GEAR TERMINOLOGY EXPLAINED !!

Face of tooth:It is defined as the surface of the tooth above the pitch circle is known as face.


Flank of tooth:The surface of the tooth below the pitch circle is known as flank.

Top land:The top most surface of the tooth is known as the top land of the tooth.


Face width:Width of the tooth is known as face width.


Pitch Circle:It is an imaginary circle which is in pure rolling action. The motion of the gear is describe by the pitch circle motion.


Pitch Circle diameter:The diameter of the pitch circle from the center of the gear is known as pitch circle diameter. The gear diameter is described by its pitch circle diameter.


Pitch point:When the two gears are in contact, the common point of both of pitch circle of meshing gears is known as pitch point.


Pressure angle or angle of obliquity:Pressure angle is the angle between common normal to the pitch circle to the common tangent to the pitch point.


Addendum:Distance between the pitch circle to the top of the tooth in radial direction is known as addendum.


Dedendum:Distance between the pitch circle to the bottom of the tooth in radial direction, is known as dedendum of the gear.


Addendum circle:The circle passes from the top of the tooth is known as addendum circle. This circle is concentric with pitch circle.


Dedendum circle:The circle passes from the bottom of the tooth is known as dedendum circle. This circle is also concentric with pitch circle and addendum circle.


Circular pitch:The distance between a point of a tooth to the same point of the adjacent tooth, measured along circumference of the pitch circle is known as circular pitch. It is plays measure role in gear meshing. Two gears will mesh together correctly if and only they have same circular pitch.


Diametrical pitch:The ratio of the number of teeth to the diameter of pitch circle in millimeter is known as diametrical pitch.


Module:The ratio of the pitch circle diameter in millimeters to the total number of teeth is known as module. It is reciprocal of the diametrical pitch.


Clearance:When two gears are in meshing condition, the radial distance from top of a tooth of one gear to the bottom of the tooth of another gear is known as clearance. The circle passes from the top of the tooth in meshing condition is known as clearance angle.


Total depth:The sum of the addendum and dedendum of a gear is known as total depth. It is the distance between addendum circle to the dedendum circle measure along radial direction.


Working depth:The distance between addendum circle to the clearance circle measured along radial direction is known as working depth of the gear.


Tooth thickness:Distance of the tooth measured along the circumference of the pitch circle is known as tooth thickness.


Tooth space:Distance between the two adjacent tooth measured along the circumference of the pitch circle is known as the tooth space.


Backlash:It is the difference between the tooth thickness and the tooth space. It prevents jamming of the gears in meshing condition.


Profile:It is the curved formed by the face and flank is known as profile of the tooth. Gear tooth are generally have cycloidal or involute profile.

Path of contact:The curved traced by the point of contact of two teeth form beginning to the end of engagement is known as path of contact.


Arc of contact:It is the curve traced by the pitch point form the beginning to the end of engagement is known as arc of contact.


Arc of approach:The portion of the path of contact from beginning of engagement to the pitch point is known as arc of approach.


Arc of recess:The portion of the path of contact form pitch point to the end of the engagement is known as arc of recess.

KNOW WHY GEARBOX IS NOT USED IN ELECTRIC VEHICLES !!

Internal combustion engines generate usable torque and power in a narrow band of engine speeds. To accelerate the vehicle, multispeed transmissions step that down, in varying gear ratios, to keep the engine in its power band. Keeping the engine in its power band also proves to be the most efficient and durable. An engine, in first gear, can easily accelerate a car to 30 mph, but would also shake itself to bits attempting to accelerate to highway speed. Likewise, that same engine would hardly be able to accelerate from a stop in 6th gear.So,we require gearbox in case of internal combustion engines because usable torque and power is generated in a narrow band of engine speeds.The variation of torque is very high at different engine speed range.

