https://en.wikipedia.org/wiki/Leibniz_wheel

I can't help myself and have to link some of my favorite youtube channels.

Engineerguy: https://youtube.com/@engineerguyvideo

Chris Staecker: https://youtube.com/@ChrisStaecker

I think the Japanese really mastered the pencil, though others have done their own wonders. I sometimes consider the work and design iterations behind the best designs and really admire it. Some designs are astonishingly sophisticated, with mechanical 'sensors' and more. I prefer the sweet spot of simplicity and reliability though, which I find in the Pentel.

The mechanical pencil is a modern magic wand for me.

Note: in a time of what I consider anomie and war on quality, I am pleased to have witnessed Pentel really standing behind their products. They repaired or replaced two pencils without fuss, and one rep even compiled and mailed a brochure of pens and pencils exclusive to my preferences.

As for pens, however, I am a Fisher Space Pen zealot, and push them upon all who do not defend themselves. But I do recommend the fine cartridge over the menacingly rotund default, which you can request with each pen order.

The description above comes from the following post on mastodon: https://merveilles.town/@rek/116658587354593919

I dropped in a suggestion to do one on an umbrella. There's a lot going on in these. One can study the differential geometry of surfaces. The mechanism design of opening and closing.

I find both the spring ones (push button) and the ones without spring quite fascinating. In fact the ones without a spring has implicit ones imposed by the bending of the spokes.

"What one man can invent, another can discover" -- Sherlock Holmes in The Adventure of the Dancing Men.

Apparently, Japan reigns supreme in the manufacture of mechanical pencil components w/ brands such as Rotring and Skilcraft importing, or contracting to Japanese companies either for manufacture (my Rotring Quattro is labeled as Made in Japan), or parts sourcing (my Skilcraft B3 Aviator multi-pen was noted as including mechanical pencil components imported from Japan).

One of my favourite mechanical pencils is a "357" imported from Japan which uses a Rotring-like gravity mechanism to select a 0.3mm, 0.5mm, or 0.7mm lead.

Wasn't always so --- I can still remember playing w/ a Norma 4-colour mechanical pencil my father had (which sadly wasn't among his effects when he passed --- just ordered a replacement off eBay...) Unfortunately, the page on this at: http://www.roger-russell.com/ is off-line.