T-Rex 250 SE build!!

[elkmaster01]

Here we go!!!!

Got the box!! Check out the cigarette pack for size!! The box it came in was torpedo-proof,,LOL




Here's all the parts laid out!!



I got the head assembly done,,,it took 1 1/2 hours,,LOL



I took everything apart and lock-tite it all. I used very little locktite. The hardest part was the flip'n flybar rod and paddles. When you screw on the paddles, it is VERY difficult to hold the flybar rod. I used needle-nose pliers and had to really clamp down on it. The set-screws in the flybar cage won't hold it,,the paddles go on very tight. Once together, the head is very nice,,,everything is solid and lines up great. NO slop anywhere!!

I also 'glued' the pinion on the motor shaft. I'm not sure I like that. The pinion wasn't very snug on the shaft at all. I would rather had see them key the shaft and use a set-screw,,even though it would have to be tiny.


OMG,,,My EYES,,,My EYES!!!!! These parts are tiny. I laid it all out on a towel so I wouldn't lose anything. I have to quit for now,,,tomorrow is Christmas so it will have to wait a day or so!

More to come!!!

Randy

For a list of all the parts,,see;
rchelitalk.proboards.com/index.cgi?action=display&board=yourhelissetup&thread=2529&page=1

[Solitaire]

I think we'll sticky this, elk. Should be easier to find.

[nunyabizniss34]

Just a side note on the pinion being glued on Randy. I did mine yesterday so the glue would have time to set, and I just took it out and tried quite hard to pull it off with pliers to see how well it held, and I couldn't get it off. So I think it should be fine.

Colin

[elkmaster01]

I got a little work done today(Christmas Day).



These are the little servo mounting clips,,,you can see the ones installed on the forward lower servo mount. Pretty sweet,,the servos fit in perfectly and just two screws,,,,waalaaa!



Here the servos are installed. Note; you HAVE to mount the motor before you install the servos. The forward left cyclic servo is in the way of the left motor mount screw. You CAN loosen and tighten that motor screw after the servo is installed,,,but you can't get the screw 'in' with the servo installed.



At this point I hooked up the receiver,,AR6110e,,and set my servo arms. With the throttle at 50% I set the arms perpendicular to the main shaft,,,not the servo cases. The servos are at a tilt. Oh,,,when installing the linkage balls on the servo arms,,,,the elevator linkage ball is shorter that the forward cyclic linkage balls. I really 'micro tuned' the servos. I ended up with sub-trims of; pitch (forward left servo) at '0' sub-trim,,,,,,aileron +3,,,and elevator at -11. Not bad,,,the servo arms were very close to start with.



I installed the head assembly and the main gear. Adjusted the pinion gear mesh. The main gear has a bronze spacer that sets on top of the gear case and then a screw/washer that installs straight up the bottom end of the main shaft to hold the gear. Then I slid the shaft up taught and set the shaft collar. I hooked up the Rx again and cycled the servos while turning the head. Everything is smooth with no slop anywhere. The DS410 servos seem very quick and strong.




The very first heli I ever built was a T-Rex 600 ESP in May this year,,,,,then I built a T-Rex 500 ESP,,,,this 250 SE is every bit the same quality as those. The CF frame is VERY strong,,,everything fits perfect. I have a total of about 2 1/2 hours into this so far,,,the TINY,,tiny screws and parts are slowing me down,,,LOL. But it's a easy fun build so far!!!

[nunyabizniss34]

I'm pretty much where you are Randy, I do have the tail on though as well. I can't get the damn end caps on the skids!!!! I am going to try heating the skids slightly to expand them. You're right though, this is a fun and pretty easy build. Zero slop, and I mean ZERO. Pics to follow

Colin

[nunyabizniss34]

OK here's some pics of the build so far. This is the flybar assembled.



The assembled head. Randy is right, getting the flybar paddles on is tricky. I got each one started on the thread of the flybar, then twisted them in opposite directions while I held both of them. Worked great! You can also see how small the head is.



Hard to see but here are the plastic servo mounting nuts installed on the frame. I wish every heli had them! Be sure to sand down the sharp edges of the frame, I cut myself twice on them while installing the servos. Clumsy oaf!



This is where I'm at now. I removed the elevator servo to make it easier to get the belt on, you don't have to but it does make it easier. I got the fins from helidirect ($6.95). I think they will make the heli easier to see which will help orientation.



All in all it's been very easy. The only problem I had was getting the end caps on the skids. They still aren't on! Pretty much all that's left to do is the electronics. I am hoping to have her flying by tomorrow. More pics to follow.

Colin

[Dave]

You guys are doing a great job here with this thread. Colin hope you don't mind I did a little editing on your last post so the picture would show on the forum and you don't have to go off site to view ;D

Dave

[nunyabizniss34]

OK I'm pretty much done with the build. One drawback of a heli this size is where to mount the Rx. I ended up mounting the gyro upside down and have the Rx above it on the other side of the plate that sticks out the back of the frame. Very tight wiring, the ESC is mounted underneath the heli and the wire is JUST long enough to reach the Rx, but barely. If anyone else is going to mount the ESC where I did I would recommend getting an extension.

