Ball and Detent A simple mechanical arrangement used to hold a moving part in a temporarily fixed position relative to another part. The ball slides within a bored cylinder, against the pressure of a spring, which pushes the ball against the detent, a hole of smaller diameter than the ball. When the hole is in line with the cylinder, the ball falls partially into the hole under spring pressure, holding the parts at that position. Additional force will push the ball back into its cylinder, compressing the spring, and allowing the parts to move.
Bearing The part of a machine within which a rotating or sliding shaft is held. In some bearing types, balls or rollers are used between the bearing surfaces to reduce rolling friction.
Bell crank A pivoting double lever used to change the direction of applied motion.
Boss A cylindrical projection, as on a casting or a forging. Usually provides a contact surface around a hole.
Broach To finish the inside of a hole to a shape other than round, as in a keyway. The tool for the process, which has serrated edges and is pushed or pulled through the hole to produce the required shape.
Burnish To smooth or polish by a rolling or sliding tool under pressure.
Bushing A smooth walled bearing (AKA a plain bearing). Also, a tool guide in a jig or fixture.
Cam A mechanical device consisting of an eccentric or multiply curved wheel mounted on a rotating shaft, used to produce variable or reciprocating motion in another engaged or contacted part (cam follower). Also, Camshaft.
Casting Any object made by pouring molten metal into a mold.
Chamfer A flat surface made by cutting off the edge or corner of an object (bevel).
Clevis A U-shaped piece with holes into which a link is inserted and through which a pin or bolt is run. It is used as a fastening device which allows rotational motion.
Collar A cylindrical feature on a part fitted on a shaft used to prevent sliding (axial) movement.
Collet A cone-shaped sleeve used for holding circular or rodlike pieces in a lathe or other machine.
Core To form the hollow part of a casting, using a solid form placed in the mold The solid form used in the coring process, often made of wood, sand, or metal.
Counterbore A cylindrical flat-bottomed hole, which enlarges the diameter of an existing pilot hole. The process used to create that feature.
Countersink A conical depression added to an existing hole to accommodate and the conic head of a fastener recessing it below the surface of a face.
Coupling A device used to connect two shafts together at their ends for the purpose of transmitting power. May be used to account for minor misalignment or for mitigating shock loads.
Die One of a pair of hardened metal plates or impressing or forming desired shape. Also, a tool for cutting external threads.
Face To machine a flat surface perpendicular to the axis of rotation of a piece.
Fillet A rounded surface filling the internal angle between two intersection surfaces. Also Rounds
Fit The class of contact between two machined surfaces, based upon their respective specified size tolerances (clearance, transitional, interference)
Fixture A device used to hold a workpiece while manufacturing operations are performed upon that workpiece.
Flange (see bushing example) A projecting rim or edge for fastening, stiffening or positioning.
Gage A device used for determining the accuracy of specified manufactured parts by direct comparison..
Gage blocks Precision machined steel blocks having two flat, parallel surfaces whose separation distance is fabricated to a guaranteed accuracy of a few millionths of an inch;
Gear Hobbing A special form of manufacturing that cuts gear tooth geometries. It is the major industrial process for cutting involute form spur gears of.
Geneva Cam A device to turn constant rotational motion into intermittent rotational motion.
Gusset (plate) A triangular metal piece used to strengthen a joint.
Hasp A metal fastener with a slotted, hinged part that fits over a loop and is secured by a pin, bolt, or padlock.
Idler A mechanism used to regulate the tension in belt or chain. Or, a gear used between a driver and follower gear to maintain the direction of rotation.
Jig A special device used to guide a cutting tool (drill jig) or to hold material in the correct position for cutting or fitting together (as in welding or brazing)
Journal The part of a shaft that rotates within a bearing
Kerf A channel or groove cut by a saw or other tool.
Key (Woodruff key shown) A small block or wedge inserted between a shaft and hub to prevent circumferential movement.
