Tail powertrain help + maingear possible replacement - HeliFreak
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Old 05-04-2012, 07:46 PM   #1
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Join Date: Apr 2012
Location: Berkeley, CA
Default Tail powertrain help + maingear possible replacement

I had my first flight today! I flew my new trex 700 F3C, and ended up landing it sideways and destroying the blades. Upon closer inspection, I noticed that the tail gearbox was really hard to turn. The gears are intact, but I need to know how to loosen them up again. There doesn't seem to be anything wrong with the gears, but somehow, the crash force made the gear mesh very tight.

The maingear doesn't seem to have problems either, but I noticed nylon shreds all over the pinion. I spun the motor and it seemed to run normally. Can I just keep using it? Would the crash somehow weaken the teeth? I have the slant gears 112 tooth and 12 tooth pinion. Thanks for the help.
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Old 05-05-2012, 06:19 AM   #2

Join Date: Jul 2010
Location: From Utah, transferred from u of u to u of washington

I would take the tail case apart and see which gear is binding or if you have a bad bearing. It could be that you somehow were able to get some loctite where it should not be. That is the only way you can really find out.
If this is due to a crash, then you may be replacing the torque tube umbrella gears and auto and main gear. If i saw that I had shreads of plastic on the pinion I would automatically order a new main gear. I would also test your main shaft bearings as well, they usually go out after a crash, and also check the entire head system. sorry for the crash!
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Old 05-05-2012, 11:05 AM   #3
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The umbrella gears can move a bit. Try pushing them back toward the torque tube. As for the shavings, a small amount is normal - particularly when the heli is new. Many users have noticed a small accumulation between the frames adjacent to the pinion. But there should be no identifiable wear on the maingear itself. Chipped or eneven teeth would indicate a problem. Same goes for the pinion which has been reported to fail on very rare occasions.
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