What is a "Transmission"?

The transmission is a device that is connected to the back of the engine and sends the power from the engine to the drive wheels. An automobile engine runs at its best at a certain RPM (Revolutions Per Minute) range and it is the transmission's job to make sure that the power is delivered to the wheels while keeping the engine within that range. It does this through various gear combinations. In first gear, the engine turns much faster in relation to the drive wheels, while in high gear the engine is loafing even though the car may be going in excess of 70 MPH. In addition to the various forward gears, a transmission also has a neutral position which disconnects the engine from the drive wheels, and reverse, which causes the drive wheels to turn in the opposite direction allowing you to back up. Finally, there is the Park position. In this position, a latch mechanism (not unlike a deadbolt lock on a door) is inserted into a slot in the output shaft to lock the drive wheels and keep them from turning, thereby preventing the vehicle from rolling.
There are two basic types of automatic transmissions based on whether the vehicle is rear wheel drive or front wheel drive.

On a rear wheel drive car, the transmission is usually mounted to the back of the engine and is located under the hump in the center of the floorboard alongside the gas pedal position. A drive shaft connects the rear of the transmission to the final drive which is located in the rear axle and is used to send power to the rear wheels. Power flow on this system is simple and straight forward going from the engine, through the torque converter, then through the transmission and drive shaft until it reaches the final drive where it is split and sent to the two rear wheels.
























On a front wheel drive car, the transmission is usually combined with the final drive to form what is called a transaxle. The engine on a front wheel drive car is usually mounted sideways in the car with the transaxle tucked under it on the side of the engine facing the rear of the car. Front axles are connected directly to the transaxle and provide power to the front wheels. In this example, power flows from the engine, through the torque converter to a large chain that sends the power through a 180 degree turn to the transmission that is along side the engine. From there, the power is routed through the transmission to the final drive where it is split and sent to the two front wheels through the drive axles. There are a number of other arrangements including front drive vehicles where the engine is mounted front to back instead of sideways and there are other systems that drive all four wheels but the two systems described here are by far the most popular. A much less popular rear drive arrangement has the transmission mounted directly to the final drive at the rear and is connected by a drive shaft to the torque converter which is still mounted on the engine. This system is found on the new Corvette and is used in order to balance the weight evenly between the front and rear wheels for improved performance and handling. Another rear drive system mounts everything, the engine, transmission and final drive in the rear. This rear engine arrangement is popular on the Porsche.

Question and Answers related to the October current affairs 2013

Q 1: When the Cabinet approved the methodology for auctioning coal blocks?

a) 07 September

b) 24 September

c) 14 September

d) 27 September

Ans. 24 September

Q2: India becomes ‘Authorizing Nation’ for which product?

a) Leather products

b) Wooden products

c) Electronic /IT products

d) Fiber products

Ans.  Electronic /IT products

Q3: Who receives the “Peter J. Gomes Humanitarian Award” in the month of September?

a) Malala Yousafzai

b) K N Tilak Kumar

c) Hiroshi Yamauchi

d) A.K.Kutty

Ans. Malala Yousafzai

Q 4: On which date ‘Hiroshi Yamauchi’ President of Former Nintendo Co Ltd Died?

a) 02 September

b) 25 September

c) 10 September

d) 19 September

Ans. 19 September

Q 5: Who wins the Bronze World Junior Chess Champion Ship

a) Mercy Kuttan

b) Peter J. Gomes

c) Vidit Gujarathi

d) K N Tilak Kumar

Ans. Vidit Gujarathi

MECHANISM

1) QUICK RETURN CRANK MECHANISM
example-QUICK RETURN CRANK MECHANISM
2)RATCHET MECHANISMS
3)CRANKS AND CRANK SHAFTS
4)CRANK AND SLIDER MECHANISM

Angles of Single Point Cutting Tool

Angles of Single point cutting tool :

1: Side Cutting Edge Angle:

The angle between side cutting edge and the side of the tool shank is called side cutting edge angle. It is often referred to as the lead angle.

2: End Cutting Edge Angle:

The angle between the end cutting edge and a line perpendicular to the shank of the tool shank is called end cutting edge angle.

