FIELD OF THE INVENTION :-
The present invention relates to an improved suspension of broad gauge (1676mm)
Casnub 22 NLB bogie for increasing its axle load from 20.32 tons to about 23 tons,
and increasing its speed potential from 80 km/h in empty condition and 75 km/h in
loaded condition to about 100 km/h in empty condition and about 75 km/h under
enhanced loading condition of about 23 tons. The improved suspension also makes
the bogie track friendly.
BACKGROUND OF THE INVENTION :-
The body of the freight car / wagon is generally supported on two trucks / bogies
(spaced apart according to the length of the wagon) which permit the wagon to
travel along the railway track. Each truck assembly normally consists of two side
frames, one bolster, two wheel sets, primary and secondary suspensions, one
centre plate, two side bearers, damping and braking arrangements. The side frames
are supported over a pair of axles through roller bearings adapter and elastomeric
pads. In a wheel set, two wheels are rigidly fixed on to each axle and spaced from
each other to suit the track gauge. Braking force is generally provided by the bogie /
wagon mounted brake cylinders through linkages, brake beams and brake blocks.
BOXN/BOXNHS wagons of Indian railways have a similar arrangement wherein two
Casnub 22 NLB bogies are placed under the car body; their spacing being
determined by the spacing of car body bolsters. Centre plates and constant contact
side bearers (CCSBs) are so disposed between the car body bolsters and bogie
bolsters, that bulk of the empty car body weight is transferred to bogie bolster
through side bearers and balance of the car body weight and pay load is transferred
through centre plates.
Existing design of the Casnub 22NLB bogie as shown in Fig.1 and Fig. 1A has two
side frames and a bolster which are hollow steel castings similar in design to the
side frames and bolster of a modern 3 piece truck. A rolled steel plate spring plank,
riveted at the base of the spring pockets of the side frames rigidly connects the two
side frames together, making the construction a "H" frame. Bolster is provided with a
hemispherical bowl type centre plate in its centre and rubber spring type two
constant contact side bearers (CCSBs) equispaced from the centre plate. Primary
suspension consists of four rubber elastomer pads provided one each above the
adapter fitted over the roller bearings which in turn are fixed on the axle journals.
Secondary suspension consists of outer coil springs, inner coil springs and snubber
coil springs placed in the side frame pocket. Bogie bolster is so disposed over
secondary suspension springs and within the side frame pockets that its ends not
only have some pre-determined lateral and longitudinal clearances with the side
frames but also have sufficient vertical space to allow for vertical oscillations /
movements of the coil springs during running of the train. Snubber coil springs also
share the load on the bogie bolster. This arrangement, therefore, provides for a load
variable damping. Secondary suspension of the Casnub 22NLB bogie is a single
stage suspension i.e. it provides same vertical stiffness under empty and loaded
conditions of the wagon. Vertical and lateral damping to the bogie oscillations is
provided through rubbing of the four wedges, disposed within bolster pockets and
above snubber coil springs, against the liners fitted to the side frame columns.
In the existing design of Casnub 22NLB bogie secondary suspension consists of the
following springs.
Description Nos/Bogie Free height (mm) Vertical spring rate
Kg/mm
Outer Spring 14 260 45.95
Inner Spring 10 262 20.5
Snubber Spring 04 294 13.0
This arrangement provides a uniform stiffness of 900.3 Kg/mm under both empty
and loaded conditions. Friction damping provided by the rubbing of friction wedges
against the side frame column wear liners depends on the snubbing force which in
turn depends on the load shared by the snubber springs. In this arrangement load
shared by the four snubber springs works out to about 2010 Kg in empty condition
and about 4000 Kg in loaded condition.
Indian Patent Document 502/CHE/2004 discloses an improved three-piece truck
system for railroad cars which provides long travel side bearings for improved
stability, a wide friction shoe design or equivalent to improve side frame and bolster
squareness, a resilient pedestal pad for improved curving performance and
enhanced wear resistance , and a suspension system tuned and optimized for rail
cars to have a minimum reserve capacity of not less than 1.5 to improve motion
control and ride quality, increase resistance to suspension bottoming, and increase
hunting threshold speed. Such a motion control truck system is able to meet recent,
more stringent American Association of Railroads standards, such as M-976, for
railcars having a 286,000 lb. gross rail load rating. However, the present invention is
different from this prior art as follows.
