How does MA work?

Pretty nice dude!

Some things i note slightly differently; in this ying/yang any measure of force can help or with 1 change hinder type of puzzle. Flip-Sides:

i think with the friction your effective MA is only reduced lifting, but at hold or lower the friction is a helper/load reducer on support and your pull. Thereby to your terminology effective MA is increased(?); but really we are speaking of friction increasing of decreasing efficiency of efforts. Hurting on lift/pull but helping on hold/lower/extend. So, a pulley gives more loading at hold and lower, but less on lift; opposite of non-pulley frictional redirect properties.

Elasticity too hinders on lift, but can help on lower/catching impacting forces and keeping them off support, load connection and you, by the line giving support and shock absorbing capabilities in one device. So, elasticity too is a tool/force that can help or hinder depending on setting/use. Then flipside is you fight less elasticity in MA lift than 1:1 lift.

The support loads of the rope MA systems decrease on lift and hold as you say. But, due to the fact that the lines are less loaded (as they divde load amongst them); the lines respond with less elasticity in multiple power/rope MA systems i think. So that, in catching impact forces in a rope leverage system, the support loads are higher than if all the load force was stretching a single line, rather than 3 (like it would in 3:1).

Ummmm i kinda think there should be arrows pointing up/ not all down to show equal /opposite and rope lift.




i really think MA & Leverage werks by taking a force out of it's singular inline position with it's Equal & Opposite force. If we take the E&O force out of 'inline status' with force we create, we lengthen the distance to E&O that force is carried over. Thereby maniputlating distance part of :
Total Power = Force X Distance, to give more distance, thereby more power in system. This power increases load on support leg(Leverage). Whereby if we furthermore bend the E&O all the way around 180 to pull on load again, we divide the load on the support leg(s)(MA).

But, whether we are increasing (leveraging) or decreasing (giving MA) load on a support leg device; in either case we are taking the E&O force that the initial force seeks and making the inital force travel longer as it seeks it's E&O; thereby manipulating things. Until the initiating force finds the point of it's E&O; the systems loads can't be calculated. A plum-bob works, for it can't resist, so thereby lines up at singular/minimal inline status. As all positions this is a unique event/ math loading in system. But this one just happens to be minimal forces!
 
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Cary, very well done! That is a very snazzy looking chart!

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Thanks Mark. If anyone is interested I can provide you with the primitives I used to build the figures.

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Yeah, Cary. But view it in "display" or "xv"!

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Arg, at first I was going to chide you for using antiquated tools that didn't correctly support the alpha channel, but then I looked and found I had forgotten to add a background. I guess you don't like all that transparency showing through! A simple fix though, just recompile xv and Imagemagick to use white instead of the gray squares to signify transparency /forum/images/graemlins/wink.gif. If you are real lucky it may be a configuration option.

Ken,

My idea was to provide something that was simple and hopefully intuitive to understand. You are correct that friction helps when you are lowering, but I purposely omitted this fact since lifting is usually the hard part. To me friction and its nuances are best left as a footnote in introductory material. Get the basics first and then start adding complexity.

Catching is a dynamic process and has nothing to do with the MA so why complicate things? And as I stated earlier elasticity does not change the MA either! If you size a rope accordingly you can get the same stretch at any MA. The reason you usually get less stretch with a high MA system is that each section of rope is only supporting a fraction of the load. Which effectively gives you a larger rope.

I think we all know that the forces at a point must sum to zero, unless there is acceleration. As far as the arrows go they are there to show how the forces are split and shared by the various components. You may even notice that they are sized relative to their magnitude. To me graphic design is about conveying an idea and to do that best you have to carefully balance detail vs clarity. In this case I chose to maximize clarity!

As far as the rest is concerned I would summarize it as conservation of force*distance (weight= force). One note on the plumb-bob. It points to the local center of mass (gravity). This is not always vertical since the earth and its surface are not homogeneous.

Cary
 
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One note on the plumb-bob. It points to the local center of mass (gravity). This is not always vertical since the earth and its surface are not homogeneous.