3: Side Relief Angle:

The angle between the portion of the side flank immediately below the side cutting edge and a line perpendicular to the base of the tool.

4: End Relief Angle:

The angle between the end flank and the line perpendicular to the base of the tool is called end relief angle.

5: Back Rake Angle:

The angle between the face of the tool and line perpendicular to the base of the tool measures on perpendicular plane through the side cutting edge. It is the angle which measures the slope of the face of the tool from the nose, towards the rack. If the slope is downward the nose it is negative back rake.

6: Side Rake Angle:

The angle between the face of the tool and a line parallel to the base of the tool measured on plane perpendicular to the base and the side edge. It is the angle that measure the slope of the tool face from the cutting edge, if the slope is towards the cutting edge it is negative side rake angle and if the slope is away from the cutting edge, it is positive side rake angle. If there is no slope the side rake angle is zero.

Boiler sizing and indirect water heaters

What size boiler do I need if I’m using an indirect water heater? Quite a common question, and for the vast majority of residential applications, the answer is: The same size as without an indirect. Whenever boiler sizing is in question, oversizing is never the right answer. The short cycling and reduced efficiency  with oversizing are common knowledge. “Yes, but I’m using a XX gallon indirect and the I&O manual says you need 180K BTU/Hr to get the rated output.” True enough, but how do you know that’s the right size indirect and that you need the full rated output?
Not many do it but the correct procedure is do the math rather than just guessing as to the size indirect tank needed. You need to know the GPM and temp rise needed. The wild card is duration: how long do you want to maintain that GPM flow rate? This where a thorough site inspection and customer interview are vital. Two identical 1,500-sq/ft  Cape Cod-type homes with identical heat losses can have wildly varying DHW loads. A full body shower and a few teenagers in one and a  retired couple in the other  means a huge difference in requirements. In one case, a 30-gallon is more than enough, in the other an 80-gallon may be insufficient, but without doing the math you just don’t know!
Ask the customer what they want and need, and size to that but keep in mind there are many ways to get to the same end result and all of them will be more efficient than over sizing the boiler. What ways can you deliver the required DHW without a boiler larger than the heat loss of the structure? Quite a few! Oversize the indirect for starters. Most indirect manufacturers rate their tanks at varying BTU/Hr inputs. For example, a 30-gallon tank paired with a 160K boiler may yield the same first hour rating as a 60-gallon tank and a 90K input boiler. Manufacturer’s specs are the place to start. Every water heater should have a mixing valve, correct? Absolutely! And what does maintaining the tank temp at 150 degrees vs 120 degrees do for DHW production?  Going from 120 degrees to 150 degrees will increase the effective size of the tank by 25% just like that a 40-gallon tank can give the initial output of a 50-gallon tank, and help prevent Legionnaires as a bonus! If needed, multiple indirects can be used or a storage tank on a single indirect. If none of these will give the desired quantity of DHW needed, a tankless water heater or multiples are the way to go. These will provide their rated GPM output forever and not require a boiler three or four times the heat load of the home.
There is no good excuse to oversize a boiler, and I know many will think this is heresy, but you don’t have to do a full-blown heat loss calculation on every job. After you do quite a few heat loss calculations, you start to realize that similar sized and designed homes have nearly identical heat loads and that this number is usually less than the smallest boilers available. Of course, homes that don’t fit the standard ranch, cape or colonials will require a calculation. Don’t add a “fudge factor” to the inputs or the final number. The software has plenty of fudge already baked in! Oversizing is a disservice to the consumer and the hydronic industry as a whole. Homeowners depend on us to provide efficient solutions to their problems, and it is incumbent on us to do so.

Top 10 Reasons – Why should one be a Mechanical Engineer ?

