CONSTRUCTION OF SOLAR CELL

 A brief information that gives you how to make a solar cell.

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HYDRAULIC PUMPS

HYDRAULIC PUMPS

Hydraulic pumps are used in hydraulic drive systems and can be hydrostatic or hydrodynamic.

Hydrostatic pumps are positive displacement pumps while hydrodynamic pumps can be fixed displacement pumps, in which the displacement (flow through the pump per rotation of the pump) cannot be adjusted, or variable displacement pumps, which have a more complicated construction that allows the displacement to be adjusted.

Hydraulic pump types

Gear pumps

Gear pumps (with external teeth) (fixed displacement) are simple and economical pumps. The swept volume or displacement of gear pumps for hydraulics will be between about 1 cm³ (0.001 litre) and 200 cm³ (0.2 litre). These pumps create pressure through the meshing of the gear teeth, which forces fluid around the gears to pressurize the outlet side. Some gear pumps can be quite noisy, compared to other types, but modern gear pumps are highly reliable and much quieter than older models.

 

 

 

Rotary vane pumps

Rotary vane pumps (fixed and simple adjustable displacement) have higher efficiencies than gear pumps, but are also used for mid pressures up to 180 bars in general. Some types of vane pumps can change the centre of the vane body, so that a simple adjustable pump is obtained. These adjustable vane pumps are in general constant pressure or constant power pumps: the displacement is increased until the required pressure or power is reached and subsequently the displacement or swept volume is decreased until an equilibrium is reached.

Screw pumps

Screw pumps (fixed displacement) are a double Archimedes' screw, but closed. This means that two screws are used in one body. The pumps are used for high flows and relatively low pressure (max 100 bar). They were used on board ships where the constant pressure hydraulic system was going through the whole ship, especially for the control of ball valves, but also for the steering gear and help drive systems. The advantage of the screw pumps is the low sound level of these pumps; the efficiency is not that high.

Bent axis pumps

Bent axis pumps, axial piston pumps and motors using the bent axis principle, fixed or adjustable displacement, exists in two different basic designs. The Thoma-principle (engineer Hans Thoma, Germany, patent 1935) with max 25 degrees angle and the Wahlmark-principle (Gunnar Axel Wahlmark, patent 1960) with spherical-shaped pistons in one piece with the piston rod, piston rings, and maximum 40 degrees between the driveshaft centerline and pistons (Volvo Hydraulics Co.). These have the best efficiency of all pumps. Although in general the largest displacements are approximately one litre per revolution, if necessary a two-liter swept volume pump can be built. Often variable-displacement pumps are used, so that the oil flow can be adjusted carefully. These pumps can in general work with a working pressure of up to 350–420 bars in continuous work.

Axial piston pumps swashplate principle

Axial piston pumps using the swashplate principle (fixed and adjustable displacement) have a quality that is almost the same as the bent axis model. They have the advantage of being more compact in design. The pumps are easier and more economical to manufacture; the disadvantage is that they are more sensitive to oil contamination.

 

 

 

Radial piston pumps

Radial piston pumps (fixed displacement) are used especially for high pressure and relatively small flows. Pressures of up to 650 bar are normal. In fact variable displacement is not possible, but sometimes the pump is designed in such a way that the plungers can be switched off one by one, so that a sort of variable displacement pump is obtained.

 

 

 

Peristaltic pumps

Peristaltic pumps are not generally used for high pressures.

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Posted in: H,Hydraulic,Mechanical Engineering

TURRET LATHE

TURRET LATHE

This is one of the type of lathe, which is used for the metal cutting process. and it has wide range of applications, and can be operated easily with out much effort.

