From: "Jim Miller" 
To: "ATM" ,
        "atm_free" 
Reply-To: "Jim Miller" 


I thought others might benefit from my experience.

My scope uses 3/4" ID carbon fiber (CF) truss poles. You can see it at
http://www.jtmiller.com. The wall thickness of the CF is 0.030" making
the OD about 0.81".

The way I attached the poles to the aluminum collars may be of interest to
others. I made end collars from 1" diameter 0.049" wall 6061-T6
tubing cut to about 2.5" long. The collars were fitted on one end with
the usual threaded inserts to accept 1/4-20 bolts. In order to center the
tubing on the 3/4" ID poles I wrapped the end of the pole carefully
with 3/4" scotch tape allowing only 1/4" of the tape to be on the
pole. I added wraps of tape until the collars just slip fit onto the pole.
I then cut off the cylindrical piece of tape hanging off the pole and cut
the cylinder just removed into three strips which I placed about 1" up
the pole from the remaining circular scotch tape spacer. The three strips
were placed 120 degrees apart. This arrangement now gave me a spacer at the
bottom of the pole and three same sized spacers further up the pole to
ensure the collars were supported at both ends and therefore aligned with
the poles.

I roughed up the surface of the CF poles and the interior of the collars
with some fine sandpaper and then wrapped each with masking tape to keep
the epoxy from drooling on the pole and collar surfaces where it didn't
belong. I then just barely slipped the collars in place past the circular
spacer on the end and generously coated the pole between the circular
spacer and the three other spacers with five minute epoxy. I then shoved
the pole all the way into the collar down to the threaded insert twisting
as I went to ensure good coverage. The circular collar on the end prevented
the epoxy from fouling the threaded insert.

I then stood the poles vertically on the collar for about 15 minutes and
then removed the masking tape. I let the epoxy cure over night. They look
and function great!

The result is an excellent mechanical connection without the need for
expensive machining. Hope this helps someone else!

Jim Miller

--- BBBS/NT v4.00 MP