New machine unfriendly £1 coin

Vending machines identify coins by measuring their width. Circular coins have the same width in every direction, so designers of vending machines do not need to worry about incorrectly rotated coins causing a blockage or being misidentified. But what about seven-sided 20p and 50p coins?
Perhaps surprisingly, 20p and 50p coins also have a constant width, as show by this video. In fact, the sides of any regular shape with an odd number of sides can be curved to give the shape a constant width.
3, 5, 7 and 9 sided shapes of constant width.
Today, a new 12-sided £1 coin was unveiled. One reason for the number of sides was to make the coin easily identified by touch. However, as only polygons with an odd number of sides can be made into shapes of constant width, this new coin will have a different width when measured corner to corner or side to side. This could lead to vending machines not recognising coins unless a new mechanism is added to correctly align the coin before measuring.
Perhaps an 11-sided or 13-sided design would be a better idea, as this would be easily distinguishable from other coins by touch which being a constant width to allow machines to identify it.

Similar posts

The end of coins of constant width
New machine unfriendly £1 coin, pt. 2
World Cup stickers 2018, pt. 3
World Cup stickers 2018, pt. 2


Comments in green were written by me. Comments in blue were not written by me.
 Add a Comment 

I will only use your email address to reply to your comment (if a reply is needed).

Allowed HTML tags: <br> <a> <small> <b> <i> <s> <sup> <sub> <u> <spoiler> <ul> <ol> <li>
To prove you are not a spam bot, please type "e" then "q" then "u" then "a" then "t" then "i" then "o" then "n" in the box below (case sensitive):


Show me a random blog post

May 2020

A surprising fact about quadrilaterals
Interesting tautologies

Mar 2020

Log-scaled axes

Feb 2020

PhD thesis, chapter ∞
PhD thesis, chapter 5
PhD thesis, chapter 4
PhD thesis, chapter 3
Inverting a matrix
PhD thesis, chapter 2

Jan 2020

PhD thesis, chapter 1
Gaussian elimination
Matrix multiplication
Christmas (2019) is over
▼ show ▼
▼ show ▼
▼ show ▼
▼ show ▼
▼ show ▼
▼ show ▼
▼ show ▼
▼ show ▼


golden spiral wool the aperiodical bubble bobble tennis dates mathsteroids matt parker european cup game show probability games christmas card asteroids a gamut of games weather station finite element method folding paper inline code royal baby signorini conditions nine men's morris twitter dataset sound plastic ratio sport propositional calculus interpolation realhats javascript logic matrices football arithmetic craft programming exponential growth folding tube maps speed books php wave scattering noughts and crosses royal institution ucl radio 4 menace rugby data manchester science festival rhombicuboctahedron raspberry pi cambridge chebyshev data visualisation martin gardner pizza cutting accuracy coins chess hats london quadrilaterals matrix of minors squares reddit fractals electromagnetic field computational complexity polynomials pac-man simultaneous equations python ternary geometry palindromes cross stitch mathsjam graphs graph theory captain scarlet chalkdust magazine determinants video games christmas big internet math-off machine learning bempp pythagoras world cup manchester reuleaux polygons london underground latex puzzles logs map projections preconditioning phd matrix multiplication numerical analysis curvature statistics matrix of cofactors tmip flexagons triangles misleading statistics weak imposition inverse matrices final fantasy game of life oeis harriss spiral golden ratio frobel trigonometry people maths news national lottery sobolev spaces mathslogicbot gaussian elimination advent calendar light convergence hexapawn draughts hannah fry braiding bodmas gerry anderson platonic solids error bars geogebra boundary element methods binary talking maths in public probability countdown dragon curves go estimation stickers sorting approximation


Show me a random blog post
▼ show ▼
© Matthew Scroggs 2012–2020