1.You get the opportunity to create something tangible and useful.Ur creations will be used by others.It gives u the greatest joy.
2.Its the broadest branch of engineering…so your career options are open even after u graduate:-
Defence,Civil services,High end R&D,Manufacturing,Design,Energy sector,Management,Entrepreneurship,Masters(ME/MS)
3.Variety to be learnt- u learn how to design and make things ranging from a Safety Pin to a Spacecraft.
4.Easy to imagine and visualize whatever u learn
5.Develop a range of skills – u learn the work of a machine operator (machinist), a smith, a foundryman, a mechanic,a plant manager,a researcher and a policy maker.
6.U work with massive machines (majestic in nature) to tiny precision instruments,micro and nano devices.
u’ll be savviest engineer.
7.Importance of ur work.U form the human resource that is required for the survival of any industry and forms the backbone of modern human life.u r the person who may generate power/energy from natural resources,make equipments and processes to mine minerals,make cars, bikes ,buses, trucks, planes,ships(transportation can be compared to human blood that transports nutrients), make machines that manufacture products ranging from food to surgical instruments to weapons,mange factories and businesses.
8.Get paid handsomely(after gaining a few years experience even if not as a fresher).
9.Not much of girls hanging around(they usually don’t prefer to opt for this course,its thought to be a manly course).U dont have to worry about getting dressed perfectly for class or for girls giggling at u for some silly or not so silly but serious reason.Ur in a man’s world.But there are a few out of the ordinary and brainy girls who do take up this course and luv it.
10.It sounds and feels nice to be called a Mechanical Engineer.

TATA Motors Recruitment Test

Some of the questions that were asked in this test include:
1. When boiler bursts, whom u would inform?
2. What does one mean by modular ratio?
3. What is ‘envelope of damped free vibration’?
4. A ball with a mass M is falling on to the ground with some velocity V1 and rising with velocity V2 . Find the impulse?
5. Contd.. for 5th problem. When time of contact is given then find force exerted on the ground.
6. Two masses are connecting with string on to pulley coefficient of friction of mass m1 is given and also m1 and m2 are given. Find the relation b/n m1 and m2 , to make m2 move downwards .
7. In a damped free excitation system maximum amplitude occurs
a. before resonance             b. after resonance
8. What are set screws?
9. A four bar link mechanism is given with moment m acting on crank and also a force given at crank end. Find the reaction at hinged end of crank.
10. Deflection due to self weight of a uniform rod of diameter D and unit density and length is given by____________.
11. Name the type of key used in wrist watch?
12. Bending stress is proportional to_____________
13. The hypoid gears are __________
14. Hollow cylinder of outer D0 is given. Find the diameter of solid cylinder for the same material and same torsional strength ?
15. What is the principle plane ?
16. Two masses are resting on a inclined plane with 30 degree angle and the two masses are welded with weightless rod and coefficients of friction is given. Find the common acceleration of a two masses.
17. Two masses are of different weights smaller one is placed on the bigger mass. If the force is acting on bigger mass (given),  find the acceleration of smaller mass.
18. Stress on minor diameter of bolt when bolt is subjected to longitudinal force.
19. no of independent elastic constants required for isotropic material?
20. pitch of the bolt of 30 mm metric thread dia meter is?
21. the ratio of natural frequency on earth to moon?
22. upper portion of set screw is given fig shown and asked which type of set screw is ?
23. Efficiency of screw jack formula?
24. which of the parts given is harder one? Ans a). inner case b)outer case like that?
25. Max efficiency of screw jack formula?
26. Given some c/s of diffirent types which is having more torsional strength ?
27. Max principle stress theory is valid for which material?
28. efficiency of reveted joints of different types has given which is having max efficiency ?
29. if the roots are real then which type of vibrations will occur in damped systems ?
30. problem on transmissibility ?
31. when the disc is rotating on which on man is standing at the edge then what is the possibility of increase in speed of the disc? A).man moves towards centre b)out ward? Like that
32. what is the principle behind the collisions of ball ?which is related to Q.7 ? ans constant linear momentum.
33. Find the elongation of the bar due to self weight
34. Problem on the cantilever deflection
35. Problem on the two blocks connected by string one is on table and on is hanging from the pulley…mechanics’ problem
36. Ratio of the tension of the band block breaks
37. max and normal efficiency of the power scew
38. what is monel metal
39. for which material max normal stress theory is used
40. efficiency of the riveted joints
41. coefficient of friction for the greased ball bearing
42. which key is used in wrist watch
43. bending stress is proportional to 1. directly/inversely proportional to section modulus
44. find the width of the strongest beam that can be cut of cylindrical log of wood whose dia is ‘d’
45. if the phi is friction angle then which of the following can not be the value of the tan(phi) a) 0 b) 1.5 mu etc. ans is 0
46. problem on the transmissibility …to calculate dynamic amplitude
47. what is the poison’s ratio?

