Technology

Technology

Railway Technology Today 5 (Edited by Kanji Wako)

How Bogies Work
Isao OkamotoRole of Bogie

Railcar bogies usually go unnoticed by railpassengers, but despite their obscurity,
they are very important in safe railway
operations and perform the following
functions:• Support railcar body firmly• Run stably on both straight and curved
track• Ensure good ride comfort by absorbing
vibration generated by track irregularities and minimizing impact of centrifugal forces when train runs on curves
at high speed• Minimize generation of track irregularities and rail abrasion
To help clarify the basic mechanism ofbogies, this article explains bogies usedon conventional railcars. Bogies used on
shinkansen will be discussed in more detail in the next article in this series.

Bogie Configurations

Types
Bogies are classified into the various types
described below according to their configuration in terms of the number ofaxles, and the design and structure of thesuspension.
Number of axles
Since bogies run on two steel rails, theminimum structural requirement is an axle
and two wheels, which are usuallypressed onto the axle (Fig. 1). Bogies areclassified into single-axle, two-axle, threeaxle, etc., based on the number of axles.
The two-axle bogie is most common. In
addition to its relatively simple structure,it has the advantage of decreasing theimpact of track irregularities on the railcar at the car suspension point, in comparison to the single-axle bogie whichtransmits the impact to the car directly(Fig. 2). The three-axle bogie has a more
complex structure that tends to adversely

52

Figure 1 Wheel and Axle Set
Wheel tread
FlangeWheel

Treadgradient

Axle

Wheel
diameter

Rail

Gauge

affect the running performance andstrength of the bogie frame, so none areused for passenger railcars in Japan today.
Non-articulated and articulated bogies
Bogies can be classified into non-articulated and articulated types according to
the suspension. Two non-articulated
bogies usually support one railcar body(Fig. 3a), but one articulated bogie supports the back end of the forward car andthe front end of the rear car (Fig. 3b) as
seen in the Spanish Talgo, French TGV,Japan Railway & Transport Review 18 • December 1998

and some express trains of the Odakyu
Line in suburban Tokyo. Although thearticulated bogie has some disadvantages,
such as a complex structure, increased
axle load due to the support of one bodyby one bogie, and difficult maintenance,
it offers various advantages including alower centre of gravity, better ride comfort because car ends do not overhang
bogies, and less effect of running noiseon passengers because seats are not overbogies.

Figure 2 Comparison of Effect of Track Irregularity between
Single-Axle Bogie and Two-Axle Bogie

Smaller effect of
track irregularity
on car suspension point
Car suspension
point

Car suspension
pointSingle-axle bogie

Two-axle bogie

Copyright © 1998 EJRCF. All rights reserved.

Figure 4 Swing Hanger andSmall Lateral Stiffness
Bolster Spring Bogies

Figure 3 Non-articulated Bogie and Articulated Bogie(a) Non-articulated cars

Swing Hanger Bogie

Centre pin

Non-articulated bogie
Upper
swing
bolster(b) Articulated cars

BolsteranchorSwing
hangerSide bearer
Bogie frame
Bolster spring
Lowerswing bolster

Small Lateral Stiffness Bolster Spring Bogie

Articulated bogie
Centre pin

Swing hanger bogie and small lateral
stiffness bolster spring bogie
Based on the structure of the suspension
gear, bogies are classified into two types:
the swing hanger type, and the small
lateral stiffness bolster spring bogie type(Fig. 4). To ensure good ride comfort onpassenger cars, the bogie must absorb therolling motion that passengers are mostsensitive to. Conventional swing hanger
bogie designs support the body by using
lower swing bolster beams suspended
from the bogie frame by means of a linkconsisting of two vertical members thatwiden toward the bottom, together withbolster springs and upper swing bolster
beams (to support vertical movement).
Although the swing hanger type (Fig. 5)
achieves good ride comfort by minimizing horizontal stiffness of the suspension
gear, its maintenance is relatively difficult
due to the complex structure and large
number of wearing parts. In the 1960s,
bolster bogie with air spring that absorbs
vibration due to its small lateral stiffness,
was developed (Fig. 6). It soon replaced
the swing hanger type and was used in
the first shinkansen in 1964, contributing
greatly to their size and weight reduction.
Most recent bogies are of the small
lateral stiffness bolster spring bogie typebecause of its simplified suspension
design.