In case of electric vehicles, electric motor-generators (MG) generate 100% of their torque at very low speeds, DC MGs near stall (zero rpm), and AC MGs around 1,000 rpm, as a general rule. As rpms increase, torque falls off at a fairly linear rate, at the same time that power is increasing. Toyota Prius, for example, the MG generates up to 300 N•m of torque around 1,500 rpm, trailing off to about 50 N•m at 6,000 rpm. At its most-efficient, 93%, the MG is pushing only 100 N•m at 2,250 rpm, perfect for cruising. In any case, a multispeed electric vehicle transmission is unnecessary because even 100 N•m is plenty of torque at cruising speed.Torque is necessary for acceleration, the most of which is generated near stall. Power is necessary for cruising, the most of which is developed at high rpm.

At lower speeds we need high torque which electric motor generates but in case of engines it is not so.This is shown in the graph above.The curve is almost linear in case of electric vehicle which shows that torque is almost same for wide range of operation.

DIFFERENCE BETWEEN POLISHING AND BUFFING EXPLAINED !!

Buffing and polishing both are surface finishing process but there is a slight difference between two:

Polishing:


  • Finishing processes that utilize abrasive belts are referred to as polishing.
  • Polishing generates a brushed or lined finish. 

Buffing:

  • Processes that use cloth wheels with compound applied is called buffing.
  • Buffing removes the lines and creates a bright luster finish. The process of buffing generally requires surface refinement polishing prior to buffing.
Polishing by abrasive belts or discs is required to level surfaces, remove scratches, pits, scale and polish the surface enough so the cut buff can remove the polishing lines. The first polishing step should be done with the finest abrasive possible that efficiently removes the welds, levels, or refines the surface imperfections. From that point on, the subsequent process works to remove the first polishing scratch lines.

Buffing is a rotating cloth wheel that is impregnated with fine abrasive compounds, and it produces a bright-luster finish on metal and composites. Buff wheels are impregnated with liquid rouge or a greaseless compound-based matrix of specialized fine abrasive called compound. The compound is sprayed or pressured into the rotating buffing wheel. The buff wheel acts as the carrier of the compound, which ultimately does the surface finishing.

TOP 5 LAUNCHES OF AUTOEXPO 2018 !!

The Auto Expo 2018 is setting out to be an exciting event for two-wheeler aficionados in the country, with the promise of many new launches and unveils. Scroll down to find the top launches and unveils that took place at the 14th edition of the motor show.


1.Yamaha YZF-R15 3.0 
India Yamaha Motor (IYM)  launched the new version of its sports bike YZF-R15 (Version 3.0) priced at Rs 1.25 lakh (ex- showroom Delhi).The new bike’s engine appears to be different from that of the outgoing R15 in India; this means we could get the new 155cc, single-cylinder, liquid-cooled, fuel-injected engine from the international spec bike. However, this motor features Yamaha's Variable Valve Actuation (VVA) system which helps it make 19.3hp and 14.7Nm of torque.

2.BMW F 750 GS and F 850 GS

These new models feature sharper styling, new technology, a monocoque frame and a bigger 853cc engine – an upgrade to their 798cc predecessors, the F 700 GS and F 800 GS. The new 853cc parallel-twin engine is tuned to make different power figures in both bikes – 77hp and 83Nm of torque in the F750, and 85hp and 92Nm of torque in the F850. The'F 750 GS' and 'F 850 GS', priced at Rs 12.20 lakh and Rs 13.7 lakh (below), respectively.

3.BMW G 310 R
The G 310 R weighs 158kg and comes with a 313cc, single-cylinder engine with twin-overhead camshafts that puts down 33.6hp and 28Nm of torque. Like the TVS Apache RR 310, the G 310 R will come with a reversed-cylinder design that slopes towards the rear wheel, instead of the conventional engine layout.The G 310 R is expected to hit the market sometime in the fourth quarter of this year and is expected to be priced between Rs 2.25-2.4 lakh (ex-showroom).

4.Kawasaki Ninja 400
The 400 in the Ninja’s all-new 399cc parallel-twin engine that makes a claimed 45hp and 38Nm of torque. The motorcycle also comes with a larger 310mm disc up front with Nissin ABS. 

