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> Gary LaPook:
> ... forming tubes of exactly the right size to fit tightly
> enough together to provide enough friction so they maintain
> their alignment but not too tight to prevent easy manipulation.

I did exactly opposite: I started with available tubes and then
printed scales to fit them. The tubes I tried to use were PVC
drain pipe, box of Pringles and box of non-dairy coffee creamer.
I do not recommend Pringles because of fatty residue that
eventually finds its way outside.

As for may comment about keeping scales flat, I did not mean to
be nagative, just try to relay some personal experience. Here is
some more -- for those who will try to make an instrument.
It maybe nitpicking, but the distortions I am talking are visible
to the naked eye.

Another unpleasant finding was that same scales had different
length when printed on regular paper and on the transparency.  I
guess this is related to the fact that medium is being heated and
stretched when rolled into the paper feeding mechanism of laser
printer and paper and transparency, apparently, stretch at
different rates. Inkjet may be better for this kind of work.
The stretch is only present along the long edge of the page (the
direction it is being pulled), so it is better to print both
scales in the same direction.
What's worsens things further, the stretch is not uniform across
the length of the page and does not seem to be consistent from
page to page (although the effect is minimal, while still
noticable).

When stored, transparency with anything printed on it, tends to
stick to whatever

Here are is couple more words of wisdom that I acquired by
lurking into slide rule forum once in a while.

a) Scales do not have to be slanted if you are not going to wrap
them around a cylinder. Strictly horizontal scales look way
better when printed because of absence of pixelation.

b) You do not have to use transparency and may instead use
dividers to transfer distances between scales (in fact, this is
exactly how Gunther scale, the precursor for slide rule, works).
Some care is required when dividers span several steps of
multi-piece scale (as in your case) -- they should span same
number of steps when the distance is transfered to the second
scale.

Trick b) suggests the following development of your method:
instead of Bygrave formulas, we may switch to Ageton formulas.
Since Ageton uses  only sec/csc (which are, essentially, the same
scale) you do not need second scale and can perform sight
reduction by means of a single printed scale and a dividers.

Andrew Nikitin




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