Copyright © 1998 EJRCF. All rights reserved.

Bolster and bolsterless bogies
Bolster and bolsterless bogies (Fig. 7) are
differentiated by their suspension gear.
The bolster bogie was developed first. A
fundamental characteristic of the bogie isthat it must rotate relative to the body on
curves, while retaining high rotational
resistance during high-speed running on
straight sections in order to prevent
wheelset hunting (Fig. 8) that reduces ride
comfort. To achieve these characteristics,
the bolster bogie has a centre pivot thatserves as the centre of rotation, and side
bearers that resist rotation.
In the 1980s, a bolsterless bogie was commercialized to improve performance bySide bearer
Bolster
BolsteranchorAir bolster
spring

Bogie
frame

reducing the number of parts and thebogie weight (the bolsterless bogie forshinkansen was commercialized in the
1990s). In recent years, most narrowgauge and shinkansen cars use thebolsterless bogie, which permits rotational
displacement on curves through the horizontal deformation of bolster springs (alsoknown as secondary suspension springs)

Figure 5 Swing Hanger Bogie

Swing hanger(Author)Japan Railway & Transport Review 18 • December 1998

53

Technology

Figure 6 Lateral Stiffness Bolster Bogie

Centre plate

Centre pivot

Bolster

Centre pivot
wearing plate

Bogie frame

Bolster anchor
Wheelset

Traction motor

Air spring under bolster

Axle spring

Gears

Figure 7 Bolster and
Bolsterless Bogies
Bolster Bogie

on both sides of the bogie. Rotation isresisted by longitudinal anti-yawing
dampers on both sides of the bogie,
resulting in better rotational resistancethan conventional side bearers.

Basic Bogie Elements
Air bolster
springBolster anchor
Bolster
Bogie
frame

Side bearer
Centre pivot

This section describes key components
and parts of the bogie, including theirstructure and performance. However, it
should be noted that the parts vary widely
according to the bogie type, and this

discussion focuses on the bolsterless DT50
type (Fig. 9) which is widely used in commuter passenger railcars of JR companies.
The DT50 was first commercialized in1985 by the former JNR when it was used
for the Series 205 railcars.

Suspension gear
The suspension gear (bolster spring, traction transfer device, anti-yawing damper,and lateral damper) plays an importantrole in supporting the body, allowing thebogie to rotate relative to the car body on
curves, isolating the body from vibration(including high harmonics) generated by
the bogie, and transmitting traction force
from the bogie to the body. For these
purposes, the bolsterless bogie has air
springs that permit large horizontal displacement, as well as a traction transfer
device (classified into permanent-link
type, the Z-link type and laminatedrubber type) at the virtual rotational
centre of the bogie for transmitting thetractive force to the car. In addition, thebolsterless bogie used for express trains
and shinkansen has anti-yawing dampers(Fig. 7) at the outer side of the side beamof the body and bogie frame (parallel tothe side beam) to prevent wheelset hunting that reduces ride comfort.
Coil springs were originally used asbolster springs to support the body, but inthe 1960s, air springs were commercialized for railcars in Japan and were used
for high-speed trains. Since the 1980s,
they have been used for commuter andshort-distance trains in order to take

Bolsterless Bogie

Figure 8 Wheelset Hunting
Tractiontransfer
deviceAir bolster
springAnti-yawing
damper54

Bogie frame

Japan Railway & Transport Review 18 • December 1998

Copyright © 1998 EJRCF. All rights reserved.

Figure 9 DT50 Bogie
for Series 205 EMU
advantage of their improved ride comfort
and ability to maintain body height.

