I’ve followed Mikey’s RC video guides and things went smoothly. The only annoying part is getting the two front servos in place, as you have to bend the frame a little bit to insert them.
Like Mikey explained, do not connect the servo arms to the servos yet!
I’ve updated my post about assembling the frame, as there is no need to apply thread lock to certain screws until you reach this step and install the servos. At least for the HXT900 servos, there is no other way besides bending the frame… So these are the frame screws to remove (only from one side):
Motor installed! I actually did this last weekend but got a chance to blog it only now…
I’ve soldered the bullet connectors of the ESC and motor and got the pinion gear installed at the correct height on the motor shaft. Then it was just a matter of screwing the motor to the motor mount and making sure the gap between the pinion and main gear is OK.
Items required:
Motor pinion gear (I’m using a 11T pinion on the Typhoon 2215H motor)
Two button head screws to attach the motor (the screw size depends on your motor — both the the 2215H and 2836-3700 use M3 screws, and 5mm is enough)
Steady hands to screw the motor in a hard-to-reach location
Before you screw the motor into the frame, decide where in the frame you’ll want to have your battery, ESC and receiver installed. Depending on the ESC location, you’ll want your motor wires pointing towards the front or back of the helicopter. Check this Finless Bob video on electronics placement options. I’ve decided to have my wires pointing towards the front as my ESC will stay at the horizontal mount in the front.
Make sure to buy a pinion gear for the correct motor shaft size (they’re usually 3.17mm). Both Turnigy 2215H and 2836-3700 motors use 3.17mm.
The 2836-3700 motor has (in theory) a 3.17mm shaft, but it is actually a bit larger than 3.17mm. My pinion gear wouldn’t fit so I had to sand the shaft a little. Anyway, I decided to use the 2215H for now.
When attaching shrink wrap to the motor and ESC connectors, don’t make them too long otherwise it’s harder to bend the wires. In my motor I used 20mm long shrink wrap but 12mm would have been enough. Not a big deal, though:
The Mystery gyro G401B (sold by DealExtreme, HobbyKing, xmseller, etc) requires some modifications before using it. It’s a $20 gyro$14 gyro, so don’t expect it to have the same build quality of a $150 Futaba GY401
Two major problems were reported in the G401B forum threads:
The gyro circuit board is not firmly attached to the plastic case, causing problems to the gyro operation.
The solder joints of the tiny switch for digital/analog/normal/reverse mode can break off the board when flipping the switches.
Items required:
Hot glue gun (I used a small 10W dual temp gun)
Small piece of soft foam – 2.5cm x 2.5cm, about 0.8cm thick (1″ x 1″, 1/3″ thick)
How to fix:
It seems like a lot of work but this is actually a 5-minute job:
Unscrew the gyro case lid and carefully remove the circuit board from the plastic case.
Add hot glue to the solder joints of the switch block (both sides) so it is secure on the board. If you add too much glue, it will be harder to put it back (I had to carefully trim the excess glue with an x-acto knife).
Apply hot glue to the servo solders on the board, so the wires are held not only by the solders. Don’t let the hot glue gun touch the wires as they will melt.
While you’re there, apply hot glue to the solder joints of the two vertical circuit boards.
Apply hot glue to each corner of the case and insert the board again. Use something long and thin (like a small screw driver) to press the board against the glue so it gets fixed on the plastic case.
Insert the square piece of foam when screwing the case lid back. It will help keep the board in a tight, fixed position.
NOTE: Steps 3 and 4 are optional and might be considered overkill by some. I did them anyway as I didn’t see any disadvantages.
Gyro circuit board, before applying hot glue:
Board glued and gyro ready to be closed:
Soft foam:
UPDATE 02/Dec/2010:Trainboy64 has posted a nice video on YouTube showing basically the same thing:
I prefer to use cheap but reasonably reliable parts than crashing expensive ones. At $4 each servo, I don’t mind stripping the plastic gears whenever I crash. The replacement gear set is only $0.90 and I’ve got a few of those stocked already. It’s quite a difference between spending $12 (3x $4) vs. $90 (3x $30) for a brand-name servo. Anyway, I might upgrade my cyclic servos to digital and/or faster ones later.
I did like Mikey suggested: install the rubber O rings on the inside of the landing struts to avoid losing them.
The CopterX manual says to use CA glue on the screw that goes to the bottom plate. I decided not to, at least for now, because the T-Rex manual doesn’t mention CA glue in there.
Note: I didn’t have to drill the screw holes like Mikey had to on his EXI 450. I think it’s just a difference between factories (CopterX vs. EXI).
The main rotor, head, linkages, etc all came already assembled with this kit. Still, we want to disassemble it completely to apply thread lock to all screws and adjust the length of all linkage rods.
Items required:
Digital caliper — otherwise you’ll go crazy measuring tiny fractions of millimetres of the linkage rods (dealextreme.com)
Thread lock everything according to the manual except for the flybar rod, flybar weights and the screw that connects the main rotor housing to the main shaft. Later on, you’ll have to remove the flybar rod in order to level the swashplate using a swashplate leveler. Make sure to insert at least the flybar rod so you can install the flybar control arm.
The instructions show washers on both sides of some screws, but the kit came with washers enough only for one side. Because of that, insert a washer between the washout control arm* and washout base. Hopefully this won’t be a problem.
It didn’t come with the two collars for the radius arms, but it looks like it is not required as the screw is not threaded in the section that goes through the washout control arm.
This is the easiest way I’ve found to measure the linkage rods: measure the distance between the inner top part of one hole and the inner lower part of the other — huh? like this:
Use a digital caliper to make your life easier:
PS: I’m using the same terms of the T-Rex manual so it’s easier to know exactly which parts I’m talking about.
Keep the two lower screws of the boom block loose. So no thread lock yet.
First loosely screw the lower frame in the upper one so it stays fixed in place, then start re-inserting them with thread lock. It’s easier than having the lower frame hanging while trying to insert the first screws.
Install the bottom plate only after installing the bottom frame. You just bend the frame a little bit to insert the bottom plate. No thread lock on plastic!
Hooray! I’ve started building my helicopter and I’ll be posting here my progress — or lack of
Whoever is building a T-Rex 450 (or clones like my CopterX) could use the following posts as a building guide. I’ll include tips, links to existing videos of each step, my own notes and, especially, mistakes to avoid (i.e., mistakes I’ve made).
First step: disassemble the frame to apply thread lock on every screw connecting metal to metal. Why? Even though the frame comes already assembled, the screws don’t have thread lock applied. You need them because the screws will get loose with the vibration once the heli is flying.
Use the original T-Rex 450SE V2 manual for the whole build. It’s way more detailed than the CopterX one, but sometimes you’ll have to use the CopterX manual to find out what screw size to use.
Make sure the tail drive gear spins freely — mine wasn’t because I had the boom case too tight or something else wasn’t properly straight.
Build the upper frame first, insert the main shaft without the two gears and make sure it spins easily. Insert both gears in the main shaft and confirm the tail drive gear still spins freely.
Don’t use thread lock neither tighten the boom block yet. You’ll need it a little bit loose so you can insert the tail boom later on.
Update: do not use thread lock on these screws yet, because you’ll have to remove them to install the HXT900 servos later on:
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