Straight Business

In 2014 I described the Peaucellier–Lipkin linkage, a mechanism that transforms a rotary motion into a perfect straight-line motion:

https://commons.wikimedia.org/wiki/File:Peaucellier_linkage_animation.gif
Image: Wikimedia Commons

That linkage was invented in 1864 by French army engineer Charles-Nicolas Peaucellier. A decade later, Harry Hart invented two more. “Hart’s inversor” is a six-bar linkage — links of the same color are the same length. The fixed point on the left is at the midpoint of the red link, and the “input” and “output” are at the midpoints of the two blue links:

https://commons.wikimedia.org/wiki/File:Hart%27s_Inversor.gif
Image: Wikimedia Commons

In “Hart’s A-frame,” the short links are half the length of the long ones, and the center link is a quarter of the way down the long links:

https://commons.wikimedia.org/wiki/File:Hart%27s_A-frame.gif
Image: Wikimedia Commons

Pleasingly, the motion perpendicularly bisects a fixed link across the bottom, which is the same length as the long links.

Please Help!

I spend hundreds of hours each month researching and writing Futility Closet, and that effort is supported entirely by the readers. If you value this site, please consider making a contribution to help keep it going.

You can make a one-time donation on our Support Us page, or you can pledge a monthly contribution on Patreon to receive bonus posts and other rewards — you choose the amount to contribute, and you can change or cancel it at any time.

Thanks for reading, and thanks for your support!

Please Help!

This website takes many hours to research and write, and it’s supported entirely by its readers. If you value Futility Closet, please consider making a contribution to help keep it going.

You can make a one-time donation on our Support Us page, or you can pledge a monthly contribution to receive bonus posts and other rewards.

Thanks for your support, and happy new year!

Greg

Books

FC book covers

Just a reminder — Futility Closet books make great gifts for people who are impossible to buy gifts for. Both contain hundreds of hand-picked favorites from our 12-year archive of curiosities. Some reviews:

“A wild, wonderful, and educational romp through history, science, zany patents, math puzzles, wonderful words (like boanthropy, hallelujatic, and andabatarian), the Devil’s Game, self-contradicting words, and so much more. Buy this book and feed your mind!” — Clifford A. Pickover, author of The Mathematics Devotional

“Futility Closet delivers concentrated doses of weird, wonderful, brain-stimulating ideas and anecdotes, curated mainly from forgotten old books. I’m hooked — there’s nothing quite like it!” — Mark Frauenfelder, founder, Boing Boing

“Meant to be read in pieces, but impossible to put down.” — Gary Antonick, editor, New York Times Numberplay blog

“Futility Closet is a dusty museum back room where one can spend minutes or hours among seldom-seen curiosities, and feel that none of the time was wasted.” — Alan Bellows, DamnInteresting.com

Both books are available now on Amazon. Thanks for your support!