[HN Gopher] Pulley system composition - a systematic approach (2...
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Pulley system composition - a systematic approach (2020)
Author : timjver
Score : 39 points
Date : 2024-05-08 12:48 UTC (10 hours ago)
(HTM) web link (www.kiipeilytuomas.fi)
(TXT) w3m dump (www.kiipeilytuomas.fi)
| poszlem wrote:
| 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 wrote:
| Kind of like knots...
| tempnow987 wrote:
| Pulleys and knots can go hand in hand.
|
| With ropes you can start with a basic loop that acts as a
| pulley. Butterfly, wireman's loop, farmers something - I
| forget the names.
|
| But you basically create a loop that let's you double back
| your rope. With a lot of modern rope they are slippery enough
| you get pretty good mechanical advantage. Some folks then go
| to a taught line hitch or something to even keep things
| adjustable basically. Key is usually to give yourself enough
| space to tighten, and I skip the taughtline hitch in most
| cases.
| istjohn wrote:
| They are forgetting that pulleys can be coaxial.
| esafak wrote:
| I was waiting for the mathematical abstraction or software
| analogy; obviously, there's some composition going on.
| araes wrote:
| 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 wrote:
| 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.
| Geee wrote:
| 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
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