Submerged Arc Welding SAW | Submerged Arc Welding Deposition Rates | Submerged Arc Welding Flux Composition

Submerged arc welding: (SAW)

In submerged arc welding also known as hidden arc welding, submerged melt welding, or sub-arc welding the arc is struck between a metal electrode and the work piece under a blanket of granular flux. The welding action takes place under the flux layer without any visible arc, spatter, smoke or flash. 

Here the weld arc is shielded by granular flux, consisting of Lime, Silica, Manganese Oxide, Calcium Fluoride, and other elements.

The filler wire used may be bare or slightly copper coated. The consumable electrode is a coil of bare round wire 1.5 to 10 mm in diameter.

Operation of Submerged Arc welding Process:

The welding action can be initiated by introducing a piece of high resistance conducting material like steel wool or carbon between the electrode and the work piece. Once the welding action has been initiated the intense heat produced by the flow of current in the high resistance path melts a path of the flux around the electrode forming a conducting pool. The molten filler displaces the liquid flux and fuses with the molten base metal forming the weld. The molten flux coating over the molten metal pool forms a blanket that eliminates spatter losses and protects the welded joint from oxidation. As welding proceeds, the molten weld metal and the liquid flux cool and solidify under a layer of unused flux. The molten flux on solidification forms a brittle slag layer which can be easily removed.

Unused granular flux material can be reclaimed and reused.

Characteristics of Submerged Arc welding Process:

• Electric current is 300 to 2000A.
• Power supply is 440 V.
• Velocity is 5m / Min
• The SAW process provides very high welding productivity, depositing 4 – 10 times the amount of weld metal per hour.

Advantages of Submerged Arc welding Process:

• Thin plates can be easily welded in one pass without any edge preparation while only a slight bevelling is necessary in most other cases.
• The quality of welds produced in submerged arc welding is very high with good toughness, ductility and uniformity of properties.
• Submerged arc welding is most suitable for welding in the down hand or flat position although welds can be made on a straight slope.
• Materials successfully welded by the process include low carbon steel, medium carbon steel, heat resistant steel, corrosion resistant steel, high strength steels and non ferrous metals like Monel metal, nickel and others.
• High  speed of execution due to the use of high currents in one or more electrode wires
• No smoke
• The arc is concealed, enabling the operator to work without a mask and without disturbing others nearby

Limitations of Submerged Arc welding Process:

• Solid flux submerged arc welding can be used only on alloy and non-alloy carbon steel, stainless and refractory steel
• The use of a powder flux means that welds must be executed horizontally, unless special measures are taken
• The process cannot weld plate less than 1.8 mm thick (due to its high penetration)
• It is not possible to butt joint work pieces more than 16 mm thick ; thicknesses greater than 16 mm require special preparation (bevelling).

Application of Submerged Arc welding Process:

• Shipbuilding
• Heavy Duty Pressure vessels
• Off shore engineering

Linear actuator

From Wikipedia, the free encyclopedia
A linear actuator is a device that develops force and motion, from an available energy source, in a linear manner, as opposed to rotationally like an electric motor. There are various methods of achieving this linear motion. Several different examples are listed below.

Types of Linear Actuators

Mechanical actuators

Mechanical actuators typically convert rotary motion of a control knob or handle into linear displacement via screws and/or gears to which the knob or handle is attached. A jackscrew or car jack is a familiar mechanical actuator. Another family of actuators are based on the segmented spindle. Rotation of the jack handle is converted mechanically into the linear motion of the jack head. Mechanical actuators are also frequently used in the field of lasers and optics to manipulate the position of linear stages, rotary stages, mirror mounts, goniometers and other positioning instruments. For accurate and repeatable positioning, index marks may be used on control knobs. Some actuators even include an encoder and digital position readout.[1] These are similar to the adjustment knobs used on micrometers except that their purpose is position adjustment rather than position measurement.

