Name: screw jack force and friction analysis
Uploaded: 2023-09-22T11:49:29.000Z
Duration: 1 min 21 s
Channel: JoVE

Considere un gato de tornillo de rosca cuadrada. La aplicación de una fuerza en su mango da como resultado un momento de torsión, lo que provoca un movimiento inminente hacia arriba del tornillo. Esto se logra superando la fricción estática entre las roscas del tornillo y el gato.
Considere la rosca completamente desenredada como un bloque en contacto con la ranura del gato y dibuje su diagrama de cuerpo libre.
El momento de torsión produce una fuerza horizontal que empuja la rosca móvil hacia arriba por la inclinación fija de la rosca del gato, y la carga aplica una fuerza axial sobre la rosca.
La ranura ejerce una fuerza de reacción sobre la rosca del tornillo. Esta reacción tiene componentes normales y de fricción, que se relacionan a través del coeficiente de fricción.
El ángulo de fricción estática para el movimiento inminente es igual al inverso tangente del coeficiente de fricción.
Ahora, aplica las ecuaciones de equilibrio para las fuerzas a lo largo de los ejes horizontal y vertical.
Reorganizando las ecuaciones en términos de la fuerza de reacción e igualándolas se determina la ecuación de equilibrio de momento para el movimiento ascendente inminente.

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	<li>Hibbeler, R.C. (2016). Ingeniería Mecánica: Estática. Decimocuarta edición, Nueva Jersey: Pearson. Págs. 432-433.</li>
	<li>Meriam, J.L., Kraige, L.G. y Bolten, J.N. (2016). Ingeniería Mecánica: Estática y Dinámica. Octava edición, Singapur: John Wiley & Sons. Págs. 355-356.</li>
	<li>Beer, F.P., Johnston, E.R., Mazurek, D.F., Cornwell, P.J. y Self, B.P. (2016). Mecánica vectorial para ingenieros. Undécima Edición, Nueva York: McGraw-Hill Education. Págs. 451.</li>
</ol>

movimiento ascendente inminente

Un gato de tornillo con rosca cuadrada es un dispositivo mecánico ampliamente utilizado para elevar cargas pesadas o aplicar fuerza considerable. Su funcionamiento se basa en convertir la fuerza aplicada en su mango en un momento de torsión, lo que provoca el movimiento ascendente inminente del tornillo. Este movimiento se logra al vencer la fricción estática entre las roscas del tornillo y el gato. Para comprender mejor cómo funciona un gato de tornillo, considera el hilo completamente desenrollado como un bloque en contacto con la ranura del gato. Al dibujar un diagrama de cuerpo libre de este escenario, podemos analizar las fuerzas que actúan sobre el sistema. <img alt="Figure 1" src="/files/ftp_upload/14319/14319_PT_Figure_1v2.svg" style="text-align: center; height: 300px;"> El momento de torsión producido por la fuerza aplicada en el mango genera una fuerza horizontal que empuja el hilo móvil hacia arriba por la inclinación fija del hilo del gato. Al mismo tiempo, la carga que se eleva aplica una fuerza axial sobre el hilo. La ranura del gato ejerce una fuerza de reacción sobre el hilo del tornillo. Esta fuerza de reacción comprende componentes tanto normales como de fricción, que están relacionados a través del coeficiente de fricción. El ángulo de fricción estática para el movimiento inminente se puede determinar encontrando la tangente inversa del coeficiente de fricción. <img alt="Equation 1" src="/files/ftp_upload/14319/14319_PT_Equation_1.png" style="text-align: center; height: 18px;"> Con esta información, aplicamos las ecuaciones de equilibrio para las fuerzas a lo largo de los ejes horizontal y vertical. <img alt="Equation 2" src="/files/ftp_upload/14319/14319_PT_Equation_2v2.svg" style="text-align: center; height: 28px;"> <img alt="Equation 3" src="/files/ftp_upload/14319/14319_PT_Equation_3v2.svg" style="text-align: center; height: 13px;"> Re-arreglando las ecuaciones en términos de la fuerza de reacción y igualándolas, obtenemos la ecuación de equilibrio de momentos para el movimiento ascendente inminente. <img alt="Equation 4" src="/files/ftp_upload/14319/14319_PT_Equation_4v2.svg" style="text-align: center; height: 13px;"> Al resolver esta ecuación de equilibrio de momentos, se puede determinar la fuerza mínima requerida en el mango para iniciar el movimiento ascendente del gato de tornillo. Este cálculo permite optimizar el diseño y funcionamiento del gato de tornillo para diversas aplicaciones, asegurando que pueda elevar cargas pesadas o aplicar grandes fuerzas según sea necesario.

