Improvements in Preventing or Diminishing Vibrations Due to Steam Engines and other Machines.
Year: 1895

page_text: Date of Application, 17th May, 1895
Complete Specification Left, 15th Feb., 1896-Accepted, 4th Apr., 1896
Improvements in Preventing or Diminishing Vibrations Due to
Steam Engines and other Machines.
A communication from abroad by JOHN HENRY MACALPINE, Engineer, residing at
Howard Avenue, Mount Pleasant, Washington, United States of America.
I, GEORGE WATSON MACALPINE, of Parkside, Accrington, in the County of
Lancaster, Engineer, do hereby declare the nature of this invention to be as
follows, that is to say:
--
This invention has for object to prevent or diminish the communication of vibrations
due to steam engines and other machines, or, in other words, to wholly or partly
counterbalance forces and couples due to inertia of moving parts of machines, an
important application of the invention being the prevention or diminution of the
vibrations communicated to a steam ship by marine engines of various kinds as
heretofore arranged.. Another important application is to the motors and other parts
of electric-light installations.
may
On mathematically analysing the unbalanced forces of a set of engines, it is found
that they tend to set up vibrations of different periods. Vibrations which be
termed those of the first period, have the same period as a single revolution of the
crank shaft, whilst other periods are generally submultiples (or in some cases, multiples)
of the first period.
In carrying out the invention, in any particular case, the amount of vibratory-action
to be counterbalanced having been ascertained, calculated, or estimated, and the
relative amounts of first-period and other-period vibrations having been deduced there-
from, provision is made for imparting from the crank shaft opposite reciprocating
movements to suitably arranged weights, the amount of each weight combined with
its extent of movement being made such as to be equivalent to that of the vibration to
be counteracted.
In one modification of apparatus for effecting the object in view, there is fixed in a
proper position on the crank shaft one or more cams each arranged to act on a weight
either directly or through a lever centered on a fixed point, the acting part of the cam
being shaped so as to impart to the weight the movements required. In the case, for
example, of a set of inverted-cylinder screw engines, the lever or levers will be
horizontal or nearly so in middle position, and the weight or weights will reciprocate
vertically. In some cases it may be desirable to have one or more other cams arranged
to give reciprocating movement to a weight or weights moving at a right angle or
other angle to the main weight or weights.
In a second modification an eccentric is fixed on the crank shaft or a crank is fixed
on the end of the shaft and acts through the usual strap and rod upon one arm of a
bellcrank centered on
a fixed axis the other arm having a weight on it; or
the weighted arm may form any suitable angle with the arm on which the
eccentric acts.
In a third modification there is a fixed eccentric through which the crank shaft
passes loosely; or there may be a fixed eccentric or eccentric stud beyond the end of
the crank shaft. One or more levers or disks are fixed on the shaft near the eccentric
and each has centered at its outer end a bellcrank or lever weighted and connected by

page_text: a rod and strap to the eccentric or stud. The rotation of the shaft causes the parts
fixed and connected to it to revolve, and the action of the eccentric or stud produces a
reciprocation of each weight combined with its revolution.
The counteracting weights and other parts may be made adjustable, so that in cases
in which the vibratory action to be dealt with can, conveniently, be only approximately
calculated or estimated, the weights or other parts can have their adjustment altered,
if necessary, after trial.
Instead of the cam or other counteracting parts being upon or directly connected to
the crank or main shaft, they may be on one or more separate shafts geared to the
crank or main shaft.
Dated this Sixteenth day of May 1895
EDMUND HUNT,
Applicant's Agent.
Improvements in Preventing or Diminishing Vibrations Due to
Steam Engines and other Machines:
A communication from abroad by JOHN HENRY MACALPINE, Engineer, residing
lately at Howard Avenue, Mount Pleasant, but now at 3303, Sixteenth Street,
Washington, United States of America.
I, GEORGE WATSON MACALPINE, of Parkside, Accrington, in the County of
Lancaster, Engineer, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement, that is to say :-
This invention has for its object to prevent or diminish the communication of
vibrations due to steam engines and other machines; or, in other words, to wholly
or partly counterbalance forces and couples due to inertia of moving parts of
machines; an important application of the invention being the prevention or
diminution of the vibrations communicated to a steam ship by marine engines of
various kinds as heretofore arranged. Another important application is to the
motors and other parts of electric-light installations.
On mathematically analysing the unbalanced forces of a set of engines, it is found
that they tend to set up vibrations of different periods. Vibrations which may be
termed those of the first period have the same period as a single revolution of the
crank shaft, whilst other periods are generally submultiples, (or in some
multiples) of the first period.
cases
In carrying out the invention in any particular case, the amount of vibratory action
to be counterbalanced having been ascertained, calculated, or estimated, and the
relative amounts of first-period and other-period vibrations having been deduced
therefrom, provision is made for imparting from the crank shaft opposite recipro-
cating movements to suitably arranged weights, the amount of each weight combined
with its extent or range and time of movement being made such as to be equivalent to
that of the vibrations to be counteracted by it.
The vibrations dealt with in carrying out the invention may be those due to recipro-
cating or periodically reversed movements; and vibrations due to other periodically
unequal or varying movements or strains, such as those involved in the torsional action
of the crank shaft, may be counteracted in a similar manner.
And in order that the said invention and the manner of performing the same may
be properly understood I hereunto append two sheets of explanatory drawings to be
hereinafter referred to and comprising diagrams illustrating the manner of applying
the invention, and a few examples of the numerous devices which may be employed
for obtaining counteracting movements.

