5 to 1 fiddleblock set

Wow, very powerfull stuff! And, the implications about the forces inside the tight, hidden bights of a knot as a microcosm of a rig are immediately evident.

i kinda disagree; or am sure i'm reading the meaning wrong here:

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A rope going over a pulley has no external friction,
but it does have internal friction.

[/ QUOTE ]

For, of course; it is the friction that turns the sheave??


i think 1 important point is bourne out; is that there is energy conservation/ no loss-no gain only conversion. So the forces seem infinite; but at the same confined and reduced, there is no perpetual motion machine; for at each point of conversion, the forces must break into the yin and yang of efficiency and loss; so that other things can be birthed in this world. This law prevails so much; that even our gasoline; is from fossil fuels-just the energy left over from millions of years ago; as all that is left of those life forms is this murky goop!

i think it helps to look at distance as a force; and it is this distance force X the power; that gives the work force. So that 5' of pull X 100# gives 500'#s of work force. Placed thru a "converter" of a gearshift on a 10 speed bike, a prybar/lever or rolling levers of our pulley systems; we can get 1' of distance force X 500# of power as an output from our input; but this still equals the original 500'#s of work force <u>potential</u>; then less the inefficiencies of loss/friction conversions to heat force(but still all forces equal the original work force, some are just now heat and not mechanical force). All energy comes from the Sun; and this trickle of heat escaping is just some heat energy released back to the atmosphere.

So, we can't assume that we have just 1 input pull, and just count the pulls on load. We could contrive a system that had 3 pulls on load, but we pulled from a pulley to get 3:2 or 1 1/2x power @2/3speed of the load to our input(the reciprocal of the power). Thus, we might also might also invert a 2:1, to have 1 pull on load, and pull from the pulley with a truck. If the run was 50' for the truck and we needed a 100' pull on the load; and had power to spare. Very good for pulling brush out of a back yard or even up a grade; with little sound ground for truck! But, we'd have to remember; we'd only have half power of the truck pull on the load (the other half going to anchor). We'd also have to be carefull, because the load would be 'flying' 2x as fast as the truck; and it would be easy to hurt someone, or tear something else up!
 
[ QUOTE ]
...implications about the forces... microcosm... important point is bourne out... energy conservation... forces seem infinite... perpetual motion machine... yin and yang...murky goop...

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TreeSpyder, you kill me!
Every time I see your avatar I make the obviously incorrect mental association that you're just a mustachioed, muscled tree rat. Then I wonder from where your extremely detailed, technical and (usually) correct analyses come!
 
[ QUOTE ]

i kinda disagree; or am sure i'm reading the meaning wrong here:

[ QUOTE ]
A rope going over a pulley has no external friction,
but it does have internal friction.

[/ QUOTE ]

For, of course; it is the friction that turns the sheave??


[/ QUOTE ]
In my Cavers Digest message I was discussing sliding friction with rappel devices.

Thinking about mechanical advantage, it occurred to me that the theoretical or nominal MA is never achieved. There may be losses with bearing friction. Even with perfect frictionless bearings there will be internal friction in the rope. I searched for numbers on pulley efficiency. Only CMI gives any numbers and they do not say how they got their numbers. The efficiency should vary with the kind of rope used.

If the 10:1 block and tackle shown in this thread has sheaves that are 90% efficient then the tenth line will have only 35% of the haul line tension and the attachment on the running block would have 5.8 times the haul line tension.
 
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Y'all know that BobT and TheTreeSpyder are outta control. Who is taking bets they have an engineering background?

[/ QUOTE ]
My degree was in physics. I did a lot of engineering that does not fit neatly into a standard category. My hobby is caving. I do not have the strength to climb into trees like you guys do.

I lurk here because of an interest in friction hitches. I wrote a long article on techniques for ascending a rope in 1967 that was expanded into a thin book in 1973. The techniques were invented by mountaineers and later taken up by cavers. The action in developing friction hitches has shifted to arborists now.
 
i hail more from philosophy; no physics or engineering; but not a great fear of math neither. So; as i face the largest creatures ever on the planet; and their forces; i just do as any other amongst us could. i always and all ways ask things like Why?, What could be maximum?; What are the commonalities that could be distilled out and carried as properties/building blocks to other things? etc. That and inter-actions at places like this; with sum of ye going back to the first ISA bored has brought me to wherever i am now.

The Law of the Equal and Opposite Reactions plainly states that we are all so lucky; to be able to rise to this work(that is like no other), and have it to sharpen our talons on. Truly, truly it gives an education and forging of a person like few other things; if'n ya let it.

i do have a small 100 page sight; MTL
 
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i hail more from philosophy;

[/ QUOTE ]


Now it all clicks into place....


cool.gif
 
i kinda am quick to quip though; that at the base, the first philosophers were the first physicists/engineers(?). That it was more all one body of knowledge, of the power of forces on the same planet, under the same conditions.

The electricians + and -; the biologists male/female; the philosophers yin/yang are in many ways like the mechancials of equal and opposite. All seeking balance and needing it's matching to have power. All move to seek their opposite and be satiated in balance/the world is in balance of forces; because if something isn't in balance it moves until it meets it's matching.... So, fer me the study of this thing we due; like no other, with such raw and power-full forces; has lent insight into many things. And is more fun to study 85' up cooking your brains; busting your butt; viewing it all as a romance and dance of forces ye usher...

Orrrrrrrr sum-thing like'dat!
(translation: i guess i'll stop (t)hear!)
-KC

[ QUOTE ]
"Nature to be commanded; must be obeyed"
-Sir Francis Bacon

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