Mechanism for Drawing a Logarithmic Spiral

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This Demonstration shows a mechanism for drawing a logarithmic spiral . A pivot point holds a rod with a sharp wheel at the far end. The axis of the wheel is at an angle
to the rod;
is chosen such that
. As the wheel digs into the plane, it gradually pulls away from the pivot point and traces the spiral.
Contributed by: Izidor Hafner (January 2013)
Open content licensed under CC BY-NC-SA
Snapshots
Details
For , the derivative with respect to
is
. For the angle
between the radius vector to a point
and its tangent, we have
. For the angle
, we have
. (If
, the curve is a circle; as
, the curve tends to the straight line
.)
Reference
[1] A. A. Savelov, Plane Curves (in Croatian), Zagreb: Školska knjiga, 1979 p. 265.
Permanent Citation