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- Capstan_equation abstract "The capstan equation or belt friction equation, also known as Eytelwein's formula, relates the hold-force to the load-force if a flexible line is wound around a cylinder (a bollard, a winch or a capstan). Because of the interaction of frictional forces and tension, the tension on a line wrapped around a capstan may be different on either side of the capstan. A small holding force exerted on one side can carry a much larger loading force on the other side; this is the principle by which a capstan-type device operates. For instance in rock climbing with so-called top-roping, a lighter person can hold (belay) a heavier person due to this effect.The formula is:where is the applied tension on the line, is the resulting force exerted at the other side of the capstan, is the coefficient of friction between the rope and capstan materials, and is the total angle swept by all turns of the rope, measured in radians (i.e., with one full turn the angle ).Several assumptions must be true for the formula to be valid: The rope is on the verge of full sliding, i.e. is the maximum load that one can hold. Smaller loads can be held as well, resulting in a smaller effective contact angle . It is important that the line is not rigid, in which case significant force would be lost in the bending of the line tightly around the cylinder. (The equation must be modified for this case.) For instance a Bowden cable is to some extent rigid and doesn't obey the principles of the Capstan equation. The line is non-elastic.It can be observed that the force gain grows exponentially with the coefficient of friction, the number of turns around the cylinder, and the angle of contact. Note that the radius of the cylinder has no influence on the force gain. The table below lists values of the factor based on the number of turns and coefficient of friction μ.From the table it is evident why one seldom sees a sheet (a rope to the loose side of a sail) wound more than three turns around a winch. The force gain would be extreme besides being counter-productive since there is risk of a riding turn, result being that the sheet will foul, form a knot and not run out when eased (by slacking grip on the tail (free end), or in land talk, one lets go of the hold end. It is both ancient and modern practice for anchor capstans and jib winches to be slightly flared out at the base, rather than cylindrical, to prevent the rope (anchor warp or sail sheet) from sliding down. The rope wound several times around the winch can slip upwards gradually, with little risk of a riding turn, provided it is tailed (loose end is pulled clear), by hand or a self-tailer. For instance, the factor 153552935 means, in theory, that a newborn baby would be capable of holding the weight of two USS Nimitz supercarriers (97 000 ton each, but for the baby it would be only a little more than 1 kg).".
- Capstan_equation thumbnail Capstan_equation_diagram.svg?width=300.
- Capstan_equation wikiPageID "21265224".
- Capstan_equation wikiPageRevisionID "579700396".
- Capstan_equation hasPhotoCollection Capstan_equation.
- Capstan_equation subject Category:Concepts_in_physics.
- Capstan_equation type Abstraction100002137.
- Capstan_equation type Cognition100023271.
- Capstan_equation type Concept105835747.
- Capstan_equation type Content105809192.
- Capstan_equation type FundamentalPhysicsConcepts.
- Capstan_equation type Idea105833840.
- Capstan_equation type PsychologicalFeature100023100.
- Capstan_equation comment "The capstan equation or belt friction equation, also known as Eytelwein's formula, relates the hold-force to the load-force if a flexible line is wound around a cylinder (a bollard, a winch or a capstan). Because of the interaction of frictional forces and tension, the tension on a line wrapped around a capstan may be different on either side of the capstan.".
- Capstan_equation label "Capstan equation".
- Capstan_equation sameAs m.05f3_w2.
- Capstan_equation sameAs Q5036361.
- Capstan_equation sameAs Q5036361.
- Capstan_equation sameAs Capstan_equation.
- Capstan_equation wasDerivedFrom Capstan_equation?oldid=579700396.
- Capstan_equation depiction Capstan_equation_diagram.svg.
- Capstan_equation isPrimaryTopicOf Capstan_equation.