mscroggs.co.uk
mscroggs.co.uk

subscribe

Blog

New machine unfriendly £1 coin

 2014-03-19 
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

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 "jump" in the box below (case sensitive):

Archive

Show me a random blog post
 2021 

Jan 2021

Christmas (2020) is over
 2020 
▼ show ▼
 2019 
▼ show ▼
 2018 
▼ show ▼
 2017 
▼ show ▼
 2016 
▼ show ▼
 2015 
▼ show ▼
 2014 
▼ show ▼
 2013 
▼ show ▼
 2012 
▼ show ▼

Tags

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

Archive

Show me a random blog post
▼ show ▼
© Matthew Scroggs 2012–2021