CrazyEngineers Archive
Old, but evergreen and popular discussions on CrazyEngineers, presented to you in read-only mode.
@PuneetVerma • 26 Aug, 2012 • 1 like
Hi..

In this thread I will be posting some popular Mechanical Interview Question and there answers too..

Just Click Watch Thread for future updates to this thread.
@PuneetVerma • 26 Aug, 2012 • 3 likes What happens if gasoline is used in a
Diesel engine?Diesel engine will work ?

No, It will not work,as the Compression ratio of
Petrol engine is 6 to 10 & that of Diesel engine
is 15 to 22. Thus on such high compression,
gasoline gets highly compressed & it may blast.
@PuneetVerma • 26 Aug, 2012 • 4 likes Which Mechanism is used in
Automobile gearing system ?

Differential mechanism


Why different types of sound are
produced in different bikes though
they say run on SI engine ?

Engine specifications are different in different
manufactures like as Bore Diameter(CC),
Ignition timing.Also the exhaust
@PuneetVerma • 26 Aug, 2012 • 1 like Why entropy decreases with the
increase in temperature?

ds=dQ/TEntropy is inversely proportional to
the temperature so.as temp. increases,entropy
decreases.
@PuneetVerma • 26 Aug, 2012 • 2 likes 1 hp how much watt?
746.2Watt
@PuneetVerma • 26 Aug, 2012 • 4 likes How to calculate bearing number to
diameter of the inner and outer ?

Divide the shaft diameter size by 5, it will give
last two digitof the bearing no. and according
to type of load we have tochose the type
of bearing and that will give prior no. ofthe
bearing.
@ganesh kalkutaki • 27 Aug, 2012 Amongs these two which have grater elasticity? Steel or rubber. ans- steel. because steel have grater youngs modulus elasticity than rubber. steel- 200GPA rubber-106N/M2
@dhamu91 • 28 Aug, 2012 what is seeback effect?
@PuneetVerma • 28 Aug, 2012 • 2 likes Definition of Octane number & Cetane
number
Octane No.- Octane number is defined as the
percentage, by volume, of iso octane in the
mixture of iso octane and h-heptane. It is the
measure of rating of SI engine.
Cetane No.- Cetane number is defined as
the percentage, by volume, of n-cetane in
the mixture of n-cetane and alpha methyl
naphthalene. It is the measure of rating of CI
engine.
@PuneetVerma • 28 Aug, 2012 • 1 like Poisons ratio is higher in (rubber/
steel/wood) ??
When a material is compressed in one
direction, it usuallytends to expand in the other
two directions perpendicular tothe direction
of compression. This phenomenon is called
thePoisson effect. Poisson’s ratio is a measure
of the Poisson effect.
For rubber = 0.5
For steel = 0.288
For wood < 0.2
Thus Poisson’s ratio is higher in RUBBER.
@PuneetVerma • 28 Aug, 2012 The Fatigue life of a part can be improved
by ?
Improving the surface finish by Polishing &
providing residual stress by Shot peening.
@zaveri • 28 Aug, 2012 • 2 likes This question was asked to a guy, who specified his area of interest in his C.V as "power plant engineering".

A wind turbine helps to generate electricity. so does a still ceiling fan rotating due to the passing wind, generate any power. ?

No it does not, because, the fan motor is a single phase induction motor, and A.C motors , unlike D.C motors cannot be used as alternators.
@NAVATHE SACHIN • 30 Aug, 2012 • 2 likes How to know whether the valve is inlet or exhaust by seeing the engine?
Inlet valve has more diameter than exhaust valve.
@NAVATHE SACHIN • 30 Aug, 2012 steam engine is discovered by jameswatt
@NAVATHE SACHIN • 30 Aug, 2012 what is the rpm of steam engine?
200rpm
@NAVATHE SACHIN • 30 Aug, 2012 • 1 like Is cooling is necessary in the engines?
yes, cooling is necessary in the engines to satisfy the second law of thermodynamics.
@NAVATHE SACHIN • 30 Aug, 2012 Is two strokes engines are suitable for S.I engines?
No,two stroke engines are not suitable for s.i engines, because loss of fuel is more during scavenging process
@CE Designer • 30 Aug, 2012 I was asked in my interview a very basic question yet I panicked.
What are the different classes of metal alloys?
@zaveri • 31 Aug, 2012 • 1 like
CE Designer
I was asked in my interview a very basic question yet I panicked.
What are the different classes of metal alloys?
and what is the answer to that (i am panicking too).

is it ferrous alloys and non-ferrous alloys ?
@CE Designer • 03 Sep, 2012 😀 Yes Ferrous ( cast iron---carbon steels---high alloy steel (tool steel & stainless steel)
and Non Ferrous like Aluminium, Copper, Magnesium, Titanium, Zinc...
@PuneetVerma • 03 Sep, 2012 What is the difference between BSP
thread and BSW thread?
The British Standard Pipe thread (BSP thread) is
a family of standard screw thread types that has been
adopted internationally for interconnecting and sealing
pipe ends by mating an external (male) with an internal
(female) thread.

