T-Rex 250 Build Thread

[litehawkdown]

Originally Posted by wkma7six

I have my ESC mounted on the side of the frame pretty close to the gyro, and the receiver is just above the gyro on the same mounting plate. No issues with it so far. Hard to space everything apart in that little heli. I'm going with the Spektrumized beast x controller and Align FBL head conversion soon. Hopefully there won't be issues there either.

My goal was to keep as much of the electronics in the frame as possible. I had to use a AR 8000 receiver (The only one I had) Bit of a pig that one. Not easy to stick that anywhere but on the side. I have the sat for the RX under the gyro. I stuck my speed controller under all that between the rails of the bottom frame. I Push it as far forward as I could with out hitting the motor. I could stick it under the battery if I have too. But I figure it would not get much cooling happening in there with a hot battery right above it in the small canopy. I saw this set up in some pics online so I figure it is fine. Then I caught that 5 cm warning in the instructions

[Jasmine2501]

Originally Posted by litehawkdown

Has anyone heard of interference being caused by a speed controller being to close to the gyro ? I noticed on the instructions that you are suggested to have 5 cm separating the two. But then they suggest to stick the ESC on the back of the heli right where the Gyro is.

The two devices don't really interfere with each other, but their wires can. It's the ESC wire that is the funky one because it's powering the receiver with a PWM source - so it creates a signal which can affect a nearby wire, and if that wire is carrying a different signal, they can interfere. So, keep the wires apart and run the ESC cable through a toroid, IF you are using the built-in BEC. If you're using a separate BEC, none of that matters and you run your wires wherever you want.

[litehawkdown]

I think I should be ok then. I have the motor wires going under the heli all alone. And the only wires running beside the RX power lines from the ESC are the two front servo wires. Should I Move those?

I was told to be cautious only with the three wires going to the motor as well as the battery leads to the ESC. So I ran those wires all on one side of the heli. All the stuff that plugged into the Rx I have on the other side.

[Jasmine2501]

Should be fine. Tie it all down and post a photo for us

[litehawkdown]

Originally Posted by Jasmine2501

Should be fine. Tie it all down and post a photo for us

I just added a 250 wiring album to my profile. I still need to attach my Rx I won't try and fly like that. LOL I also still need to set pitch and play with TX settings more. Swash is crooked because I accidentally pushed one of the cyclic servos with my thumb while putting something on the heli with a little force. Tell me what ya think. I have no heli gurus out my way.

[litehawkdown]

I had a week off of building since I had some company. But I revisited a few things and changed the placement of the servo horn on the rudder. Now I have the recommended 4.5 mm from center. I also tightened up the tail assembly by filing down the blade grip screws .5 mm (seemed to work for me). looks like all that's left to do is set up the gyro rates and the pitch settings on the tx. Any starting points for stock with a dx7s would be very much appreciated. I also need to file down all the blades. They seem to fit a bit too snug in the grips.

[Blade201]

I just started my Trex 250 SE Super Combo build today and after inspecting each part, I found two loose screws in the box and a screw inside the motor. Thank goodness I checked! Just a caution for everyone beginning this build. Been watching Finless Bob and Jasmine's videos, very helpful.

[litehawkdown]

Originally Posted by Blade201

I just started my Trex 250 SE Super Combo build today and after inspecting each part, I found two loose screws in the box and a screw inside the motor. Thank goodness I checked! Just a caution for everyone beginning this build. Been watching Finless Bob and Jasmine's videos, very helpful.

A lot of the parts that look like they are put together are not really put together if you get my drift? The motor needs to be adjusted to the main gear so it is not locktighted or screwed together yet. But it is a must to check all the screws.

[Blade201]

Originally Posted by litehawkdown

A lot of the parts that look like they are put together are not really put together if you get my drift? The motor needs to be adjusted to the main gear so it is not locktighted or screwed together yet. But it is a must to check all the screws.

Ha! Yes, but when I mean loose, I mean inside the motor, so if it was started it would have been inside and ruined it! Yeah, I also noticed many screws hanging by a thread. Also, looking at the back of the manuel it says Feb 2011, I take it that some things have been updated since Finless Bob and Jasmine videos correct?