5.HERO XPULSE 200

The new Hero XPulse will be drawing power from a 199.5 cc single-cylinder, fuel-injected engine.The unit is the same as the newly unveiled Hero Xtreme 200R and is tuned to produce 18.1 bhp at 8000 rpm and 17.1 Nm at 6000 rpm. The motor is paired to a 5-speed gearbox. Price-₹ 1 - 1.2 Lakh *(Expected)

DIFFERENCE BETWEEN CRANKSHAFT AND CAMSHAFT EXPLAINED !!

Crankshafts:
The crankshaft is an engine component that converts the linear (reciprocating) motion of the piston into rotary motion. The crankshaft is the main rotating component of an engine and is commonly made of ductile iron.
All major components of the engine like piston,connecting rod etc. are supported by this shaft.
Construction Of Crankshaft:
A crankshaft is simply the same as an eccentric, except the eccentric is a much smaller diameter than the shaft itself Crankshaft length mainly depends on number of cylinders are present in engine .Firing order also considered while designing the Crankshaft .

Location :  Crankshaft is located in crank case . On Crankshaft, Connecting rods and pistons are mounted. The crankshaft rides on bearings which can wear down over time. The bearings support the crankshaft and also the rods which connect the pistons to the crankshaft.

Applications :It actually part of an engine where the power is available , and this power is transferred in the form of torque to clutch and thereby  gearbox and wheels.The main function is to convert liner motion of the piston to useful rotary motion.


Camshafts:
Camshaft is a part of engine which is responsible for opening and closing of exhaust and inlet valves.As the engines work they need to breathe out exhaust gases and take in fresh air ( charge) for the next cycle to take place . All these processes need to take place at a designated time with respect to each other. These processes are timed through opening and closing of valves and actuation of fuel pumps through a actuating mechanism which is triggered by movement of the crankshaft. The camshaft comes into picture here. The Crankshaft drives through a belt or chain drive the camshaft on which the inlet,exhaust, fuel pump cams are fitted for each unit when the crankshaft rotates it in turn rotates the camshaft which precisely actuate the valve and fuel pumps.

Construction Of Camshafts:
 A camshaft is a long bar with egg-shaped eccentric lobes, one lobe for each valve and fuel injector.
The relationship between the rotation of the camshaft and the rotation of the crankshaft is of critical importance. Since the valves control the flow of the air/fuel mixture intake and exhaust gases, they must be opened and closed at the appropriate time during the stroke of the piston. For this reason, the camshaft is connected to the crankshaft either directly, via a gear mechanism, or indirectly via a belt or chain called a timing belt or timing chain.

Location : Depending on the location of the camshaft, the cam operates the valves either directly or through a linkage of pushrods and rockers. Direct operation involves a simpler mechanism and leads to fewer failures, but requires the camshaft to be positioned at the top of the cylinders.
Applications :This shaft receives the power from crankshaft  (1:2) and operates the engine valves through cam and follower mechanism(generally mushroom headed follower is used to reduce friction b/w cam and follower).

DIFFERENCE BETWEEN ROCKWELL,BRINELL & VICKERS HARDNESS TEST EXPLAINED !!

Hardness is the property of a material that enables it to resist plastic deformation, usually by penetration. However, the term hardness may also refer to resistance to bending, scratching, abrasion or cutting.

The usual method to achieve a hardness value is to measure the depth or area of an indentation left by an indenter of a specific shape, with a specific force applied for a specific time. There are three principal standard test methods for expressing the relationship between hardness and the size of the impression, these being Brinell, Vickers, and Rockwell. For practical and calibration reasons, each of these methods is divided into a range of scales, defined by a combination of applied load and indenter geometry.


Comparison between Rockwell, Brinell, Vickers  hardness test. 


ELECTRON BEAM WELDING EXPLAINED !!

Electron Beam Welding (EBW) is a fusion welding in which coalescence is produced by heating the workpiece due to impingement of the concentrated electron beam of high kinetic energy on the workpiece. As the electron beam impinges the workpiece, kinetic energy of the electron beams converts into thermal energy resulting in melting and even evaporation of the work material.

