Just a little doodle to set me thinking. Even limiting myself to concentric circles for the most part, I kept coming up with possibilities for using Volvelles. I started with the idea of surveying what could be done with a circle and a pivot. Information can be obscured, indicated, or illuminated with a Volvelle. The second circle below could be a changing face. I’m not sure how you illustrate or derive a function with such a thing. But, like I say, “just a little doodle.” Transparent colored circles could illustrate combinations and layered traces could illustrate circuits. The final Volvelle on the bottom right plays with the idea of a spiral around a pivot, that is a turntable. Is the needle on the top or the bottom? Is there a needle guide? Maybe musicians could use them to demonstrate a musical passage. Just run an amplifying stylus through the grooves and you have yourselves a tune.

# Month: August 2014

# The Chuckram Board

StandardThe Chuckrum Board is a lovely device from India used for counting coins.

From *The Land of Charity: A Descriptive Account of Travancore and Its People *by Samuel Mateer:

Chuckrams being so small and globose are exceedingly troublesome to count or handle. They slip out of the fingers and run over the floor, and are only discovered again with difficulty. £1,000 pounds sterling amounts to 28,500 chuckrams, weighing 24 pounds avoirdupois, and hours would be wasted in reckoning this small amount of coins. They are therefore measured, or counted, by means of a “chuckram board” — a small, square, wooden plate with holes the exact size and depth of a chuckram, drilled in regular rows on its surface . . . a small handful of coins is thrown on the board, and it is shaken gently from side to side, so as to cause a single chuckram to fall into each cavity, and the surplus, if any, is swept off the board.

# Sectors

Standard

From the Science Museum:

**Example of how a sector is used**

Suppose you want to divide a line that is six inches long into five equal parts. Measure off six inches with dividers, and open the sector until 5 and 5 on the two linear scales is six inches. By the principle of similar triangles the distance between 1 and 1 on the linear scales is then one fifth of the distance between 5 and 5. Measure the distance 1 to 1 with the dividers and the five equal lengths can then be marked off on the original six inch line.

I wrote an Instructable for the sector. By using the principle of similar triangles, the Pythagorean Theorem, or trigonometric tables, you could play with these babies for hours. The only problem is that dividers get a little stabby. I’m wondering if a bit of graduated wire might be a more useful partner for the sector.

# Volvelles

StandardIf I may muse for a bit, volvelles are a fascinating way to arrange a table. A pivoting table? Wheels within wheels. If you stack two logarithmic number lines, you have a slide rule. Clocks are volvelles with arms instead of discs. There are not only volvelles for calculation, but volvelles for remembering state capitals and volvelles for learning grammar rules.

So many departures on a thing which turns upon itself. You might even wind up with Willie, Freddie, and Flaco.

*Come back, come back to your arms again. I’ll come back to where you are.*

# Whirligig

StandardLast Sunday’s trip to Brighton was a happy one, although it was cloudy for most of the day. Here I am in front of Whirligig Toys, one of a handful of toy vendors who get it. They have the stuff: Kites and gyroscopes and Timberkits and a knitted version of the Brighton Ferris Wheel. Go there; have fun.