My report about Balancing of coupled locomotivies in Mechanical engineering , vibration Lab

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Balancing Of Coupled Locomotivies
Student Name: Rawa Abdullah Taha
Class: Third-Group A
Course Title: Theory of Machine
Department: Mechanic and Mechatronics
College Of Engineering
Salahaddin University – Erbil
Academic Year 2020-2021

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ABSTRACT
line traffic-locomotives were first used for the movement of mainElectric
over 45 years ago. This early application was for tunnel work but it may
line transportation. In this-ra in mainbe taken as the beginning of a new e
era the steam locomotive has been transformed in appearance and
characteristics. More recently the Diesel engine has been applied to
passenger and freight trains. During all this period of development the
tics of the electric locomotive have continued to be superior tocharacteris
electric locomotive. Many of the-those of either the steam or the diesel
early ideas with regard to the application of electric locomotives are still
on engineering has become sovalid today, but progress in transportati
accelerated that a periodic review of each type of motive power must be
made by those who are responsible for their application. A discussion of
the engineering fundamentals which enter into the selection of an electric
line work will be presented. An-power unit for mainmotive
understanding of these fundamentals is essential to the specification of a
balanced design. A locomotive which is specified on this basis will give
highall of the advantages of momentum operation augmented by
electrical horsepower at high speed. This is one of the unique advantages
.of the electric locomotive

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TABLE OF CONTENTS
ABSTRACT……………………………………………………..2
TABLE OD CONTENT ………………………………………..3
INTRODUCTION………………………………………………4
INTRODUCTION………………………………………………5
INTRODUCTION………………………………………………6
INTRODUCTION………………………………………………7
INTRODUCTION………………………………………………8
INTRODUCTION………………………………………………9
SOME OF LOCOMOTIVIES…………………………………10
SOME OF LOCOMOTIVIES…………………………………11
REFERENCES…………………………………………………12

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INTRODUCTION
The best introduction to the subject of balancing would appear to be the
consideration of the simplest of all cases in which balancing is necessary.
This is clearly the case of a revolving shaft with a weight fixed at the end
of an arm, which is attached to the shaft at some point.
Fig(1)
Fig. 1 shows such a shaft, which has a weight, W, attached to an arm
fixed at the point C. Now, suppose the shaft, together with the weight W,
to rotate. At once centrifugal action comes into play, producing a force
pulling at C in the direction of the length of the arm ; that is to say, along
C W. Anyone may satisfy himself that this force exists by swinging a
weight round on the end of a piece of string. The reason why the force
exists is almost as simple as the practical proof of its existence. One of
Newton’s laws of motion states that any moving body tends. to continue
moving at the same pace, and also to move in a straight line.
Whenever a heavy substance of any kind moves along a curved path,
there must be some force applied to cause it to do so. Also, as long as the
path remains curved, the force must continue to act. Now, the weight at
the end of the arm follows a circular path, which is obviously curved at
all points. Therefore, there must always be force acting on it to pull it, so
to speak, into this circular path. This force is supplied by a tension in the
arm C W. This tension produces a pull on the weight W, which
overcomes the centrifugal force due to rotation, and at the same time
produces a pull on the shaft at C ; and the method of balancing this pull it
is the object of this paper to explain.

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Fig(2)
:itself to everyone that
the simplest way to balance this force would be to place an equal weight
on an arm of equal length exactly opposite to the weight W. This is a
perfectly true and ideal method, but unfortunately there are
insurmountable difficulties in the way of its practical application. The
nearest possible approach to it consists in extending the webs on the
opposite side of the crank to the crank pin, and there placing balance
weights as in Fig. 2. This method is sometimes seen in gas engines and
high speed steam engines. In the case of locomotives, however, the
weights to be balanced would require the balance weights to be
excessively massive and bulky, or else cause the length of the webs to be
so great as to be inadmissible in the case of inside cylinder engines with
any reasonable height of boiler centre. The expense 40 would also be
greater than with the present form of balancing. In locomotives, the
almost universal practice is to place balance weights on the wheels just
inside the tyres. The equivalent, to this in the simple case now under
consideration will be to place weights on arms attached to the ends of the
shaft. The function of these weights will be to produce such centrifugal
forces as will place the shaft in a state of equilibrium. The problem of
finding these forces is identical with that of finding the reactions of a
beam bearing an isolated load. Fig. 3 represents the shaft A B ; at C is the
force F produced by the rotating weight. The forces f 1 and f 2 at A and B
respectively are =
and act in the opposite direction to F. This is equivalent to asserting

