Do You Know Where Mechanical Advantage Comes From?

[chris_girard]

Rigging work is my favorite part of tree work and I love the engineering principles behind mechanical advantage. Below is a link to Brion Toss' Fairleads archives and a short article on "how to get power from a pulley". It is by far the best discription of mechanical advantage that I have found.

http://www.briontoss.com/education/archive/miscjuly03.htm

 

[treesmith]

This one is pretty interesting and easy to understand.....http://www.mytreelessons.com/Flash/pulley21xRig.swf. It's one Kenny (TheTreeSpyder) put together. Breaks it down pretty well.

 

[HolmenTree]

I can't find a link to it but I heard probably one of....... or if not the best book on rigging.

Handbook of Rigging [3rd edition], by W.E. Rossnagal.

 

[HolmenTree]

Funny thing just happened after my last post I googled "handbook of rigging 3rd edition we ross" and up popped a Tree Buzz thread from 2004 with Chris quoting on the book [from an exact quote from ISA's The Art and Science of Practical Rigging].

 

[Al Smith]

It depends upon what search criteria you use .I used "seamanship block reeving " on this one .http://www.globalsecurity.org/military/library/policy/army/fm/55-501/chap20.htm .

It goes into detail pretty much . It's all interesting but for all intents it's nothing more than basic high school physics which in itself is the study of mechanical properties .My favorite course of study BTW .

 

[Al Smith]

I might add some time ago this discussion arose . I noted that a 10 percent reduction in actual force was neccessary to be part of the mathematical formula to determine actual lift mechanical advantage as taken by the number of block sheeves involved .

That subject was debated in conversation at that time but mentioned in that link I provided .

 

[chris_girard]

Funny thing just happened after my last post I googled "handbook of rigging 3rd edition we ross" and up popped a Tree Buzz thread from 2004 with Chris quoting on the book [from an exact quote from ISA's The Art and Science of Practical Rigging].

That's funny Holmen, but I do remember posting a lot about MA in the past over at treebuzz. Handbook of Rigging is a great resource and that quote that The Art and Science of Practical Rigging has as the beginning pretty much sums it up...both good books.

Al, like you said, it's all basic high school physics and as long as riggers understand that and don't try to mathimatically figure out every single load that they rig, then they should be all right.

Jerry B's Working Climber Series 2 really is the best resource for tree riggers and should be in everyone's collection.

 

[bonner1040]

Chris, dont be silly...Mechanical advantage comes from tying a bull rope to a big pickup truck and hitting the gas.

 

[Al Smith]

Well I've seen skidloaders tied off with a tad bit of slake too .They hit it a mighty lick about 20 miles per hour and amazing things happen .Namely the tree misses the lay by about a mile in most of those examples posted on various web forums .

I often wondered exactly what might happen if given a stout rope , a tough tree and and a tiny skidloader .Would it be possible for a stubborn tree to launch a skidloader much akin to a rock from a slingshot on the back flip ? That would be hard to explain I'd imagine .

 

[bonner1040]

I was only kidding.. As far as your slingshot question goes I have a feeling you keep watching ol'Murphs videos and one day you might get to see it, or least read about in the Awakenings..

 

[Al Smith]

Yeah but ole Murph isn't usually the skidloader jockey or perhaps if in the case of a launch redubbed the pilot .

Ha I doubt you could launch a skidloader but this yahoo at work drug a 9N Ford tractor backwards trying to stave off a leaner .Didn't work very well for him .

 

[bonner1040]

mythbusters submission?