Align T-Rex 250 Build log

12:49 PM giovanni 0 Comments

After flying for almost a year with my loyal Blade 400 I decided to sell it to a local bloke and buy a 250 class size. At first i was very tempted with the 250 clone from Hobbyking, but then I decided that I would treat myself good and went for the real deal. So I convinced my local hobby shop to make me a super price on a 250 Pro Super Combo and walked away with an enormous grin on my face.

This was my first heli build, and I have to say that I enjoyed it...A LOT! So much that after that I purchased a 450 Pro too, and let's see what the future will bring!

This article is about how I built it (well, following the manual, but hey!) and I also experimented a bit with an iphone app which allows me to produce stop motion movies. Love it. But here we go!

The box is SO small, it is incredible that it can hold an helicopter

These are the electronics, the kit comes with a 15A ESC, a 3400kv brushless motor, the Align GP790 gyro, a DS420 digital tail servo and three digital DS410 cyclic servos. I had to add my receiver, which as usual is the awesome Orange R615, which I stripped of the case to save some weight.

This is the full content of the box (minus the electronics). From the top left there is a pair of tweezers, thread lock, screw and hex drivers, battery and rx straps, velcro, two types of tail feathers, blade holder, ball links and dog bones, swash and other head parts, flybar paddles, tail bits and bobs, main gear (which has got a one way bearing in it), canopy, landing skids, pushrods, frame parts and main blades.

I strongly recommend, actually I force you to take the head completely apart (it comes partially assembled) to check for threadlock. Usually there is none, and a friend who didn't check the head of his 450 was about to make some damage not long ago. Luckily we caught that in time.
The instructions to build the head are very well done, so you won't have any issue in building it. Just make sure to apply thread lock to any metal to metal screw and not to tighten them up too much. Also a drop of thin oil in every bearing is a good idea. While you build the head make sure that all parts move freely. And I mean really freely, almost no pressure must be needed to move the flybar and the linkages.
Make sure all the links are mounted the correct way (there is a little "A" on one side, that is the side facing away from the ball link) and that the flybar is PERFECTLY in the center of the head. I use a digital caliper to measure the two sides. This will ensure that each side of the head weighs the same as the other.

The landing gear, which is very sturdy, and dead easy to build.

This is the frame built up, with the servos mounted and in the process of centering. This is an operation which is at the same time fundamental, slightly complicated and great fun. There are loads of tutorials on how to do it, the best I found are these by Finless Bob. In specific you want to look for CCPM setup 01 and 02. Another great guide is by John Salt, which you can buy from his site.

This is the bottom half of the frame, and this is when you install the motor, making sure you have the proper gear mesh. How you do it? Like this.

Time to assemble the tail and assemble the heli together. It starts to look good now!

An operation I find quite tedious is to run the wires to make sure they don't get caught anywhere, and that they look good too. The eye has to be pleased!
In this case I didn't do a very good job, I was very impatient (mistake!) and the heli is so small that you have to have incredibly small hands to get inside the frame. I did what I could, hiding the ESC underneath the battery tray, the gyro under the main gear, the rx outside the frame, on the right side. This balances the heli (two cyclic servos are on the left side) and allows to have all the wires on hand something should happen.
I like to run my wires in a wire mesh, which holds them together perfectly, and hides them too.

Boom! She's ready, let's go outside and try her out!