Hydraulic actuators
Hydraulic actuators or hydraulic cylinders typically involve a hollow cylinder having a piston inserted in it. The two sides of the piston are alternately pressurized/de-pressurized to achieve controlled precise linear displacement of the piston and in turn the entity connected to the piston. The physical linear displacement is only along the axis of the piston/cylinder. This design is based on the principles of hydraulics. A familiar example of a manually operated hydraulic actuator is a hydraulic car jack. Typically though, the term "hydraulic actuator" refers to a device controlled by a hydraulic pump.

Piezoelectric actuators
The piezoelectric effect is a property of certain materials in which application of a voltage to the material causes it to expand. Very high voltages correspond to only tiny expansions. As a result, piezoelectric actuators can achieve extremely fine positioning resolution, but also have a very short range of motion. In addition, piezoelectric materials exhibit hysteresis which makes it difficult to control their expansion in a repeatable manner.

Electro-mechanical actuators

Electro-mechanical actuators are similar to mechanical actuators except that the control knob or handle is replaced with an electric motor. Rotary motion of the motor is converted to linear displacement of the actuator. There are many designs of modern linear actuators and every company that manufactures them tends to have their own proprietary method. The following is a generalized description of a very simple electro-mechanical linear actuator.

Simplified Design
Typically, a rotary driver (e.g. electric motor) is mechanically connected to a lead screw so that the rotation of the electric motor will make the lead screw rotate. A lead screw has a continuous helical thread machined on its circumference running along the length (similar to the thread on a bolt). Threaded onto the lead screw is a lead nut with corresponding helical threads. The nut is prevented from rotating with the lead screw (typically the nut interlocks with a non-rotating part of the actuator body). Therefore, when the lead screw is rotated, the nut will be driven along the threads. The direction of motion of the nut will depend on the direction of rotation of the lead screw. By connecting linkages to the nut, the motion can be converted to usable linear displacement. Most current actuators are built either for high speed, high force, or a compromise between the two. When considering an actuator for a particular application, the most important specifications are typically travel, speed, force, and lifetime.

Principles

In the majority of linear actuator designs, the basic principle of operation is that of an inclined plane. The threads of a lead screw act as a continuous ramp that allows a small rotational force to be used over a long distance to accomplish movement of a large load over a short distance.

Variations
Many variations on the basic design have been created. Most focus on providing general improvements such as a higher mechanical efficiency, speed, or load capacity. There is also a large engineering movement towards actuator miniaturization.

Most electro-mechanical designs incorporate a lead screw and lead nut. Some use a ball screw and ball nut. In either case the screw may be connected to a motor or manual control knob either directly or through a series of gears. Gears are typically used to allow a smaller (and weaker) motor spinning at a higher rpm to be geared down to provide the torque necessary to spin the screw under a heavier load than the motor would otherwise be capable of driving directly. Effectively this sacrifices actuator speed in favor of increased actuator thrust.

Some lead screws have multiple "starts". This means that they have multiple threads alternating on the same shaft. One way of visualizing this is in comparison to the multiple color stripes on a candy cane. This allows for more adjustment between thread pitch and nut/screw thread contact area, which determines the extension speed and load carrying capacity (of the threads), respectively.

Linear motors
A linear motor is essentially a rotary electric motor laid down on flat surface. Since the motor moves in a linear fashion to begin with, no lead screw is needed to convert rotary motion to linear. While high capacity is possible, the material and/or motor limitations on most designs are surpassed relatively quickly. Most linear motors have a relatively low load capacity compared to other types of linear actuators.

Wax motors
A wax motor typically uses an electric current to heat a block of wax causing it to expand. A plunger that bears on the wax is thus forced to move in a linear fashion.

Segmented spindles
KATAKA actuators consist of discrete chain elements which are interlinked to form a rod (the technology is known as the segmented spindle) thus making the actuator extremely compact (see www.kataka.dk).