Mechanical Advantage Systems

TOPIC: MECHANICAL ADVANTAGE SYSTEMS TIME REQUIRED: THREE HOURS MATERIALS: ROPE, WEBBING, HARNESSES, CARABINERS, FIGURE EIGHTS, ASCENDERS, PULLEYS, PRUSSIC CORDS, SLINGS, PICKETS, SLEDGE HAMMER REFERENCES: RESCUE TECHNICIAN, MARYLAND FIRE...


TOPIC: MECHANICAL ADVANTAGE SYSTEMS

TIME REQUIRED: THREE HOURS

MATERIALS: ROPE, WEBBING, HARNESSES, CARABINERS, FIGURE EIGHTS, ASCENDERS, PULLEYS, PRUSSIC CORDS, SLINGS, PICKETS, SLEDGE HAMMER

REFERENCES: RESCUE TECHNICIAN, MARYLAND FIRE AND RESCUE INSTITUTE, MOSBY

PREPARATION:

MOTIVATION:

There may be occasions when a fire department is called upon to perform a rescue involving a heavy load or removal of a victim from above or below ground. Mechanical advantage systems increase the lifting capability of on-scene personnel.

OBJECTIVE (SPO):

The student will demonstrate a basic understanding of the use of rope and rope accessories to construct mechanical advantage systems through participation in class discussions and practical activities.

OVERVIEW:

Mechanical Advantage Systems

   * Rope Software and Hardware

   * Anchor Points and Use

   * Constructing Mechanical Advantage Systems

   * Practical Activity

 

MECHANICAL ADVANTAGE SYSTEMS

SPO The student will demonstrate a basic understanding of the use of rope and rope accessories to construct mechanical advantage systems through participation in class discussions and practical activities.

EO 1-1 Demonstrate an understanding of software and hardware used with rope in rescue.

EO 1-2 Demonstrate an understanding of anchoring points and the various means of securing to them.

EO 1-3 Demonstrate an understanding of mechanical advantage systems such as the Z-rig and the piggyback Z-rig.

EO 1-4 Demonstrate using anchor points and constructing a mechanical advantage system.

Before beginning the material in this drill, it may be worthwhile to review basic knots and rope terminology so that the skills can be performed.

 

I. ROPE SOFTWARE AND HARDWARE (1-1)

A. Webbing

  1. Flat or tubular

  2. Used in place of or with rope

  3. Ends connected together using a water knot (overhaul knot reweave) to form a loop

  4. Strength

       a. 1-inch - 4,500 lbs. tensile strength

       b. 2-inch - 6,000 lbs. tensile strength

B. Harnesses

  1. Constructed of sewn webbing

  2. Worn by rescuers during certain rescues

  3. Types

       a. NFPA/ANSI Class I - seat-style for emergency escape

       b. NFPA Class II/ANSI Class IV - seat-style for rescue

       c. NFPA/ANSI Class III - full body

       d. ANSI Class IV - sit

NOTE: Only full body harnesses should be used when there is any likelihood that the rescuer will be turned upside down.

C. Carabiners

  1. Constructed of steel or aluminum

  2. Used for connecting rope or webbing to objects or other pieces of rope or webbing

  3. Types

          . Steel - 6,700 lbs. tensile strength

          . Aluminum - 5,500 lbs. tensile strength

D. Figure Eights

  1. Constructed of aluminum

  2. Used for descent control or equipment collection (attaching several carabiners)

  3. 20,000 lbs. tensile strength

E. Ascenders

  1. Constructed of aluminum

  2. Used for descent control or as part of a mechanical advantage system

  3. 2,500 lbs. tensile strength

NOTE: Caution students that most manufacturers do not allow ascenders to be used in systems with loads over 1,000 lbs.

F. Pulleys

  1. Constructed of aluminum

  2. Used as part of a mechanical advantage system or to change direction of pull

  3. May be single pulley or multiple pulleys

G. Prussic cords

  1. Formed using 7/16-inch kernmantle rope

  2. End connected together using double fisherman knot

  3. Used in place of ascenders to control descent or as part of a mechanical advantage system

  4. Attached to a rope by wrapping one loop inside the other two or three times while keeping the 

      knot to the side

  5. Loops may be of varied lengths

H. Slings

  1. Formed from nylon webbing with end generally sewn to form eyes

  2. Used to secure rope to anchor point or object being moved

 

II. ANCHOR POINTS AND USE (1-2)

A. Selection of Anchor Points

  1. Fixed objects such as large rocks or trees or similar sturdy objects

  2. Building components such as structure supports or heavy equipment mountings

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