Author Topic: Playing with forces  (Read 7093 times)

TheTreeSpyder

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Playing with forces
« on: July 25, 2011, 12:52:04 AM »
To understand rigging and climbing on rope, i think it is best to understand the forces in rope. Also, the same science will hold true within the microcosm of a knot, commanding it's properties.

To live on rope, dependent on it for support, rigging , pulling, knotting, tie down etc. all day, everyday; one needs to understand and obey it rules to command it!



TheTreeSpyder

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Re: Playing with forces
« Reply #1 on: July 28, 2011, 10:50:48 PM »
This shows using a  3:1 rig; but only 100# effort  for 850# pull; but same theory of using bodyweight + effort + equal and opposite force
 of effort; all pulling on target.

Rope force studies are the same science in a rig, or inside a knot IMLHO.  Rig forces can be like knot forces under a microscope; same device (rope), forces, angles, tensions, frictions etc.; only easier to see outside of knot sometimes!


DerekSmith

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Re: Playing with forces
« Reply #2 on: August 07, 2011, 12:22:35 PM »
Very clever- took me a while to get my mind around it though.

Derek

squarerigger

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Re: Playing with forces
« Reply #3 on: August 08, 2011, 02:42:16 AM »
Depends on what you consider to be effort - human weight in a loop can easily be displaced with disastrous consequence.  Also, the distance moved of the 850# is minimal compared with the human movement.  Overall a cleverly convincing 'proof' of effort expressed as it should be as arm effort and not total (i.e. potential mass) effort.  It does assume that no friction is involved which will take some additional arm effort to overcome.

SR   :-\

TheTreeSpyder

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Re: Playing with forces
« Reply #4 on: August 13, 2011, 02:03:38 PM »
Very clever- took me a while to get my mind around it though. - Derek

Please let me know of any better wording etc., am trying to get wording right; collect in some type of 'album' interface  And, actually; i have assumed sum knowledge of pulley systems , as they are normally displayed as 'open' systems rather than these more 'closed' ones that conserve more forces, focussing them to target.

Depends on what you consider to be effort - human weight in a loop can easily be displaced with disastrous consequence.  Also, the distance moved of the 850# is minimal compared with the human movement.  Overall a cleverly convincing 'proof' of effort expressed as it should be as arm effort and not total (i.e. potential mass) effort.  It does assume that no friction is involved which will take some additional arm effort to overcome.

SR   :-\

Effort is exertion, here we use what would be exerted anyway + it's equal / opposite force captured + bodyweight as system inputs/ conserving more forces to target, rather that 'distracting' them to outside the system.

THANK-YOU  for safety reminder: These ARE NOT to illustrate/ recomend person only supported by loop; the man here is in the loop, only to illustrate that all his bodyweight is in system(can hang and pull with toes barely on ground).  Usually, 1 would just pull against own bodyweight as equal/opposite.  Here, we recognize all 3 forces (effort, equal/opposite of effort, bodyweight) as potential inputs, not just effort!

The trade off of distance/power as a force volume to show more force output (after conversion by a machine) will be the same volume of force, but the power can that is now 'stacked' higher; demands that less distance be incurred by output.  i think of an aquarium with same volume of water, and one end movable.  Stretch out the end, and less pressure on side glass, but more distance traveled, same volume, same total weight on bottom glass.  Push in on end, water goes higher, more power on side glass volume of force/ will drain from bottom faster, but covers less distance across.  So, DISTANCE x POWER becomes X (times) Y; as equal/opposites to the same volume of force product. i realize you know this and am just sorting thoughts.  i think your biggest point here was safety; which i'm totally with.

The scenario does assume 100% efficiency of the pulleys, but then 100% assertion of all possible forces.  The forces are finite, they are less than their potential(no system is 100%, there is no perpetual motion, generally friction/heat will be incurred), systems are usually shown applying just effort, so are much less output from same machine and same effort.  But, i always and all ways look at total, peak, potential to include all as outside constraint, then it's equal / opposite as together total range.  Then degrade from there evenly towards Zer0 with the incurred/ applied inefficiencies (that will be within the finite constraint of 100% efficiency as starting point).  So here, show 100% of forces + 100% efficiency (as 'big picture'); and then person's choices are fairly within that range.




Thanx for the comments!
« Last Edit: August 13, 2011, 02:06:18 PM by TheTreeSpyder »

TheTreeSpyder

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Re: Playing with forces
« Reply #5 on: August 13, 2011, 02:17:20 PM »
APPLICATIONS and CROSSOVERS:

Generally, if can find a 1st class lever situation (input/output in opposite directions) can use it to capture both effort and equal/opposite of effort, then add bodyweight (who's equal/opposite is your own body as a mass).    Usually, on ground, i'd hang on line to pulley except for 5-10# of bodyweight for stability (feet barely touching ground), then exert effort as shown, or impact both at same time.  Can also, hold something 'fast' with weight or effort input, then impact with other input as strategy is very useful.

