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