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Fig(3)
that the balance weights must
be exactly opposite to the weight to be balanced when the shaft is viewed
from either end. The next problem is : Given the magnitude of the
centrifugal forces f 1 and f 2 to find the weights which are necessary to
produce them, and at what distance from the Centre these weights must
be placed. This involves the use of the formula for finding centrifugal
force (3) F= 1·24 r N2 W where F = centrifugal force, r = distance of
Centre of gravity of rotating weight from axis of rotation in feet, N =
number of revolutions per second, and W = weight of rotating mass. Now
call the weight to be balanced W at radius R, and let the centrifugal force
it produces be F. In the same way let the balance weights be w1 and w2,
their radii r1 and r2, and the centrifugal forces they produce f 1 and f 2.
The number of revolutions will be N in both cases, as all rotate together.
Then (4) F = 1·24 RN2 W. (5) f 1 = 1·24 r1 N2 w1 and (6) f 2 = 1·24 r
N2 w2.
ofdriving wheelsconnects thedside roordcoupling roA
in particular usually have them, butSteam locomotives.locomotivea
,Shunterlocomotives, especially older ones andelectricanddieselsome
also have them. The coupling rods transfer the power of drive to all
.wheels
In general, all railroad vehicles have spring suspension; without springs,
irregularities in the track could lift wheels off the rail and cause impact
damage to both rails and vehicles. Driving wheels are typically mounted
so that they have around 1 inch (2.5 cm) of vertical motion. When there
are only 2 coupled axles, this range of motion places only slight stress on
the crank pins. With more axles, however, provision must be made to
allow each axle to move vertically independently of the others without
bending the rods. This may be done by hinging the side rod at each
intermediate crank pin, either using the pin itself as a hinge pin, or adding
a hinge joint adjacent to the pin, as shown in the illustration.
An alternative is to use a side rod that spans multiple axles with a scotch
yoke used at each intermediate axle. This approach was quite common
when side rods were used to link a jackshaft to 2 or more driving

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wheels on electric locomotives and some early internal combustion
locomotives. The Swiss Ce 6/8II Crocodile locomotive is a prominent
example, but there were others.
Balancing: The coupling rod's off-center attachment to the crank pin of
the driving wheel inevitably creates an eccentric movement and vibration
when in motion. To compensate for this, the driving wheels of an inside-
frame locomotive always had built-in counterweights to offset the angular
momentum of the coupling rods, as shown in the figures above.
On outside-frame locomotives, the counterweight could be on the driving
wheel itself, or it could be on the crank outside the frame, as shown in the
adjacent figure.
Where the motion of the side-rods is purely circular, as on locomotives
driven by jackshafts or geared transmission to one driver, counterweights
can balance essentially all of the motion of the side rods. Where part of
the motion is non-circular, for example, the horizontal motion of a piston
rod, counterweights on the wheels or drive axles cannot be made to
balance the entire assembly perfectly. On a driving wheel supporting both
side-rods and the connecting rod to a piston, the counterweight needed to
balance the horizontal motion of the piston and connecting rod would be
heavier than the counterweight needed to balance the vertical weight of
the rods. As a result, a counterweight chosen to minimize the total
vibration will not minimize the vertical component of the vibration.
The vertical component of the vibration that could not be eliminated
because of the weight needed to balance the pistons is called hammering.
This is destructive to both the locomotive and the roadbed. In some
locomotives, this hammering can be so intense that at speed, the drivers
alternately jump from the rail head, then slam down hard on the rails as
the wheels complete their
rotation. Unfortunately,
hammering is inherent to
conventional two-cylinder
piston-driven steam
locomotives and that is one
of the several reasons they
have been retired from
service.
Fig(4)

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technologyassteelInitially, coupling rods were made of:Materials
progressed and better materials became available, the connecting rods
which in turn permittedalloyswere manufactured of lighter and stronger
.smaller counterweights and also reduced hammering
Most stationary engines balanced on scientific principles are high speed
engines, and these are seldom balanced by any other method than that of
placing weights on extended crank webs. A locomotive engine is a high
speed engine, often running between three and four hundred revolutions
per minute, and is also perfectly suited to show up any defects in
balancing, being mounted on springs and free to move longitudinally. A
single cylinder stationary engine is, however, more suitable than the
complicated locomotive for explaining the principle of balancing. Fig. 5
represents diagrammatically the crank, connecting rod, piston rod, etc…
intermediate parts of the connecting rod move in oval paths, and produce,
more or less, the effect of rotating weights according to their proximity to
P or A. From this it follows that a certain portion only of the connecting
rod must be considered as a rotating weight moving round O at the same
radius as the crank pin. This portion of the weight may be approximately
equal to the weight of the big end plus half the weight of the body of the
rod. There are numerous formulas, some simple, others extremely
complicated, for obtaining the portion of the connecting rod which ought
theoretically to be considered as rotating.
Some of these formula are exact, some only approximations. The subject
does not, however, appear to be one of vital importance, for the following
reasons: The simple formula already mentioned will give results with an
error of probably not more than one-fifteenth or one-twentieth of the
whole weight of the rod. Also the question is not one of balancing or not
balancing, but only one of balancing the whole or two-thirds of the
weight, as that portion of the rod not treated as rotating is treated as a
reciprocating weight, and as such about two-thirds of it is balanced. The
total possible error is, therefore, only about one-forty-fifth or one sixtieth
of the weight of the connecting rod. A little consideration of some of the
assumptions usually made when calculating balance weights will show
that this error is altogether insignificant compared with others that are
unavoidable.

