Determining Mechanical Advantage using the T-Method with an added Pulley on the Load


Calculating mechanical advantage: the T-system
The subtle but significant difference to this system… a pulley on the load and the main line terminated at head of the tripod. We have a 6:1 mechanical advantage in the pulley system.

1. Assume continuous strands of rope have the same amount of tension.
If we start at the point where effort is applied and assume that we apply one unit of tension (1T) then we can assume that the tension along this single strand of rope will be the same throughout. Any time this strand passes 180 degrees around a pulley there are effectively two strands of rope applying tension to the pulley attachment. This means that the pulley must oppose these strands with a force of 2T,

2. Rope grabs add tension.
Previously we saw that pulleys apply two units of tension (2T) to their attachment carabiner in order to oppose the tension of the two input strands of rope. Whenever a rope grab is placed on a rope under tension, the rope grab effectively adds its tension to that of the host rope. So the pulley in this example has the 2T on the carabiner added to the 1T on the host rope to produce a new strand tension of 3T and an overall Ideal Mechanical Advantage of 3:1.

3. Redirection pulleys.
Some pulleys add mechanical advantage while others perform the task of ‘folding’ systems to fit within operational spaces. Here we have a high redirection pulley in the apex of a tripod which allows a horizontal effort to raise a load vertically.

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Fast Fours Mechanical Advantage System

Fast Fours Mechanical Advantage System
Fast Fours.
The Fast Fours is a simple variation on a standard set-of-fours. The difference is that the far end of the rope is not terminated on the becket of a pulley. Instead it is run through another progress capture pulley. This means that an operator can either pull on both ends simultaneously to yield a fast take up 2:1 or a single strand for a 4:1.
There is another unique advantage of this system for fallen worker and confined space recovery. If capable, the fallen worker can pull on one end of the system while the rescuer pulls on the other which speeds the recovery, halves the individual work, and involves the victim in the task.


T Method Applied To Mechanical Advantage Systems Using Rope Grabs

T Method Applied To Mechanical Advantage Systems Using Rope Grabs.
Calculating mechanical advantage: the T-system
1. Assume continuous strands of rope have the same amount of tension.
If we start at the point where effort is applied and assume that we apply one unit of tension (1T) then we can assume that the tension along this single strand of rope will be the same throughout. Any time this strand passes 180 degrees around a pulley there are effectively two strands of rope applying tension to the pulley attachment. This means that the pulley must oppose these strands with a force of 2T,

2. Rope grabs add tension.
Previously we saw that pulleys apply two units of tension (2T) to their attachment carabiner in order to oppose the tension of the two input strands of rope. Whenever a rope grab is placed on a rope under tension, the rope grab effectively adds its tension to that of the host rope. So the pulley in this example has the 2T on the carabiner added to the 1T on the host rope to produce a new strand tension of 3T and an overall Ideal Mechanical Advantage of 3:1.

3. Redirection pulleys.
Some pulleys add mechanical advantage while others perform the task of ‘folding’ systems to fit within operational spaces. Here we have a high redirection pulley in the apex of a tripod which allows a horizontal effort to raise a load vertically.

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Tension and Compression Study | Rigging Physics II

Tension forces are two forces acting on one object, moving in opposite directions (away from one another) to stretch the object. Compression forces are two forces acting on one object, moving in opposite directions (towards one another) to compress or deform the object. In this video, the Arizona Vortex is used as a compression member, with the tension forces coming from mechanical advantage systems on either side. Sterling Rope is the Official Rope of Rescue Response Gear’s The Rigging Lab. The Lab uses Sterling’s 11mm HTP Static for many of our rigging systems. A multi-use rescue/rappel rope that resists moisture and has high abrasion resistance. 100% polyester static provides significantly lower elongation and is perfect for any haul system. Ideal for high traffic expeditions, mountain rescue, military, industrial rope access, and swift-water rescue uses. Certified to NFPA 1983, 2006 Life Safety Rope – Light use

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Multi-Point Anchors | Rigging Physics II

Multi-Point Anchors _ Rigging Physics II

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In this video, Pat discusses, front and center, vector forces their affects on anchors, structures and the materials used. Sterling Rope is the Official Rope of Rescue Response Gear’s The Rigging Lab. The Lab uses Sterling’s 11mm HTP Static for many of our rigging systems. A multi-use rescue/rappel rope that resists moisture and has high abrasion resistance. 100% polyester static provides significantly lower elongation and is perfect for any haul system. Ideal for high traffic expeditions, mountain rescue, military, industrial rope access, and swift-water rescue uses.
Certified to NFPA 1983, 2006 Life Safety Rope – Light use

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    A portable artificial high directional system with the ability to be a tripod, a monopod, and a bipod all in one. With a precision two point head, the CMC Arizona Vortex can be rigged in various applications such as, a standard tripod or advanced set ups such as an A-frame, gin pole or multiple other imaginative configurations.

    Read more
  • Pro Deal
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Rigging Physics | Rigging Physics II

Physics apply to all of our lives. Ropes and rescue and rigging are no different. Pat discusses applied physics of rope rescue, hauling systems and the effects of gravity on raising and lowering objects. Sterling Rope is the Official Rope of Rescue Response Gear’s The Rigging Lab. The Lab uses Sterling’s 11mm HTP Static for many of our rigging systems. A multi-use rescue/rappel rope that resists moisture and has high abrasion resistance. 100% polyester static provides significantly lower elongation and is perfect for any haul system. Ideal for high traffic expeditions, mountain rescue, military, industrial rope access, and swift-water rescue uses.
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