page_text: Figure, 1, on Sheet, 1, is a diagram of an ordinary inverted triple expansion screw-
propeller engine. The weights for the second period comprise those of the pistons
and all parts moving therewith, including proportionate weights for the connecting
rods, which if moving in the same lines as the pistons would occasion the same inertia
forces as those actually due to the connecting rods. The weights for the first period
include those mentioned for the second period and also parts of the weights of the
cranks (with proportionate weights for the connecting rods) which only give inertia
forces of the first period.
For the
The second-period forces in the case under consideration can be balanced by
applying compensators at suitable points, A, and, B, of the shaft.
purposes of the calculations hereinafter explained engines such as are shown in
the diagram, Figure, 1, are assumed to have, between the compensators, A, B, and
the centre lines of the cylinders, distances which are in the same proportions to
each other as the quantities shown by numerals in the figure. And the weights for
the first period are assumed to be in the same proportions as the following numerical
quantities, HP, cylinder 1.80; I, cylinder 2.05; L P cylinder 2.40; and for higher
periods 1.00; 125; and 1.60 respectively. The angles of the various cranks, and of
the eccentric of the L P valve gear (which gear it is proposed also to balance in the
example) are shown in Figure, 2. The compensators at, A, and, B, consist of cams
fixed on the shaft and made each to raise a weight twice during one revolution of
the shaft.
T
that her to ba balonand Lat

page_text: Assuming the analysis to be applied to the known motion of the valve to give the
following value for second-period forces.
M.2
ẞ = 20°. 26'.
The half stroke should be determined so as to admit of the smooth working of
the cam, and the weight can then be deduced from the equation; thus if=15
then B34. This completes the determination of the compensator at B.
Similarly for the compensator at A the moments about B have to be calculated
and the dimensions deduced in the same manner as for the compensator at A.
They are, A a = 0167 and a = 118°. 57'.
The compensators for. any other period may be determined by the same method.
The same compensators can be designed to balance the inertia forces of more
periods than one.
Under certain conditions an engine may be balanced by means of a single
compensator.
With regard to vibrations occurring in torsional actions, it may be mentioned
that in a marine engine, for example, the steam and inertia forces produce in the
crank shaft turning moments which are continuous but vary periodically the

page_text: variations tending to set up vibrations in the ship. These vibrations are in the
nature of partial rotations or angular movements about a longitudinal axis passing
through the centre of gravity of the ship; and can be prevented by applying a
contrary equal and variable couple near the engines. This compensating couple
may be made to balance the variations due to the distribution and varying
expansion of the steam (say at a particular power and speed) as well as those due
to inertia; or it may simply balance the inertia turning moments, which if balanced
for one speed are balanced for all.
Figures, 3, and 4, show one mode of effecting a torsional balance. By means of a
cam, C, and levers a wheel, W, is made to rotate through a definite angle. The
couples which are to be balanced are carefully calculated, and the wheel is made of a
mass and diameter, and has imparted to it. a motion, which are combined so that the
inertia forces produced by it balance those set up by the engines.
Suppose the variable part of the turning moment to be represented by the
equation
-
C = 1.2 cos (0 - 50°) + 5.6 cos 2 (0 − 6°) + 20-8 cos 3 (0 – 25°) + &c.
and that it is required to balance the moments of the third period which are
renresented in this canation br