Bogie frame
The bogie frame accommodates various
bogie equipment and is generally fabricated by welding together two side beams
and two cross beams into an H-shaped
frame, (Fig. 10). In 1955, compound side
beams were developed using press welding and this structure is used to manufacture most bogie frames in Japan. The
thickness of the side and cross beams wasincreased from 6 mm (used in someframes around 1960) to 9 mm. It was increased again to 12 mm in the 1970s,
when some bogie frames of express trains
were found to have minor faults. However, since the DT50, as a result ofsimpler construction and improved welding technology, bogie frames use 8 or 9
mm plates to reduce weight. Finally,around 1980 (1976 for shinkansen), thematerial of major bogie frame members
for narrow-gauge railcars was improved
from SS400 (rolled steel for general structures) to SM400B (rolled steel for welded
structures).
Some bogie frames since the DT50 use
seamless steel pipes for cross beams to
reduce weight and cost.

Axle box suspension
This device supports the axle via the bearing from the bogie frame. It is a criticalcomponent determining the running performance of the bogie, ride comfort andbogie frame construction, due to the suspension method and support rigidity.
Various designs are used (Fig. 11). The
pedestal swing spring design supports theaxle box using sliders around the pedestal on the bogie frame and was usedwidely in a variety of railcars of the former
JNR. While its construction is simple, thesliders wear with time, creating play inthe suspension and cause wheelset hunting, so it is not suitable for high-speed operation. The IS type was developed for

Copyright © 1998 EJRCF. All rights reserved.

Traction transfer device

Series 205 EMU

Brake equipment(Author)Bolster spring

Bogie frame(side beam,cross beam)

Lateral damper
Traction motor

Axle bearing and axle box
Axle spring, axle box suspension(Brake disc for trailing bogie)
Wheelset

Gear

Brake disc

Figure 10 Bogie H-Frame
Cross beam

Side beam(Author)Japan Railway & Transport Review 18 • December 1998

55

Technology

Figure 11 Various Axle Box Suspensions(1) Pedestal swing spring type
Axle box(2) IS type
Axle box

Axle
springCushion rubber

Axle spring
Sliders(3) Leaf spring type(4) Axle beam type

Axle spring

Leaf spring

Leaf spring(5) Coil spring withcylindrical laminated rubber type

Axle spring

Axle box

Axle box Guide arm
Cushion rubber(6) Conical laminated rubber typeCushion rubber

Axle spring

Cylindricallaminated
Axle box rubber(7) Roll rubber typeRoll rubber
ConicallaminatedrubberAxle box
Axle box

shinkansen and its good cushion rubber
stiffness effectively eliminates play
between the axle and bogie frame. However, it has several disadvantages, such asincreased bogie frame length and severe
maintenance requirements for leaf springs.
As a result, recent bolsterless bogies forshinkansen use other types, including thecoil spring with cylindrical laminated rubber type. Similarly, narrow-gauge railcars
are increasingly using the conical laminated rubber type, the roll rubber type(serving both as the axle box suspension
and axle spring) and axle beam type inorder to simplify construction and reduce
manufacturing costs.

56

Wheels, axles and bearings
Wheels of conventional railcars are a solidrolled type, and generally 860 mm indiameter when new. Corrugated wheels(Fig. 12) with a corrugated outer face havebeen commercialized to boost rigidity,
while reducing plate thickness andweight. They have been used for commuter and short-distance trains since the1980s. The wheel tread is heat-treatedand has the profile shown in Fig. 13.
Wheels are susceptible to mass imbalance, which causes vibration of the axle
and wheel and is transmitted to the body,
producing uncomfortable resonance at
certain speeds. To prevent this, efforts

Japan Railway & Transport Review 18 • December 1998

have been made since 1984 to hold theimbalance per wheel to below 25 kgf•cm
and to balance the wheels when pressing
them onto the axle.
The axle is generally solid, but hollow
types are used for weight reduction without affecting bending strength. Hollow
axles with a central void were used forhigh-speed electric railcars and passenger cars in the late 1950s, but their use
was abandoned due to manufacturing
problems. Around 1975, to improvereliability, a hollow axle was developedby boring a solid axle (Fig. 14). It was
first used in 1981 to make lighter drive
axles for high-speed diesel railcars

Copyright © 1998 EJRCF. All rights reserved.

