ATM Carbon Fiber Pole End Attachment

["Jim Miller" <jim@jtmiller.com>]

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