UNIT 6.Machines and mechanisms Vocabulary

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1 UNIT 6.Machines and mechanisms Vocabulary Cam /kæm/ leva pendulum / pendjʊləm/ péndulo Crank-handle /kræŋk-hændl/ manivela Pulley polea Crank-shaft Kræŋk- /ʃɑ:ft/ cigúeñal Rack and pinion /ræk&pinion Piñóncremallera cylinder /sɪlɪndəʳ/ cilindro Ramp /ræmp/ rampa fulcrum fulcro Reciprocating [rɪsɪprəkeɪti alternativo hydraulics /haɪ drɒlɪk/ hidraúlica resistance /rɪ zɪstəns/ resistencia Lever /livəʳ/ palanca Rod-crank /rɒd/- /kræŋk/ Biela- manivela Linear [lɪnɪər] lineal Rotary / rəʊtərɪ/ rotativo Machine /mə ʃi:n/ máquina Screw /skru:/ tornillo Mechanisms /mekənizəm/ mecanismos Shaft /ʃɑ:ft/ eje Motion /məʊʃən/ movimiento Thread /θred/ hilo movement /mu:vmənt/ movimiento Wedge /wedʒ/ cuña Nut na:t tuerca Wheel /wi:l/ rueda Technology Department IES ArabuleilaCúllar Vega Granada page 1

Machines and mechanisms 1. Machines. 2. Mechanisms. 3. Levers. 4. The inclined plane and wheel. a. Lever elements b. Types of levers c. Mechanical advantage. d. The lever law. 5. La polea. 6.

1 Machine definition There are many types of machines and it is not easy to find a definition that fits-all. However all of them have some common features: They need power to operate.

2 Machines and mechanisms 1. Machines. 2. Mechanisms. 3. Levers. 4. The inclined plane and wheel. a. Lever elements b. Types of levers c. Mechanical advantage. d. The lever law. 5. La polea. 6. Los sistemas de transmisión circular. 7. La relación de transmisión. 8. Mechanisms for transforming the motion. 1. Machines 1.1 Machine definition There are many types of machines and it is not easy to find a definition that fits-all. However all of them have some common features: They need power to operate. This energy can be electrical, chemical, mechanical or otherwise. They convert the energy they receive into another type or types of energy.usually the operation of a machine produces more than one energy transformation. Produce effects. move, sound, crushed, pushed, off heat. Have been manufactured.with one intention: to facilitate a task, reducing the effort required to perform a job. Technology Department IES ArabuleilaCúllar Vega Granada page 2

1.2 Types of machines There are many different ways to classify machines. According to the technology they use.

Depending on the number of steps they need to perform their function.

3 Simple machines and compound machines. Simple machines. These do the work in one step. Essentially there are three: pulley, inclined plane and the lever.

Mechanisms. 2.1 Movements on a machine Machine movements might be complex. However all movements can be achieved by combining four basic movements.

3 1.2 Types of machines There are many different ways to classify machines. According to the technology they use. Machines can be electrical, mechanical, hydraulic. Most machines combine several technologies. Depending on the number of steps they need to perform their function. They can be simple or compound Depending on the number of parts and the difficulty of their installation. They can be simple or complex. 1.3 Simple machines and compound machines. Simple machines. These do the work in one step. Essentially there are three: pulley, inclined plane and the lever. Compound machines. They need to connect several steps to perform their function. Compound machines are built by combining two or more simple machines 2. Mechanisms. 2.1 Movements on a machine Machine movements might be complex. However all movements can be achieved by combining four basic movements. Linear: in a straight line that goes in one direction. Rotary: circular motion in one direction. Reciprocating:in a straight line, but one that continually changes direction, which produces continuous forward and reverse movements. Swinging or Pendulum: a forward and backward motion that forms an arc. Technology Department IES ArabuleilaCúllar Vega Granada page 3

