Mechanical Bearing

by: muhammad suhandi

Bearing is the one of the most important and as basic element of machinery. The function of bearing is to reduce friction. Bearing is the one component to be sacrificed. Bearing also limits the motion of two parts. Material used to make bearings are weaker that the shaft or components where those bearings should be installed.

There many types of bearing but mainly in mechanical engineering, bearing is divided as sliding bearing means that shaft is sliding in inner face of bearing and antifriction bearing means that this bearing reduce large portion of friction than sliding bearing. Antifriction bearing further divided into two types, roller bearing and ball bearing. Antifriction bearing has three main parts, the inner race, outer race and balls or rollers. Balls or rollers slide and rotate between inner and outer race.

Sleeve bearing and sometime called bushing used in high speed application such as in connecting rod and crankshaft of internal combustion engine. Antifriction bearing has more rigid construction and used in low speed high load application such as transmission and differential.

Although bearings reduce large portion of friction, they still need lubrication. Bearing that running in unlubricated condition will instantly collapse. There is varying method of lubrication. From the simplest one which we could lubricate in scheduled time by putting enough lubrication manually until pressurized system that contains complex components to assure all the bearing get its lubrication.

Whit the advance in technology and the complexity, some bearing even do not need lubrication. Such bearing could be made using magnetic action or use pressurized air as bearing so there is no contact between metal. Also now the manufactures have produced bearing made of plastic and rubber.

Electric Motor

by: muhammad suhandi

Electric Motor is a device that converts electrical energy to mechanical energy. Principally there are two types of electric motor, DC motor and AC motor. AC motor is sometime named induction motor. It is used to make distinction between synchronous motor and asynchronous motor. All types of electrical motor have the same main construction. It is formed by two main parts. The rotor that rotates and stator that always in stationer.

Other terms we usually encountered in electrical motor is armature and field. Armature is the component that housing the winding or the conductor, which the electrical power comes. Field is winding provides the magnetic field to as an important factor to convert electrical energy into mechanical energy.

Every electrical motor has its armature and field. Now we explain the DC motor. DC motor is the motor supplied by DC voltage and current source. Its armature is in the rotor and the field in it’s a stator. DC motor usually used in industry because its rotation is easy to manipulate. But because our utility supplied AC sources, the need for a rectifier is rised. So it is rather expensive if we use this type of motor for large application. Now the DC motor is dominant in low power spectrum.

Because the nature of our utility industry is AC, the need for motor that supplied by this type of sources is rised. First is syncronous motor. This type of motor actually same as generator but work in reverse direction. Its contruction is all the same as generator. This motor has limited application because its dificulty to handle its speed. Syncronous motor is mainly used as synchronous capacitor.

In early twentieth century, Tesla an electrical engineer came with idea to design the motor that supplied by AC sources. Its construction is actually same as a transformer except it has an air gap to make it rotates. The induction motor has two types that depend on its rotor construction, squirrel-cage rotor and wound rotor. The analysis of induction motor is the same for transformer except we should introduce the speed parameter.

Induction motor is mainly used to drive large load in industry. These motors supplied by three phase AC source. For home appliances because our utility outlet is single phase in nature we used single phase induction motor.

The isueses of global warming, increase oil price has force the engineers to install electrical motors in our cars. The type of motor could be DC or even induction motor. There is hybrid car that moved by two sources, the internal combustion engine and electrical motor supplied by batteries. For pure electrical cars, no engine installed. All wheels moved by electrical motor supplied by batteries that could be charged from our utility outlet. That is the future.

Gas Turbine

by: muhammad suhandi

Gas turbine is a energy conversation that covert thermal energy from burning fuel into mechanical energy. Gas turbine is second popular from internal combustion engine like diesel engine and gasoline engine.

Gas turbine is installed in air plane, power plant, large ship and even vehicle.

How the turbine gas works?. Gas turbine is constructed from three main parts, a compressor, combustion chamber and turbine. This arrangement depends on for what application the gas turbine installed. The simplest arrangement is for air plane. In this type the compressor and turbine are in one shaft.
Compressor is used to compress air for combustion. The fuel for gas turbine is a form of gasoline but lighter. This fuel is very easy to flash. In power plant, the fuel is natural gas. The burning fuel results very high temperature and pressure. This pressure is then used to rotate the turbine. In here the energy conversion is take place.

The principal of turbine gas is from Brayton cycle. The efficiency of turbine gas can achieves as high as 50%.

Base on its application, in aviation, the turbine section is made short because the function of turbine is just for rotates the compressor. Actually the turbine gas for aviation is used to make a trust from burning gas. In power plant, the turbine section connected directly to generator. It is relatively long because almost all the power resulting from burning is used to rotate generator.

Turbine gas in power plant also has modification. Its exhaust gas is usually reused by recycling it to rotate the turbine once more or to rotate another turbine. From this mechanism, the efficiency of turbine gas is increase.