Springs Introduction & Types – Design of Springs – Machine Design I


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from Ekeeda Hello friends welcome back to a subject of machine design 1 we are
starting with the module number 6 which is our the last module and where we are
going to learn about it is an of various Springs we are basically going to look
at only two types of Springs as far as your curriculum is expected so they are
a helical Springs and the lip Springs so let us begin with the introduction so
friends spring is a mechanical member which is used on the principle of
deflection and reverse retention how does it work that is very important so
it is made up of number of coils which have a cross-section mostly circular and
those coils when applied with the external force they change their length
the length may change in the form of deflection or it may change in the form
of extension or retention and vice versa when the force is removed they will
undergo the extension or compression so basic fundamental is a deflection and
retraction based on the applied load load can be compressive or it can be
tensile let’s move ahead now generally these are the terminologies which are
very important first of all spiral is the nature of the spring the springs are
generally how spiral nature and the path or the trajectory that they follow is
called helix or helical trajectory thereafter they’re made up of wires
generally the helical Springs are made up of wires so why are the normal wires
which are the mechanical members with certain cross section circular most of
the time and how length of course they are formed in the form of Felix so as to
make spiral structure which is called spring the next thing is heat treated no
spring being complete structure because that’s not a straightforward structure
they have certain bends they have certain spirals the nature the path the
curvature is different and that’s why to sustain different loads and to
sustain the different mechanical structure this plane has to undergo
certain heat treatments and that’s why in majority of the cases the springs are
heat treated or the materials that I use for Springs are heat treated let’s go
for the uses different uses that we have for Springs in industry are first off is
very important that is shock absorption whenever the Sharks come into play or
the loads which form the shocks in order to absorb the shop’s we generally use
Springs the next is vibration damping if you see this properly major of the cases
where the dynamic loads come into picture where the vibrations are
possible in that cases we need to absorb the vibrations otherwise they will be
harmful for the machines and the operation in majority of the cases they
use springs to damsel vibrations or certain vibrations absorb certain
vibrations the next is energy storage now this is a very day-to-day life
example you can use your wrist watch where we give or the batteries where the
batteries were not involved in that case we used to give certain rotation power
to the springs in the form of energy used to be stored and these things as
they used to get unwind the energy was utilized for running the wristwatch
so wristwatches or the coils I generally use or the springs are generally used to
store the energy also and release it at appropriate times the next is a
measurement devices many of the measurement devices do use the same
principle of energy storing and retrieving it back and for that we need
to do Springs the next is transmitted force again many of these Springs are
used to transmit different forces again based on the storage of the energy or
just simply transmitting the force for example clutches collisions is a
mechanical device we already have studied this terminologies in the
subject of theory of machines so in that case clutches to transmit
different forces or they resist the forces by means of spray
last but not least they are making mechanical applications where Springs I
use may be a simple dynamometer or maybe something else that they generally use
the transfer of the power transmitter the forces where springs are measured
Tilly use so spring is a very essential though it is small in nature but it’s
very essential part in order to work the mechanical systems let’s move ahead let
us begin with the types of Springs now since we are learning about it design
and design aspects we should know which are the types of Springs now there are
various types of Springs of course facialized one as far as the industries
are concerned but as per your syllabus we are going to look at only two types
the first type you can see is the helical Springs and the second type you
can see is the lip Springs now helical Springs are generally made up of wires
and wires do have the cross section circulating majority of the cases and
that’s why helical Springs are made up of wires the next thing is there are
subtypes of Fela concering helical Springs are generally used as the
compression springs or they are used for the tension or extension Springs or they
are used for the torsion spring so these are basically their application point of
view the next is lip springs now lip springs are made up of different
materials or the strips of materials or metals you can say and the general form
of lip spring is semi elliptic lip spring where the curvature goes into the
elliptical way and they are see me because the only half portion of them is
utilized for storing or what are the purpose they are being used of course we
are going to do with their detailing afterwards we are going to look at the
design aspects afterward and then we are going to look at the new miracles that
can be solved so these are the important things so when these types are
distinguished in let us look at the application point of view
let me quickly draw them so this is a kind of spring of course there are
simple Springs which are shown where the lower which is acting has the
compressive nature this Springs use are basically called compressive Springs
when the nature of force is such that the force will act away from this spring
or they act towards the end points in that case the spring utilizes called
tension Springs or extension Springs the last but not the least it’s the same
spring but in that case the forces do act in such a manner that they induce
the torsion inside the given body of the spring and that’s why they’re called
torsion springs this is the main pipe whereas the lip Springs they have
different lifts like them little lips are nothing but the metallic strips
which have undergone certain curvature so certain many lips are the strip’s