1. Constant Contact Side Bearers ( CCSBs ):
(i) The prior art has a pre-set height of 128.59 mm (as per US railway freight
car requirements) whereas the present invention has a pre-set height of
124 mm (as per Indian Railway freight car requirements).
(ii) CCSBs in the present invention share 90% of the empty car body weight
as against 85% in case of the above cited document.
(iii) The pre-set load of CCSBs in the present invention is different from the
pre-set load of CCSBs in the above cited document.
(iv) Each CCSB in the present invention has a vertical stiffness of about 150
kg/mm which is different from the stiffness of the CCSB in the above cited
document,
(v) The shape & size of Housing, Cover and Wear liner in the present
invention are different from those in the above cited document,
(vi) Self lubricating Liner sleeve fitted with cover is the unique feature in the
present invention which is absent in the above cited document.
2. Elastomeric Pad :
Elastomeric Pad in the present invention is unique in design because it extends
beyond the Adapter Lugs in the transverse direction to the track and thus
different from that in the above cited document.
3. Secondary Suspension Springs :
Secondary Suspension Springs (Outer, Inner & Snubber )in the present invention
have been designed to suit the 23.0 tonne axle load requirement of Indian
Railways and have stiffnesses quite different from those in the above cited
document.
4. The above cited document pertains to a freight car bogie design for a Standard
Gauge (1435 mm) of railway track whereas this invention pertains to 1676 mm
Broad Gauge railway track of Indian Railways.
On Indian Railways, Casnub 22 NLB Bogie is predominantly used under open
wagons type BOXN / BOXNHS which have an operating speed of 80 Km/hr in empty
condition and 75km/hr in loaded condition. These wagons are used for carrying bulk
commodities like Coal, Iron ore, Lime stone, Gypsum, Steel, Food Grain, Fertilizer,
and Cement etc. These wagons with axle load of 20.32 tons have a carrying
capacity of 58.81 tons. During the year 2005-06, Indian Railways decided to
increase the carrying capacity of these wagons by 10 tons, thereby increasing the
axle load to approx 23 tons. Research Design and Standards Organization (RDSO)
Lucknow was asked to take up this upgradation as a project. RDSO accordingly
upgraded the suspension of Casnub 22 NLB bogie and conducted oscillation trials in
April 2006. However, lateral forces encountered during the trials almost reached the
Prud-Homme limit at 70 Km/hr. The wagon could, therefore, be cleared in loaded
condition only upto 60 km/h.
Subsequently RDSO approached the indigenous bogie and component
manufacturers to come up with a solution consisting of complete suspension
covering primary and secondary suspensions and constant contact side bearers
(CCSBs).
Therefore, the invention is aimed at providing suspension design of broad gauge
(1676mm) Casnub 22 NLB bogie for increasing the axle load from 20.32 tons to
about 23 tons, and increasing its speed potential from 80 Km/h in empty condition
and 75 Km/h in loaded condition to about100 Km/h in empty condition and about 75
km/h under enhanced loading condition.
OBJECT OF THE INVENTION :-
An object of the present invention is to provide an improved suspension that
increases axle load of Casnub 22 NLB bogie to about 23 tons.
Another object of the present invention is to provide an improved suspension that
would increase speed of Casnub 22 NLB bogie to about 100 Km/h in empty
condition and about 75 Km/h under enhanced loading condition.
A further object of the present invention is to provide an improved suspension that
would increase a service life of elastomeric pad which is 3 to 4 times of the existing
18 months.
Yet another object of the present invention is to provide an improved suspension
that would retrofit in the existing Casnub 22 NLB bogie.
These together with other objects of the invention, along with the various features of
novelty, which characterize the invention, are pointed out particularity in the claims
annexed to and forming a part of this disclosure. For a better understanding of the
invention, its operating advantages and the specific objects attained by its uses,
reference should be had to the accompanying drawings and descriptive matter in
which there are illustrated preferred embodiments of the invention.