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Oh, it's vertical. It just might not be perpendicular to the horizon. hahaha!

I'll get right on the recompilation.

Glen
 
You might want to double check your definition(s) of vertical. The one in my dictionary is “Forming a right angle with the plane of the horizon”. Which as we both know is almost but not exactly what a plumb-bob does.

Cary
 
Hey Cary.

Check the link "vertical", under "See Also" within the link I provided above; then in the resultant page look at the first bullet: "In science".

I's just bein' clever.

:)
 
I guess you were too clever for me! I should have been thinking Newtonian reference, not Euclidean reference. Of course to be thorough we need to factor in relativistic effects /forum/images/graemlins/grin.gif.

Cary
 
Well, i guess i been stupid enough to lower in a 2/1 or 3/1 so have caught some impact forces inadvertantly in such a system and had to figure out what was going on myself and why. Never knew such rigging had nothing to do with MA. Had to prove elasticity stuff i theorized to myself with rigging software too as 1 of the first things when i bought that software.

i'd run into the no spar or plum-bob is totally unleveraged; but seem to fumble with them as simple Zer0 inline/unleveraged examples in my head to compare other systems by; but i guess there are probably other easy examples.

Take Care.
 
hi guys,

in case anyone else has been struggling through this thread, wishing for understanding but not quite getting it (like me..) i thought i'd put in a plug for an upcoming workshop in seattle taught by Brion Toss and geared specifically toward arborists. he will be covering some splicing as well as rigging and mechanical advantage specifically in tree-work contexts, and in my experience if people show up with questions/scenarios that aren't on the syllabus he's happy to incorporate them. see his website for more info.

http://www.briontoss.com/education/workshop.html#arborist

k.
 
Hey Nick, did this answer your question in laymen's terms?

the energy or work required is the same on either side of the MA. W= Force x distance, So if the work needed is constant then in order to reduce the amount of force the distance has to increase. Just try pulling a set of block apart in a 5:1. When you pull on load side it's a lot harder to move the blocks apart. Once apart and you start to pull the blocks together from the tail end, you'll find it easier. The difference is the distance you're force is applied over.

Oh and all the other stuff mentioned before.
 
I discovered the article on Brion Toss' page myself one day, and I am still so lucky to have found his explanation of the leverage effect of a moving pulley. And its even written in so easy words that I can understand it!
THANK YOU!
 
I know that tree guys mostly use simple or compound pulley systems, but I am wondering if any of you know of any really good references for complex pulley systems (other than "On Rope")? I have been playing with complex pulley systems and have a fairly simple question that I am trying to answer. Here goes: If there is at least 1 pulley in the system that moves towards the load, then that is by definition a complex system. If I turn that system upside down, the pulley now moves away from the load. In the latter case, what are the rules that make it possible to tell that this is a complex system? Differential rates of movements by pulleys in the system don't help because both compound and complex systems can have pulleys that move at different rates.
 
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Best I can understand is it's a piggyback like a compound system but not using an additional rope like a compound would. For Instance a 3:1 then make another 3:1 with the pulling end and marry the system to the orig 3:1. SO basically the second 3:1 pulls the 1st 3:1 and that pulls the load. Seems like the variable is where you want to put it into the system and the second 3:1 is piggy backed in with a grab of some sort
 
Here is what I am getting at. The diagram on the left illustrates a compound 4:1 with a simple 2:1 acting on another simple 2:1 Both moving pulleys move away from the load, but at different speeds. Now take the same system and flip it upside down as in the configuration on the right. Now when you pull on the rope it is a Complex 3:1 system with the moving pulley moving towards the load. So I guess a system that is Compound in one orientation relative to the load becomes a Complex system when flipped on its head?? That had never dawned on me until today. And that led me to ask if anybody knows of any really good references that help to explain these differences? Or is it simply the case that ALL Complex systems have at least 1 pulley that moves towards the load?

DSC_2345.webp
 
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