you'd want. Often I buy cheap clone canopies that look similar to the align ones.

Parts



Addendum


The main shaft


Finding a fitting main shaft for this kind of build can be a bit hard. The SE V2 is a very old model and DFC heads came a long time after its creation. There are a lot of different main shafts out there and it's not unlikely that there is one that will fit this particular setup. But push rod and and rotor head control arm lengths affect which shaft length is the correct one. Buying a DFC upgrade kit can be a good option since it comes with swashplate and push rods of the correct lengths from the beginning.


The difference between the longest and the shortest shaft I've found is about 8mm. This is equivalent of about 24 degrees of pitch angle, hence you may end up really wrong. I finally found a shaft that was 2mm too long. 2mm can possible be corrected by adjusting the push rod lengths, which was my case, and I can now enjoy 90 degree servo horn adjustment at zero degrees pitch angle.


Flight results


The setup has turned out to fly quite alright. The machine is not even close to high performing but does fly stable and reliably. I initially needed to turn down the default gyro gain values quite a lot which is an indication that the servos are not performing as expected, they are simply slower than required.

Over time the performance of the setup seems to have improved. Later flights have turned out very nice and in terms of stability and reliability it performs close to my Align 450. Right now the machine is suffering from heavy vibrations at a particular head speed, but little otherwise. Also the motor is not as strong as a brand motor and the gyro does crazy things sometimes, in particular during rolls.

2 comments :

  1. Great build... What Is the landing gear you used ?

    ReplyDelete
    Replies
    1. That is an Align 450 PRO landing gear, part number H45050. You can get almost any brand of landing gears for a machine like this. I've tried the HobbyKing, RCX and CopterX ones, none of them are crap. But the Align ones does take a little more beating than the rest.

      Delete