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SurfCity
08-25-2011, 01:46 AM
Tonight I'm up about 15 feet up, working on slow, small circles, when I hear a strange grinding noise; the heli begins to lose altitude and at three feet loses all power to the rotor and drops to the ground. No damage, except the main gear is stripped nearly smooth, and white plastic dust is everywhere!

Motor runs fine. Belt tension is fine. Gear mesh had been fine. I disassemble things and discover that both top and bottom main bearings are shot; they turn like they're full of sand and basically froze, so the pinion ground down the main gear. I replace the main gear, replace the bearings, and all is well.

Question is, what might have caused this? As far as I know, those bearings were fine. A few weeks ago I bought some Scorpion motor lube, and after lubing the motor I put a drop in each main bearing. The lube is made specifically for Scorpion motors, so could it have attacked the main bearing? Seems impossible.

Anyone have a clue?

Inverse
08-25-2011, 10:21 PM
Do you fly in a sandy/gritty/dusty environment?

akshaw
08-26-2011, 02:41 AM
Sounds to me like the lube somehow gummed up the bearings.

SurfCity
08-26-2011, 10:06 AM
Do you fly in a sandy/gritty/dusty environment?

No I don't. The bearings had hundreds of flights on them and were just fine until after I applied the lube. I posted this question on the main forum, and Finless told me that oil will flush out the grease, and once you start oiling you have to do it regularly or the bearings will go dry. He said that main bearings should not have to be oiled.

Inverse
08-27-2011, 12:23 AM
To be honest I usually tri-flo my mains and tails every 5 or so flights.

akshaw
08-27-2011, 06:24 AM
What's the rational behind applying lube to bearings? Aren't they already sealed with some sort of lubricant inside??? I've never lubed bearings and never had any issues with them.

Inverse
08-27-2011, 06:26 AM
They aren't sealed but they do have shields on the races.
You still need to replenish the lubricant in them.

akshaw
08-27-2011, 07:00 AM
Hmm. I have a scorpion on my beam that has hundreds of flights, have never done anything with the bearings, motor or main, and it's performance hasn't changed. I haven't flown my beam for some time, but flying it yesterday my friend and I were shocked at how fast the climbout was!

SurfCity
08-27-2011, 12:25 PM
Hmm. I have a scorpion on my beam that has hundreds of flights, have never done anything with the bearings, motor or main, and its performance hasn't changed.

This is my experience exactly and corresponds to what Finless said. My Beam had hundreds of flights with zero bearing issues until after I applied the oil. Finless says don't oil them unless you plan to do it regularly. They CAN be repacked with grease, but that's a different issue.

dk31
08-29-2011, 03:06 PM
I don't think that the oil itself would cause that much trouble. Maybe it attracted something such as dust and made the bearing go wrong.
Another thing i would check, is if the motor sits tight on its mount. If not, that could shave off the main gear teeth, create the grinding noise and drop your heli. If that's the case, the bearings have nothing to do with the damage; they just got stuck AFTER the incident, by the plastic "cloud" of the grinded gear. It has happened to me, but bearings survived as they weren't oiled.