[ATM] friction, stiction, ball bearings for triangles, assortedmadness

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

Whoa, I'm confused. I think the question I'm wondering about is: how
perfect does floatation have to be? My most elongated upper triangle has
1/2 " edges outside the apices of the support points. this makes it out of
balance by almost 1/4 oz or 1/10" toward it's longest end. Divide that by 3
points and that's 1/12 oz per point. My mirror is resting on 1 inch
diameter pads. That 1/10" off centeredness is well within that 1" pad. Plop
indicates that you can be off by as much as Berry/Kriege's formula and
still get a great cell. And I made each triangle not in a jig or all at
once deliberately so that they would not all be identical, so that any
errors I made in the drilling, shaping, etc, would be different in each
part and hopefully average out. I did make each part to the best of my
ability. 
	Given all the leeway that seems inherent, I don't see that minute errors
in making the cell translate into anything that would effect performance.
How many thousands of Plop, Kriege/Berry, commercial cells are in use
giving stunning visual views, catching light for amazing astrophotos, doing
even more amazing things with CCDs and web cams? The mirror is what's
supposed to be the perfect piece. The cell is only supposed to allow the
mirror to do its job. And not introduce errors of its own. And certainly
most mirror cells seems to be doing that just fine. Even the ones made with
just a drill press and hacksaw. In my case, add an angle grinder. So I'm
not so manly as some. 
	But to have the most equilateral of all your upper support triangles
require 300 grams at one tip to balance???  If that's not a misprint, and
looking at the photo it might not be, that is 2/3s of a pound. That's more
than 10 oz. That's 40 times more than my most unbalanced triangle is
unbalanced. 10 oz is serious pressure. That is not a mirror cell that is
not doing something to the shape of a mirror. I don't see how that can be
due to the fairly standard 1/2" lip around the points. That balance point
has to be in the wrong place or something is binding most horribly. 
	Raphael, maybe you should post your cell specs so someone on the group
who's fluent in Plop can take a look at the numbers. Physically, do each of
your triangles balance reasonably when they are disengaged from other
components of the cell? To the naked eye, does everything look symmetrical
when the cell is assembled? Are any of the joints (or keeper posts - it
looks like you have those, too) binding? Obvious questions I'm sure you've
gone over 3,000 times already, but  this is driving me crazy(ER).
	Jay
	


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