Ropes, Pulleys, Rigging Systems, and Avoiding Dangerous Resultants

I am excited about sharing this with you, and hearing your comments and questions.

There is too much info to list it all here, but these of the working files and topics I address, in depth,  and comment on:

Just a some of the information included:

The answer the cable clamp question.  The clamps are on backwards, if the clamps are tightened to the proper torque, they will weaken the cable to less 1/3 its rated strength!  If they are over tightened it weaken it even further because it is crushing the fibers or steel strands of wire.  We use the old saying, "Never Saddle a Dead Horse."  Well the live side is the load or working side of the steel rope,  and the dead side is the side without load on it.  The broad surface area of the saddle spreads the force out, thus not crushing the steel rope strands. 

The above sample page does not include friction of the pulley nor or the friction
 of the rope bending around the pulleys.

Falls, rope strength, and . . .

How dynamics, like a fall, effect the breaking strengths of a rope?  Most published MBS's (minimum breaking strengths) are determined using a slow pull method, with each end wrapped around large diameter bars.  These affect heat *dissipation and **critical radius; when combined they can cause a rope to break at as high as 75% "below" many published breaking strengths. 

Our rescue team had the unpleasant task of retrieving a young climber's body, who experienced these unpleasant circumstances.  He had bought a length of high strength nylon cordage; which had a published MBS of 600 lbs.  He then he tried rappelling down a cliff, and had a parting experience . . . 

At first thought, it seems logical.  A person might feel safe considering most published knot strengths show they are 50% to 75% efficient.   Factor in his weight of less than 250 lbs, including his gear, it might seem logical?   Unfortunately, dynamics created heat, which reduced the knot's efficiency even further; and it ruined his entire day . . . 

With this in mind we conducted some tests to find the MBS of low stretch rope, with various knot tied in them, by pulling the slowly, medium fast, and at the speed gravity created using as solid (a body absorbs part of the energy) mass of weighing about 225 lbs. 

Resultant angles of force (pull), in the above (left) case, there is only about 1,410 lbs of force on the anchor, but the right example has a resultant force of 2,000 lbs (friction is not factored in)

Avoiding Dangerous Resultants...  In this picture we are demonstrating a resultant angle of force, which will cause the tripod to over turn (Solid arrow) and a resultant force of 1.81 multiplied by the force on the rope, i.e.:  One person (225 lbs x 1.81 = 407 lbs) pulling in the direction of the solid arrow.  In this case, the arrow or force is focused outside of the "magic triangle."  If this force is outside of the triangle created by the base of the tripod, it will tip over.  

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As my bod, and circumstances allow,  I look forward to sharing these and other skills in an effort to contribute technical rescue, work, and training.  I appreciate the opportunity to work, train, and enjoy the natural environment with you.  During this part of my career I plan to spend time with my family, friends, and myself, sharing these skills and ideas.