Here is
view looking down. 5/8” bolts thread
directly into plywood arms on each tube.
Twisting the lower knob moves the left hand tube toward the top or
toward the bottom of picture. Twisting
the left hand knob moves the right hand tube to the left or the right of the
picture. The left hand tube pivots in
the cradle only vertically and the right hand tube pivots in the cradle only
horizontally. The coupler allows each
tube to “work against the other” to achieve desired orientation for image
convergence/fusion.
Here’s
side view showing the bolts passing over each other in the center block. The bolts are threaded about 3” into each arm
on the tubes and provide a very stout coupling with no flexure. Bolts go through 5/8” holes on center block
and are held with self-locking nuts on each side of the center block – the
self-locking nuts are snugged up enough to permit easy rotation but stop end
play, so there is no slop in the adjustment system. The bolts are self threaded into ¼” holes in
arms, backed out, lubricated with candle wax and then threaded back into arms
Note the added ¼” masonite extensions on the tube arms – added to stop tube
flexure as arms didn’t spread forces over a large enough area when originally
installed.
Here’s
images showing left hand tube attachment point in cradle center (opposite
attachment is coincident with center of left hand altitude bearing) and showing
right hand tube lower attachment point (opposite attachment is on top of cradle
directly opposite lower) The pivots are
5/8” bolts threaded into tnuts set in ¾” plywood tube reinforcements and are all
that attach the tubes to the cradle.
There is enough cradle clearance to permit each tube to swing on its
axis several inches – more than the coupler adjustment limits.
This
convergence system was still working smoothly without noticeable wear in my 17
½ “ binocs after 7 years of use.