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 Boxes for Transporting the Mirrors

I needed two boxes to hold the primary and secondary mirrors during flights.  The magnitude of the whole  project was driven by the airline rules regarding carryon luggage limiting the size to 9x13x23 inches, thus defining 12.5 inches as the largest diameter mirror that can be carried on, assuming you make a box of 1/4" plywood that fits snugly against the sides of the mirror.

Thus, I made a box 13" square  (o.d.) out of 1/4" baltic birch (right) for the primary mirror.  I had hastily made a small box to hold my secondary (left) out of ordinary 1/4" ply intending to make a better box later.  This one worked so well, I used it anyway even though it is ugly.
 
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The box for the secondary mirror has a top that velcroes closed and is shown close-up in
the image at the bottom.

The box for the primary was conceptually interesting to design and construct.  It had to
fit snugly to the edges of the mirror which made it impossible to build a box that you could
reach into and lift out the mirror (it weighs 20 pounds and I can't get my hands into the box
well.  The solution turned out to be a box in which both the top and the bottom are
removable.  Thus, following removal of the top and the bolts that hold the bottom, the
sides then just lift off the mirror.  The sides are 2 1/8" high so there is 1/8" clearance
between the top of the mirror and the top of the box. To prevent the mirror from rattling
around during transport, I designed a gentle, but firm, capture method shown here that
uses rubber stoppers pushing on four sides of the mirror to immobilize it.  
This is shown in greater detail in the next image.

The sides of the box are 13"x2 1/8" (o.d.) and are formed into a square and the corners strengthened by gluing and screwing in triangles of 3/4" baltic birch that are 2 1/8" high.   The 3/4" ply was made by gluing 1/2" and 1/4" together.  Into the top and bottom of each of the four corner trianges was put a brass threaded insert (the top one is seen here near the X). These inserts allow the top and bottom of the box to be bolted onto the sides.  To hold the mirror in place firmly, a 1/4-20 tee nut was put into the face (hypotenuse) of the triangle as seen here.  Into that tee nut was screwed a piece of 1/4-20 threaded rod.  On the rod (from upper left to lower right) was  (1) a lock washer, (2) a nut, (3) a 1/4-20 lock nut (not seen) recessed into a dug out portion of the back of the  (4) #5 one-hole rubber stopper.  The hole in the rubber stopper turned out to be the perfect size as the 1/4-20 rod screwed firmly into it.  The end of the rod is about 1/2" from the end of the rubber stopper.  Thus, metal never contacts the mirror.

To tighten the rubber stoppers firmly against the mirror you simply turn them (unscrewing the 1/4-20 rod) till they are finger tight (hard) against the mirror. To ensure that nothing loosens during transport, the nut is backed tightly against the lock washer as seen above.  The box carries nicely onto the plane and stows in the overhead compartment.  I put it in a canvas shoulder bag to make it easier to carry.

The secondary mirror, glued  (silicone) onto the holder designed and built by Gary Wolanski, goes through a hole drilled into the 3/4"-thick piece of poplar and, to ensure that it doesn't come out during transport, a #8 thumb screw holds it tightly in place.  The thumb screw is threaded into a brass threaded insert placed in the edge of the poplar.

This box, with mirror inside, was in my suitcase to Australia.   It travelled well, with the mirror staying in place.

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