Re: REFLECTOR: Bearing AD

[jpr@ix.netcom.com]

As a matter of fact, I'm just putting in the rear bearing bracket in a
few days, and discovered that I, too, have the countersunk screws. 
Looks to me like it would make the perfect ramp for the bearing to ride
over and past the retaining lip.

My front bearing bracket has the round-head screws which look like
they'd work much better - except that one of them is canted off to the
side (so was one of the rear screws too).  I know there isn't much
likelihood of vibration causing it to tilt any further, but it just
doesn't look right to me.  As a matter of fact, there's a picture of it
in Wicks catalog labeled "Wrong" (page 182).  Are yours like that? 
Looking in AC43.13-1A/2A I don't see any mention of it/against it, but
it just doesn't "look right".

Your idea of 7/8" washers under each screw is probably better, but it
still doesn't "look right" to me, and there would still be some side
load.  

The only thing I can think of that wouldn't put any side load in the
retaining screws would be some kind of retaining collar.  Should be easy
to make one out of a scrap piece of 3/16 or 1/4 aluminum..  has anyone
else done that?

Think I'll see about whipping something up like that tomorrow.  If I
can't get milling bits big enough, I think I'd just use a 2.25"OD/1.5"ID
washer (or fabricate one) by 1/16" thick to provide a surface for the
screw equal to the level of the bearing lip, and another washer with the
same OD and thickness but with an ID of 1"  to actually do the
retaining.  After it's mounted I can grind away the excess on top. (If I
really wanted to go overboard, make the second part 1/8" thick and add a
third washer with an ID of 3/4" to retain the inner race in case it
fails - but I don't really think that's necessary)

I was just reminded that milling bits that big are pretty expensive - so
I'll probably just describe what I want to a local machine shop and have
them do it for 10 bucks or so!

-john r.


Peter Beaty wrote:
> 
> I took a peek at the bearing situation in my RG-E.  The forward bearing was
> secured very nicely with two AN screws and nuts as described in the AD.
> There was good overlap of the flat screw-head surface onto the outer race
> of the bearing.  Being a conservative type, however, I installed a 7/8-in.
> OD flat washer under each screw head, as shown by Dave Black in VV.  I even
> put a dab of Locktite on the threads.
> 
> I also looked at the aft end bearing, and what I saw bothered me.  This
> bearing was held in with countersink type screws, and the edge of each
> screw head barely overlapped the bearing outer race.  I can believe that
> this arrangement would not hold up if subjected to axial force; the thin
> edge on the head of the screw would only need to deform a little bit before
> the bearing could be pushed out.  Fortunately, the aft bearing is not
> retaining axial load, as is the forward bearing.  However, I replaced the
> countersink-head screws with the recommended AN screws anyway, along with
> flat washers.