square hole
Post on 13-Jul-2015
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REULEAUX
The term ‘Reuleaux
triangle’ was derived
from the name Franz
Reuleaux, a 19th-
century German
engineer who did
pioneering work on
ways that machines
translate one type of
motion into another.
REULEAUX TRIANGLE
Shape formed by
the intersection of
three circles of
equal radii, each
of which
intersects the
centres of the
other two.
This shape created by the rotating
Reuleaux is about 99% the size of the
theoretical square it is trying to reproduce.
The difficulty lies in reproducing the path
that the centroid of the Reuleaux triangle
travels. It can be closely approximated by
a super-ellipse |X|^r+|Y|^r= a^r.
Reuleaux’s position in a
square
The triangle is
normally tangent to
two sides of the
square with two
vertices touching the
square directly
opposite the points of
tangency (why?), as
in Figure 4a.
The exception is
Figure 4b, where the
Reuleaux triangle has
one point of tangency
and all three vertices
on the square (one
directly opposite that
Actual drill for cutting square
holes
The actual drill bit
for the square is a
Reuleaux triangle
made concave in
three spots to allow
for unobstructed
corner-cutting and
the discharge of
shavings
Other aspects Because all diameters are the same length, the Reuleaux
triangle, with all other curves of constant width, is an answer
to the question "Other than a circle, what shape can you
make a manhole cover so that it cannot fall down through
the hole?“
Several pencils are manufactured in this shape, rather than
the more traditional round or hexagonal barrels. They are
usually promoted as being more comfortable or
encouraging proper grip, as well as being less likely to roll
off tables.
A Reuleaux triangle can roll but makes a poor wheel
because it does not roll about a fixed center of rotation. An
object on top of rollers with cross-sections that were
Reuleaux triangles would roll smoothly and flatly, but an
axle attached to Reuleaux triangle wheels would bounce up
and down three times per revolution
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