Same with non-flexible / non-rope devices (stiff enough across device to use as lever); if barrel needs lifted few feet over edge of dock etc.   Press down with body on high end  of barrel as also pulling up on low end.  With edge as pivot, barrel must incur bodyweight + 2xEffort,  and then also higher part of barrel (above edge as pivot) acts as ballast  against lower part of barrel to aid in lift.  Totally different then pure lift or just pressing lifting low end over rail/edge etc.  And that is a static example, without showing carefully impacting side of barrel down (not to 'injure' barrel / contents), then at same moment as impact, impact with bodyweight and  pull, even roll slightly to side (to leverage on that axis at right time).  This places thought and timing ahead of brute force with less fatigue in many situations. 

Sometimes after several hours , days, weeks, years of work, we might fall finally into a maximum/ near maximum work pattern Naturally, perhaps even unconsciously somewhat 'body knowledge' takes over.  The actions can often times even look the same, or perhaps jsut be seen as different order of same etc.  But, 1 person can be working the forces differently to higher maximum, even with less fatigue.  If the little man can teach the big man the tricks he gets by, the big man can be amazed at what he can do now!  If we can define these patterns truly to their basis, we can more confidentally carry them to the next scenario, and call out/ conjure the forces up on day one of work.

Rigging and knotting both use the same device forces (rope) so are commanded by the same forces.  Rigging being larger, to me shows under a microscope the forces that play out, hidden inside of the 'microcosm' of a knot.  If we really, truly define the forces of 1, we should be able to define the other (rigging / knotting) forces.  Just as the principals of a non-flexible (wood, metal) remain the same as a table leg, lever, spear, knife blade etc.  The rope / wood / metal is just a device, carrying forces.   Flexible devices (like rope, chain, webbing) only support on inline axis of the length of the device, and only in the tension direction.  Whereby non-flexible (wood, metal) would resist / support force on the inline and across axis(es), and in both the tension and compression directions.  So can make some comparisons between flexible to non-flexible scenarios that resist / support on inline axis, and in tension direction/ share info between to understand all more fully.

Just as seeing pulley as first class lever re-direct, how to apply effort + effort(equal/opposite) + weight, and do same to first class lever setup on barrel; lessons can be carried over for more understanding quicker, then the differences shown between the 2 to define more what principal properties are the same, and which different etc.

struktor

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Re: Playing with forces
« Reply #6 on: August 13, 2011, 06:12:22 PM »
Nihil novi sub sole   :)

Architectura Martialis,  Furttenbach Joseph 1630
http://digital.bibliothek.uni-halle.de/hd/content/pageview/117680

Della trasportatione dell'obelisco Vaticano et delle
fabriche di Nostro Signore Papa Sisto V, fatte dal caualier
Domenico Fontana architetto di Sua Santita, In Roma, 1590
http://purl.pt/6256/1/P37.html
http://purl.pt/6256/1/P41.html
http://purl.pt/6256/1/P45.html

Struktor
« Last Edit: August 13, 2011, 06:37:47 PM by struktor »

swanoonie

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Re: Playing with forces
« Reply #7 on: August 13, 2011, 09:57:02 PM »
In primary school, I'd been duly instructed that block systems don't provide mechanical advantage unless one of the blocks moves with the load. Because of this, the hand pulling down case baffled my teenaged mind. Although I experimentally verified it in my basement at the time, I couldn't reconcile it with what I'd been told until I thought of it in the following way (although I did not then command the vocabulary to articulate it): placing my coordinate system's origin at myself with inverted gravity, I was pulling the 150# 'weight' of the joist toward a stationary me.

Thy first illustration, TreeSpyder, clearly shows that scenarios are indeed possible in which blocks can provide mechanical advantage augment muscle power without 'moving with the load'. I also enjoyed thy discussion of effectively exerting one's own muscles and weight using the principles of simple machines. Thank goodness I no longer work as a mover, but the idea of maximizing my efficacy was obviously quite seductive then!

This all reminds me of some earlier university coursework. Forces can, indeed, take some 'getting one's head around'. They can also necessitate getting one's spine uncompacted . . .