SUMMARY OF THE INVENTION :-
According to one aspect of the present invention there is provided an improved
suspension of broad gauge (1676mm) Casnub 22 NLB bogie for increasing its axle
load from 20.32 tons to about 23 tons comprising :
rubber elastomeric pads for primary suspension resting on adapters fitted over roller
bearings fixed on axial journals;
snubber coil springs, outer coil springs, and inner coil springs for secondary
suspension placed in the side frame pocket; rubber spring constant contact side
bearers (CCSB's) equispaced from and on either side of the centre plate on a bogie
bolster;,
said bolster provided with a hemispherical bowl type center plate in its center;
the improvement wherein comprising four number of elastomeric pads extending
beyond the adapter lugs for primary suspension, four number of stiffer snubber coil
springs, fourteen number of outer coil springs, and fourteen number of inner coil
springs for secondary suspension, two number of triple nested steel coil spring
constant contact side bearers (CCSB's) having a vertical stiffness of about 150
kg/mm, and a bolster provided with a flat center plate in its center and the lateral
clearance between bolster and the side frames increased from 09 mm to about 15
mm.
According to a preferred embodiment the four number of elastomeric pads for
primary suspension are made up of rubber elastomer placed between the top and
bottom plates to obtain a shear stiffness of about 300 kg/mm.
According to a preferred embodiment the four number of stiffer snubber coil springs
having a free height of 279 mm and vertical spring rate of 31.95 kg/mm, the fourteen
number of outer coil springs having a free height of 273 mm and vertical spring rate
of 14.21 kg/mm, and the fourteen number of inner coil springs having a free height
of 244mm and vertical spring rate of 38.04 kg/mm for secondary suspension has a
stiffness 326.8 kg/mm under empty condition and 859.36 kg/mm under loaded
condition.
According to a preferred embodiment the two number of triple nested concentric
steel coil spring constant contact side bearers (CCSB's) comprises outer, inter, and
inner concentric steel coil springs are placed in a housing, a cover fitted with non
metallic liner sleeve by using countersunk (CSK) head screws on the inside and a
wear liner on top, the cover rests on the nest of the coil springs and moves up and
down during service, and the housing also serving as a vertical stop provides for a
long travel up to 16 mm from set up height and prevents the coil springs from going
solid in service. Therefore, the constant contact side bearers (CCSB's) share 90% of
the empty car body weight and the balance car body weight and the pay load are
borne by the centre plates.
According to preferred embodiment of the invention the flat center plate has about
3mm radial clearance and the lateral clearance between the bolster and the side
frames increased from 9mm to about 15 mm to improve lateral ride behavior.
According to further embodiment of the invention the metallic wear liners can be
replaced by non-metallic wear liners (polymeric materials like polyurethane etc.,) if
the non-metallic wear liners reduce the maintenance further
The suspension increases the speed of Casnub 22 NLB bogie to about 100 km/h in
empty condition and about 75 km/h under enhanced loading conditions is capable
of being retrofitted in the existing Casnub 22 NLB bogie.
BRIEF DESCRIPTION OF THE DRAWINGS :-
The invention will be better understood and objects other than those set forth above
will become apparent when consideration is given to the following detailed
description thereof. Such description makes reference to the annexed drawings
wherein:
Fig. 1 illustrates the existing design of Casnub 22 NLB Bogie.
Fig. 1A illustrates the side view of the existing bogie indicating the location of
constant contact side bearers (CCSBs) and Centre Plate.
Fig. 2 illustrates the friction wedge and snubber coil spring arrangement in
accordance with the present invention.
Fig. 3 illustrates the spring plank with nest of outer and inner coil springs as also the
snubber coil spring in accordance with the present invention.
Fig. 4 illustrates the sectional view of the triple nested concentric steel coil spring
constant contact side bearer in accordance with the present invention.
Fig 5 illustrates the sectional view of the elastomeric pad in accordance with the
present invention which has been designed to provide a long service life.
Fig. 6 illustrates the sectional view of the existing hemispherical top and bottom
center plates.
Fig. 7 illustrates the sectional view of the fiat top and bottom centre plates in
accordance with this invention.
DETAILED DESCRIPTION OF THE INVENTION :-
The ride behaviour and the critical speed of the freight car depends on a number of
factors Viz empty / loaded condition, track gauge, design and condition of the rails,
structure and the condition of the track, design and the condition of the wheels,
primary suspension, secondary suspension, constant contact side bearers, design of
the centre plate and various clearances in the system etc., and these parameters
differ from one railway system to other railway system. Therefore, a bogie
suspension has to suit the given set of parameters of a particular railway system.
In view of the above, in response to the request from RDSO, Lucknow, an Indian
Railway specific design of the suspension including primary suspension, secondary
suspension, constant contact side bearers and flat centre pivot has been invented.
