Making a motor small enough to pass through the eye of a needle

YouTube description: "In this video, Mike Godfrey attempts to reproduce the famous McLellan electric motor that fits within a 0.4 mm cube."

*Although smaller devices have been made with lithography, the McLellan motor is the smallest handmade electric motor in the world.

Back story from Hackaday:

How small can an electric motor be without resorting to manufacturing methods like lithography? In a recent YouTube video [top], Chronova Engineering tried to replicate the 1960 McLellan motor that fulfilled Richard Feynman's challenge requirements.

This challenge was part of Feynman's legendary 1959 lecture titled There’s Plenty of Room at the Bottom, on the possibilities of miniaturization.

A $1,000 reward was offered to anyone who could build an electric motor that was no larger than 1/64th inch cubed (~0.0625 mm³), with the expectation that new manufacturing methods would be required to manufacture a motor this small.

As reported in the December 1960 issue of The Month at Caltech, William McLellan walked into Feynman's lab with a tiny marvel that took him 2.5 months of lunch hour breaks to build.

Weighing in at 250 micrograms and consisting of 13 parts, it was constructed using a microscope, a watchmaker's lathe, and a toothpick.

Surely replicating this feat would be easy today, right?

The main challenge is that everything is incredibly small.

The rotor shaft is 90 micrometers in diameter, and the four coils require winding incredibly thin wire at scales where typical manufacturing methods do not apply.

Suffice it to say that it takes massive amounts of patience, creativity, and the best stereo microscope you can get, yet even with modern optics and materials this first attempt mostly failed.

At the end we're left with SEM shots of this replication attempt and an immense amount of respect for the skills of William McLellan who made a working version in 1960 using far more basic tools.

[via Natasha Balwit-Cheung]