main shaft collar slipping up?

[matthewcornell]

Hi All. I had a crash yesterday on my Protos 500 where it simply dropped out of the sky. I still had servo control so I was thinking ESC or motor, but of course it could be a number of things. But when I started repairs I noticed the main shaft had slipped down, and at first I attributed it to the crash. But today I was test flying and I found that the collar had slipped a few mm, creating play in the main shaft, so I'm wondering if it might have slipped on me yesterday (happened during tic tocks), allowing the belt to slip off the main pulley. My question is whether you've had this happen. Two factors make me suspicious. First, I've been milking the very last of my loctite (242) and I'm thinking that the stuff from the bottom of the barrel has lost its stuff. Second, I use the Greaser to grease my bearings, including main shaft ones, and they leak a little while flying. Maybe some grease worked its way under the collar. Thank you.

[BHChieftain]

I am wondering if when you initially put the collar on if you had it snugged too tight against the bearing. It should not be pushed down too tight (just low enough to remove up/down play). If it were pushed down tight I am wondering if it was rubbing when spinning, heating up, then breaking the loctite bond...

Chief

[matthewcornell]

Originally Posted by BHChieftain

I am wondering if when you initially put the collar on if you had it snugged too tight against the bearing. It should not be pushed down too tight (just low enough to remove up/down play). If it were pushed down tight I am wondering if it was rubbing when spinning, heating up, then breaking the loctite bond...

Chief

Good point, though I'm pretty careful to do exactly as you say - snug but not too tight. Thank you.

[crickr1]

Originally Posted by matthewcornell

Good point, though I'm pretty careful to do exactly as you say - snug but not too tight. Thank you.

If any grease squeezed out top bearing under collar it could have seeped into collar bolt and effected loctite bond or you just simply did not tighten enough? Other option is top bearing not fully seated when you set collar, as you started flying forces set bearing thus leaving gap at collar.