Posted tagged ‘gears’

Latest Updates in Mechanical Engineering

September 25, 2011
01-job-interview-easy selection in interview
  • 1hp=how much rpm

We need Torque to find out.

Apply this formula:

T = HP x 5252
           rpm

T = torque (in lb-ft)
HP = horsepower
5252 = constant
rpm = revolutions per minute

  • 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 passage take more responsible for sound.

  • why entropy decreases with the increase in temperature?

ds=dQ/T

Entropy is inversely proportional to the temperature so.as temp. increases,entropy decreases

  • What type of metal is used in a propeller

Aluminium,stainless steel,magnesium bronze,NIBRAL(nickel,brass,aluminium)

  • why involute curve used in gear

1) it’s smooth to drive the gear.
2) in gears contact is only point, this type is curve take the more load than normal one

  • How Trains take turns, though there is no any differential

Purpose of the differential is to enable vehicles to take turn, by allowing both the wheel to rotate with different speed. This is required when wheels, like in car, are connected with same axle. Interestingly, wheel in trains are not connected with the axle, they are independent and hence can take turns without ant differential. This is same as how the bullock cart takes turns, without any differential.

  • Why freezer in the fridge is placed in top level?

Because density of cold air is higher than warm air,hence itis placed at top.Cold air comes downward & cool the bottom part.

  • what is more dangerous longitudinal stress or Hoop stress and why?

Hoop stress is more dangerous thanlongitudinal stress, because the dangerous area coming underthe hoop stress is circumferential,while in longitudinal,theaxial area will come under dangerous area will will be lessthan circumferential area.So the hoop stress is more dangerous than longitudinal stress

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TYPES OF GEARS

September 13, 2011

A SPUR GEAR

is cylindrical in shape, with teeth on the outer
circumference that are straight and parallel to the axis (hole).
There are a number of variations of the basic spur gear,
including pinion wire, stem pinions, rack and internal gears.
(See Figure 1.17)

PINION WIRE
is a long wire or rod that has been drawn
through a die so that gear teeth are cut into its surface.
It can be made into small gears with different face widths,
hubs, and bores. Pinion wire is stocked in 4 ft. lengths.
(See Figure 1.18)

STEM PINIONS
are bore-less spur gears with small numbers of
teeth cut on the end of a ground piece of shaft. They are
especially suited as pinions when large reductions are
desired. (See Figure 1.19)

RACK
are yet another type of spur gear. Unlike the basic spur
gear, racks have their teeth cut into the surface of a straight
bar instead of on the surface of a cylindrical blank. Rack is
sold in two, four and six foot lengths, depending on pitch,
which you will learn about starting in chapter 2.
(See Figure 1.20)

INTERNAL GEARS
have their teeth cut parallel to their shafts
like spur gears, but they are cut on the inside of the gear blank.
(See Figure 1.21)

HELICAL GEARS
A helical gear is similar to a spur gear except that the teeth
of a helical gear are cut at an angle (known as the helix
angle) to the axis (or hole). Helical gears are made in both
right and left hand configurations. Opposite hand helical
gears run on parallel shafts. Gears of the same hand operate
with shafts at 90-degrees. (See Figure 1.22, 1.23, 1.24, 1.25)

BEVEL GEARS
A bevel gear is shaped like a section of a cone and usually operates
on shafts at 90-degrees. The teeth of a bevel gear may be straight
or spiral. If they are spiral, the pinion and gear must be of opposite
hand in order for them to run together. Bevel gears, in contrast
to miter gears (see below), provide a ratio (reduce speed) so the
pinion always has fewer teeth. (See Figure 1.26, 1.27)

MITER GEARS
Miter gears are identical to bevel gears except that in a miter
gear set, both gears always have the same number of teeth.
Their ratio, therefore, is always 1 to 1. As a result, miter gears
are not used when an application calls for a change of speed.
(See Figure 1.28, 1.29)

WORMS & WORM GEARS
WORM Worms are a type of gear with one or more cylindrical
threads or “starts” (that resemble screw threads) and a face that
is usually wider than its diameter. A worm gear has a center
hole (bore) for mounting the worm on a shaft. (See Figure 1.30A)

WORM GEARS – like worms – also are usually cylindrical and
have a center hole for mounting on a shaft. The diameter of
a worm gear, however, is usually much greater than the
width of its face. Worm gears differ from spur gears in that
their teeth are somewhat different in shape, and they are
always formed on an angle to the axis to enable them to
mate with worms. (See Figure 1.30B)

Worms and worm gears work in sets, rotating on shafts at right
angles to each other, in order to transmit motion and power
at various speeds and speed ratios. In worm and worm gear sets,
both the worm and worm gear are of the same hand. (Because
right- hand gearing is considered standard, right-hand sets will
always be furnished unless otherwise specified.) (See Figure 1.30)

 

Mission Malfunction…!

August 23, 2011

sometimes i found happiness thinking of my redrawn strategies and changed gears!
Suddenly i will get involved in Holmsian thinking of philosophy(I used to call it so…Don’t care if othr ppl think something else…!!)all these happen just after getting my semester results..
What happened to me…?
What came over my typical brain which stood sensible during my intermediate ,3 years ago!
The ecstasy i have felt after excelling beyond my expectations ! I never knew then that it might be my swan song.!
As my performance in engineering is always far below my caliber!
Some turbulence which i had experienced during my 2-2 semester exams suddenly flashed before my eye balls.!
To be frank i’m at my wits end ..
In a desperate situation to strike back under any circumstances i have to strike back….
Get back to 70+
Tossing and turning emotions But all i knew that is i had to hold on…!
The support i’ve got from my fewest pals could be a good reason for my striking back.
Ofcourse for other ppl its nothing(71.2) But for me its something considerable thing of my life.!
I got that when i was a textaholic….
Atleast 400 sms’s daily i used to forward …
Every damn thing i received i used to forward.!
But there is some regular chat with two people whom i consider somewhat closer than others ..!
Its good to share experiences of studying ..
Hey I have selected these chapters what u gonna do chap….
can we find those chapters in that book..?
Was that book good enough..?
How many chapters u were going through..?
Ofcourse that was a silly thing…
But it builds some confidence..
Thanks to those two.!
But now every one had stopped texting…
even i had recovered from my textaholic state…!!
Only one who still text is Kittu only…
He remained same since 1st yr…!!
I have chosen this trade only to satisfy me endless love for machines..Still i’m infinite far from getting what i deserved..I have had the count of things that i dint had…
I was very impeccable at planning of course every one do..
and i was insane enough to fail at execution.!
And now there are no people to share them tooo.. 😦

Some times i feel like shouting ” A hell hound is outta thr to give u ppl a great hell..”
But the same thing of failing at execution scares me like anything….!
All i hope is that my life is busy in preparing something extra normal and large for me..
I ended up inn writing the same sentence as i always do…
“LET THE DESTINY TO PLAY ITS BELATED ROLE”
And there is something hot on the board for this summer….
” Some one is about to get caught in a tarantula’s web called Love..
He may get sucked outta his life again….
Increased instances of pirated emotions made me to think so…””

Lets see what this summer got for me
A Huge Gift box or The Same Size Pandora’s Box…!!!
And i have started another mission for 3-2 exams…
i.e Mission Malfunction…!!