REASONS FOR ENGINE SEIZE EXPLAINED !!

Engine seize is a condition when engine stops working due to some external or internal cause.In other words,engine seize is when some portion of the engine has lost lubrication and the moving parts have started to abrade each other, either from friction, heat or mechanical failure (example: broken piston ring) to the point that the engine stops turning.Unusual engine noises, low oil pressure, engine overheating, loss of power, misfiring, hard starting and similar driveability and performance complaints can all be indications of problems that need attention.

Causes of Engine Seize :

The major causes of engine failures can be lumped into four basic categories:

• Overheating (excessive heat)
• Lubrication (or the lack thereof)
• Detonation (Spark Knock )(Detonation)
• Misassembly

1.Overheating:

Overheating can be caused by any number of things. It is often the result of coolant loss or a low coolant level, which is turn may be due to leaks in hoses, the radiator or the engine itself. A weak radiator cap that leaks pressure can allow coolant to escape from the system. Not getting the cooling system completely filled after changing the antifreeze can allow steam pockets to form that make the engine overheat or run hot. An electric cooling fan that fails to come on due to a faulty thermostat, relay, wiring or motor may be an overlooked cause of overheating. So too can a slipping fan clutch. Even a missing fan shroud that reduces the fan's effectiveness may be a contributing factor.

Too much heat in an engine can cause serious problems because heat causes metal to expand. The hotter the engine gets, the tighter clearances become until there are no more clearances left. Overheating can cause valve stems to gall and stick, and pistons to scuff and seize. So if you see either of these conditions when you tear the engine down, it is a pretty good clue that overheating caused the engine to fail.

2.Lubrication:

Every engine needs oil between its moving parts not only to reduce friction but also to carry away heat. Oil is the primary means by which the rod and main bearings are cooled, as well as the pistons. So any reduction in oil flow may cause these parts to run hot, gall and seize.Overhead cam engines are even more vulnerable to oil starvation and low oil pressure problems than pushrod engines because the cam and valvetrain are farther from the pump. When an OHC engine is first started, it takes awhile for oil pressure to reach the cam bearings.

If you suspect engine damage may have been caused by a low oil level, check the dipstick to see how much oil is in the pan. A low oil level may be the result of neglect, oil leakage and/or oil burning.

3.Detonation:

Detonation (Spark Knock ) is a form of abnormal combustion that results from too much heat and pressure in the combustion chamber. The fuel ignites spontaneously causing a sudden rise in cylinder pressure. The result is a sharp hammer-like blow on the piston that produces a metallic knocking or pinging noise. Light detonation is considered normal and should not cause any damage, but heavy or prolonged detonation can crack rings, pound out piston ring grooves, punch holes through the tops of pistons, smash rod bearings and blow head gaskets.

Causes of detonation include excessive compression, elevated engine operating temperature, preignition, overadvanced ignition timing (spark knock), lean fuel mixture, spark plugs that have too hot a heat range for the application, low octane fuel, and even bad driving habits such as lugging the engine excessively with a manual transmission.

4. Misassembly:

You can probably ignore misassembly as a factor in a high mileage engine failure. But in a newly rebuilt engine or a low mileage failure, it should certainly be considered as a possibility. Some common mistakes to look for:

• Incorrect engine bearing clearances (too tight or too loose). Galling or seizure would tell you bearing clearances were too tight, while fatigue failure would point to excessive clearances.

• Insufficient Valve-to-Piston Clearance, or Piston-to-Cylinder clearance. Not checking clearances may result in valves hitting pistons (especially with high lift cams or rocker arms) or pistons sticking in cylinders.
• Misalignment. If the center main bearings show much greater wear than the end bearings, the crankshaft may be bent or the main bores may be misaligned. The underlying condition must be corrected by straightening or replacing the crank and/or align boring the block. The same applies to camshafts and cam bearings (pushrod & OHC).
• Failure to clean parts properly during engine assembly (not scrubbing out the cylinder bores with soap and water to remove debris and honing residue after they have been bored or honed, for example). Any junk that is left in the engine can scour bearings and wear surfaces.

RIDE-BY-WIRE TECHNOLOGY EXPLAINED !!!

The technologies in case of motorcycles is evolving at a faster rate.

ABS,Cornering ABS,Cruise control,adaptive cruise control etc. are the common examples.  Among these Ride by Wire is again a new technology.Let's understand this technology in this article.

Ride by wire refers to the absence of mechanical linkage between accelerator and throttle. Instead, various sensors and actuators (connected by wires) control the fuel-air supply going to the engine. Yamaha pioneered the use of ride by wire technology in 2006 on YZF-R6.