NUCARS (software) simulations of the same by RDSO, using Indian Railways main
line worn out track data file have indicated that Casnub 22 NLB bogie with the new
improved suspension for 231 axle load is
i) Capable of operating at about 100 km/h in empty condition and about 75 km/h
in loaded condition,
ii) Lateral forces encountered upto 110 Km/h on a tangent track and upto 85 km/h
on a 2 deg track remain considerably below the Prud-Homme limit.
Fig 1 shows the elevation view of the existing Casnub 22 NLB bogie with half the
secondary suspension shown in section. This view indicates the side frame (1),
bolster (2), center plate (3) fixed on bolster (2), friction wedge (4) fitted in the bolster
(2) pocket, snubber coil spring (8) fitted below friction wedge (4), nests of outer and
inner coil springs of secondary suspension (9) etc. Spring plank (10) rigidly connects
the two side frames of the bogie. Secondary suspension springs are placed between
spring plank and the bolster within the side frame pockets. It also shows the fitment
of adapter (6) over the roller bearings (7) fitted on the axle journals. Elastomeric
pads (5) are shown fitted over the adapters (6) in the side frame jaws. Friction
wedges (4) rub against the side frame column friction liners (11) in service.
In rail freight cars, payload to empty car weight ratio is normally high and the
suspension is expected to be able to cater for both empty and loaded conditions. A
freight car should also be able to maintain contact with the track while negotiating its
irregularities and contours, both in empty and loaded conditions. Therefore, the
freight car and the truck assemblies must have the operating characteristics that
enable them to operate safely on all track conditions at all speeds upto the
prescribed limits in all the conditions of loading which should be as uniform as
possible.
Track irregularities and contour conditions can induce various kinds of oscillations in
the freight car and trucks which if not controlled can create unstable operating
conditions. Such a phenomenon gets more pronounced on curves. Necessary
control over such oscillations is provided by damping the relative movements of
bolster and side frames in a truck assembly. This is achieved by way of friction
between friction wedges provided in the bolster pockets and the vertical columns of
the side frames. Friction force exerted by the wedges depends on the vertical load
shared by the snubber springs over which they are supported (Fig 2). Thus the
damping so provided is a load variable damping and the same is so very necessary
for freight cars with high payloads.
Conicity provided on the wheel tread results in sinusoidal movement of the wheel set
on the rail track. Lateral amplitude of such movement, if left unattended, would grow
with speed of the train and would reach a stage when wheel flange starts hitting the
rail. Such a state of motion is referred to as 'hunting of the wheel set' and the speed
at which it is reached is called the 'critical speed'. In case of bogies, stiffness of the
primary suspension provides restraint / damping to the lateral motion of the wheel
set and, therefore, critical speed is higher than that of a free wheel set. At speeds
higher than the critical speed, hunting oscillations tend to become violent and the
flange impacts against the rail can be very severe increasing the possibility of
derailment.
A bogie having very stiff longitudinal primary suspension springs has its wheel sets
essentially held parallel to one another and they are unable to yaw appreciably
relative to the bogie frame. Therefore, when such a bogie traverses a curve, its
wheel sets are unable to adapt a radial alignment to the curve, which may even lead
to derailment. Therefore, a compromise between stability (higher critical speed) and
curving is often arrived at to meet the system requirements. Keeping this
compromise in view, lateral and longitudinal shear stiffness have been fine tuned in
the present invention.
After the clearance available at axle box and bolster level in a bogie are used up, the
hunting oscillations of the wheel sets induce similar oscillations in the bogie frame
and then in the car body. Car body being the heaviest mass, once it starts hunting,
the oscillations tend to get sustained unless damped. Such damping is provided by
the friction between the top and bottom centre plates and that between CCSBs on
the bogie bolster and the corresponding wear liners of the side bearer on the car
body bolster. CCSBs also provide a restraint to the car body roll which again has a
bearing on the lateral ride behaviour of the car, thus improving the critical speed.
Fig 2 shows a sectional view of bolster (2), friction wedges (4), snubber coil springs
(8) and nest of outer and inner coil springs (9) of secondary suspension placed
within side frame (1) pocket. The arrangement shows that increase in the vertical
load on the bolster would correspondingly increase the horizontal thrust of the
friction wedges on the friction liners fitted with side frame columns resulting in load
variable damping.
