motor pinion is slipping...I think.

[ChrisRain]

hey guys, ive been flying my Gaui 425 for about 6 months now and its been doing great, i recently have been starting to do more advanced stuff and i upped the headspeed, after upping the headspeed everything was fine for a couple weeks, but the other day when i switched into idle up the motor pinion slipped, walked its way up the shaft and i had to auto-rotate down. I took out the grub screws holding the pinion in, DROWNED them in locktite, and put them back in, very next flight...same thing.

I tried it again by tightening the grub screws back up and putting locktite, and it flew great for two flights. However again on the third flight the motor slipped and i had to auto-down again.

this time i decided to get two NEW grub screws and i put some retaining compound on motor's shaft and the pinion, and then i put the new grub screws in with plenty of locktite, it flew good after that for a single flight, however i just went out to fly and again, when i switched into idle up the motor pinion slipped...again. D:

HOWEVER whats interesting, the last two times its slipped, it only slips for an instant, and then it grabs back on and its fine....until i give a large collective input, it then slips again.

so my question to you guys is, what can i do to stop the pinion from slipping? OR Do you think that my problem is something else?


any help is greatly appreciated!

Thanks

[papa38]

The solution is to grind a small flat spot where the grub screws sit,with a small file, or a dremel.And give your loctite at least ten hours to cure if you're not.It could also be your one way bearing giving up the ghost.Are there circular marks around the motor shaft from the grub screws from the pinion spinning? If not,I would suspect the one way.

[ChrisRain]

there arent circles from the grub screws dragging across the shaft, however there is a big circular area on the shaft thats been shaved down. I dont remember it being there when i put the motor pinion on the first time so im assuming it happened during all the pinion slipping.

I really dont know what to think right now, the first two times that the pinion slipped it actually walked its way up the shaft, but the past two times its slipped, it stays there and after it slips i check it, and the grub screws are completely tightened and i have to try reeeeally hard to make the thing move.

Im gonna replace the motor shaft, grind two flat spots like you said, and if that doesnt work ill replace the one-way bearing as well.

[PTcaflyer]

...It could be that the pinion is not tapped all the way through and the grub screw could not bite enough...IMHO, new pinion, motor shaft, OWB(20t gear) and intermediate shaft...all while you have it "Opened up"...
PT

[Mikej]

Grind the flats and that should solve your problems in one ...

[Jerrymac]

Could be 3 things, from my experience. Do like these guys suggested, grind a flat spot on the motor pinion shaft. Could be that the OWB is starting to go bad and is not locking up. Also check the grub screws at the top of the OW shaft in the primary gear. There are 2 small 'indents' in the shaft that the grub screws go in to from the primary gear. Sometimes these come loose and let the primary gear spin on the OW shaft.

[ChrisRain]

Thanks everyone for the replies, ill check these things and get back to you.

[Oldmustang]

+1 on the OWB

I just replaced the same on one on my 425's. Good luck if that's it. Mine was seized and I had to split half the frame to get mine off. It did act like a loose pinon and I found the same as you, set screws were always tight so that's what sent me looking for another potential problem

[ChrisRain]

Got the OWB on order. Also got a new motor pinion to see if that was the problem or part of the problem.