4 2.2 Mechanisms Machine movements have to be precise. To achieve this we use mechanisms. Mechanisms are used to: Transmit movements and forces from one point to another of a machine, as do the levers, pulleys and gears. Transform movements, changing speed, direction, or type of movement. For example, making a circular motion into a linear, as is the case of nut and screw mechanism. Steer, regulate and control the movements 3. Levers. A lever is a rigid beam that can rotate around a fixed point on which it is supported Lever elements A lever has the following elements: The power or force applied. The resistance that we have to overcome. The support point or fulcrum. The power arm, which is the distance between the fulcrum and the point where the power is applied. The resistance arm, which is the distance between the fulcrum and the point where the resistance is located. 3. 2Types of levers Depending on how the elements of a lever are applied, there are three types of levers. First-class lever. Has the power at one end, the resistance at the other, and the fulcrum is between these two. Second-class lever. Has the fulcrum at one end, applying power at the other, the resistance is between both. Third-class lever. Has the fulcrum at one end, the resistance at the other, the power is applied between both. Technology Department IES ArabuleilaCúllar Vega Granada page 4

5 3. 3 Combinations of levers These can combine two or more levers to work together, for example scissors, forceps and nutcrackers are combinations of two levers that share the same fulcrum The mechanical advantage When power applied is smaller than the resistance to overcome, we say that there is a mechanical advantage, because we have managed to multiply force. The mechanical advantage is the mathematical relationship between the resistance and power. To have mechanical advantage, the power arm must be longer than the resistance arm. The longer the power arm and the smaller the resistance arm, the lower the effort The lever law For a lever to be balanced, so as not to rotate, it must meet the following equation: Power x Power arm = Resistance x Resistance arm 4. The inclined plane and wheel These two machines are based on the same principle as the lever: a small force applied over a long distance has the same effect as a large force applied over a small distance. Technology Department IES ArabuleilaCúllar Vega Granada page 5

4.1 The inclined plane The inclined plane or ramp is a machine that can be used to lift objects with less effort. The longer the ramp the less effort required.

Consists of a cylinder or cone which is surrounded by a ramp HELIX called thread. 4.2 Wheel A wheel consists of a round body (cylinder or disk) which rotates about an axis or integrally with it.

The mechanical advantage is dependent on the radius of the shaft and the wheel. 8. Mechanisms for transforming the motion. The input motion is different from the output motion. 8.1 Circular linear transformation a.

6 4.1 The inclined plane The inclined plane or ramp is a machine that can be used to lift objects with less effort. The longer the ramp the less effort required. The wedge is the union of two inclined planes for their supports. It is used for separating and cutting. The screw is a special type of inclined plane. Consists of a cylinder or cone which is surrounded by a ramp HELIX called thread. 4.2 Wheel A wheel consists of a round body (cylinder or disk) which rotates about an axis or integrally with it. Applying a force on the edge generates a much larger force in the shaft. This force will be greater the larger the radius of the wheel. The mechanical advantage is dependent on the radius of the shaft and the wheel. 8. Mechanisms for transforming the motion. The input motion is different from the output motion. 8.1 Circular linear transformation a. screw and nut: This consist of a screw and a nut, one of which is fixed and the other movable. It's able to transform a rotary motion in lineal one, with a great speed reduction and therefore with greatly increased strength. b. Rack and pinion Technology Department IES ArabuleilaCúllar Vega Granada page 6

Cam This mechanism consists of an axis that rotates, the cam can be a more or less eccentric wheel, and the follower is moved by being pushing by the cam when it rotates. 8.

7 Consists of a sprocket (pinion) which is crimped to a toothed bar (zipper). The rack advances and retreats by the rotation of the pinion. c. Cam This mechanism consists of an axis that rotates, the cam can be a more or less eccentric wheel, and the follower is moved by being pushing by the cam when it rotates. 8.2 Circular-alternative transformation d. Crank handle and crank shaft A crank handle is a rigid rod bent at a right angle. A crank shaft is a set of crank handles mounted on the same axis. e. Rod-crank A rod is a rigid bar, that connects a rotating body by articulated joints to another which performs a reciprocating movement. Technology Department IES ArabuleilaCúllar Vega Granada page 7

Mechanisms. Prepared by Juan Blázquez, Alissa Gildemann

Mechanisms. Prepared by Juan Blázquez, Alissa Gildemann Unit 9 Mechanisms 1. Mechanisms Mechanisms are devices that transmit and convert forces and motions from an input to an output element. They enable us to use less effort to carry out a task. We can classify