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HDK · 05-20-2018, 01:29 PM

Hi guys,

The front bearing that hold the umbrella gear seized up, and the umbrella gear failed on the 28th flight.

Waff · 05-22-2018, 01:33 AM

Ouch! How bad was the damage? Did it seize up mid air, or when you landed?

I think I might go check mine. I'm coming up on 28 flights soon...

Waff

HDK · 05-22-2018, 02:33 AM

Hi Waff,

Yes, please check yours, that's why I am posting here... to help fellow X/XT with torque tube. Maybe put a drop of oil on the front umbrella bearing. Needed blades, spindle, front LG, boom, TT, links. I think this is a light crash.

There isn't any indication that the gear is about to fail (sound/vibration). The umbrella gear wear pattern are the same, front and back (tail case) indicating that the mesh/back-lash is perfect. it was just all of the sudden piro uncontrollably. I was inverted and hit the hold-mode prior to the crash.

I am actually impress with the XT performance so far other than the umbrella gear.

JEEPWORLD2002 · 05-22-2018, 02:34 AM

When you did you build was that gear a little snugg? I just replaced my 500 pro tail tt gears n I had to lathe down that gear with Emory cloth to get bearings on

I hate when tolerances go out the window.

HDK · 05-23-2018, 09:02 PM

Hi JEEP,

The umbrella gear is pre-installed from the combo kit, I did check the mesh and smoothness before installing the whole block to the chasis. Every 5 flights I check on the wear pattern on both front and back umbrella, they look fine to me.

In addition, on the mini-V, I have the stop gain L/R set that it soften the stop/changing direction. The whole setup is govern by Hobbywing 80A, and does a pretty good job.

I do fly the 500XT hard, just like I do with my 700X

DKS_ONE · 05-24-2018, 06:43 PM

Quote:

Originally Posted by HDK

Hi guys,

The front bearing that hold the umbrella gear seized up, and the umbrella gear failed on the 28th flight.

Hey HDK, was just searching anything Trex 500xt related as I just bought a kit. I've got the airframe together now and everything was cake, so nice to build one of these kits again... but the one thing I DID notice was that there seemed to be high spots on the umbrella gears front AND rear when they mesh. So when I would do a full revolution of each of those gear sets (prior to install on tail or airframe) they would rotate and then bind just a bit in the same spot each revolution. I don't see anything stuck in between gear teeth or anything and with my aging eyes I don't see any out of round situations with any of the gears but I dunno how much I trust that. Did you notice anything of that sort with your build? I am just getting back into flying again after a bit of a break and this heli will (hopefully) be as good a rocket as the ESP I build a few years back. I just don't wanna be caught with pants down so to speak haha!

HDK · 05-25-2018, 12:15 AM

Hi DKS,

The gear is done without any machining, so hi spot on the umbrella gear is typical. Sometimes, I had the high spot trimmed of by sanding the particular tooth gingerly, but do keep track the high spot between the 2 umbrellas and this method only works for 1:1 ratio. If the mesh feel snug, the bearing installation is not done properly. A little high spot is tolerable, after several flights, the high spot should wear away.

DKS_ONE · 05-28-2018, 11:48 AM

Quote:

Originally Posted by HDK

Hi DKS,

The gear is done without any machining, so hi spot on the umbrella gear is typical. Sometimes, I had the high spot trimmed of by sanding the particular tooth gingerly, but do keep track the high spot between the 2 umbrellas and this method only works for 1:1 ratio. If the mesh feel snug, the bearing installation is not done properly. A little high spot is tolerable, after several flights, the high spot should wear away.

Excellent, I kind of assumed it would likely wear in but wanted to see if anyone else had experienced any vibes. I spun up with and without tail blades (no mains) and didn't get any notable, could feel a bit but wasn't howling and I think all I'm feeling is pretty norm. We'll see at maiden! 😉

HDK · 09-24-2018, 01:09 AM

To date, I have flown 168 flights on the Trex 500xt, and can safely say that the umbrella gear and bearings are a non issue, granted that the bearings are lubed every 50 flights.

