Repeated tail grip bearing failure on T-rex 450 Pro V2

[rcflyersd]

I have 3 1/2 year old Rex 450 Pro V2 flybarless (pre-DFC) that has served me well for hundreds of flights. Problem is as of late, I have seized up 3 tail grip bearings within 25-30 flights. Replacing the grip bearings and at one point replacing the entire tail gear box and rotor hub assembly.

Last evening while doing some simple pirouettes, releasing the rudder stick. It just kept piro-ing, (again). Set it down and found one of the tail grip outer bearings had completely disintegrated. Upon removal of the spindle bolt, little bearing balls came falling out.

I'm just pondering what the root cause of so many tail rotor failures only just lately.
Possibly too high of head speed? Not sure of exact RPM, but running a 100-75-100 throttle curve with stock 3400KV 450MX motor on 3 cells. It is reasonably higher head speed than what I used to run as at that speed, the heli just feels so much tighter and responsive.

Just curious if anyone has experienced similar issues. Only theory I come up with is too high of centrifugal force on grips at high RPM?

Mark

[alyon187]

Is it the older black tail assembly w just the radial bearings or is it the newer silver one w the radial and thrust bearings? If it's the black set then I would probably say that the increased headspeed is causing your radial bearings take too much thrust load. I suggest replacing the whole tail assembly to the newer silver w thrust bearings to remedy the situation. Just my opinion though, I'm still pretty new to the hobby.

[rcflyersd]

Yes, it is the black tail grips and there are no thrust bearings in them, just 2 radial bearings. Usually it's the outer (smaller) of the two that fail.

On a side note, it is probably time to invest in an optical tachometer. On my 600 and 700 machines, I run Castles ESC governor using it's calculated RPM's and it works well. On the smaller T-rex's (250 & 450's), I am just using throttle curves on the Align ESC's so my head speed is based on flight "feel" and is relatively high.

Mark

[alyon187]

Sounds like that is more than likely the problem then. The centrifugal force is riding on those outter bearings so getting the newer tail blade grips w the thrust bearings will help take those centrifugal forces instead of rhe radial bearings.

[slamdance]

Interesting issue. I've had an older trex 450s awhile back. No thrust bearings in the tail grip. True, the rpms at the tail is 4x the head, so centrifugal force is tremendous. However, that's always been the case. You've flown it before so, you know it's not a design issue. Must be 2 things:
1.) You are getting substandard bearings, lately.
2.) Parts wear: The mounting hole/shaft/alignment has gotten sloppy causing binding or undesirable bearing movement in mount. Accelerating wear.

I suspect the tail shaft might have a slight bend if you crashed recently. It's very hard to detect minor bends on those unless you swap that part out. A cheap check.

3.) Lastly, it could be tail blades out of balance. This will be apparent with increased vibration. Keep an eye on that. Again, a quick swap is a cheap check.

Good luck.

[Yfbb]

I had this issue too. Align had some bad batches. They didn't work in mine. Kept dying. I put in some bocas and surprisingly some hk bearings and they were fine. If you want this problem to go away for good, get the tarot grip with thrust bearings or the align one. No problems ever again.

[helirifick]

I recently bought a flybarred 450 Pro V2 super combo and according to the diagram in the manual, the tail grips don't have thrust bearings.

I bought p/n H45T002XX metal tail rotor holder which has thrust bearings -- haven't received it yet.

Link:

https://www.aligntrexstore.com/450-M...XX_p_2345.html

PS: does 450 Pro V2 mean either FB or FBL (DFC) ??? My kit's part # is KX015082T) and I thought 450 Pro V2 meant it was only flybarred, however, people could upgrade it using an FBL head. Confused.

[Yfbb]

Originally Posted by helirifick

I recently bought a flybarred 450 Pro V2 super combo and according to the diagram in the manual, the tail grips don't have thrust bearings.

I bought p/n H45T002XX metal tail rotor holder which has thrust bearings -- haven't received it yet.

Link:

https://www.aligntrexstore.com/450-M...XX_p_2345.html

PS: does 450 Pro V2 mean either FB or FBL (DFC) ??? My kit's part # is KX015082T) and I thought 450 Pro V2 meant it was only flybarred, however, people could upgrade it using an FBL head. Confused.

Pro v2 was just the v1 with small frame tweaks and a new canopy. The original pro v2, which I have one of, was fbl but not dfc. Then there is the pro dfc which is the pro v2 with a dfc head. The fbl versions have all been discontinued while I believe it is still possible to purchase the flybar version of the pro v2.

[rcflyersd]

It looks like the later silver grip and hub assembly with thrust bearings is the way to go, meanwhile I have another set of Align bearings I can press into place in the grips as we have a small funfly and campout get together this weekend. Parts wouldn't make it here in time. I could reduce the headspeed significantly to lower the stress on the tail grips. Just for this weekend.

I just would like this heli up and running as I have it outfitted with LED's and Night Magic blades for some awesome night flying. Hopefully new tail rotor should be here for the 4th weekend. Flying while fireworks are being launched makes for an awesome show!!

Mark

[CrashNburn420]

The tarot grips with thrust bearings work good. Mine have somewhere around 600+ on them without any issue. Only $12 with shipping.