Now I am trying to set up the blade pitch. The first time I checked it was WAY off. I couldn't even get it right with the swash mix settings in the DX6i so I will have to play with the linkages a little, even though I have them set exactly like the manual says in terms of length. The battery died in the Tx so it's charging now, I will post more pics later.

Colin

[elkmaster01]

I'm was done,,,,,once,,LOL. You would think that as small as this heli is, you'd have plenty of wires to work with. As Colin said,,the ESC is a pain in the butt. I ran the motor leads inside the frame and mounted the ESC on the left side. I had it all hooked up and actually ran it,,,everything worked great. Then,,I wanted to start programming the head and pitch but I couldn't get to the motor leads to disconnect the motor. So,,I started over. Here's what I have;




I turned the motor around and ran the leads out the front and back down the side. Once I get the programming done I'll secure the wires.
There isn't a lot of options on the forward servo wires either. You can't run then inside the frame, no room to get past the pinion, gear, and main shaft.
So,,,I'm going to take my time and see if I can wrap some of these wires and try to clean it up. The gyro wires are going to be a headache, this is the same gyro I have on my 500 and 600, it's going to be tough to tuck them away.
My receiver,,AR6110e, will set on the frame bottom under the gyro,,,the throttle wire and the forward servo wires just reach.

I probably won't have it flying today, but a maiden-hover should be no problem tomorrow!

All and all,,,,VERY impressive heli!!!

Randy

[nunyabizniss34]

I knew it was too good to be true. I am not familiar with the GP750 gyro and it seemed easy to set up. The thing is, in HH mode the tali pitch slider will go right when I hold left stick (looking from the back, which is correct)....but it stays there and doesn't move when I re-center the rudder stick. Same on the other side. I have to apply opposite rudder in order for it to move back. It's fine in rate mode, everything centers back as it should. There is no binding at all in the tail, it slides like a knife thru butter. What am I missing? I had her spooled up outside and that little motor screams! Spins violently clockwise too. Probably just need to reverse the gyro. I am also getting a lot more negative pitch than positive pitch. I have -12 at low, +3 at mid and only +5 at high. That's no good, and I can't get it right in the swash mix settings. I think my head is all fuzzy from staring at tiny parts all day

Colin

[elkmaster01]

Colin,,,,,the gyro is fine,,,in HH mode,,the slider will stay where you put it. If you put full rudder one way and simply center the stick,,the slider will stay all the over,,you have to use the stick to center it. In rate mode,,the slider will center when the stick is centered. If the heli spins wildly,,,,and your rudder stick has the correct responses,,then the gyro needs to be reversed. In my swash mix,DX7,,,I left the default settings of +60,,,+60,,+60. My initial pitch range was - 12 to + 14,,,,I just used my pitch curves to set it at;
Normal -2,,,INH,,,0,,,,INH,,,+11
STNT 1 -10,,INH,,,0,,,,INH,,,,+11
STNT 2 same as 1

Randy

[elkmaster01]

The FINISHED product!!!






The only wires I didn't wrap was the tail servo,,,,the loops would have made it too bulky and look weird so I just folded them and zip-tied,,,works for me.

I programmed my pitch and throttle curves and mimmic'd the settings on my 500 and 600. I spooled it up in my garage,,got it light on the skids and checked tracking,,,it was PERFECT. But,,,I'm not confident enough to get it in the air in my garage, so I'll wait for some calm wind and take it for a ride outside and check tracking at eye-level. But so far,,,this thing ROCKS! I'm really happy with it!!
Total time for the complete build---9 hours over 3 days!

I'll post a video of the maiden flight,,,hopefully tomorrow!!

Randy

[nunyabizniss34]

Looks great Randy, great job! I figured out the pitch curves.... I was just being a dumba$$ ;D I now have -3 low, 0 mid and +10 high in normal. -10 low, 0 mid and +10 in idle up. I held it in my hand and spun it up...I can feel how it wants to fight when I try to jerk the tail so the gyro is doing it's job and I think I got it figured out now (famous last words lol). Tomorrow is the test flight for me as well, weather permitting. I really enjoyed this build! It's a really well-made heli and surprisingly powerful for it's size. My build time was approx the same as Randy's, maybe an hour longer for me. The hardest parts were dealing with the tiny screws/washers/ball links and the skid end caps (I still don't have them in ), other than those minor things it went smoothly. The head assembly was very easy, as was the tail. Highly recommended! I still have some pics to post too.

Colin

[elkmaster01]

A couple complaints about the intructions. It never gave measurements for the servo arm balls for the cyclic, but the pictures were clear enough. But,,there was NO intructions, or pictures, for setting the servo arm on the tail servo. I made a 'wag' (wild-assed-guess) and use the second hole out from the center. It wasn't until I was going thru the gyro programming later in the book when I saw they advised setting the tail servo arm ball at 4.5mm from center,,,,,the inner-most hole on the servo arm. Quick fix,,,,but I'd spent some time earlier trying to find out how to set the tailservo arm.

Other than that,,,,everything is straight-forward,,,an easy build. This heli is VERY close to the same set-up and parts as the 500 and 600 ESPs.

[akent]

Most excellent build posts!!!

As usual, I am very impressed with your wiring, Elk! VERY clean!

One of these is on my wish list now!

Thanks!
Kent