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Pulley system composition – a systematic approach (2020)

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Re: Pulley system composition – a systematic approach (2020)

#11

Post by araes »

aidenn0 wrote: post #9
araes wrote: post #7

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 s…

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.

Cool, thanks. Why I said "appears". Figured I was probably missing something. Author has spent way more time on pulleys.

Re: Pulley system composition – a systematic approach (2020)

#12

Post by quickthrowman »

Geee wrote: post #8

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/w…

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.

Re: Pulley system composition – a systematic approach (2020)

#13

Post by jzwinck »

araes wrote: post #7

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 s…

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.

Re: Pulley system composition – a systematic approach (2020)

#14

Post by raelming »

jzwinck wrote: post #13
araes wrote: post #7

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 s…

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.

Just about every forklift uses a 1/2:1 pulley system in the the chains that lift the fork carriage up the mast. The main lifting pistons push a pulley upwards with chains tied to the fork carriage and mast base routed through the pulley.

Re: Pulley system composition – a systematic approach (2020)

#15

Post by raelming »

quickthrowman wrote: post #12
Geee wrote: post #8

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/w…

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.

Modern chainfalls use one loop of chain to drive a gear reduction which drives a separate load chain. Differential chain hoists with an upper and lower pulley and no gear reduction are found in museums.

Re: Pulley system composition – a systematic approach (2020)

#16

Post by araes »

jzwinck wrote: post #13
araes wrote: post #7

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 s…

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.

Thanks. Figured there might be something, why the "might" have a use.

Maybe it's implied, yet the author didn't seem to care about fast, and mostly appeared to be counting whole numbers for greater lift. Guess most of the furthers probably also have uses if force is not an issue 1/3:1, 1/4:1, ect...

Sailing's not one I'd thought of much. Guess if large scale sailboats ever make it around again, hauling large scale ripstop nylon clipper sails might use a really fast spinnaker halyard.

Re: Pulley system composition – a systematic approach (2020)

#17

Post by araes »

raelming wrote: post #14
jzwinck wrote: post #13

Earlier quoted context omitted.

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.

Just about every forklift uses a 1/2:1 pulley system in the the chains that lift the fork carriage up the mast. The main lifting pistons push a pulley upwards with chains tied to the fork carriage and mast base routed through the pulley.

Maybe I don't understand what you're describing. That sounds like a system where you'd prefer slow, and really heavy lift capacity?

Re: Pulley system composition – a systematic approach (2020)

#18

Post by jzwinck »

araes wrote: post #16
jzwinck wrote: post #13

Earlier quoted context omitted.

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.

Thanks. Figured there might be something, why the "might" have a use. Maybe it's implied, yet the author didn't seem to care about fast, and mostly appeared to be counting whole numbers for greater lift. Guess most of the furthers probably also have uses if force is not an issue 1/3:1, 1/4:1, ect... Sailing's not one I'd thought of much. Guess if large scale sailboats ever make it around again, hauling large scale ri…

Really fast lines are used to drop spinnakers on big boats: https://www.youtube.com/watch?v=MiAo3KQ89no - this uses gears more than pulleys but same idea, light loads and high speed.
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