static plate 4:1?

[ArboristMaximus]

I have been using MA for years and am thinking of adding a static dual sheave pulley to my next rope brake I build (see Meet Lumpy) without the two pulleys moving toward each other as in a standard MA configuration will the same force be applied to the line? In other words is the force multiplication of 2 pullies (2:1) due to the two sheaves or because they move towards each other as the rope is fed through?

 

[JeffL]

As I understand it, if the block is stationary, wouldn't it just be redirect?

 

[Tom Dunlap]

Which pulley configuration are you planning on using?

Look at this page and find out...

http://www.smackdock.co.uk/tackles.htm

I don't understand how you plan on configuring your blocks.

 

[ArboristMaximus]

Jeff that is what I am trying to get my head around. Tom I looked and did not see any that fit my plan. Picture a standard 4:1 pulley setup, as the rope is being pulled on the working end is the force ( say ten pounds of pull to generate fourty on the line) being generated because the pulleys are moving together? Or if the same setup were used and the blocks were not moving together will the same equation apply. If I built a plate with two double pulleys spaced 12" apart and threaded my rope around those and then up into the tree do I now have a 4:1. I can't think this one out because I do not know the fundamental physics.

 

[Tom Dunlap]

If I understand you, no, no MA. All you've done is created a serpentine path much like a larger diameter sheave. No MA is generated unless the axles of the sheaves move.

What is your goal for having the rope go around the sheaves?

You'd generate some friction from the axles in the sheaves moving and a tiny bit of friction of the rope on the rotating sheaves. I can't see how this will be any advantage in a design.

 

[boreality]

Crazy stuff. So each little "axle" takes some of the load and with minimum friction materials and design it does the work for you. That old Egyptian or whoever must of been pretty excited when he figured it out.

 

[ArboristMaximus]

Tom, I have the fabricator buzz and wanted to build a lowering device with integrated MA that could be quickly and easily be threaded with little or no extra equipment. My logic is the easier and faster a particular piece of equipment is to deploy, the more likely it is to be used. Thank you for the clarification, I will modify my design accordingly.

 

[Tom Dunlap]

The Mayan and many other North and South American cultures never came up with the wheel. They still built fabulous civilizations, cultures and structures.

 

[boreality]

The canoe, kayak and many other stuff was perfected long ago. Who needs wheels. We never had skis either.

I think levers, gears, pulleys or hydraulics are the options for gaining advantage, if that helps... to stay on subject.