Principle:

In general, electron beam welding process is carried out in vacuum. In this process, electrons are emitted from the heated filament called electrode. These electrons are accelerated by applying high potential difference (30 kV to 175 kV) between cathode and anode. The higher the potential difference, the higher would be the acceleration of the electrons. The electrons get the speed in the range of 50,000 to 200,000 km/s. The electron beam is focused by means of electromagnetic lenses. When this high kinetic energy electron beam strikes on the workpiece, high heat is generated on the work piece resulting in melting of the work material. Molten metal fills into the gap between parts to be joined and subsequently it gets solidified and forms the weld joint.

Advantages of EBW:

1) High penetration to width can be obtained, which is difficult with other welding processes.
2) High welding speed is obtained.
3) Material of high melting temperature can be welded.
4) Superior weld quality due to welding in vacuum.
5) High precision of the welding is obtained.
6) Distortion is less due to less heat affected zone.
7) Dissimilar materials can be welded.
8) Low operating cost.
9) Cleaning cost is negligible.
10) Reactive materials like beryllium, titanium etc. can be welded.
11) Materials of high melting point like columbium, tungsten etc. can be welded.
12) Inaccessible joints can be made.
13) Very wide range of sheet thickness can be joined (0.025 mm to 100 mm).

Disadvantages of EBW:

1) Very high equipment cost.
2) High vacuum is required.
3) High safety measures are required.
4) Large jobs are difficult to weld.
5) Skilled man power is required.

Applications:

1. Electron beam welding process is mostly used in joining of refractive materials like columbium, tungsten, ceramic etc. which are used in missiles.
2. In space shuttle applications wherein reactive materials like beryllium, zirconium, titanium etc. are used.
3. In high precession welding for electronic components, nuclear fuel elements, special alloy jet engine components and pressure vessels for rocket plants.
4. Dissimilar material can be welded like invar with stainless steel.

ENGINE CONTROL UNIT-SIMPLE AND PRECISE INFORMATION !!

ECU-Engine control unit, is a control unit that controls your engine. It determines the amount of fuel, ignition timing and other parameters whether a bike or a car needs to keep running smoothly.

Your bike or car equipped with it has got many sensors that continuously monitors the engine. The ECU reads the input values and decides what is the correct value required at the given condition. The input values can be collected from various sensors like crankshaft position sensor, air temperature sensor, oxygen sensor, Throttle position sensor and gives the data values to the ECU.

So a bike equipped with an ECU don't have a carburetor instead it uses a fuel injector to deliver the fuel. Suddenly if you raise the throttle, the ECU can sense it and can deliver the optimum amount of air/fuel required. 

Suppose If you ride your machine in a hilly terrain on higher altitudes more than 4000 metres, the oxygen level will be marginally less when compared to the sea level. The bike which uses an ECU will be more efficient when compared to a carburetted one, since it optimizes the right amount of fuel to be delivered for the changing conditions in environment. Optimum performance and efficiency - both can be obtained by using an ECU.

DIFFERENCE BETWEEN GAUGE PRESSURE AND ABSOLUTE PRESSURE EXPLAINED !!!

Introduction:

Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Mathematically, it is symbolized with a ‘P’. To put it briefly, it is the amount of force acting on a unit area. The simple formula for pressure is:
P = F / A; where P = pressure
F = force
A = area
The SI unit for pressure is in Pascals (Pa). Other non-SI units are PSI and bar.
There are two kinds of references to measure pressure ‘“ the gauge pressure and the absolute pressure. 

Absolute Pressure:

The actual pressure at a given position is called the absolute pressure and it is measured relative to absolute vacuum. One concept should be taken into consideration is that to measure any quantity we require a base line with respect we are going to measure it.

To learn this concept let us take an example, suppose we need to measure distance of Chennai.Distance can be measured in meter. Can we measure distance of Chennai by this input? Obviously your answer is no because we need a reference from which we want to measure distance. Now suppose we need to measure distance of Chennai from Delhi. Now we are able to measure this distance in some meters or kilometers.

Similarly pressure cannot be measured without a reference. When we take vacuum or no pressure condition as reference, the measured pressure is called absolute pressure.