while the turret lathe is essentially a tool for the production of work in large quantities, a 6-in. lathe of the type described  will be found exceedingly useful in the small experimental shop. With a center held in the main turret, the machine may be used as a simple engine lathe, and when a number of similar pieces are to be turned out in a hurry the work may be performed in almost as expeditious a manner as on a commercial turret lathe. This machine was built and used by the author in his own workshop,

on fine precision work, and many accurate jobs have been done with it very quickly. Most of the work of  building can be done in a workshop equipped only with a vise and bench drill, with the necessary small tools, as flat cold-rolled steel is used for the ways, carriage, and other parts of that character; it will be necessary, however, to have certain things, such as the machining of the headstock and the cuttingof the feed screw, done in a machine shop, but this is a small item.The headstock is made of gray iron, and is fitted with an  overarm steadyrest, which allows the carriage to travel the full length of long work, as the work is supported from the top and rear. The spindle is carried, at the rear, by a doublerow ball bearing, .75 in. wide, of the combined axial and radial-load type, and at the front by a single-row bearing, .629 in. wide. Both of these bearings have an outside diameter of 2.441 in., and an inside diameter of 1.181 in. Care must be taken to bore the bearing housings a push fit for the bearings, and to have all faces square and parallel with each other.The spindle should be made of a good grade of steel, of about .3-per-cent carbon content, and is hollow. It is best to bore the spindle first, then re-center and finish the outside. The nose is taper-bored to take the collets, and threaded eight threads per inch, U. S. standard, to fit the faceplates and chucks. The taper seat for the collets should not be finished until the lathe has been completely assembled; it should then be machined with tools held in the toolpost of the lathe itself. The inner races of the ball bearings should be a good fit on the flat threads on the rear of the spindle, and on the outside of the spindle at the front. Bearing retaining rings are fitted at the rear, clamping the outer race of the bearing firmly, and taking up the end thrust.

These are fitted with felt dust rings, bearing on the collars on the spindle; the rings at the front are also fitted with dust rings, running on the spindle, but these rings do not clamp the single-row bearing, which is permitted to float. When the headstock is assembled, the bearing housings should be packed with a good grade of vaseline, which will last a long time; see that the vaseline supply is at all times sufficient for good lubrication.

Spindles fitted in this manner are far superior to those fitted with plain bearings, as they consume less power, are free from vibration, and allow of accurate as well as heavy work.

•   To know full details about TURRENT LATHE(click here to download)pdf.

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Posted in: L,Mechanical Engineering,T

MECHANICAL ENGINEERING DESIGN(ebook)

MECHANICAL ENGINEERING DESIGN TEXT BOOK

A MECHANICAL ENGINEERING TEXT BOOK FOR DESIGN AND THIS IS THE RIGHT BOOK TO ACQUIRE ALL THE BASICS. AND ALSO THE SOLVED PROBLEMS IN THIS TEXT BOOK ARE GIVEN.

• MECHANICAL ENGINEERING TEXT BOOK(click here to download)ebook.
• SOLVED PROBLEMS OF THIS TEXT BOOK(click here to download).rar.

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Posted in: D,Mechanical Engineering

WELDING

WELDING

Welding is a fabrication or sculptural process that joins materials, usually metals orthermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material (the weld pool) that cools to become a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to produce the weld. This is in contrast with soldering and brazing, which involve melting a lower-melting-point material between the workpieces to form a bond between them, without melting the workpieces.

Many different energy sources can be used for welding, including a gas flame, an electric arc, a laser, an electron beam, friction, and ultrasound. While often an industrial process, welding may be performed in many different environments, including open air, under water and inouter space. Welding is a potentially hazardous undertaking and precautions are required to avoid burns, electric shock, vision damage, inhalation of poisonous gases and fumes, and exposure to intense ultraviolet radiation. Until the end of the 19th century, the only welding process was forge welding, which blacksmiths had used for centuries to join iron and steel by heating and hammering. Arc welding and oxyfuel welding were among the first processes to develop late in the century, and electric resistance welding followed soon after. Welding technology advanced quickly during the early 20th century as World War I and World War II drove the demand for reliable and inexpensive joining methods. Following the wars, several modern welding techniques were developed, including manual methods like shielded metal arc welding, now one of the most popular welding methods, as well as semi-automatic and automatic processes such as gas metal arc welding, submerged arc welding, flux-cored arc welding and electroslag welding. Developments continued with the invention of laser beam welding, electron beam welding, electromagnetic pulse welding andfriction stir welding in the latter half of the century. Today, the science continues to advance. Robot welding is commonplace in industrial settings, and researchers continue to develop new welding methods and gain greater understanding of weld quality and properties.