Keyseat A slot or groove cut in a shaft to fit a key. Key rests in a Keyseat.
Keyway A slot cut into a hub to fit a key. A key slide in a keyway. See Broach.
Knurl To roughen a turned surface, as in a handle or a knob.
Lug Projection on (typically) a cast or forged part to provide support or allow mounting or the attachment of another component.
Neck To cut a groove around a shaft, usually toward the end or at a change in diameter. A portion of reduced diameter between the ends of a shaft.
Pad A rectangular or irregular projection, as on a casting or a forging. Usually provides a contact surface around a set of holes.
Pawl A device used to prevent a toothed wheel (ratchet) from rotating backwards, or a device that stops, locks, or releases a mechanism.
Pillow Block A bearing housing which typically mounts to a single planar face. May be split or unsplit to accommodate insertion /removal of the bearing.
Pinion A plain gear, often the smallest gear in a gearset, often the driving gear. May be used in conjunction with a gear rack
Planetary Gears A gearset characterized by one or more planet gear(s) rotating around a sun gear. Epicyclic gearing systems include an outer ring gear (known as an annulus) with the planetary system.
Ratchet A mechanical device used to permit motion in one direction only.
Relief A groove or cut on a part used to facilitate machining.
Retaining Ring A tool steel ring used in conjunction with a shaft groove or internal groove to located or control position of a component.
Rocker Arm A pivoted arm-like lever used to transfer the application direction of a linear force.
Scotch Yoke Mechanism used to convert rotational motion to linear motion.
Sheave A grooved wheel used to accommodate a belt for the transmission of power. Sometimes referred to as a pulley sheave.
Shim A thin strip of metal inserted between two surfaces to adjust for fit.
Shoulder A plane surface on a shaft, normal to the axis, produced by a change in diameter.
Spline A cylindrical pattern of keyways. May be external (L) or internal (R)
Spotface a round machine surface around a hole on a casting or forging, usually to provide a contact surface for a fastener or other mating component.
Standoffs A mounting designed to position objects a predetermined distance above or away from the surface upon which they are mounted.
Tap To cut internal machine threads in a hole, the tool used to create that feature.
Undercut A cut having inward sloping sides, to cut leaving an overhanging edge
Yoke A clamp or vise that holds a machine part in place or controls its movement or that holds two such parts together. A crosshead of relatively thick cross section, that secures two or more components so that they move together.
Rotary and reciprocating compressors are both components of gas transfer systems. They both have the same purpose–to bring a gas into the system, inhale exhaust, then repeat the process. They both do this by changing the pressure at certain points in order to force gas in and exhaust out.
One key difference is that reciprocating compressors use pistons while rotary compressors do not. A reciprocating compressor has a piston move downwards, reducing pressure in its cylinder by creating a vacuum. This difference in pressure forces the cylinder door to open and bring gas in. When the cylinder goes back up, it increases pressure, thus forcing the gas back out. The up-and-down motion is called a reciprocating motion, hence the name.
Rotary compressors, on the other hand, use rollers. They sit slightly off-center in a shaft, with one side always touching the wall. As they move at high speeds, they accomplish the same goal as the reciprocating compressors–one part of the shaft is always at a different pressure than the other, so gas can come in at the low pressure point and exit at the high pressure point.
Advantages and Disadvantages
Reciprocating compressors are marginally more efficient than rotary compressors, generally being able to compress the same amount of gas with between 5 and 10 percent less energy input. However, since this difference is so marginal, most small-to-medium level users are best off using a rotary compressor. Reciprocating compressors are more expensive and require more maintenance, so it is often not worth the extra cost and headache for such a small difference in efficiency.
Large users, however, are generally best-served by reciprocating compressors. These are users for whom 5 percent represents a substantial figure, often substantial enough to justify the added expense.
