FIELD OF THE INVENTION :-
The present invention relates to the design and development of a long travel coil spring
type constant contact side bearer for the improved design of suspension of broad
gauge (1676mm) Casnub 22 NLB bogie for increasing its axle load from 20.32 t to 23 t,
and speed potential from 80 km/h in empty condition and 75 km/h in loaded condition to
100 km/h in both empty and loaded conditions and also make it 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 22 NLB bogie (Fig 1) consists of 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 equispaced
from the centre plate.

Existing CCSB, as shown at Fig-2, consists of a metal bonded rubber pad placed in a
housing. It has a vertical stiffness of 200 Kg/mm and the CCSBs share 67% of the car
body weight. Because of rubber, its pre-load characteristics change with time and
temperature which affects the ride behaviour of the bogie in service. It has a service life
of about 18 months and there have been lots of premature failures of this design in
service.
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, Cement etc.
These wagons with axle load of 20.32 t have a carrying capacity of 58.811. During the
year 2005-06, Indian Railways decided to increase the carrying capacity of these
wagons by 10 t, thereby increasing the axle load to approx 23 t. Research Design And
Standard Organization (RDSO) Lucknow was asked to take up this upgradation as a
project. RDSO accordingly upgraded the suspension of Casnub 22 NLB bogies and
conducted oscillation trials in April 2006. However, lateral forces encountered during
the trials almost reached the Prud- Homme limit at 70 Km/h. 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 (CCSB) etc.
Therefore, this invention is directed to the design and development of a suitable coil
spring type CCSB (the pre-load characteristics of which would not change in service)
for the new improved suspension of Casnub 22 NLB bogie of Indian Railways for
increasing its axle load from 20.32 t to 23 t, increasing its speed potential from 80Km/h
in empty condition and 75 Km/h in loaded condition to 100 Km/h in both empty and
loaded condition and also making the same track friendly

OBJECT OF THE INVENTION :-
Primary object of the present invention is to design and develop a constant contact side
bearer for the 23 t axle load Casnub 22 NLB bogie comprising of a nest of three
concentric coil springs as outer, inter and inner springs; a housing to accommodate the
nested springs; a cover fitted with a non metallic liner sleeve on its inside and a wear
liner on its top, resting on the nest of the coil springs and being able to move up and
down during service.
Another object of the present invention is to design and develop CCSBs that share 90%
of the empty car body weight and the balance car body weight and the pay load are
borne by the centre plates.
Another object of the present invention is to provide a friction liner over the cover of
CCSB which provides sliding friction with corresponding wear liner fitted on the car
body bolster to provide necessary constraint against bogie yaw and lateral movements.
Another object of the present invention is to design the CCSB with a vertical stop which
permits a long travel upto 16 mm from the set up height and yet prevents the springs
from bottoming in service. The design also does not permit any lateral loading of the
springs.
As per yet another object of the present invention is to design the CCSB that can be
easily retrofitted on the existing 20.321 axle load Casnub Bogie for converting the same
to a 231 axle load bogie.
These together with other objects of the invention, along with the various features of
novelty, which characterize the invention, are pointed out with 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.

BRIEF DESCRIPTION OF THE ACCOMPANYING 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 Casnub 22 NLB Bogie.
Fig.2 illustrates the existing design of the metal bonded rubber type CCSB;
Fig 3 illustrates the sectional view of the constant contact side bearer arrangement in
accordance with the present invention
DETAILED DESCRIPTION
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 suite 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 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 100Km/hr both in empty and loaded conditions.
ii) Lateral forces encountered upto 110 Km/h on a tangent track and upto
100km/h on a 2 deg track remain considerably below the Prud-Homme limit.

