INTRODUCTION TO MACHINE
A machine is an apparatus that is designed and build by application of physics and material science to have an apparatus that utilizes mechanical power, it comprises several parts that have a definite function and perform a particular task. Machines are known in conservation of energy by making work easy. Machines work under principles of moving parts which are usually powered by chemical, thermal, mechanical or electrically means. Machines are often motorized there are few machines that start on their own.
However there are large numbers of more complex machines do exist. Example of easy machine includes simple machine, pulley, wedge, screw and wheel and shaft. Mechanization helps human operators with machinery that assists them with muscular requirements of work or displaces muscular work. However advance technology have brought up electrical technology which has led to development op power tool without moving parts and are considered machines. A simple machine can be defined as device that simply transforms the magnitude or direction of a force.
Back to the years of machine history, Archimedes was Greek philosopher who innovate simple machine by discovering principle of mechanical advantage in the lever, there after he defines the classic five machines. Standardized components are assembling to form machines. These elements that consists mechanization control movement in various ways such as gear trains, belt, chain drivers and transistor switches. The colour, shape and texture of cover provide a styling and operational interface between the mechanical components of a machine and its user.
MECHANICAL ADVANTAGE
This term describes the amount of force that is utilized internally by some sort of mechanical device. Mechanical advantage helps a device to perform the task for which is designed to function. A pulley is a wheel with a groove; a belt runs inside the groove. The mechanism is advanced and can be connected with other pulley in a pulley system. Mechanical advantage can be defined as a factor by which a mechanism multiplies the torque applied to it.
Increase in number of pulleys in the system leads to less force required to lift an object. Pulley makes lifting the load easier because it reduces the effort required to lift. However the rope travels greater distance that the height in which the load is going to travel. The extra distance decreases one’s effort by giving a mechanical advantage. The mechanical advantage of a movable pulley is equal to the number of ropes that support the movable pulley.
How to calculate mechanical advantage
- Find the mechanical advantage of pulley system by noting number of doubled up stretches of rope for the load to be lifted. Number of ropes is denoted by letter n.
- Note how far the load’s point of contact on the lever is from the focal point (fulcrum) and denote it with letter L.
Figure showing a fixed pulley
VELOCITY RATIO OF ROPE BLOCKS PULLEYS
This is a term that is used in simple machines that refers to the result of dividing the distance moved by the point of effort and the distance moved by the point of load. Therefore the Velocity Ratio = effort distance/load distance. The velocity ratio creates efficiency in the pulley system where a large pulley is used to drive a small pulley which actually makes more revolutions than the larger pulley.
ROPE BLOCKS
This is a very useful form of machine for lifting heavy loads. It is a type of simple machine which is among the Archimedes work. It was used to lift buckets of water. Rope block consists of a grooved and a pulley. By holding rope a and b above and by lifting the load may be by 1 meter, one can easily calculated the velocity ratio of the simple machine.
Therefore velocity ratio is the ratio between the distanced moved by effort divided by the distance moved by the load. Mathematically can be represented as;
EFFICIENCY OF MACHINES
So far, you have got learned that the work you set into a machine is strictly capable the work done by the machine. In a perfect scenario, this equation is true. In reality, however, the output work is always but the input work. Friction and Efficiency, in each machine, some work is wasted overcoming the force of friction. The less friction there's, the nearer the output work is to the input work. To determine the machine’s efficiency, the output work is divided by the input work and multiplies the result by 100%. This can be summarized by the subsequent formula. The efficiency of a machine compares the output work to the input work. Efficiency is expressed as percentage the upper the %, the a lot of economical the machine is. If you recognize the input work and output work for a machine, you'll calculate a machine’s efficiency.
MECHANICAL EFFICIENCY
Machine efficiency is used to measures the usefulness of a machine in converting the power and energy that is input to the device into an output movement and force. In general efficiency is measured as a ratio of the measured performance to the performance of an ideal machine
While in Rope Block pulley the efficiency is equal to the ratio of mechanical advantage over velocity ratio multiplied by hundred to make it percentage, as represented mathematically below
The three types of Pulley are used in daily basis for instance raising national flags; convey belts, elevators, blinds on windows operate under the principle of pulley system. The types include pulley that has fixed axle, moveable axle and lastly a compound that consists of two pulleys.