they are brought together so as to sustain different loads all these lip
springs are going to sustain transverse loads in that case like in this case we
have compressive tensile and torsion in this case the loads that are going to
act on our torsion mainly lip springs are utilized for the heavy automobile
vehicles for their suspension systems because in that case it’s very difficult
or it’s not that feasible to use the helical Springs let’s move ahead now
there comes an important thing which is called terminologies since we need to
understand different design aspects of this particular member we need to
understand various terminologies or various notations they use for this
particular spring so let us begin with the helical spring as you can see on the
screen there is a schematic given for this pin it’s a cross section given and
you can see the spring wires on only one half are shown let us look at them if
you see this particular structure they are nothing but the cross sections of
this Springs of course they’re circular in nature on both sides this is the axis
about which they are going to be symmetric let us start with the length
the total length from the beginning of the spring till the end of the spring no
matter where the end is it’s called the free length of the
spring so free length is the maximum length of this spring which is possible
when there is no force acting on that particular spring the next thing is the
small D small D stands for the diameter or the cross-section diameter of the
wire which is used for that particular spring so in that case you can see this
circular cross-section it’s nothing but this small D next thing comes is the
diameter D capital D it is nothing but the mean diameter of the coil now if you
see from this end to this end this particular round or this particular term
is called coil so this coil the mean diameter is called capital D now there
are two different terms associated inner diameter and outer diameter the inner
diameter if you see will be the distance between the innermost layer of this
cross-sections of whose circular they are in nature and outer will be the
distance between the outermost layer of this particular dimensions the next one
last terminologies which is very important here is speech now pitch if
you see is proper the distance between two consecutive points of this plane so
let me quickly summarize this small D is nothing but the wire diameter capital D is the mean diameter of course it is associated with coily
do that is the outer diameter again of coil and di is nothing but
inner diameter again associated with the coil there
comes LF that is the Freeland of the spring this is the pitch and so
that the D will be given by the bisection point of the outer
diameter and the inner diameter there comes another particular term that’s
called spring index which is given by C the spring index is nothing but the
ratio of the mean diameter of the given coil to the wire diameter of the given
coil we can see the mean diameter which is this is always greater than smaller
diameter and hannes C will be always greater than one now this factor spring
index is going to be used frequently whenever we are going to solve the
numerical based on the design of this particular spring so these are the some
of the important terminologies which are going to be used in the helical spring
let’s move ahead with some another terms are not called M terminologies but terms
which we are going to use for that particular inspection so the first one
is the solid length now solid length is no further compression is possible the
students when a spring is compressed in that case the coils will touch each
other since that is metal and that is not a plastic material it will not
deform beyond us so when the maximum force maximum possible force is applied
on this structure then the coils will touch each other so that the length form
will be a solid where no further compression is possible so in such case
the length obtained is called solid length and it will be given by n into B
where small n is the number of coils into D is the diameter of one wire so if
we need to draw thee compressed structure let me call this is
the first coil the second coil is attached to it since they are closely
attached there is no gap between them let me add the third one
fourth one and so on for the N number off for the n number of
coils and that’s why this solid length up to n number of coils will be n which
is 1 2 3 4 and so on up to n into 1 diameter 1 diameter of any respective
coil next thing is compressed length now there is a minor difference between this
compressed length and soldered length both are obtained when they are
compressed no doubt in that but compared length is obtained when of
maximum allowable forces of line it’s not a maximum possible force is the
maximum allowable force and you should understand that maximum allowable force
has to be smaller than the maximum possible force so when maximum allowable
force is acted upon by this plane naturally it will compress but it will
not compress to the full extent there will be some gap maintained by two coils
and considering this gap whatever total length comes out to be is called
compression length so if you need to draw this schematic it will be somewhat
like this let me call this is the first coil there’ll be certain gap between they
second third and so on so that from the first thing up to the last it will be
the compressed length and if you see logically it will be given by n minus 1
total number of coils minus 1 because we are considering this playing gap also
into gap between the coils now see if the gap is 1 to 2 millimeter in that
case we have to consider this gap into the coil minus 1 or the number of coils
minus 1 that will give me the comparison the next term is free length the free
length is the length of that particular spring where there is no load acting
since there is no load acting it will undergo its natural length which is
possible for the spring to obtain and that’s why it is called unload condition
so in that case the free length which is designated by L F will be given by the
compress name plus the maximum deformation possible for a spring which
will be also given by this solid length plus the maximum axial gap that is
nothing but this 2 plus the maximum deflection possible so either of this
empirical formula we can use to find out defray length let us go to the next
which is very important like we have discussed page which is the axial
distance between two consecutive points on a coil so it’s the actual distance
