Divide This!


…says the Italian renaissance astronomer Galileo Galilei to a young student as he demonstrates a pair of proportional dividers. So how do these ingenious scaling devices work? The answer is embedded in the geometry of the sectioning of a circle. Here’s an excerpt from “From Truths to Tools” (shipping now) that presents an intuitive understanding:

Dividers 1

Dividers 2

Dividers 3


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5 Responses to Divide This!

  1. calebjamesplanemaker says:

    This book is awesome. >


  2. holtdoa says:

    This book and the other in the “series” are inspiring me to create a new blog: Isn’t there an app for that?


  3. Craig Regan says:

    Proportional dividers are still used in the pipe organ trade. The ratio between the pipe diameter and pipe length is crucial in developing the pipes timbre. Also the width and hight of the mouth determans the pipes tone (bright, dark, soft, loud, etc.) Proportional dividers can apply the same ratio to pipes of different sizes with out lengthy computations


  4. Glen Walls says:

    Navigators used proportional dividers in the USAF for time speed and distance calculation right off the chart without having to use the circular slide rule to make the same same calculations.


    • davelehardt says:

      I still have mine from my days as a B52 and C130 navigator. That was my go to tool when we had to re-plan in-flight.


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