Types of weld joints:

•  Square groove.
• V-groove.
• Bevel groove.
• U-groove.
• J-groove.
• Flare-v.
• Flare bevel.
• Edge flange.
• Corner flange.
• Fillet.

• To know the full details of different types of (click here to download)pdf

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Posted in: Mechanical Engineering,W

RIVETED JOINTS

RIVET

A rivet is a permanent mechanical fastener. Before being installed a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite the head is called the buck-tail. On installation the rivet is placed in a punched or pre-drilled hole, and the tail is upset, or bucked(i.e. deformed), so that it expands to about 1.5 times the original shaft diameter, holding the rivet in place. To distinguish between the two ends of the rivet, the original head is called the factory head and the deformed end is called the shop head or buck-tail.

Because there is effectively a head on each end of an installed rivet, it can support tension loads (loads parallel to the axis of the shaft); however, it is much more capable of supporting shear loads (loads perpendicular to the axis of the shaft). Bolts and screws are better suited for tension applications.

Fastenings used in traditional wooden boat building, like copper nails and clinch bolts, work on the same principle as the rivet but were in use long before the term rivet came about and, where they are remembered, are usually classified among the nails and bolts respectively.

Types of riveted joints and joint efficiency:

Riveted joints are mainly of two types

1. Lap joints

2. Butt joints

Lap Joints: The plates that are to be joined are brought face to face such that an overlap exists,Rivets are inserted on the overlapping portion. Single or multiple rows of rivets are used to give strength to the joint. Depending upon the number of rows the riveted joints may be classified as single riveted lap joint, double or triple riveted lap joint etc. When multiple joints are used, the arrangement of rivets between two neighbouring rows may be of two kinds. In chain riveting the adjacent rows have rivets in the same transverse line. In zig-zag riveting, on the other hand, the adjascent rows of rivets are staggered.     

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Posted in: Mechanical Engineering,R

HYDROELECTRIC POWER PLANT

HYDROELECTRIC POWER PLANT

Hydroelectric power plants convert the hydraulic potential energy from water into electrical energy. Such  plants are suitable were water with suitable head are available. The layout covered in this article is just a simple one and only cover the important parts of  hydroelectric plant.The different parts of  a hydroelectric power plant are


DAM:

Dams are structures built over rivers to stop the water flow and form a reservoir.The reservoir stores the water flowing down the river. This water is diverted to turbines in power stations. The dams collect water during the rainy season and stores it, thus allowing for a steady flow through the turbines throughout the year. Dams are also used for controlling floods and irrigation. The dams should be water-tight and should be able to withstand the pressure exerted by the water on it. There are different types of dams such as arch dams, gravity dams and buttress dams. The height of water in the dam is called head race.

SPILLWAY:

A spillway as the name suggests could be called as a way for spilling of water from dams. It is  used to provide for the release of flood water from a dam. It is used to prevent over toping of the dams which could result in damage or failure of  dams. Spillways could be controlled type or uncontrolled type. The uncontrolled types start releasing water upon water rising above a particular level. But in case of the controlled type, regulation of flow is possible


PENSTOCK OR TUNNEL:

Penstocks are pipes which carry water from the reservoir to the turbines inside power station. They are usually made of  steel and are equipped with gate systems.Water under high pressure flows through the penstock. A tunnel serves the same purpose as a penstock. It is used when an obstruction is present between the dam and power station such as a mountain. 

SURGE TANK:

Surge tanks are tanks connected to the water conductor system. It serves the purpose of reducing water hammering in pipes which can cause damage to pipes. The sudden surges of water in penstock is taken by the surge tank, and when the water requirements increase, it supplies the collected water thereby regulating water flow and pressure inside the penstock.

POWER STATION:

Power station contains a turbine coupled to a generator. The water brought to the power station rotates the vanes of the turbine producing  torque and rotation of turbine shaft. This rotational torque is transfered to the generator and is converted into electricity. The used water is released through the tail race. The difference between head race and tail race is called gross head and by subtracting the frictional losses we get the net head available to the turbine for generation of electricity.




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Posted in: H,Hydraulic,Mechanical Engineering