When would you give up? Prototype 15, when performance still isn't matching calculations? Prototype 2,567, when the time you've spent precisely adding 140 air inlets proves wasted (one works just as well)? Or prototype 4,774, which has just swallowed the last of this month's income?
In the five years it took to develop the world's first bagless vacuum, there were many low points. Some that pushed James Dyson's belief in his idea to its very limit. But after each failure, he picked himself up and started again. Carrying on until he achieved success. (Prototype 5,127, as it turned out.)
But we've come a long way since then.
Today, the process from initial idea to finished Dyson machine encompasses multiple RDD locations in the UK and South East Asia. Thousands of engineers instead of one man. State-of-the-art prototyping equipment instead of cardboard and duct tape. And acres of engineering laboratories instead of a backyard coach house.
What hasn't changed is the standard of performance we expect from our technology. And the risk-taking entrepreneurial spirit that drives its inception and development.
At the heart of Dyson's current engineering projects is the same resilience and perfectionism that drove the development of our very first machine.
But now, you'll find it being applied at a speed and on a scale unrecognisable from the day James completed his 5,127th prototype.