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 "tcesib" backwards in the box below (case sensitive):

Archive

Show me a random blog post
 2019 

Sep 2019

A non-converging LaTeX document
TMiP 2019 treasure punt

Jul 2019

Big Internet Math-Off stickers 2019

Jun 2019

Proving a conjecture

Apr 2019

Harriss and other spirals

Mar 2019

realhats

Jan 2019

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

Tags

sport chess talking maths in public noughts and crosses game show probability football platonic solids chalkdust magazine accuracy christmas sorting reuleaux polygons propositional calculus mathslogicbot ternary curvature game of life twitter machine learning craft speed go misleading statistics latex books realhats php interpolation bubble bobble dates approximation people maths golden spiral captain scarlet bodmas asteroids light countdown london matt parker chebyshev christmas card triangles binary estimation world cup nine men's morris statistics gerry anderson inline code stickers flexagons harriss spiral puzzles data javascript tmip fractals rugby graph theory draughts final fantasy weather station polynomials folding paper radio 4 python cross stitch oeis pythagoras folding tube maps electromagnetic field braiding logic dragon curves dataset mathsjam national lottery map projections cambridge raspberry pi video games mathsteroids tennis hexapawn manchester science festival sound royal baby plastic ratio european cup reddit big internet math-off coins the aperiodical rhombicuboctahedron pizza cutting error bars trigonometry frobel hats menace geometry arithmetic london underground manchester programming wool news golden ratio palindromes probability a gamut of games pac-man martin gardner games

Archive

Show me a random blog post
▼ show ▼
© Matthew Scroggs 2019