Comparison Between Reciprocating and Rotary Compressors
Comparison between Reciprocating and Rotary Compressors can be done in aspects like pressure ratio, handled volume, speed of compressor, vibrational problem, size, air supply, purity of compressed air, compression efficiency, maintenance, mechanical efficiency, lubrication, initial cost, flexibility and suitability.
||Discharge Pressure of air is high. The pressure ratio per stage will be in the order of 4 to 7.
||Discharge pressure of air is low. The pressure ratio per stage will be in the order of 3 to 5.
||Quantity of air handled is low and is limited to 50m3/s.
||Large measure of air handled can be handled and it is about 500 m3/s.
||Speed of Compressor
||Low speed of compressor.
||High speed of compressor.
||Due to reciprocating section, greater vibrational problem, the parts of machine are poorly balanced.
||Rotary parts of machine, thus it has less vibrational problems. The machine parts are fairly balanced.
||Size of compressor
||Size of Compressor is bulky for given discharge volume.
||Compressor size is small for given discharge volume.
||Air supply is intermittent.
||Air supply is steady and continuous..
||Purity of compressed air
||Air delivered from the compressor is dirty, since it comes in contact with lubricating oil and cylinder surface.
||Air delivered from the compressor is clean and free from dirt.
||Higher with pressure ratio more than 2.
||Higher with compression ratio less than 2.
||Higher due to reciprocating engine.
||Lower due to less sliding parts..
||Lower due to several sliding parts..
||Higher due to less sliding parts.
||Complicated lubrication system.
||Simple lubrication system.
||Greater flexibility in capacity and pressure range.
||No flexibility in capacity and pressure range.
||For medium and high pressure ratio.
For low and medium gas volume.
|For low and medium pressures.
For large volumes.
Basic terms for Mechanical Engineering
List of basic terms for Mechanical Engineering
1. Torque or Turning Force
7. Specific Weight
8. Specific Volume
9. Specific Gravity
10. Specific Heat
13. Discharge of Fluid
14. Bernoulli’s Equation
15. Device for Fluid
16. Mach Number
17. Hydraulic Machine
18. Draft Tube
19. Thermodynamics Laws
- zeroth law
- First law
- second law
21. calorific value of fuel
22. Boiler/Steam Generator
24. Air Preheater
25. Boiler Draught
32. Rating of fuel-
33. Stoichiometric Mixture/ Stoichiometric Ratio
34. Heat Transfer
35. Thermal Conductivity
36. Heat Exchanger
38. 1 tonne Refrigeration
41. Gear Train
42. Gyroscopic Couple
43. Heat Treatment
45. Non-ferrous metal
52. Nuclear Fission
53. Nuclear Fussion
55. Machine Tool
56. Cutting Tool
Torque or Turning Force:
It is the total amount of force which is required to create acceleration on moving substance.
Two forces those acts on equally,parallely & oppositely on two separate points of same material.
It is the amount of moving effect which is gained for action of turning force.
It is the force that can prevent equal & opposite force. That means, it is the preventing force. If one force acts on outside of a material, then a reactive force automatically acts to protest that force. The amount of reactive force per unit area is called stress. e.g. Tensile Stress, Compressive Stress, Thermal Stress.
If a force acts on a substance, then in that case if the substance would deform. Then the amount of deformation per unit length of that substance is called strain.
It is one type of device which is being distorted under certain amount of load & also can also go to its original face after the removal of that load.
- To store energy.
- To absorb energy.
- To control motion of two elements.
Load per unit deflection. The amount of load required to resist the deflection.
Weight per unit volume of the fluid.
Volume per unit mass of the fluid.
It is the ratio of specific weight of required substance to specific weight of pure water at 4 degree centigrade temperature.
The amount of heat required to increase 1 unit temperature of 1 unit mass.
The amount of resistance of one layer of fluid over other layer of fluid.
It is the ratio of dynamic viscosity to density.
When a body is immersed in a liquid, it is lifted up by a force equal to weight of liquid displaced by the body. The tendency of liquid to lift up an immersed body is buoyancy. The upward thrust of liquid to lift up the body is called buoyancy force.