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One of the problems with the conventional type of steam locomotive is
the presence of forces caused by the pistons, piston-rods, crossheads etc.
moving back and forth. As these masses are accelerated and decelerated,
the reaction forces cause the locomotive to also accelerate and decelerate
by a much smaller amount; it is still enough to make the riding rough and
uncomfortable. These forces do not cancel as the two side of the
locomotive operate 90 degrees apart to prevent dead-centre problems.
This problem can be minimized by adding weights to the driving wheels.
These already have balancing weights which nullify the effect of purely
rotating masses such as the crank pins and coupling rods. Adding more
mass to these weights can balance the back-and-forth forces, at the
expense of upsetting the rotational balance; the latter has bad
consequences, generating an up-and-down force on the rail. When acting
downwards this is known as "hammer-blow" and puts serious extra
stresses on the track and its foundations, the forces increasing with the
square of the speed. 180 degrees later in the rotation of the wheel it acts
upwards, and in severe cases can almost lift the wheel off the rail, with
dire consequences for stability. As a result, it was conventional practice
to balance only a third to a half of the reciprocating mass. (The Austerity
locomotives designed for military use in WW2 had no reciprocating
balance at all, so they could work on hastily-laid track. Comfortable
riding was not a priority; however in these conditions speeds were low
and it was a perfectly sound design choice)
At least two designers appreciated that a good way to obtain good balance
for both the rotating and reciprocating masses was to fit two pistons on
each side, driving crank-pins set at 180 degrees so that one piston would
move forward as the other moved back.
The only real difficulty was fitting two cylinders where one had grown
before. Burch solved the problem by having two pistons in one cylinder,
driving two different wheels. John Haswell solved it by fitting one
cylinder above the other, set at a slight angle. Shaw had enough room to
put two cylinders side-by-side.

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SOME OF LOCOMOTIVIES
Fig(5)
The Burch Oscillating
Cylinder Locomotive: 1837
This drawing is taken from a patent granted to Richard Burch of
Heywood in 1837. On each side there is an oscillating cylinder C - C with
two opposed pistons; horizontal reaction forces would have cancelled out,
but not vertical ones. Balanced drive however does not appear to be the
aim. Burch's motivation seems to have been simply the driving of both
axles without the use of a connecting rod, though why that would be
inferior to this more complicated arrangement is not clear.
No balance weights are visible on the wheels.
Fig(6)
The Haswell Duplex Locomo
This remarkable locomotive had two cylinders on each side, angled
slightly so that both piston rods aligned with the centre of the driving
wheel. It was designed by John Haswell of the Austrian State Railway

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Works at Vienna and was exhibited in the International Exhibition of
1862. John Haswell had previously built the "Vindobona", one of the
competitors in the famous Semmering locomotive trials in Austria. The
cylinders were 10.8 inches diameter by 24.8 stroke, and the driving
wheels were 7' 9" in diameter.
Fig (7)
The H F Shaw Locomotive: 1881
Shaw's four-cylinder balanced locomotive was modestly called the H F
Shaw ; it was built by the Hinkley Locomotive Works in 1881. It was
advertised which as being completely free from the pounding and
oscillating action of conventional two-cylindered engines.
This locomotive also had two cylinders on each side, but mounted beside
each other, a solution that was probably only made possible by the larger
American loading gauge. These drove crank pins diametrically opposite
each other on the driving wheel.

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REFERENCES
,U.S. Patent 1,951,126Tracy V. Buckwalter, Locomotive Drive,.1
.granted Mar. 13, 1934
U.S. PatentLocomotive Driving Rod Connection,William G. Knight,2
.., granted May 18, 19311,807,217
, granted Oct.U.S. Patent 391,148Rod,-Robert Humble, Connecting3.
.16, 1888