Probably the simplest similar adapter would have been a piece of insulation from a chunk of number fourteen copper house-wiring cable. From each foot of wire you could produce about 36 of the 3/8 inch long adapters, and at about 90 cents a foot for the two conductor cable it would have been quite cheap. But those spacers are a more elegant way to do it.
I thought of making a powered propeller hat a few years ago. I wanted the propeller to turn slowly enough to be able to see the blades (2 or 3 revolutions per second or so). I programmed a PIC to PWM the motor, but I found that there were a bunch of things that affected the speed (temperature, humidity, battery voltage...) and since I was trying to run at the hairy edge, it just didn't work very well.
This must be a magic adapter. The ID and OD are the same.
A long time ago I designed a fabricated part. The machinist insisted there was a dimension problem, I of course insisted it was correct. He later came in with a handful of metal shavings.
"Here's your part" I learned my lesson.
As we unveil EE Times’ 2015 Silicon 60 list, journalist & Silicon 60 researcher Peter Clarke hosts a conversation on startups in the electronics industry. Panelists Dan Armbrust (investment firm Silicon Catalyst), Andrew Kau (venture capital firm Walden International), and Stan Boland (successful serial entrepreneur, former CEO of Neul, Icera) join in the live debate.