Movimiento Ascendente Inminente

Un gato de tornillo de rosca cuadrada es un dispositivo mecánico ampliamente utilizado para levantar cargas pesadas o aplicar una fuerza considerable. Su funcionamiento se basa en ...

Education

Educación

JoVE Core

Mechanical Engineering

Ingeniería Mecánica

Unit 1

Unidad 1

Friction

Fricción

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

Upward Impending Motion

screw jack force and friction analysis

A square-threaded screw jack lifts heavy loads by turning handle force into a twisting moment. Its upward motion depends on overcoming static friction between the screw threads and the jack. To study this motion, the thread can be treated as if it were a block on the groove of the jack after the thread is completely unraveled.

A free-body diagram helps show the forces acting on this simplified system. The force at the handle creates a horizontal force that pushes the movable thread up the fixed incline of the jack thread. At the same time, the load acts downward as an axial force on the thread.

The groove of the jack also pushes back on the screw thread with a reaction force. That reaction force has both normal and frictional parts, and they are linked by the coefficient of friction. The angle of static friction for impending motion is found by taking the inverse tangent of the coefficient of friction.

With these force relationships, equilibrium equations can be written for the horizontal and vertical directions. These equations describe how the applied force, the reaction forces, and the motion of the screw jack are connected. Rearranging the equations in terms of the reaction force and setting them equal leads to the moment equilibrium equation for upward impending motion.

Solving that moment equilibrium equation gives the minimum force needed at the handle to start the screw jack moving upward. This result is useful for understanding how the jack is designed and operated. It also helps the jack lift heavy loads or apply large forces when needed.

Screw Jack Force and Friction Analysis

dry friction

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static friction

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kinetic friction

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frictional forces on screws

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Square-threaded screws use a helical thread to turn force into lifting motion. They are common fasteners, but they are also useful for transmitting power and motion in machines. A jack with a square-threaded screw lifts heavy loads when force is applied at the handle and the screw turns. A screw can be viewed as a cylindrical shaft with an inclined square ridge wrapped around it. The distance between two neighboring threads is called the pitch. The lead is the distance the screw advances in...

upward impending motion

A square-threaded screw jack lifts heavy loads by turning handle force into a twisting moment. Its upward motion depends on overcoming static friction between the screw threads and the jack. To study this motion, the thread can be treated as if it were a block on the groove of the jack after the thread is completely unraveled. A free-body diagram helps show the forces acting on this simplified system. The force at the handle creates a horizontal force that pushes the movable thread up the...

self-locking screw

Screw Jack Self-Locking Behavior

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screw: problem solving

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pivot bearings

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collar bearings

Friction Torque in Collar Bearings

Collar bearings support axial loads on rotating shafts, and their friction helps determine the torque needed to start motion. They are used in many machines and may have a single collar or multiple collars, depending on the application and load needs. For a single collar bearing under an axial load, the contact area is the ring-shaped region between the external radius and the internal radius of the collar. If the bearing is assumed to support the load evenly, the uniform normal pressure is...

journal bearings

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rolling resistance: problem solving

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key terms and concepts

Explore how a square-threaded screw jack uses force, friction, and equilibrium equations to lift loads and find the minimum handle force needed.

Screw Jack Force and Friction Analysis | JoVE K12

JoVE Core Mechanical Engineering offers concise, easy-to-understand animated videos covering key topics such as equilibrium, forces, truss analysis, and structural mechanics. Explore their real-world applications, and witness these concepts in action through scientist-led experiments.

mechanical engineering

Screw Jack Force and Friction Analysis

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