[ATM] Back to original "ball bearing for triangles" thread?

[Jay Kirkland <jaykirk2@compusmart.ab.ca>]

Raphael, I'm sorry, I think I misunderstood your original question. It may
not be that your triangles don't balance, it may be  that your large
triangles exert enough pressure on the collimation bolts that when you turn
the collimation bolts, that twists the triangles out of their position in
their plane. Is that what's happening? - any why you're looking for a
frictionless connection between the triangle and the collimation bolt?
	If so, the very best way to solve this is not to use the pivots of the
three triangles as the collimation points. There was a recent(?) thread on
this group where several people were of the opinion that doing so was not a
good idea for the very reason that this could stress the mirror.
	The legendary TM guru Robert E Cox believed that it was better to both
move the three collimation points further toward the edges of the mirror
and out of the equilateral triangle arrangement into what he called an
"orthogonal" system which he said was preferred by professional opticians.
So if you had a square mirror box the collimation points would move toward
one upper corner and the two bottom corners. Because of the weight of my
mirror and cell, I put a fourth non-collimating  weight-bearing pivot point
at the 4th corner. The orthogonal arrangement means that when you move a
collimation point, the mirror moves up up/down and left/right at right
angles, not diagonally, and the wide stance makes possible a more sensitive
collimation. And the whole mirror cell can become a mechanically stronger,
more stable unit in the process. 
	Mr. Cox did a lengthy article on "better" mirror cells in Telescope Making
magazine. This was one of their later issues, I believe, late 1980s?
	If this was your original concern, I apologize for my confusion. D'oh! And
hope this helps.

	Jay
	
	


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