I have a small collection of slide rules, including the British Thornton one that was recommended for my 'A' level maths course 1967 - 1969, but what I have never seen is a circular slide rule.
Presumably this is based on two screwing together components, with a square thread?
the last count?
I have certainly seen one, and I think that my pilot 'Computer' I got when I was learning to fly in the US was one such. See:
Wow and I thought that my 5 was a good collection!
If you mean "circular", then it's just two log scales printed on concentric discs - search for CRP5 for an example ... but I think you mean cylindrical(?)
Indeed I did
1/ The 'Otis King' cylindrical slide rule was about 6-8" long and about 1 1/2" in diameter. The logarithmic scales were 66" long and formed a helix on each of the two cylinders. One cylinder slid inside the other like a telescope. There was a version with a 'log-log' scale for working with powers. I had one in the early 60s but it was stolen. 2/ 'Fullers Patent Calculator' was a similar idea but on a larger scale. In the film. 'The First of the Few', a 1942 British film directed by and starring Leslie Howard as R.J. Mitchel, we see Mitchel using one to do the design calculations for the Spitfire. They were still in use in the lab where I worked in the mid 60s.
Thank-you.
How did you keep track of which turn of the helix you were using if the two helices did not intertwine with each other?
If this thread stimulates anyone elses interest as it has mine then look at:
I'm sure there are hours of "pleasure" to be had - the adopt a slide rule scheme seems a bit quirky :-)
Alan
In article , gareth writes
It's 50+ years ago so I can't recall all the details but I remember a cylindrical 'cursor' which slid over the two cylindrical scales. It had an index mark at each end and I suppose the axial length of the cursor was equal to the axial length of the scales.
You just 'followed' the line as you would on a straight one. After all, if you were multiplying two numbers on a straight one, you wouldn't set up the
1 over the first number on the normal x scales then position your cursor using, say, the x^2 scale, which is essentially what the OP is suggesting.It would seem those wanting to use a cylinder slide rule should understand and master a straight one first.
Those of us 'of a certain age' probably mastered a slide rule in our youth. I used to demonstrate using a slide rule to my pupils, including the younger ones (pre GCSE) to link into the rules of indices and standard notation. The slide rule has been dropped from the syllabus for decades but it is good to challenge pupils with such things.
The abacus can be quite good fun, too.
You cannot resis the snide remark, can you?
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