First Stage Gear Wearing

[HeliFX]

judging by your first photo which was taken on a slight angle.

seem to me the gear is not equally lined between the opening of the carbon side frame.

that gear need to sit exactly in the center as there no room for error.

CF is more durable then that gear so even if you don't see visible wear on the side could be rubbing.

just a guess

[smsodhi]

Originally Posted by jcflyer

In hindsight I remember last time I flew it I though I was hearing a noise while making hard left banking turns, maybe this is when it is rubbing.

Hmmmm could be.

[jcflyer]

A closer look reveils some wear on the bottom as well. I am thinking the pinion is actually too loose and causing this.

[jcflyer]

Originally Posted by HeliFX

judging by your first photo which was taken on a slight angle.

seem to me the gear is not equally lined between the opening of the carbon side frame.

that gear need to sit exactly in the center as there no room for error.

CF is more durable then that gear so even if you don't see visible wear on the side could be rubbing.

just a guess

It was exactly centered the wearing is making look like it is not

[crash at 42]

Jason I wonder if something was wedged between the motor carrier and the gear and as you spooled up it happened all at once? Have you cleaned it off and tried flying again to check for additional wear?
Rich

[jcflyer]

I had my friend at work look at it he is a physisis and he thinks maybe the motor mount is where it is rubbing.

[jcflyer]

Ok here's a thought I was thinking of adding shimms under the tail belt pulley, between it and the bottom bearing. That's where the manual shows to put the two shimms, now if I put shimms there isn't going to push the first stage gear up??? That would be into the area where it is rubbing makes no sense??? Unless because of the slight bit of vertical play the first stage gear is falling down below the top of the pinion and the pinion is wearing the gear away???

[jcflyer]

Ok i took it down and could find no new evidence of anything other than what I showed before. However I have arrived at the conclusion that it has to be riding up and catching on the CF frame. I can not picture this in my mind but there is no other explanation, there was just a slight bit of vertical play. Almost all of the dust was on one side of the heli so as Satnam said it must be under a load when this is happening!!! So new gear on the way and will add more shimming to totally eliminate any vertical play, that should do it. Also gonna try flying at real low HS for a while my other heli's go fast....

[smsodhi]

Jay, change the bearings also just in case.

Also double check the lower bearing block is not twisted slightly, say after a crash.

[jcflyer]

Satnam,
There was no crash and the bearings seem to be fine. Why do you say this?

[smsodhi]

You have never crashed it?
Ok as for the bearings, how many flights on them? As you have stated it may well be happening under load, so bearings may be ok on the bench but under load some axial play may be introduced while doing certain moves. Shimming will not correct this error. I routinely change bearings. Just something I like to do when it is apart for repairs even if they are fine and usually the only one that has some notchyness is the upper main shaft bearing but I change them all anyway.

In my most recent crash I did not notice a bent lower bearing block for the main shaft. When I tried to put it all together it all went in fine but needed some extra shimming. This then made me look further and noticed the damage that I initially missed. I can imaging a slight bit of damage to the lower bearing block may cause problems further up the chain, i.e. the gear.

Just my thoughts Jay. Want to help you if I can.

[jcflyer]

Hey Satnam,
No I have crashed it twice but those were a while back. I normally replace any suspect bearing after a crash, now that you mention it I did not change the lower bearing on the first stage gear shaft after the last crash but; I have a bunch of flight since then before this issue. I changed the top one and the mains but not the bottom D70 one. Maybe I just change them both to be sure... Thanks Satnam

[jcflyer]

Ok I think I may have found the reason for the gear wearing, it seems that I had about 1mm of vertical play between the gear and the tail belt pulley. I am assuming that I did not have it pushed all the way down as far as it could go. While installing the new gear I discovered this play when I went to tighten the grubs screws, I firmed them up before locktite and then checked for play and that's when I found it. Installed new bearings to be sure (Thanks Chuck) I owe you!!! So won't be long before we are back in the air!!!