P/γ +V²/2g +Z = Constant
Where, P = pressure,V = velocity,Z = Datumn Head
Devices for fluid:
It measures discharge of fluid.
It measures discharge of fluid.
It measures discharge of fluid.
Pitot tube :
It measures velocity of fluid.
It is the ratio of the velocity of fluid to the velocity of sound.
M=1 —————– Sonic flow
M> (1-6) ———– Super-Sonic flow
M>6 —————- Hyper-Sonic flow
Fluid discharge/Fluid flow:
Quantity of fluid flowing per second.
(through a section of pipe/ through a section of channel)
where, V= velocity of fluid,A= cross-sectional area of pipe/channel
Note: 1m³ = 1000 L1 cusec = 1 ft³/sec1 ft = 0.3048 m
It attaches with reaction turbine . Its function is to reduce energy loss from reaction turbine & it also reduce pressure at outlet which is must blow the atmospheric pressure.
If two body are in thermal equilibrium with a third body then these two body are also in thermal equilibrium with each other.
First Law of Thermodynamics:
In a closed system, work deliver to the surrounding is directly proportonal to the heat taken from the surrounding.And also, In a closed system, work done on a system is directly proportonal to the heat deliver to the surrounding.
Second Law of Thermodynamics:
It is impossible to make a system or an engine which can change 100 percent input energy to 100 percent output.
It is a thermodynamic property.
ds = dq/T
where, ds = change of entropy, dq = change of heat, T = Temperature.
In adiabatic process, entropy can not change. Actually,lacking or mal-adroitness of tranfering energy of a system is entropy.
Calorific Value of fuel:
It us the total amount of heat obtained from burning 1 kg solid or liquid fuel.
It is a clossed vessel which is made of steel. Its function is to transfer heat to water to generate steam.
It is a part of boiler. Its function is to heat feed water which is supplied to boiler.
It is a part of boiler. Its function is to increase temperature of steam into boiler.
It is a part of boiler. Its funtion is to preheats the air to be supplied to furnace and it recover heat from exhaust gas.
It is an important term for boiler. It is the difference of pressure above and below the fire grate. This pressure difference have to maintain very carefully inside the boiler. It actually maintains the rate of steam generation. This depends on rate of fuel burning. Inside the boiler rate of fuel burning is maintained with rate of entry fresh air. If proper amount of fresh air never entered into the boiler, then proper amount of fuel inside the boiler never be burnt. So, proper fresh air enters into the boiler only by maintaining boiler draught.
Nozzle is a duct of varying cros-sectional area. Actually, it is a passage of varying cross-sectional area. It converts steam’s heat energy into mechanical energy. It is one type of pipe or tube that carrying liquid or gas.
It is the process of removing burnt gas from combustion chamber of engine cylinder.
Actually, power output of engine depends on what amount of air enter into the engine through intake manifold. Amount of entry air if increased, then must be engine speed will increased. Amount of air will be increased by increasing inlet air density. The process of increasing inlet air density is supercharging. The device which is used for supercharging is called supercharger. Supercharger is driven by a belt from engine crankshaft. It is installed in intake system.
Turbocharging is similar to the supercharging. But in that case turbocharger is installed in exhaust system whereas supercharger is installed in intake system. Turbocharger is driven by force of exhaust gas. Generally, turbocharger is used for 2-stroke engine by utilizing exhaust energy of the engine, it recovers energy otherwise which would go waste.
Its function id to regulate mean speed of engine when there are variation in the load. If load incrases on the engine, then engine’s speed must decrease. In that case supply of working fluid have to increase. In the otherway, if load decrease on the engine, then engine’ speed must increase. In that case supply of working fluid have to decrease.Governor automatcally, controls the supply of working fluid to the engine with varying load condition.