British Standard Whitworth (BSW) is one of a
number of imperial unit based screw thread standards
which use the same bolt heads and nut hexagonal sizes.
@PuneetVerma • 03 Sep, 2012 • 1 like How Cavitation can be eliminated in a
Pump?
Cavitation means bubbles are forming in the
liquid.
· To avoid Cavitation, we have to increase the
Pump size to One or Two Inch;
· To increase the pressure of the Suction Head,
or
· Decrease the Pump Speed.
@PuneetVerma • 03 Sep, 2012 • 1 like Which pump is more efficient Centrifugal
pump or Reciprocating pump?
Centrifugal pump.
Because flow rate is higher compared to
reciprocating pump. Flow is smooth and it
requires less space to install. Lower initial cost
and lower maintenance cost.
@PuneetVerma • 03 Sep, 2012 Why Centrifugal Pump is not called as a
Positive Displacement Type of Pump?
The centrifugal has varying flow depending
on pressure or head, whereas the Positive
Displacement pump has more or less constant
flow regardless of pressure.
Likewise viscosity is constant for positive
displacement pump where centrifugal pump
have up and down value because the higher
viscosity liquids fill the clearances of the pump
causing a higher volumetric efficiency. When
there is a viscosity change in supply there is also
greater loss in the system. This means change in
pump flow affected by the pressure change.
One more example is, positive displacement
pump has more or less constant efficiency,
where centrifugal pump has varying efficiency
rate.
@PuneetVerma • 03 Sep, 2012 Why cavitation will occur in Centrifugal
Pumps and not in Displacement pumps?
The formation of cavities (or bubbles) is induced
by flow separation, or non-uniform flow
velocities, inside a pump casing. In centrifugal
pumps the eye of the pump impeller is smaller
than the flow area of pipe. This decrease in flow
area of pump results in increase in flow rate. So
pressure drop happened between pump suction
and the vanes of the impeller. Here air bubbles
or cavities are formed because of liquid vapour
due to increase in temperature in impeller.
This air bubbles are transmitted to pump which
forms cavitation.
@PRASENJIT TOMAR • 13 Sep, 2012 • 1 like NIce work ...... helpfull stuff... thanx...
@serawit • 13 Sep, 2012 How do you get the belt number for standard v belt surrounding two pulleys?
Answer:
the circumference of the imaginary belt line surrounding the pulleys in inches is the belt number.
@zaveri • 13 Sep, 2012
Itspuneet
Why cavitation will occur in Centrifugal
Pumps and not in Displacement pumps?
The formation of cavities (or bubbles) is induced
by flow separation, or non-uniform flow
velocities, inside a pump casing. In centrifugal
pumps the eye of the pump impeller is smaller
than the flow area of pipe. This decrease in flow
area of pump results in increase in flow rate. So
pressure drop happened between pump suction
and the vanes of the impeller. Here air bubbles
or cavities are formed because of liquid vapour
due to increase in temperature in impeller.
This air bubbles are transmitted to pump which
forms cavitation.
a much simple answer to this is, that centrifugal is a dynamic type of pump.
@ankush sharma • 04 Oct, 2012 • 3 likes here i also attached a file related to interview questions for mechanical engineer.
@gopi gulivindala • 06 Oct, 2012
dhamu91
what is seeback effect?
when two bodies are different temparature i.e. hot&cold.if they are connected by wires(thermo couple) power will genarate.
@The myth buster • 22 Oct, 2012 How can this be possible..so are saying that with the increase in temperature, ds becomes negative..but this isn't possible..as for any process to occur, ds shoulb be greater than or equal to zero..so it's not correct to say that entropy decreases with temperature rise..rather in the ds term there is a term for entropy generation..which settle this issue..this term is always positive or zero and keeps the total entropy change >=0.
@Sarathkumar Chandrasekaran • 15 Oct, 2013 What is meant by the term "OVERDRIVE" in automobile?
It is a term describing the process where the drive shaft speed is more than that of engine shaft speed.So attaining our target speed without stressing the engine to run to its peak speed.It also helps in minimizing the wear of engine as we are using it in optimum performance without high fatigue and also increase efficiency as the fuel consumption is decreased.
@Ankita Katdare • 17 Nov, 2015 Here are some of the frequently asked questions:

Explain the reason why big tyres are used in rear of vehicles.

Explain the basic difference between BS2 and BS3 engine.

What is an injector pressure in heavy vehicles? Why it is used?

During the drive torque, what will be the weight shift?

In a tractor, how the hydrostatic propulsion systems work?

What is the range of engine efficiency in case of two stroke engine?

What is back compressor in engines?

What is octane number and cetane number?

What is the reason for emitting the white exhaust smoke during start of the vehicle? How will you prevent this?
@Satyendr yadav • 01 Sep, 2017
PuneetVerma
Hi..

In this thread I will be posting some popular Mechanical Interview Question and there answers too..

Just Click Watch Thread for future updates to this thread.
My BEL mechanical interview is on 14 September... Can you suggest something for interview.... Thnx in advance
@vhes • 21 Sep, 2017

Nice thread:

Some of good interview Questions are available here on mechanical design 

@Tarun pal • 17 Aug, 2018

i think pre combustion ahead 

@Abhay Pandey • 03 Dec, 2018

If any one have an idea which types of questions asked in engine maintenance engineer please share questions with answer  ,thanks 

@Hassan Ndaliro • 24 Feb, 2019

I     am much happy with the Interview questions & answers that you have given here.

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