Thanks for the snippets of Romance, Struktor, and for apprising us of the Fontana Vatican scans. Solomon's words canst not be gainsaid; both they and the discussion of multiplying muscular forces clearly bear great relevance to the pyramids, Stonehenge, ziggurats, obelisks, and so forth. As captivating as the tackles shown are the friction-powered windlasses used to power them; Roo's discussions 'The Power of Friction' and 'The Rope Wrench' provide valuable insight (thanks again for pointing me to Roo's site, DerekSmith).
« Last Edit: August 14, 2011, 05:14:54 AM by swanoonie »

DDK

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Re: Playing with forces
« Reply #8 on: August 14, 2011, 05:00:21 AM »
. . .  Also, the distance moved of the 850# is minimal compared with the human movement.  . . .
. . . The trade off of distance/power as a force volume to show more force output (after conversion by a machine) will be the same volume of force, but the power can that is now 'stacked' higher; demands that less distance be incurred by output.  i think of an aquarium with same volume of water, and one end movable.  Stretch out the end, and less pressure on side glass, but more distance traveled, same volume, same total weight on bottom glass.  Push in on end, water goes higher, more power on side glass volume of force/ will drain from bottom faster, but covers less distance across.  So, DISTANCE x POWER becomes X (times) Y; as equal/opposites to the same volume of force product. i realize you know this and am just sorting thoughts.  i think your biggest point here was safety; which i'm totally with. . . .

I am not familiar with the phrase force volume.  Might it be the same as the Work Done?  The Work Done is equal to Force times Distance.  If a 100 pound object is lifted one foot, then 100 foot-pounds of work was done.  If a system applied a force of 10 pounds, then 10 feet would be needed to be pulled to do the needed amount of work (10 pounds times 10 feet) and to lift the 100 pound object one foot (a mechanical advantage of 10).

If you look at the scenario given here http://www.mytreelessons.com/ks/forcePlay_b.swf with an 850 pound object, it is interesting to ask what would be the required mechanical advantage, MA, (and movement of the human).  If only body weight (150 pounds) was considered, then the MA needed would be about 5.7 (850/150).  So every foot of movement for the 850 pound object would require the human to move 5.7 feet.   If in addition the effort (100 pounds) which is transferred through to the feet are included, such as might occur if you had pulled up (arm curled) on a firmly anchored nearby pole, then the MA would be 3.4 (850/250).  And finally, the addition of the effort of the arm curl on the leg of the 3:1 instead of the nearby pole gives a total MA of 3.  So, the effort transferred through to the feet is much more effective (in fact, three time as much) at reducing the MA than the effort from the arm curl on the leg of the 3:1.  This is due to the fact that the same effort (100 pounds) of the arm curl on the leg of the 3:1 is applied on that part of the rigging which is a 1:1.

Power can be defined as Work Done per unit time.  Saying it another way, Power is the rate of doing Work.  From this definition of Work, we can see that if Force is constant (a constant pull on a rope, for example), then the rate of doing Work will depend on the rate at which the distance (length of rope that is pulled) changes (i.e. velocity).  Therefore, Power equals Force times Velocity.  In the example I gave above with an MA of 10, the 100 pound object moves at one-tenth the speed of the pulled rope.

DDK
« Last Edit: August 14, 2011, 05:39:57 AM by DDK »

DerekSmith

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Re: Playing with forces
« Reply #9 on: August 14, 2011, 08:38:17 AM »

Nihil novi sub sole   :)

Struktor

Yet, under the first sun, everything was new...

So perhaps, just perhaps, there are still new things for us to find and be excited by...  but only if we wear our minds wide open...

Derek

TheTreeSpyder

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Re: Playing with forces
« Reply #10 on: August 14, 2011, 11:34:14 AM »
Force Volume/ volume of force was something i showed some time ago, trying to simplify a quantity of work force by compairing to more familiar and tangible volume of water.  Each a finite value, each could be spread far (distance) or high (power), and could not just magically make more from it's own self on top of this volume (only the either/or of power/distance).  Also, neither would be 100% efficient on transfer; some water would evaporate, be stuck to the sides of previous vessel, spill etc.

And yes, if anything is taught of pulleys, it is generally, that a pulley on anchor is 1:1 redirect (no force increase, 1st  class lever-that only changes direction between effort input and work output, pulley as pivot is between input and output  just like a non-flexible lever).  Also, if the pulley is on the load, it increases power (2nd class lever, effort and work move in same direction, power increase but more distance required in trade off, here the work load/output is between the pivot of anchored end, and the input effort just like a non-flexible lever).

But, what isn't shown normally(nor is shown in pics here): Is a 3rd position of the pulley in between the anchor  of 1 end AND WORK OUTPUT end, with the input effort on the pulley (yielding 1/2 power at 2x speed, a 3rd class lever  just like a non-flexible lever).  Several times we had very steep 120' hill to pull loads of tree lumber up to 60' drive way, so i made this setup, with 1 end anchored high on hill, 1 end low to load at base of hill, and pulley in between to be pulled by truck up hill.  Worked very well, but had to move truck slow, as load was moving at 2x speed, and either side of hill was full of tropical (some rare) plants at this fancy place.  Over the years, any job we did there was known as 'Hell Hill' to the guys, and we always made this setup (No of course we didn't tell new guys they didn't have to drag it all manually, and perpetuated legend of  'Hell Hill' for 1 week prior to job...).