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
by way of friction between friction wedges provided in the bolster pockets and the
vertical columns of the side frames. In case of Casnub 22 NLB bogie friction force
exerted by the wedges depends on the vertical load shared by the snubber springs over
which they are supported. Thus the damping so provided is a load variable damping,
and the same is so very necessary for fright 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.
After the clearances 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.
Under this invention constant contact side bearers (CCSBS) (Fig 3), equispaced from
and on either side of the centre plate on the bogie bolster, are disposed between bogie
bolster and car bogy bolster in such a way that they share 90% of the empty car body
weight and the balance car body weight and the pay load are borne by the centre
plates. A CCSB, designed under this invention mainly consist of a nest of three

concentric coil spring viz outer (13) inter (14) and inner (15) placed in a housing (12)
and a cover (16) placed above them. The cover is provided with a non-metallic liner
sleeve (17) on its inside and can move up and down 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 vertical
stop provides for a long travel of 16 mm from set up height and yet prevents the coil
springs from going solid in service. This provides effective control over car body roll. A
wear liner (18) has been provided over the cover. Sliding friction between the same and
corresponding wear liner on the car body bolster provides the necessary constraint
against bogie rotation and the tendency to hunt.
This invention makes the Casnub bogie (with the increased 23 t axle load) a track
friendly bogie suitable for operation upto 100 Km/h in both empty and loaded conditions
of the Wagon on the existing 1676 mm gauge track of Indian Railways and thus finds a
unique solution to the problem faced by Indian Railways.
Constant Contact Side Bearers (CCSB) used in this invention has been so designed
that the same can be easily retrofitted on the existing 20.32 t axle load Casnub Bogie
for converting the same to a 231 axle load bogie.
As per an exemplary embodiment, the wear liners provided with CCSB's can be made
out of non-metallic materials with suitable characteristics so that the life of the wear
liners is increased and the maintenance requirements of the bogie are reduced further.
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. A steel spring type constant contact side bearer for the 23 ton axle load Casnub 22
NLB bogie comprising of a nest of three concentric coil springs viz outer (13) , inter (14)
and inner (15) springs; a housing (12) to accommodate the nested springs; a cover (16)
fitted with non metallic liner sleeve (17) with the help of CSK head screws (19) on the
inside for the said cover and a wear liner (18) on top, rests on the nest of the coil springs
and moves up and down during service.
2. A constant contact side bearer as claimed in claim 1, wherein the constant
contact side bearers (CCSBS) are equispaced from and on either side of the centre
plate on the bogie bolster and are disposed between bogie bolster and car body bolster
in such a way that they share 90% of the empty car body weight and the balance car
body weight and the pay load are borne by the centre plates.
3. A constant contact side bearer as claimed in claim 1, wherein the triple nested
steel springs have a vertical stiffness of about 151 kg/mm.
4. A constant contact side bearer as claimed in claim 1, wherein CCSB further
comprises of a vertical stop which permits a long travel of 16mm from set up height and
yet prevents the coil springs from going solid in service and provides effective control
over car body roll.
5. A constant contact side bearer as claimed in claim 1, wherein the wear liner
undergoes rubbing against the corresponding wear liner fitted on the car body bolster
and provides necessary friction damping against bogie rotation / hunting.
6. A constant contact side bearer as claimed in claim 1, wherein pre-load
characteristics do not change with time and temperature and do not affect the ride
behaviour of the bogie in service.
7. A constant contact side bearer as claimed in claim 1, wherein the nest of coil
springs is subjected to practically no lateral loading in service.

8. A constant contact side bearer as claimed in claim 1, wherein steel wear liner
can be replaced by a non-metallic wear liner if the same can reduce the maintenance
further.
9. A constant contact side bearer as claimed in claim 1, wherein the said CCSB's
are so designed that the same can be easily retrofitted on the existing 20.321 axle load
Casnub Bogie for converting the same to a 231 axle load bogie.
10. A constant contact side bearer for the 23 ton axle load Casnub NLB bogie as
herein described with particular reference to the accompanying drawings.

A steel spring type constant contact side bearer for the 23 ton axle load Casnub 22 NLB bogie comprising of a nest of three concentric coil springs viz outer (13) , inter (14) and inner (15) springs; a housing (12) to accommodate the nested springs; a cover (16) fitted with non metallic liner sleeve (17) with the help of CSK head screws (19) on the inside for the said cover and a wear liner (18) on top, rests on the nest of the coil springs and moves up and down during service.