One of the main aspects of using the ride-by-wire technology is that motorcycle manufacturers can stick to strict emission norms, while still being able to make high displacement motorcycles. The bigger the displacement, higher the emission and ride-by-wire technology keeps emission under control as air-fuel mixture can be fine-tuned.

Why it is needed?

In a conventional setup, the butterfly throttle valve is directly controlled by the throttle control on the handlebar. As the rider twists the throttle for hard acceleration, the abrupt, large flow of air in the combustion chamber causes the bike to momentarily stall. This results in poor combustion and harsh ride. The ride-by-wire technology eliminates this problem.Also,as emission standards are getting stricter, it is becoming very difficult for motorcycle manufacturers to employ higher capacity engines while maintaining emission limit.So ride by wire is a solution.

How does Ride-by-wire work?

In earlier bikes having carburetor, accelerator had a direct cable connection with the butterfly valve in the carburetor body. Thus, in such engines, a twist of the accelerator would directly control the supply of fuel-air mixture to the engine. However, this is not the case with ride by wire system as there is no cable connection between accelerator and throttle. 

In this system, when rider twists the accelerator, actuators in the electronic throttle body sense this movement and change the throttle opening accordingly. The movement of throttle alters air supply to the engine.

Throttle position sensor senses this change and sends a signal to ECM. Based on this signal, ECM calculates the exact amount of fuel required and orders fuel injection system to supply it. Hence, engine receives correct amount of air-fuel mixture in every situation.

What are the Advantages of Ride-by-wire?

To sum it up ride-by-wire offers the following advantages

• Smooth acceleration
• Improved fuel economy
• Enables rider aids like Cruise Control, Traction Control
• Enables ride mode control

Limitations:

• Skilled person required for troubleshooting.
• Cost of repair is high.

The Ride By Wire technology is responsible for features like Cruise Control, Traction Control and Variable Power Modes in high end bikes. These features obviously demand premium and hence come with almost all sorts of supersports bikes by different names.

WHY LONG WINDSHIELD IN CRUISER AND RACING BIKES ???

A windshield is typically installed to provide a fair bit of aerodynamic leverage for a rider riding at high speeds. It is primarily present to deflect the wind hitting your chest area, this is because the chest region forms one of the biggest wind barriers whist riding a motorcycle.

There are multiple reasons behind this,lets discuss all of them on detail:

1.Track racers will use it to tuck/crouch forward so as to only expose the top of the helmet to the wind blast. Being most aerodynamic is essential for that edge in performance.

2.While tourers use bigger versions of the windshield to aid in deflecting debris, bugs and wind being blasted on their helmets.

3.Windshield diverts hot and dry air in summer season and will also divert cold and wet turbulent air in winter season.At the same time it protects you from rain, its very difficult to ride in high intensity rain.It act as a shield to high intensity rain hitting your face and chest.

4.After installing windshield,less air is pushing your face and body resulting in less faitigue,back pain,arm strain and more comfortable and fun ride. Less turbulence from wind results in more miles you can ride without fatigue.

5.While riding at night,usually it happens that flying ants attracted towards motorcycle’s beam light and sometimes hit our helmet instead.You can ignore this with windshield installed on your bike.Some strong fiber windshield even protect you from minor head on collision with road side animals or other vehicles.

6.Also windshields not just block the air flow coming onto you but they divert it in other directions causing a streamline effect. This gives the bike a bit more aerodynamic effect provided the windshield is properly fit, shaped and angled; else it could end up into all ways of bad. It is not that serious though.

So remember that having a windshield is always beneficial if you are into touring and high speed riding. But if you are riding in the city, you would not really feel a difference and this is the reason why windshield are provided in motorbikes of either high speed or that is supposed to cover longer distance.

WHY RAILWAY BRIDGES ARE MADE UP OF STEEL RATHER THAN CONCRETE ??

Trains are quite heavy and they generate high frequency vibrations when moving through the bridge.

Bridge can be made up of 2 materials i.e steel or concrete.Concrete is brittle in nature as a result small vibrations may break it.For example you might have seen jack hammer.How does it break concrete on which it is used? Does it generate very large force? No. It vibrates very quickly and splits up concrete into smaller chunks. This is because of brittle nature of concrete and low fatigue value.

But steel is not brittle, it is ductile. It can sustain such oscillations and has higher fatigue strength. As a result it can absorb high vibrations and sustain.

WHY TIRES ARE BLACK IN COLOUR ??

Although the natural colour of rubber is a milky white, the black colour we see is because of carbon black.Actually Carbon Black is not added as a coloring agent,it is a filler. 