between two coils or the consecutive points on the coil for example if this
is of the spring is structured I’ve shown only the cross-section
the other side of spring is not shown so in that case this is the first coil and
this is the next coil so in that case these two points are same I’ll call them
consecutive points so that the distance measured along the axis or parallel to
the axis will be called pitch and hence which will be given by the free length
of a coil divided by this particular term which is number of coils minus one
because we are not considering the last coil in that case because we are taking
the difference between two consecutive coils the next important thing that we
need to understand is these spring ends now
spring is a continuous member which has certain constraints for its dimension so
somewhere it has to aim but it’s not a skip and or if not they are random and
we have to predefine the end so as to place the spring properly in the given
mechanical system because spring has to interact with multiple section multiple
fragments multiple surfaces and in that case we should have a provision so as to
fix the spring properly and that’s why certain ins are used for such popular
ends we are going to look at the very first end that we see is the planing let
me draw this schematic of a spring if you see the aims are the aims are
fixed with certain angle again so it continues with the helix angle of course
that angle is called helix angle the particular angle that it makes with
horizontal is called helix angle beta generally they call it so the spring
which has the end where the helix angle is maintained such a spring will be
called a plain spring or it will call a plane and spree since the most simple form of the spring
in the second form is little modified and which is called plane and ground
ground term is used for the flattening of the given aim so in that case the end
will look like if you see unlike the first type the
aims are flattened they don’t have the helix angle maintained there so that
this is a horizontal one in this case and that’s why the call plane and ground
end of this spring so this was the second type
the third type is quite different where it is called a square end in such case if you see it’s not Midway
it is akin to the n points where the aims are properly done with this square
kind of T the next modified version of square is nothing but square and ground
where agree in the square in some mid-ground where if you see properly that particularly
ground where they’re cut in the shape where it is required and that’s why
these are the four different spring nails that may have to be used so it’s a
small portion of the numerical that we are going to look at where at the end we
have two predefined or we have to select a predefined given kind of ale which has
a small impact on the for the part of the in America let’s move it now arrived
at the last segment of this particular lecture we are going to look at the
terminologies that I use for the lip spring we have seen so far the
terminologies they are used for the helices ringing but this is for the lip
spring now this is the schematic of the leaf spring is given I have drawn just a
schematic it’s not a proper diagram but I think it is explanatory you can see
the different curves are nothing but the lips the cold lips because they appear
to be lips they’re made of metals and we already have seen the cross section I
will draw it for you again these are basically metallic strips
which undergo certain bending now the layers in which the act they
have got certain significance if you see properly of course they’re symmetric
about both the layers the topmost thing is bolted properly and the force to act
on this of course these bolts do represent a fixture where the spring is
going to be fixed the layer one the next and the next layer if you observe it
properly the lens are going on increasing one by one and that’s why
they’re called graduate level slips now that depends upon the application
how many graduate level lips we have to use sometimes they can be two three four
or five also as soon as the graduate level lips are aimed they’ll start to
equal length lips and these are called full-length lips so these are the
fillets the length which is possible and they’re equal in length there comes the
last lift which has got a different paint ins and this lift is called master
lift the master lift is going to be attached to the application to which
this spring is going to be attached know the forces that do act on the spring are
called P let us call them P on either sides so that the reactive force or the
supportive force will become twice the be the last terminologies that they use
is this bent end of the master lip is called I it’s called an eye so these are
the important terminologies that we are going to look at the last thing is
between two eyes the center to Center distance is defined as twice the length
now let us look at them quite rapidly the first one is the N F that is nothing
but the number of full length Springs number of full-length lips in our case
there only two one and two the next one is ng wet it’s called as number of number of gradual level leaves in our
case they are 1 2 & 3 the next one is the total number of lips so in this case it will be equal
to an f-plus ng the next is the B which is
nothing but the width so in this case this particular dimension is nothing but
the width of a sprain or live the next is the thickness in this case what are
the thickness they use for one strip is called a thickness of the lift next is the length so it’s the length so it is the length of one side of flip
that is the master leaf from the center pond at the point of symmetry in our
case if this is going to be the point of symmetry this particular length will be
only L so that the combined length will be 2 L the last is nothing but P which
is the load acting so these are the important terminologies they are used in
the lip springs so guys may be in with the first segment where we have gone
through the introduction we have quickly seen what are the springs what are the
kind of forces that they act we have seen the types of Springs then we have
gone through the terminologies that they use for the helical Springs and now it
was a terminologies that they use for the lip Springs in the next video we are
going to look at the design aspects that is generally used for helical spring
design thank you so much for watching this video if you liked this video
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