Looking back, very high head speed (and over-speed flying) also contributes to the umbrella bearing failure. I have since dialed the rpm back to just enough to hold the tail on all cases.

The Trex 500xt is seriously fun, and such a pocket rocket that my Goblin 570 is a hangar queen now... Lol

05-20-2018, 01:29 PM	#1 (permalink)
HDK Registered Users Join Date: Sep 2005	500XT - Umbrella Gear Failure Hi guys, The front bearing that hold the umbrella gear seized up, and the umbrella gear failed on the 28th flight. Attached Thumbnails

05-22-2018, 02:34 AM	#4 (permalink)
JEEPWORLD2002 Registered Users Join Date: Jan 2008	When you did you build was that gear a little snugg? I just replaced my 500 pro tail tt gears n I had to lathe down that gear with Emory cloth to get bearings on I hate when tolerances go out the window. __________________ Trex_600n,Trex_500,MR25,MikadoLoGo5003D_KDE,CastleCreations,Ys,JR XG8,Sab Goblin 380/X_Nova/Bk_Servos, JR TagsMini//Sab Goblin 500Pulse Edition, Sab Goblin570Carbon_SABUSA_X_Nova_BkServos_KDE,RJX-Swash,JR-SPG-Tail/TagsMini_JRX-Bus.

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05-22-2018, 01:33 AM	#2 (permalink)
Waff Registered Users Join Date: Dec 2007	Ouch! How bad was the damage? Did it seize up mid air, or when you landed? I think I might go check mine. I'm coming up on 28 flights soon... Waff

05-22-2018, 02:33 AM	#3 (permalink)
HDK Registered Users Thread Starter Join Date: Sep 2005	Hi Waff, Yes, please check yours, that's why I am posting here... to help fellow X/XT with torque tube. Maybe put a drop of oil on the front umbrella bearing. Needed blades, spindle, front LG, boom, TT, links. I think this is a light crash. There isn't any indication that the gear is about to fail (sound/vibration). The umbrella gear wear pattern are the same, front and back (tail case) indicating that the mesh/back-lash is perfect. it was just all of the sudden piro uncontrollably. I was inverted and hit the hold-mode prior to the crash. I am actually impress with the XT performance so far other than the umbrella gear.

05-23-2018, 09:02 PM	#5 (permalink)
HDK Registered Users Thread Starter Join Date: Sep 2005	Hi JEEP, The umbrella gear is pre-installed from the combo kit, I did check the mesh and smoothness before installing the whole block to the chasis. Every 5 flights I check on the wear pattern on both front and back umbrella, they look fine to me. In addition, on the mini-V, I have the stop gain L/R set that it soften the stop/changing direction. The whole setup is govern by Hobbywing 80A, and does a pretty good job. I do fly the 500XT hard, just like I do with my 700X

05-25-2018, 12:15 AM	#7 (permalink)
HDK Registered Users Thread Starter Join Date: Sep 2005	Hi DKS, The gear is done without any machining, so hi spot on the umbrella gear is typical. Sometimes, I had the high spot trimmed of by sanding the particular tooth gingerly, but do keep track the high spot between the 2 umbrellas and this method only works for 1:1 ratio. If the mesh feel snug, the bearing installation is not done properly. A little high spot is tolerable, after several flights, the high spot should wear away.

09-24-2018, 01:09 AM	#9 (permalink)
HDK Registered Users Thread Starter Join Date: Sep 2005	To date, I have flown 168 flights on the Trex 500xt, and can safely say that the umbrella gear and bearings are a non issue, granted that the bearings are lubed every 50 flights. Looking back, very high head speed (and over-speed flying) also contributes to the umbrella bearing failure. I have since dialed the rpm back to just enough to hold the tail on all cases. The Trex 500xt is seriously fun, and such a pocket rocket that my Goblin 570 is a hangar queen now... Lol

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