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Mechanisms : are devices that transmit and convert forces and motion from…

- - - - The driving force can be a sring, an electric motor or our own
        muscles.
        
        The motion produced by a motor is transformed and converted by those mechanisms to receiving elements such as wheels, clock hands, and so on, so that they can do the lob for which they were constructed.
- - - - Wheel (1) is called the primary drive wheel. When it moves, it turns or drives the output wheel (2), causing it to move as well.
        
        The output wheel rotates in the opposite direction to the primary wheel. If we use more than two wheels, each one rotates in the opposite direction to the one next to it.
        
        Uses: in industry — to make metal sheets, rolls of paper or other thin materials. Video players use this system to move the video tape.
  - - - Their axles are parallel and they rotate simultaneously because of the belt.
        
        The rotation of one axle is transmitted to the other via the connected pulleys.
        
        The two pulleys (and the two axles) rotate in the same direction.
        
        Uses: in industnal machines, car engines, washing machines, drills.
  - - - The cogs fit into the spaces between the cogs of another wheel, so that one wheel moves the other.
        
        They transmit a rotary motion between the two connected axles, which can be parallel, perpendicular or oblique.
        
        Gears can be cylindrical or conical.
        
        All the teeth must be the same shape and size.
        
        The two wheels and the two axles rotate in opposite directions.
  - - - Each time the screw rotates the gear moves forward as many teeth as grooves in the screw (normally a small number, 1, 2 or 3).
        
        This is used to reduce velocity as well as serving as a braking system.
  - - - They rotate simultaneously by means of a metal chain or a toothed neoprene belt stretched over both wheels.
        
        The chain transmits the rotary motion of axle 1 to axle 2 via gears 1 and 2. The two gears rotate in the same direction.
        
        This system transmits greater forces without losing velocity because the chain is attached to the gear teeth so there is no slippage between chain and the wheel.
  - - - In this system, the rotary movement of the first axle is transmitted to the second by means of wheels 1 and 2.
        
        Wheel 3 rotates with the same velocity as wheel 2 and drives wheel 4, to which it's connected.
        
        Each connected geared wheel rotates in the opposite direction to the wheel it's attached to.
  - - - There are two or more pulleys.
        
        The rotary motion of axle 1 is transmitted to axle 2 via the stretched belt that connects them.
        
        Pulleys 2 and 3, attached to the same axle, rotate at the same velocity.
        
        The motion of pulley 3 is transmitted to pulley 4 by the belt that connects them.
        
        All the wheels rotate in the same direction.
- - - - This uses a pinion that is a small cogwheel, mounted on a rack that is a toothed belt or bar.
        
        When the pinion rotates, the rack advances in a linear motion.
        
        Uses: bench dolls, corkscrews, vehicle steening.
    - - This consists of a bolt or threaded bar and a nut that has the same intenor diameter as the diameter of the bolt.
        
        If the bolt rotates and the nut can't turn, the nut moves in a linear motion along the threaded axle.
        
        If the nut rotates in a fixed position, the bolt will move in a linear motion.
        
        Uses: presses, taps, car jacks, screw tops for bottles
    - - A crank is a bar attached to an axle that is used to turn it.
        
        A winch and crank handle system consists of a drum that rotates and a crank handle that allows to pull or lift obiects.
        
        The effort needed to turn the winch is less than it would be if we tried to turn it without the crank handle.
        
        The longer the crank handle, the less effort is needed to lift the load.
  - - - This is composed of a crank and a rod called a connecting rod or link.
        
        This rod has articulated joints at each end — one is connected to the crank and the other to the slider.
        
        The slider produces a reciprocating motion.
        
        As the wheel rotates, the crank transmits the rotary motion to the connecting rod, which moves in reciprocating motion.
        
        This crank-link-slider system can work in reverse — it can transform reciprocating motion or oscillating motion into rotary motion.
        
        This device was very important in the development of steam engines.
        
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    - - This is a set of connecting rods attached to a jointed axle. Each of the joints of the axle acts as a crank.
        
        A crankshaft transforms the rotary motion of an axle into a reciprocating motion with different connecting rods moving at different times.
        
        lt can also transform the reciprocating motion of the rods into a rotary motion of the axle.
        
        Uses: combustion engines and sewing machines.
    - - This is basically a rotating object that pushes a follower as it moves.
        
        We can change the shape and the usable profiles — the outside edge of the piece — that are more or less pointed to produce more complex movements.
        
        A cam transforms rotary motion into reciprocating motion in the follower or bar.
        
        A set of cams fixed on the same axle is called a camshaft.
        
        Uses: combustion engines (it regulates the automatic opening and closing of the valves that let fuel and gases in and out), automatic systems (for producing intermittent effects).
    - - This consists of a wheel with an off-centre rotation axle that doesn't coincide with the centere of its circumference.
        
        It transforms the rotary motion of the wheel into reciprocating motion in the follower.
        
        The distance between the centre of the circumference and the rotation axle is called eccentricity.
        
        Uses: sewing machines, windscreen, wipers.
- - - - Uses: watch-making, security cables and brakes.
        
        The mechanisms used to reduce velocity are called brakes. There are several types.
        
        Disc brakes consist of pads and a disc attached to the object that we want to slow down.
        
        Band brakes consist of a metal band that puts pressure on a drum attached to the axle of the object we want to slow down.
        
        Drum brakes include one or two brake shoes that come into contact with the drum.
  - - - Springs work in different ways:
        
        By compression. The spring is compressed, in a chair for example.
        
        Uses: industrial and domestic machines, toys with cords, watches, pens,
        
        By traction. The spring is stretched, in a bed frame for example.
        
        By torsion. The spring is twisted, in a clothes peg for example.
    - - Uses: Vehicle suspension systems
  - - - Both types of clutch can be used in engines and machines with different gears that are used to change velocity or transmit the power supplied by the engine or motor.
        
        Fixed connections are used to make permanent connections between axles and shafts.
        
        Movable connections are used to connect shafts that can move along the axle or at an angle to each other. There are two main types: Oldham joints and Cardan joints.
  - - - In bushings the axle or the shaft is inserted in a plain circular piece that is placed inside a housing to provide a bearing surface.
      - Bearings are made up of two concentric rings with balls or rollers between them.
      - The inner ring joins or adjusts the axle or shaft and the outer ring is the support element.
- - - - Class 1: The load and the effort are on opposite sides of the fulcrum.
      - Class 2: The load is between the effort and the fulcrum.
      - Class 3: The effort is between the fulcrum and the load.
  - - - Pulleys are used to raise and lower loads easily because we use our own weight to counteract them.
        
        Uses: wells, gym equioment.
  - - - The effort needed to move a load with a moveable pulley is half of the effort needed with a fixed pulley. This type of pulley means we can lift weights with less effort.
  - - - Uses: ln passenger lifts, goods lifts, cranes.