But also, not shown is this concept presented were the pulley can be on anchor / not moving as reverse/ load movement as work was in opposite direction of effort input (1st class lever) and could be used to input effort + it's equal opposite on to load (curiously, we can do this too with see-saw type lever).  
this is a closed system, compaired to the normally shown 'open' systems, so more of the forces are conserved to target (bodyweight input not needed for this  closed system, but why not use, and need to show that effort pulls/pushes do not pull against bodyweight, but rather each other).  Taking a step further, if climber is load, and is being pulled up, that is 1:1, but if climber needs to go up, and pulls himself up in scenario 1, things change.  Climber has to shorten both legs of rope 1' (total of 2') to lift her/himself 1'; so forces more distance input, than output, for more return of force.  In the end, 1 100# climber in swing with own hand holding up on other side of pulley, only has 50# tension on each leg of rope from pulley (to support their 100# weight).  So, has 2:1 mechanical advantage over his own body in trade for extra distance pulled.  You might even see this in some old movies unknowingly, when man jumps inside of 'dumb waiter' and pulls themselves and dinner up to top floor (there would also be ballast weights, that about make empty dumb waiter 'float' no effort to fight 'car' or cable's weight, but friction inefficiencies keep in place).

i think there are new things to find all around as Derek states, they say we know less about inner spaces of sea and mind, than we do of outer space!  But, then too; i think there are lost things that were known, perhaps even somewhat innately known/accepted by all , but unknown now, like this, pyramid making etc. working in background of daily lives..  But, it would be best to look at all things in wonder, even if thought know; for then eyes are opened more, to perhaps even see deeper into it's depths to see if really known, or even lessons to carry to other things (leverage in learning?).  Some theories say, that everything is so interrelated, that one can know all/many things, just by knowing 1 thing so very well, and seeing the connections to to other things, including other knots, mechanical systems etc..

1 Pyramid theory of 'mind over matter':  



(There are some subtleties here at changeover point of direction reverse and moving up to same step, then higher step; that are extra well thought out; and easy to miss)

"Nature, to be commanded, must be obeyed" -Sir Francis Bacon
« Last Edit: August 14, 2011, 12:21:25 PM by TheTreeSpyder »

DerekSmith

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Re: Playing with forces
« Reply #11 on: August 14, 2011, 12:03:33 PM »
10 ton slab, some stones, sand, sticks and clear sighted imagination and one man sets out to build his own personal stone henge  Wally Wallington thinks he could build Cheops in 25 years with a team of less than 1000 men.

His rolling road for moving a 1600lb block surely has to have been at work on the pyramids, and his 'Teeter Jack' is just plain brilliance.

Derek

TheTreeSpyder

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Re: Playing with forces
« Reply #12 on: August 14, 2011, 12:29:40 PM »
Sometimes with logs diameter as tall as man, we would roll  forward (sometimes initiate or total pull by parbuckle), then on top of small log/branch to lift both ends, turn to new direction and roll off, trying to make feel like downhill as we did and then keep the inertia going.

Incidentally, don't recommend safety wise, but in all honesty, i would stand on end, with foot in 'tread' of bark texture in direction of travel, then pull up on opposite side, to get 2xEffort + bodyweight potential into this leverage system to initiate, then jump off and run behind to aid others rolling.  Best is not getting in position of such work without being able to get equipment to area, but when can't and have task, necessity can be a real mother (of invention..).

struktor

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Re: Playing with forces
« Reply #13 on: October 02, 2011, 09:01:57 PM »
The First Tackle. Eskimo landing a walrus. (Fig.9 )
''The origins of invention: a study of industry among primitive peoples'' by Otis T. Mason,  1902
http://www.archive.org/details/cu31924003643040
 
A Spanish windless is a device for moving heavy loads such as rocks and logs.
http://www.ropeworks.biz/reader/swindless.pdf

So formerly was measured stress ropes.
http://charles.hamel.free.fr/knots-and-cordages/PICASA_Slideshow/DDM-Art-Corderie-Orig/target5.html

Struktor

swanoonie

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Re: Playing with forces
« Reply #14 on: January 12, 2020, 10:36:16 PM »
Re: DerekSmith's reply - Did anybody get the "Forgotten Technology" DVD from Wally Wallington?
I see his website www dot theforgottentechnology dot com is down these days.
« Last Edit: January 13, 2020, 12:49:37 AM by swanoonie »