Gauge Pressure:

When we take atmospheric pressure as reference to measure pressure of any system, the measured pressure is known as gauge pressure. Most of pressure devices work in atmospheric condition always measure gauge pressure. We can convert this gauge pressure in absolute pressure by adding atmospheric pressure in gauge pressure. 

It should be noted that atmospheric pressure may vary, depending on many factors, such as locality. Altitude and temperature are essential factors. The standard atmospheric pressure (1 ATM) is about 14.7 PSI.

P (absolute) =  P (Gauge) +  P (Atmospheric)

Most of gauge read zero in atmosphere but there is some atmospheric pressure. They read atmospheric pressure as absolute zero pressure. Pressure below atmospheric pressure is called vacuum pressure and is measured by vacuum gauges that indicate the difference between the atmospheric pressure and absolute pressure.

P (vacuum) = P (Atmospheric) – P (Absolute)

Machines like air compressors, well pumps, and tire gauges will all use gauge pressure. 

Summary:

1. Absolute pressure is measured in relation to the vacuum, while gauge pressure is the difference between the absolute pressure and the atmospheric pressure.
2. Absolute pressure uses absolute zero as it’s zero point, while gauge pressure uses atmospheric pressure as it’s zero point.
3. Gauge pressure is commonly used, while absolute pressure is used for scientific experimentations and calculations.
4. To indicate gauge pressure, a ‘g’ is placed after the unit. Absolute pressure, on the other hand, uses the term ‘abs’.
5. Due to varying atmospheric pressure, gauge pressure measurement is not precise, while absolute pressure is always definite.
6. Absolute pressure is sometimes referred to as ‘total systems pressure’, while gauge pressure is sometimes called ‘overpressure’.

IMPORTANT TERMS OF MEASUREMENT PROCESS EXPLAINED !!

1.Sensitivity 

It should be noted that sensitivity is a term associated with the measuring equipment whereas accuracy and precision are association with measuring process. Sensitivity means the ability of a measuring device to detect small differences in a quantity being measured. For instance if a very small change in voltage applied to 2 voltmeters results in a perceptible change in the indication of one instrument and not in the other. Then the former (A0 is send to be more sensitive. Numerically it can be determined in this way for example if on a dial indicator the scale spacing is 1.0 mm and the scale division value is 0.01 mm then sensitivity =100. it is also called amplification factor or gearing ratio.

2.Readability

Readability refers to the case with which the readings of a measuring instrument can be read. It is the susceptibility of a measuring device to have its indication converted into more meaningful number. Fine and widely spaced graduation lines ordinarily improve the readability. If the graduation lines are very finely spaced the scale will be more readable by using the microscope however with naked eye the readability will be poor.
In order to make micrometer more readable they are provided with vernier scale. It can also be improve by using magnifying devices.

3.Repeatability

It is the ability of the measuring instrument to repeat the same results when measurement are
carried out
  • By same observer
  • With the same instrument
  • Under the same conditions
  • Without any change in location
  • Without change in the method of measurement
  • And the measurement is carried out in short interval of time.
It may be expressed quantitatively in terms of dispersion of the results.

4. Reproducibility

Reproducibility is the consistency of pattern of variation in measurement i.e closeness of the agreement between the results of measurement of the same quantity when individual measurement are carried out
  1. By different observer
  2. By different methods
  3. Using different instruments
  4. Under different condition, location and times.
It may also be expressed quantitatively in terms of dispersion of the results.

5.Calibration

  • The calibration of any measuring instrument is necessary for the sake of accruing of measurement process. It is the process of framing the scale of the instrument by applying some standard (known) signals calibration is a pre-measurement process generally carried out by manufactures.
  • It is carried out by making adjustment such that the read out device produces zero output for zero measured input similarly it should display output equipment to the known measured input near the full scale input value.
  • If accuracy is to be maintained the instrument must be checked and recalibration if necessary.
  • As far as possible the calibration should be performed under similar environmental condition with the environment of actual measurement
6.Magnification

    Magnification means increasing the magnitude of output signal of measuring instrument many times to make it more readable. The degree of magnification should bear some relation to the accuracy of measurement desired and should not be larger than necessary. Generally the greater the magnification the smaller is the range of measurement.