It is the one of the main parts of the I.C. engine. Its main function id to store energy in the time of working stroke or expansion stroke. And, it releasesenergy to the crankshaft in the time of suction stroke, compression stroke & exhaust stroke. Because, engine has only one power producing stroke.
Rating of fuel:
Octane number. Octane number indicates ability of fuel to resist knock.
Cetane Number. Cetane number indicates ability of ignition of diesel fuel. That means, how much fast ignites diesel fuel.
It is the chemically correct air-fuel ratio by volume. By which theoretically sufficient oxygen will be gotten to burn all combustible elements in fuel completely.
It is a science which deals with energy transfer between material bodies as a result of temperature difference.There are three way to heat transfer such as-ConductionConvectionRadiation
It is the quantity of heat flows between two parts of solid material by conduction. In this case following consideration will be important fact-
- Time—— 1 sec
- Area of that solid material——– 1 m²
- Thickness of that solid material—— 1m
- Temperature difference between two parts of that material—— 1k
It is one type of device which can transfer heat from one fluid to another fluid. Example- Radiator, inter-cooler, preheater, condenser, boiler etc.
It is the process of removing heat from a substance. Actually, extraction of heat from a body whose temperature is already below the temperature of its surroundings.
1 tonne of refrigeration:
It is amount of refrigeration effect or cooling effect which is produced by uniform melting of 1 tonne ice in 24 hours from or at 0 degree centigrade or freezing 1 tonne water in 24 hours from or at 0 degree centigrade.
It is the addition of moisture to the air without change dry bulb temperatur.
It is the removal of moisture from the air without change dry bulb temperature.
Meshing of two or more gear. It can transmit power from one shaft to another shaft.
Operation involving heating and cooling of a metal in solid state for obtaining desirable condition without being changed chemical composition.Its object-increase hardness of metal.increase quality of metal ( heat, corrosion,wear resistance quality )improve machinability.
1. Cast Iron – (2-6.67)%C, Si, Mn, P, S
2. Steel – (0-2)%C
3. Wrought Iron – 99.5% Fe
1. Brass – (Cu+Zn)
2. Bronze –
(Sn+Cu) —— Tin Bronze
(Si+Cu) ——- Silicon Bronze
(Al+Cu) ——- Aluminium Bronze
It is the difference between basic dimension of mating parts. That means, minimum clearance between mating parts that can be allowed.
It is the difference between upper limit of dimension. It is also the permissible variation above and below the basic size. That means maximum permissible variation in dimensions.
It is the difference in size between mating parts. That means, in that case the outside dimension of the shaft is less than internal dimension of the hole.
It is the ability to resist deformation.
It is the property to resist fracture.
When a material is subjected to repeated stress below yield point stress, such type of failure is fatigue failure.
It is a nuclear reaction by which one big nucleous divided into two or more nucleous.
It is also a nuclear reaction by which one big nucleus will produced by adding two small nucleus.
It is the process of joining two similar or dissimilar metal by fusion.
Arc Welding –
* need D.C current
* produced (6000-7000) Degree Centegrade Temperature
Gas Welding –
* Oxy – acetylene flame join metals
* Oxygen & acetylene gas works
* produced 3200 Degree Centegrade Temperature
It is the power driven tool. It cut & form all kinds of metal parts.
Example – 1. Lathe 2. Drill Press 3. Shaper 4. Planer 5. Grinding 6. Miling 7. Broaching 8. Boring
Tool Materials for Cutting Tool:
1. High Carbon Steel
2. High Speed Steel (W+Cr+V)
3. Carbide (W Carbide+Ti Carbide+Co Carbide)
It is the method of dividing periphery of job into equal number of division. Actually, it is the process of dividing circular or other shape of workpiece into equal space, division or angle.
It is one type of device which hold & locate workpiece and also guide & control cutting tool. It uses in drilling, reaming and tapping.
It is one type of device which hold and locate workpiece. It uses in miling, grinding, planning & turning.