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T-REX 500 › TREX 500XT Umbrella Gear Failure - Bearings
05-20-2018 07:01 PM  85 days agoPost 1
hhart

rrApprentice

San Jose, CA

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Hi All,

Just put together the Align 500XT combo kit. Maidened without any problem and on 15th flight, the flybarless was setup pretty well. On flight #28th, the tail went to pirouette un-controllably while I was inverted, and the XT was crashed in Hold mode.

Upon close inspection post crash, I saw the umbrella head snapped off. When disassembled, it is obvious that the bearings that holding the umbrella gear seized up and the umbrella gear basically heated up and snapped.

Below are the pictures, let me know what you guys think since not much news on the 500 size.

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05-20-2018 08:38 PM  85 days agoPost 2
rcflyerheli

rrKey Veteran

Granbury, TX USA

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If the bearings don't fit exactly into their slotted recession, there will be axial preload on them, and running with the preload will make them get hot.

If they fit correctly, you should not feel any roughness when rotating the umbrella gear and its mating drive gear by hand. As tough as the bearings are to get installed onto the umbrella gear, it is hard to get them perfectly aligned with the slotted area in the case. I am lucky that I was able to get a tool for installing and removing them before the guy who made them passed away. Even using the tool, I still have to fiddle for several tries to get them exact.

Goblin 700, Trex 700DFC, Gaui X7, Logo 690SX, Logo 600SX; Trex 470 Trex 500
Amain Team Rep

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05-20-2018 10:42 PM  85 days agoPost 3
hhart

rrApprentice

San Jose, CA

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The whole assembly come from the kit pre-installed. The bearings fit perfectly on the slotted recess. When I rotate the umbrella gear by hand on the tail case, it is perfectly fine without any pre-load. The gear mesh is also perfect.

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