While upgrading the Casnub 22 NLB bogie the emphasis was given on carrying out
minimum changes. Wedges and wedge pockets of the bolster were, therefore, not
changed. Requisite damping and improved warp resistance was alternatively
achieved by increasing the damping force by using stiffer snubber springs. In this
invention spring rate of the snubber springs has been fine tuned to provide the
optimum damping in both empty and loaded conditions of the freight car. In addition
to the snubber springs, other suspension springs have also been fine tuned to
achieve an improved ride behaviour and higher critical speed both in empty as well
as in loaded conditions of the freight car.
Fig 3 shows the arrangement of number of secondary suspension springs at one
end of the spring plank. Secondary suspension at each end of the spring plank or
bolster consists of 7 nests of outer and inner coil springs and 2 snubber coil springs.
The figure also indicates the sectional views of a nest of outer and inner coil springs
and also that of a snubber coil spring.
The new design of the secondary suspension for about 23 tons axle load Casnub 22
NLB bogie under this invention consists of the following springs.
Description Nos/Bogie Free height (mm) Vertical spring rate
Kg/mm
Outer Spring 14 273 14.21
Inner Spring 14 244 38.04
Snubber Spring 04 279 31.95
Under this arrangement, inner spring comes into action only in loaded condition. The
suspension, therefore, has a stiffness of 326.8 Kg/mm under empty condition and
859.36 Kg/mm under loaded condition. Friction damping provided by the rubbing of
friction wedges against side frame column wear liners depends on the snubbing
force which in turn depends on the load shared by the snubber springs. In this
arrangement load shared by the 4 snubber springs works out to about 3011 Kg in
empty condition and about 9033 Kg in loaded condition. These loads are about
49.8% and 125.8% higher respectively than those of existing bogie and thus provide
correspondingly higher damping to the bogie vibrations both vertical and transverse
emanating from the rail wheel interaction during run. Angle of the friction wedges (35
deg.) has not been changed under this invention.
Fig-4 shows the sectional view of an assembled constant contact side bearer under
present invention. Constant contact side bearers (CCSBs) equispaced from and on
either side of the centre plate on the bogie bolster, are disposed between bogie
bolster and car body bolster in such a way that they share 90% of the car body
weight and the balance car body weight and the payload are borne by the centre
plates. Constant contact side bearers (CCSBs), designed under present invention
mainly comprises of a nest of three concentric steel coil springs placed in a housing
and a cover placed above them. The cover can move up and down with the coil
springs during running of the train and it is so disposed vis-a-vis housing that coil
springs are subjected to practically no lateral/ longitudinal flexing during bogie
rotation and lateral movements in service. A non-metallic self lubricating liner sleeve
fitted with the cover avoids wear between cover and housing in service. The vertical
stop provides for a long travel upto 16 mm from set up height and yet prevents the
coil springs from going solid in service. A friction liner has been provided over the
cover. Sliding friction between the same and corresponding wear liner on the car
body bolster provides necessary constraint for bogie yaw and lateral movements.
Fig-5 shows the sectional view of the elastomeric pad used as primary suspension
under present invention. These rubber elastomeric pads have a shear stiffness of
300 kg/mm, on account of their design, shape, size and elastomeric compound, to
achieve proper curving, higher critical speed and reduction in lateral forces even at
higher axle load of about 23 tons. Service life of these new design elastomeric pads
will increase 3 to 4 times that of the existing 18 months.
Under this invention hemispherical centre plate (Fig.6) has been replaced by a flat
centre plate (Fig.7) with 3 mm radial clearance and metal bonded rubber type
CCSBs have been replaced by triple nested concentric steel coil spring constant
contact side bearers (CCSBs). This arrangement helps in controlling the bogie
rotation and car body roll thus improving the lateral ride behaviour.
To accommodate the lateral oscillations of the bogie bolster, especially on curves,
adequate clearance ought to be provided between bogie bolster and the side
frames. With this view existing clearance has also been suitably increased. In the
existing bogie lateral clearance between bolster and side frames is 9 mm. For
improvement in lateral ride behaviour it has been increased to about 15 mm under
this invention.
This invention makes the Casnub bogie (with the increased about 23 tons axle load)
a track friendly bogie suitable for operation at100 Km/h in empty condition and at75
km/h under enhanced loading condition of the wagon on the existing 1676 mm
gauge run down main line track of Indian Railways and thus finds a unique solution
to the problem faced by Indian Railways.