page_text: .
=
The cam must therefore be shaped to give the wheel a simple harmonic oscillation
of d the period of the engines. Also, when = 25°, that is when the H P crank
makes this angle with the vertical, the wheel is to be at its limiting angle, and
on the side which will produce a couple opposing the variable couple of the same
period due to the engines.
As in the case of the compensators for the vertical inertia forces, the cam may
be shaped to balance the moments of any one period or of more periods
than one.
In Figures, 5, and 7, are shown alternative arrangements, which may be better
in many cases. In each arrangement the cam, C, acting through rods and levers
is made to cause the weights, M M, to vibrate so as to produce a couple which
balances, in whole or in part, the varying turning moments of the engines. This
arrangement has the advantage that the vertical forces exactly or very nearly
balance one another. The arm of the couple may be made very long and the
weights correspondingly reduced.
Figure, 6, shows an arrangement in which vertical inertia forces of all kinds are
reduced to zero by a compensator, B, whilst couples are balanced by a compensator, K,
which may be placed anywhere near the engines.
The balancing or compensating weights and their movements being determined in
the manner hereinbefore explained, many devices for applying them in practice will
readily occur to those familiar with mechanical combinations and movements ;_a
few examples are, however, shown on Sheet, 2, of the accompanying drawings. In
Figure, 8, is shown a cam, C, fixed on the crank shaft as acting on a weighted
lever, L, and shaped to impart two harmonic reciprocations for each revolution of
the shaft. In the arrangement shown in Figure, 9, a pair of cams, C, act on a
frame, F, which is movable vertically in guides and has a weight, F1, fixed to it.
Instead of the frame having the weight fixed to it, it may be connected to a
weighted lever.
Figure, 10, shows a cam, C, acting on a lever, L, which is connected to a crank
fixed to a heavy wheel, R, this arrangement being for balancing rotational or
torsional vibrations. In Figure, 11, a vertically guided frame, F, acted on by a pair
of cams, C, is shown connected to a wheel, R, which has an added weight, R₁,
this arrangement being also for balancing rotational or torsional vibrations.
Figures, 12, and 13, show forms of cains suitable for balancing vibrations of higher
than the second period, or vibrations of different periods.
Figure, 14, shows an eccentric, C₁, as fixed on the shaft and as acting through an
ordinary strap and rod on a weighted lever, L. Instead of being on the crank shaft
of the engines, the eccentric may be on a separate shaft driven from the crank
shaft at a suitable different speed.
Figure, 15, shows an arrangement in which a weighted bellcrank lever, L, is
acted on by a suitably shaped surface formed on the side instead of the edge of the
cam, C. In another arrangement there may be a fixed eccentric through which the
crank shaft passes loosely, or there may be a fixed eccentric or eccentric stud beyond
the end of the crank shaft. One or more levers or disks are fixed on the shaft near
the eccentric and each has centered at its outer end a bellcrank or lever weighted and
connected by a rod and strap to the eccentric or stud. The rotation of the shaft causes
the parts fixed and connected to it to revolve, and the action of the fixed or stationary
eccentric produces a reciprocation of each weight combined with its revolution.
The counteracting weights and other parts may be made adjustable so that in
cases in which the vibratory action to be dealt with can, conveniently, be only
approximately calculated or estimated, the weights or other parts can have their
adjustment altered, if necessary, after trial.
->
Instead of the cams or other counteracting parts being upon or directly connected
to the crank or main shaft, they may be on one or more separate shafts geared to the
crank or main shaft.
The counteracting weights may be controlled and their movements be prevented
from exceeding those properly corresponding to the cams by the application to them

page_text: of restraining springs. Or for the purpose referred to the counteracting weights.
may be connected to dash pots, d, such as are shown in Figures, 1, 3, 4, 6.
Having now particularly described and ascertained the nature of the said inven--
tion and in what manner the same is to be performed, I declare that what I
claim is:
Preventing or diminishing vibrations due to steam engines and other machines.
by means of counteracting weights which with their movements are determined or
calculated to correspond with vibrations of both first period and second period,.
or with vibrations of first period and any one or more higher periods, the
counteracting parts being arranged and operating substantially as hereinbefore-
described.
Dated this Fourteenth day of February 1896.
EDMUND HUNT,
Applicant's Agent.