Pulley system composition – a systematic approach (2020)

[araes]

If the author reads this, since it's from 2020. The author appears to be currently investigating knot physics and drop tests.

However, the author does not "appear" to have the Luff Tackle variation. [1] I think it's close to the 6:1 variation on row two, except with the pulley directly attached to the ceiling.

The systematic approach seems to work, just appears to be missing a few combinations, or it was not really systematic. Such as, their should probably be a lot of pulley combinations that are basically "nothing", or "not helpful" combinations. 1:1, or 1/2:1, ect... combinations that just noted as discarded (or maybe curiosities that "might" have a use)

A 1:1 pulley is not "technically" significant from this perspective, yet it does change the force direction.

[1] https://en.wikipedia.org/wiki/Pulley#Method_of_operation

[aidenn0]

The 4th item in the top row of the first image is the Luff Tackle, using the authors rule that you can invert any combination and subtract one from the advantage; the non-inverted shown in TFA is 1:4 and the luff tackle is inverted and 3:1.

[jzwinck]

1/2:1 is not useless. Sometimes you want to pull a rope quickly and power is not a problem. One real world use of a 1/2:1 pulley system is in high performance sailing dinghies on the spinnaker halyard. You want to be able to hoist it as quickly as possible, before the wind puts pressure on the spinnaker.

[poszlem]

Pulleys are one of those things you never realize you need until you learn about them. Then, you suddenly understand just how useful they can be. Understanding the basics of rope rigging, pulleys, and mechanical advantage has made my life so much easier. Whether it's camping, hanging hammocks and tarps, using a pulley system to pull out tree stumps, securing things to my bike or pickup truck, or carrying a lot of gear at once, all of this becomes much simpler once you grasp the fundamentals of pulleys.

I honeslty think this should be taught in school, not just in physics classes, but as part of some kind of a "Life 101" course.

[esaym]

Kind of like knots...

[Geee]

A differential hoist [0], while not really a pulley system, is a quite interesting simple machine, which can generate infinite mechanical advantage. It has two sprockets which are connected on the same shaft. A chain loops through both of them in opposite directions so that the other wheel is feeding and other is pulling, and the load moves only by the difference of the wheel diameters.

[0] https://en.wikipedia.org/wiki/Differential_pulley

[quickthrowman]

The common/trade name for this is chain fall or chain hoist, and widely used by tradesmen to lift heavy objects when a Lull (material handling forklift) isn’t an option.

[istjohn]

They are forgetting that pulleys can be coaxial.

[esafak]

I was waiting for the mathematical abstraction or software analogy; obviously, there's some composition going on.

[Syzygies]

Yes! Which entry in https://oeis.org (The On-Line Encyclopedia of Integer Sequences) is this?