Re: [ATM] Mirror Cells - Springs vs. Push/Pull

["Tom Krajci" <tom_krajci@tularosa.net>]

>From: "James Lerch" <jlerch1@tampabay.rr.com>

>...here is my latest version of
>the mirror support / collimation method I use on each primary of my 16"
>bino-scope.  (If pointed at the horizon, left would be downward in this
image)

>http://lerch.no-ip.com/atm/Bino_Cell_Sm.jpg  (640*480  @ 108KB)
>http://lerch.no-ip.com/atm/Bino_Cell_Md.jpg (1280*960 @ 370KB)
>http://lerch.no-ip.com/atm/Bino_Cell_Lrg.jpg (2560*1920 @ 1.2MB)

>Collimation of each primary is done from the top side of the OTA by the
three
>large knobs.  As a result of the large separation between collimation
points,
>one full revolution of any knob produces approximately 12 arc minutes of
>tip/tilt adjustment of the primary optical axis.

>Each knob rotates a length of 1/4-20 stainless all thread, which is
threaded
>into the ends of the black 3/4" tubular aluminum cell support.  The ends of
the
>all thread pass thru delrin bushings in the 1-1/4" purple OTA framing,
tension
>is applied by lock nuts to remove longitudinal motion.

Does this mean the length of 1/4-20 all thread that is under tension (and
defining the collimation position) is from the purple frame members to the
black cell members...approximately 10-12 inches?  Does this reduce stiffness
of the collimation screw?

>Two L shaped delrin blocks (on the left of the image), constrain lateral
motion
>of the cell, and also apply lateral pressure on the threaded collimation
rods.
>This pressure causes the threaded rods to work as complaint springs to push
the
>cell back down onto the delrin guide blocks.  In addition the pressure also
>causes the threads between the cell and threaded rod to tightly engage,
removing
>all backlash.

I can see how the two L blocks constrain motion up/down (up/down as seen in
the image), and they constrain motion to the left of the image.  How is cell
motion to the right constrained?

>The 18 point cell is a mix of compliant and mechanical hinges.  Two nylon
10-24
>bolts provide a compliant hinge point between each bar of the cell and the
3/4"
>tubular frame.

Interesting way to make a compliant hinge.

>At each end of each bar is a 1/4" universal socket extension, which
provides the
>mechanical hinges for tip and tilt of the three support points, while
>constraining axial rotation of the support points.   In hind-site, a single
>nylon bolt to replace the 1/4" universal socket extension would have made a
much
>better hinge for the tip and tilt of the three support points.

Could you have made the flotation part of this cell 'lower profile'?  (Does
the higher profile required for the universal socket extension produce any
problems in cell performance?)

Thank you for sharing!

Tom Krajci
Cloudcroft, New Mexico



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