Don't cut the pieces out of a hollow cylinder. Cut them out of a solid cylinder. I bet George Hart can just print out the pieces for you. (Is George on this list? He should be. His daughter Vi, too.) On 8/31/12, Robert Munafo <mrob27@gmail.com> wrote:
On 8/30/12, Warren Smith <warren.wds@gmail.com> wrote:
It seems to me (fulfilling my role as Great Improver of obsolete past technologies) that the most compact way to make a high precision slide rule would be helical. Circular? Linear? Garbage.
There are the Fullers ( http://www.utsic.org/2010/11/fullers-spiral-slide-rule-more-than.html ) and Otis King ( http://retrocalculators.com/otis-king.htm ) designs but they require cursors. I've always imagined something different:
Start with a hollow cylinder (like a cardboard tube as used to ship a rolled-up blueprint) and cut it into a double helix, then place a C scale on one helix and a D scale on the other. (There are 2 available edges so you could actually have a total of 4 scales.) To operate, one helix would rotate with respect to the other.
The trouble is, it's a bit of a challenge to enforce the constant diameter of the helices. If you just apply a bit of twisting force on one end of a helix, any resistance will tend to just make the helix curl up (or uncurl) a bit.
So the C scale would need to be glued to a smaller concentric cylinder that is inside it, while the D scale would need to be glued to a larger concentric cylinder, which of course needs to be transparent. To keep things aligned one needs tight tolerances so everything fits snugly.
The worst challenge is probably getting the scales printed and mounted accurately on the scale surfaces. I almost think it would require a machine-driven lathe.
-- Robert Munafo -- mrob.com Follow me at: gplus.to/mrob - fb.com/mrob27 - twitter.com/mrob_27 - mrob27.wordpress.com - youtube.com/user/mrob143 - rilybot.blogspot.com
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