Parabola Marker
T
HIS DEVICE,WHICH TRACESa portion of a parabola, is a simplified
version of one developed by Terry Soper of Lockheed Engineer-
ing and Management Services Co. and published in the NASA Tech
Briefs. It’s just as useful for laying out parabolic shapes for boat or fur-
niture construction as it is for designing parabolic antennae.
The marker consists of just a few parts: two tracks, a sliding car-
riage, and a piece of nylon cord. For small parabolas, I recommend
maple splints about^3 ⁄ 8 in. thick and 1 in. wide for the wooden parts.
Make the carriage by screwing together four pieces of wood into a
simple lapped frame, as shown in the sketch.You want both tracks to
CHAPTER SIXY axisX axisVertexNylon cordFocusOriginBridgeSliding carriageParabola follows curve:
Y = (X^2 /4f) - a
Where:
a = distance from origin to
vertex.
f = distance between focus
and vertex.
fa