BryFlyGuy67

Hello all. I was psyched yesterday because I finally got TREX #1 back in the air after a major crash. I replaced cyclic servos, linkage rods, a head block and some other parts.

I took her for her first post-repair flight yesterday and both my wife and I noticed an odd sound coming from the Heli. At the field, I assumed that the belt was worn out and slipping. However, after close inspection on my bench, I found that there was a bad, clicking noise coming from the tail drive gear inside the frame of the Heli. See picture #1.

I have the following replacement for this unit: see picture #2

I have been looking through the threads around here and I can't find any information that describes in detail how to change this part. I've looked at this from all kinds of angles and I can't see how to get the old part out and install the new part without take a half of the frame off! Please tell me that this isn't necessary!

So, what I am asking for is a step-by-step procedure for getting the old parts out of the Heli and getting the new ones in. I am especially challenged as the bearing cups face the inside of the Heli and I can't tell if they are able to slide along the tail rotor gear shaft.

HeliSmith

What I do is this…

Remove only screws that hold the upper section of the frame to the lower section of the frame on both sides.
Remove the 6 remaining screws that are holding the bearing block for that assemble.
Gently work it out off the square dowels in one piece.
If it is a V2 the top splits so you can now just take it apart and work the lower bearing out of the bottom.
If it is a V1 you will need a pinion puller or equivalent.

I use just a little dot of green loctite on the bearing and the pulley gear to hold them in. Make sure you line it all up that you can get the bearings in with no problem before using the loctite.

Slide it back into the frame and into the dowels, replace the screws EXCEPT the one that holds the lower frame for that section. Now assemble the frames again.

Hope that helps.

BryFlyGuy67

Helismith,

Thanks for the reply. What exactly do you mean by "dowels"?

From the drawing. it looks like there are 6 screws that hold the bottom bearing block and 4 that hold the top. So are you saying that I should remove the upper frame and then the 6 screws that hold the bottom bearing, remove the pinion gear and then pull the upper bearing down out of its holder?

HeliSmith

The top section of bearing block has a little square peg that pins into the upper frame on both sides. This is the dowel I am talking about.

Because you can't get the screws for the lower bearing block out with the lower frame in the way it is simplier to split the upper frame from the lower frame. Also this way you will not have to redo your wiring usually if you are careful.

When you split the two frames, lower from upper not the frame sides, you will have 6 screws remaining in the upper and lower bearing blocks for the assemble. Remove those and slide both bearing blocks gear thingie and all out of the upper frame section I slide it down. Now you can work on it with no problem. The only tricky part is those square pins but you can wiggle it out if you are careful without spliting the upper frame sides as well saving you a lot of time.

Hard to explain in a post hope you understand.

BryFlyGuy67

I think I do... but it sounds like a major PITA! [:@]

There is nothing to do expect fix it. The bearig sounds pretty bad...

Skarn

Yep I too did it like Helismith and while it is kind of a pain, it wasn't that bad.....

Skarn

BryFlyGuy67

Thanks for the advice. I'll give it a shot.

RobBeach

I am in the process of doing the same repair.

The shaft broke just underneath the upper bearing.
(Yes I did have a crash but it wasn't a bad crash... the shaft actually snapped after
putting in a new belt... which as a noobie I had too tight... only thing I can think of is
it was a defect tail gear assembly)

Ok... as a noobie... I put the R48 on the shaft with a pin.... (cleaning the shaft previously and the gear insides with acetone)... whipped off the excess on the bottom of the gear... and put a little more R48 (aka green loctite) in the hole of the top of the gear and then slide the gear down down so it was flush with the shaft top... which was also bottoming out to the bearing.

I did some reading on Loctite products... it seams this R48 maybe the same product as the Loctite 648... I was told Loctite 609 would work but I bought the Align products for the fix.

I'll wait 24 hours before the aforementioned assembly procedure.... but.......
as a noobie... this "glueing" with the loctite product... for the gear... wow... it just seams
weird glueing metal to metal and it works. And in a environment that is supposed to be void of air.

This bird is actually a Copter X... and the original tail gear shaft was splinned... so you can see
my intimidation of "glueing" over a splinned shaft ... but obviously that's how it's done.

oly_rcer

i had the same prob with my sa trex and changed out the tail drive pulley with a metal one that has a set screw,everything works fine now but i found if i have to change a belt there is no room so i have to dissamble the frame and lower the bearing block to change the belt what a pita