All the suspension elements used in this invention have been so designed that the
same can be easily retrofitted in the existing Casnub 22 NLB Bogie.
Although the foregoing description of the present invention has been shown and
described with reference to particular embodiments and applications thereof, it has
been presented for purposes of illustration and description and is not intended to be
exhaustive or to limit the invention to the particular embodiments and applications
disclosed. It will be apparent to those having ordinary skill in the art that a number of
changes, modifications, variations, or alterations to the invention as described herein
may be made, none of which depart from the spirit or scope of the present invention.
The particular embodiments and applications were chosen and described to provide
the best illustration of the principles of the invention and its practical application to
thereby enable one of ordinary skill in the art to utilize the invention in various
embodiments and with various modifications as are suited to the particular use
contemplated. All such changes, modifications, variations, and alterations should,
therefore, be seen as being within the scope of the present invention as determined
by the appended claims when interpreted in accordance with the breadth to which
they are fairly, legally, and equitably entitled.
WE CLAIM:-
1. An improved suspension of broad gauge (1676mm) Casnub 22 NLB bogie for
increasing its axle load from 20.32 tons to about 23 tons comprising rubber
elastomeric pads for primary suspension resting on adapters fitted over roller
bearings fixed on axial journals; snubber coil springs, outer coil springs, and
inner coil springs for secondary suspension placed in the side frame pocket;
rubber spring constant contact side bearers (CCSB's) equispaced from and on
either side of the centre plate on a bogie bolster; said bolster provided with a
hemispherical bowl type center plate in its center; the improvement wherein
comprising:
a) four number of elastomeric pads extending beyond the adapter lugs for
primary suspension;
b) four number of stiffer snubber coil springs, fourteen number of outer coil
springs, and fourteen number of inner coil springs for secondary
suspension ;
c) two number of triple nested steel coil spring constant contact side
bearers (CCSB's) each having a vertical stiffness of about 150 kg/mm;
and
d) the bolster provided with a flat center plate in its center, said bolster
having an increased lateral clearance with the side frames.
2. The improved suspension as claimed in claim 1 wherein the elastomeric pads
have shear stiffness of about 300 kg/mm.
3. The improved suspension as claimed in claim 1 comprising:
four number of stiffer snubber coil springs having a free height of about 279
mm and vertical spring rate of about 31.95 kg/mm;
fourteen number of outer coil springs having a free height of about 273 mm and
vertical spring rate of about 14.21 kg/mm; and
fourteen number of inner coil springs having a free height of about 244mm and
vertical spring rate of about 38.04 kg/mm for secondary suspension providing a
stiffness of about 326.8 kg/mm under empty condition and of about 859.36
kg/mm under loaded condition.
4. The improved suspension as claimed in claim 1 wherein the triple nested
concentric steel coil spring constant contact side bearers (CCSB's) comprising:
a) housing;
b) a cover having a non - metallic liner sleeve detachably fixed on to the
inside surface of said cover by means of countersunk head screws;
c) wear liner provided on the top outer surface of said cover;
d) triple nested concentric steel coil springs placed in the said housing in
an outer, inter, and inner configuration in a manner to provide support
to the said cover such that when acted upon by a load during service,
said cover performs up and down vertical movement.
5. The improved suspension as claimed in claim 1 wherein the flat center plate
has radial clearance of about 3 mm.
6. The improved suspension as claimed in claim 1 wherein the bolster has a
lateral clearance of about 15 mm with the side frames.
7. The improved suspension as claimed in claims 1 to 6 adapted to increase the
speed of Casnub 22 NLB bogie to about 100 km/h in empty condition and
about 75 km/h under enhanced loading conditions.
8. The improved suspension as claimed in claims 1 to 6 is retrofitted in the
existing Casnub 22 NLB bogie.
9. The improved suspension as herein substantially described and illustrated with
the accompanying drawings.

A new improved suspension for the 23 ton axle load Casnub 22 NLB bogie comprising of four number of snubber coil springs provided below the friction wedges and seven sets of outer and inner coil springs per side frame pocket for secondary suspension, four number of long life elastomeric pads in the primary suspension, two number of triple nested coil spring constant contact side bearers (CCSBs) each having a vertical stiffness of about 150 kg/mm and a flat center plate on bogie body bolster and increased lateral clearance of the bolster which makes the Casnub 22 NLB bogie track friendly for operation at the speed of 100 kmph in empty condition and 75 kmph in loaded condition.