Vulcanized rubber does not have very good wear resistance and hence a tire made of pure vulcanized rubber would wear out soon.

Carbon Black also increases the damping properties of rubber, thus transferring less shock loads to the automobile.

In addition to this Carbon Black is a good conductor of heat and would help conduct heat away from the surface with contact to the road and help maintain a healthy tire temperature.

An added bonus is that addition of carbon black increases the coefficient of friction with the road surface thus making it safer to drive.

RELATION BETWEEN RPM AND TORQUE EXPLAINED !!

Torque is the twisting or rotating force that the engine exerts on the crankshaft; it is expressed in N-m or Kg-m.

It is generally measured at a radius of one meter from the crankshaft's center.

Torque and Speed ( RPM) Are inversely proportional with each other

Here is the torque-speed curve.

As the RPM Of an engine increases, torque increases upto a certain value of RPM. And as the RPM goes on increasing, torque starts decreasing.

To understand this behaviour, you need to understand one more term which is called as “ Low-End torque”. Low -End Torque is the amount of torque produced at Low RPM range of an engine ( around 1000–2000 rpm) .This low end torque is very crucial when moving a vehicle from stand-still or driving in slow-speed conditions such as in traffic. If the greater amount of torque is generated at the lower end of engine rpm, it implies that the engine has more ‘low-end-torque’ or better pulling ability at slow speeds.

It also implies that vehicle can move very quickly from rest/stand still.

Now as the engine speed keeps increasing, torque starts to decrease because of the increase in friction between engine’s moving parts.

Engine torque is also related to the gearing. The lower the gear, greater is the pulling ability of an engine and hence greater the torque because lower gears are greater in diameter and we know that,

Torque=Force x Perpendicular Distance(Larger diameter of smaller gear).

So at lower RPM we get maximum torque as we are in smaller gear.Torque helps the wheels to turn that is why it is suggested to start vehicle in first gear as toque is maximum at that point of time.

If you know the Horsepower (HP) of an engine, then you can calculate the torque using the formula :-

Torque = (HP*5252)/RPM

TECHNICAL ROUND QUESTIONS OF MARUTI SUZUKI INDIA LIMITED !!

1. The purpose of jigs and fixtures are to

a. Increased production rate
b. Increased machining accuracy
c. Facilitate interchangeable manufacturing
d. Enable employ less skilled operators
e. All of the above

Ans:e

2. Tool life of the cutting tool is most affected by

a. Cutting speed
b. Tool geometry
c. Cutting feed and depth
d. Microstructure of material being cut
e. Not using coolant and lubricant
Ans:a

3. A feeler gauge is used to check

a. Radius
b. Screw pitch
c. Surface roughness
d. Unsymmetrical shape
e. Thickness of clearance
Ans:e

4. Metal in machining operation is removed by

a. Tearing chips
b. Distortion of metal
c. Shearing the metal across a zone
d. Cutting the metal across a zone
e. Pushing the metal with tool
Ans:c

5. Ductility of material can be defined as

a. Ability to undergo large permanent deformation in compression
b. Ability to recover its original form
c. Ability to undergo large permanent deformation in tension
d. All of the above
e. None of the above
Ans:a

6. Inconel is an alloy of

a. Nickel, chromium and iron
b. Nickel and copper
c. Nickel and chromium
d. Nickel and zinc
e. Nickel and lead

Ans:a

7. Casting defects caused by the molten metal is

a) Blow holes
b) Swell
c) Scab
d) All of the above
Ans.: d

8. Forming operation which does not involve rotation of work piece is

a) Spinning
b) Thread rolling
c) Ring rolling
d) Upsetting
Ans.: d

9. Greater forging capacity is achieved with

a) Mechanical press
b) Power hammer
c) Hydraulic press
d) None of them
Ans.: c

10. Which of the following welding process uses consumable electrodes

a) TIG
b) MIG
c) Thermit
d) Laser
Ans.: b

11. The crystal structure of alpha iron

a) BCC
b) FCC
c) HCP
d) Cubic
Ans.: a

12. Severe quenching can cause

a) Blow holes
b) Warping
c) Inclusions
d) Non of them
Ans.: b

13. Glass bead peening on components done to

a) Improve creep strength

b) Improve fatigue strength

c) Improve finish

d) Impart further coating

Ans.: b

14. Trajectory of a robot mean :

a) Path traced by the end effectors

b) Kinematics of Robot

c) Robot joints

d) Robot programming
Ans: a

15. Rayleigh’s method of computing the fundamental natural frequency is based on

a)Conservation of energy

b)Conservation of momentum

c)Conservation of masses

d)Laws of statics

Ans: a

Source-https://www.freshersworld.com/