Is it Better To....

[lperagallo]

OK, so my luck continues to run cold. You are not going to believe it but again another tail issue. This time I lost the tail transmission at the main gear on the Gasser:arggg: The pinion gear set screw came loose and all hell broke loose.:wow2: So the $100.00 question.

There are two holes in the pinion gear. The front one that lines up nicely with the hole in the drive shaft, the other normally is left empty. Now I know you can't put set screws 180 degrees across from each other as they will push against each other and not make a solid connection, but since these two holes are around 90 degrees to each other wouldn't it be a stronger connection if both holes have set screws put in. My assumption is that the additional set screw will give a margin for safety if one set screw comes loose.

I will say that I have been extra careful doing pre and post flights and I know that prior to the fateful take off I did the tail drive connection test. So I must assume that the set screw was just loose enough that when I turned the tail blades and held the head it didn't slip, but under a load and some run time it slipped.:oops:

What do you guys think?

Lou

[forjer]

2 set screws at 90 or less is good.

[rbort]

The ones I fly I add the setscrew there. There is a threaded hole for it, what use is it if there is no screw in that hole? On my Minairs, both screws are used on these holes.

Not sure why on bergens two holes exist, but only 1 screw is used. Sounds like its the same part from some supplier with both threaded holes in it, minair puts two screws there and Bergen puts one.

Maybe Chris can shed some light on this subject, as he may have some other ideas in mind that I'm not aware of.

-=>Raja.

[rkeith2]

I flat spot on both set screw locations and use loctite.

[cbergen]

It's OK to put setscrews in both holes as they are 90 degrees to each other.

I'm at a loss though. If the setscrew is IN the divot, meaning the tip of the setscrew is actually in the hole in the shaft, and secured with loctite, how can it come out?? How can it spin??

Not pointing fingers at Lou, I know he does good preflights and checks his birds religiously, I've seen it.

But this just baffles me.....

[cbergen]

Ron,

How can you flatspot the shaft where the hole is?

[rkeith2]

Chris,

I have a divot on the shaft at both grub screw locations.

[kelly steed]

Make sure set screw is going in the hole,red lock tight,you may have to tapper screw very small amount.
Lou take that heli,do a complete tare down till thiers nothin left but a pile of parts .Get the monkey offf your back.

[lperagallo]

Kelly,

That was done last fall with the exception of the tail pieces. I have now done that. The only thing I didn't do was use red loctite in the tail transmission. That could help with the back out issue.

Chris,

I am puzzled about both tail failures when I do the preflights and the tails are solid. I guess it's just my bad luck. I am now checking everything over and making sure that everything is tight and properly locktiteed.


Lou

[cbergen]

That's whats got me puzzled too.....If it's in the divot, and loctited, how can it come out?

I had a discussion with someone yesterday which brought up a point about installation.

When installing the setscrew into the divot, the other 2 setscrews in that collar need to be loose to allow the one setscrew to "find" the hole and center itself into it. Then go back and loctite and tighten the other 2.

Lets say you drill the divot though the collar, or eyeball lining it up with the hole in the collar, but maybe your slightly off center. The setscrew hits the edge of the hole, NOT going down into it! It feels tight, but it's not fully secure.

Just a thought.

[rkeith2]

Chris,

I think that you are spot on.

The last tail incident I had was due to the gyro coming off the tape and after rebuild I played the one grub into the hole and then marked the shaft with a small bit at the 2nd location. I removed, flatted the spot and then reinstalled with blue on the main and then blue loctite on the secondary; after fully tightening the first.

Ron