Trex700N DFC Wagging tail - tail thrust bearing not to spec

[jogeiremil]

Trex700N DFC Wagging tail - tail thrust bearing not to spec

700N DFC, OS105HZR, BeastX

I have had a lot of trouble with my 700N DFC, wagging tail.
I have been trying to tune the gyro, engine etc. for more than a gallon of fuel, but have not been able to get rid of the wagging.

After some careful inspection, I have found the cause. One of the tail blades is locking up due to a poorly machined ball race on the outer half of the thrust bearing.

This is the original thrust bearing from the kit.

Images shows the outer half for both thrust bearings, notice the shallow ball race on the right.

[gailvin]

That is how they are suppose to be. The larger ID goes on first, then the bearing then the smaller ID. Page 18 of the manual shows this: https://www.dropbox.com/sh/edrdmd2fy...er%20Combo.pdf

Btw, was there any grease in the bearings when you took it apart?

[Shev]

Originally Posted by gailvin

That is how they are suppose to be. The larger ID goes on first, then the bearing then the smaller ID. Page 18 of the manual shows this: https://www.dropbox.com/sh/edrdmd2fy...er%20Combo.pdf

Btw, was there any grease in the bearings when you took it apart?

I believe he is talking about the depth of the grooves not the ID's of the races. The grooves should look like this:

[jogeiremil]

Originally Posted by Shev

I believe he is talking about the depth of the grooves not the ID's of the races. The grooves should look like this:

Correct, I am talking about the depth of the grooves.
I contacted my LHS, and they replaced the bearings for free. :-)

[jogeiremil]

Originally Posted by gailvin

That is how they are suppose to be. The larger ID goes on first, then the bearing then the smaller ID. Page 18 of the manual shows this: https://www.dropbox.com/sh/edrdmd2fy...er%20Combo.pdf

Btw, was there any grease in the bearings when you took it apart?

Thank you for your help :-)
I don't remember how much grease there was, but I remember adding more while building the helicopter. (Pretty dry I guess)

[LemmyD]

I take it this resolved the issue?

[RontaryUS]

Looks like you found the cause. Make sure the blade grip are smoothly rotating once you changed the thrust bearing. This is an important check when building or maintaining the tail assembly. Also check that you have the right washers at the right place and the bearings inserted properly if you still have the grip sticking and not smooth.