Ideas are funny things, aren’t they? Where do they come from? Do they just pop into the mind from nowhere, or are they some kind of inspired thought-association or mental joining of dots? Legend tells us that the idea for the force of gravity came to Isaac Newton as he chilled out under an apple tree during lockdown (plague, not Covid). But how exactly in 1898 did one Elmer Ambrose Sperry come up with the idea for the disc brake?
It’s unlikely he was inspired by the brake technology of the horse-drawn wagons or even the steam-trains of his day – both of those used simple external brake blocks, rubbing on the outer surface of their large-diameter wheels. Bicycles at the time used similar technology – the cantilever or side-pull bicycle brake was still far in the future.
