Nicomedes's Mechanism for Constructing a Conchoid

Set the mechanism, then move!

distance OB

length |AP|

move

show labels

This Demonstration gives Nicomedes's (c. 180 BC) mechanism for constructing a conchoid. The mechanism consists of three rulers. Two are perpendicular; the horizontal one has a slot

s

and the vertical one has a fixed peg at

O

. The third ruler,

PAO

, has a fixed peg at

A

that slides along

s

and a slot that lets it slide along

O

.

You can vary the distance between the points

O

and B and the length

AP

.