[Jasmine2501]

Yes, when we made the videos, the first 250 had just been released. If you have bought one recently, you almost certainly have the "V2" which has some slight differences. The placement of components is still the same and it still has the exact same parts, so you shouldn't be having any extra things in the manual. If you see something in the manual and it's not on your helicopter you need to find it and put it on.

[JoeW]

The new Pro is 99% the same too. The only real difference is the tail servo location, but the process is the same regardless.

[tommeke]

can someone help me ? the flybar is WEEIGGHH too tight, it's very unstable in a hover because it takes such a long time to get back in place. Someone had this problem and knows the solution? sorry if it was already mentioned, haven't had the time to read the whole thread

[Jasmine2501]

Originally Posted by tommeke

can someone help me ? the flybar is WEEIGGHH too tight, it's very unstable in a hover because it takes such a long time to get back in place. Someone had this problem and knows the solution? sorry if it was already mentioned, haven't had the time to read the whole thread

You should be able to tell what screws are making it tight. Loosen those up. Let the lock-tite do the job it's there for, and don't tighten the screws on the 250 very tight. All of them, the torque is what you can apply with two fingers on a skinny screwdriver - it's not very much, and it's very common for people to over-tighten them.

[hga77]

Originally Posted by tommeke

can someone help me ? the flybar is WEEIGGHH too tight, it's very unstable in a hover because it takes such a long time to get back in place. Someone had this problem and knows the solution? sorry if it was already mentioned, haven't had the time to read the whole thread

And make sure there is no binding at any point on the flybar rod where it passes through the head block. I had a head block that needed sanding down where the flybar passes through it. It was rubbing on the sides of the passage hole since it was tight, so i used a dremel bit to widen it then some sand paper to smooth it down. Flybar was free after that.

[hga77]

Originally Posted by tommeke

can someone help me ? the flybar is WEEIGGHH too tight, it's very unstable in a hover because it takes such a long time to get back in place. Someone had this problem and knows the solution? sorry if it was already mentioned, haven't had the time to read the whole thread

It might also be you flybar seesaw. It might have a faulty bearing. Either way try loosening the screws holding it as Jasmine suggested.

[RickVS]

Hi. I have read elsewhere that the tail servo arm ball should only be 4mm out from the servo, however on my 250 this makes the ball fall short of center of the tail, such that the metal rod that connects the tail assembly to the servo arm would be off to the side and not fit correctly. Where should the ball be positioned on this arm?

Also, how important is it to secure the position of the plastic brace through which the rod goes through halfway along the tail? The manual says to slip a plastic tie under it, however I can't seem to be able to do this, so the without it the brace moves along the tail boom.

Thanks.

[Jasmine2501]

Originally Posted by RickVS

Hi. I have read elsewhere that the tail servo arm ball should only be 4mm out from the servo, however on my 250 this makes the ball fall short of center of the tail, such that the metal rod that connects the tail assembly to the servo arm would be off to the side and not fit correctly. Where should the ball be positioned on this arm?

Also, how important is it to secure the position of the plastic brace through which the rod goes through halfway along the tail? The manual says to slip a plastic tie under it, however I can't seem to be able to do this, so the without it the brace moves along the tail boom.

Thanks.

The push rod must be mostly straight when the servo is centered. It will bend at extreme throws and there's nothing you can do about that. Try different positions of the servo and the mounts - there will be one position where it lines up jut fine. Try putting the ball on the other side of the arm too. The pushrod guide needs to be fixed somehow. A right size zip tie will do it, but I usually put some CA also.

[litehawkdown]

Originally Posted by Jasmine2501

The push rod must be mostly straight when the servo is centered. It will bend at extreme throws and there's nothing you can do about that. Try different positions of the servo and the mounts - there will be one position where it lines up jut fine. Try putting the ball on the other side of the arm too. The pushrod guide needs to be fixed somehow. A right size zip tie will do it, but I usually put some CA also.

I finally decided to CA my push rod guide in place after I accidentally hit it and found out about it after a few packs. Funny thing was it did not really give me much greif while it was out of wack.

[Blade201]

While following Jasmine's video I had already centered all 3 servos and everything was working fine. I powered them up again to double check center when I noticed the Aileron servo was not working. Elev and Pitch working fine. Tried to re-bind, same result. I take it the servo is shot and this happens sometimes?

[hga77]

Did you trying switching servos on the rx connectors to see if another servo would work on the Aileron channel? What battery were you using? Maybe it was running low.