Figure 12 Corrugated Wheel
operating in Hokkaido. It was later used
for bolsterless bogies of shinkansen,
contributing to reduced unsprung mass.
Axle bearings have traditionally combined
a cylindrical roller bearing (to take radialloads) and a ball bearing. Since 1965, asingle sealed flanged cylindrical roller
bearing (able to take both radial and thrustloads) has been used increasingly tofacilitate bearing weight and size reduction as well as to obtain longer periods
between overhaul.

(Author)Transmission
Figure 13 Basic Wheel Tread Profile for Narrow-Gauge JR Lines (upper)
and Circular Arc Wheel Tread Used Widely Today (lower)
Profile of wheel tread for narrow-gauge JR lines
Centre distance of wheel pair 560
60

65
53
20

1/10

30

15

1/20

2
14R

2

15R

15R

59'21"

Profile of corrected circular arc wheel tread
125
60

65

30
24.85

26.0

16

15.5

14

10

14R

14R

14R

27

1/100

320R
80R

12
900R

3'

400R

The transmission consists of gears andflexible couplings to transmit motive
power generated by the motor or engine
to the axle. For EMUs, the nose suspension device, which supports the traction
motor with the bogie frame and the axle
(via support bearings), was used until the
1950s (Fig. 15a). The nose suspension
device was large and heavy to withstandvibration generated by the axle and also
due to the slow speed of the motor, resulting in large bogie mass and unsprungmass. Around 1957, the parallel cardan
driving device (Fig. 15b and c) was put
into service by mounting a smaller, highspeed motor on the bogie frame supported
by axle springs and transmitting the
motive power to the gear via a flexible
coupling. It enabled reduction of thebogie wheelbase as well as significant size
and weight reduction of the entire bogie,
and contributed greatly to the development of shinkansen and conventional
express cars.
DMUs use either electrical or mechanical transmission. While the former is usedprimarily in other countries, the latter isused mostly in Japan. In this case, themotive power from the engine is transmitted via a torque converter and flexible
couplings to the axle using a right angle
cardan driving device (Fig. 15 d).

33.86
29
65'

Unit: mm

Copyright © 1998 EJRCF. All rights reserved.

Japan Railway & Transport Review 18 • December 1998

57

Technology

Figure 14 Hollow Bored Axle

(Author)Brake equipmentcausing the wheel temperature to rise tocritical levels. This presents a risk ofcracking and makes them unsuitable forhigh-speed operations. Disc brakes use
disks at both sides of the axle or wheels;at braking, the discs are clamped by brakepads on the calipers to impede rotation.
Traditionally, cast iron has been used forthe disc due to its superior frictional characteristics relative to the pads. However,

The brake is used to stop at the desired
position. This section focuses onmechanical braking equipment such as
wheel tread brakes and disc brakes.
Wheel tread brakes use block-shaped
brake shoes that are pushed against thewheel tread. Although they have a simple
construction, they generate large amountsof frictional heat at high running speeds,(a) Nose suspension device
Traction motor

Bogies for commuter trains

Support bearing
Wheel gear
PinionTraction motor
Nose receiver(c) Parallel cardan
driving device(d) Right angle cardan
driving device

K
M
M

K

Major Characteristics of Bogies
in Recent Narrow-gauge Railcars
This section focuses on the design andkey features of new bogies designed fornarrow-gauge lines in Japan, such as thebogie for commuter trains, the pendulum
bogie and the steering bogie (used forexpress trains).

Figure 15 Transmissions(b) Hollow-axle parallel
cardan driving device

recently, forged steel is used for highspeed railcars to prevent disc cracking
caused by frictional heating. In Japan, discbrakes were first used on some express
trains of the Odakyu Line, and they havebeen used primarily for trailer cars on
narrow-gauge lines. Nevertheless, discbrakes are costly to manufacture andmaintain, so commuter (Fig. 9 inset) andshort-distance railcars that run at relatively
low speeds often use motor braking as ameans of halving the number of discs toone (reinforced type) per axle.

K

M

K

K

M: Traction motor
K: Flexible coupling

Since commuter or short-distance trains
use a large number of bogies, the design
must be simple to cut manufacturingcosts and maintenance requirements. As
a result, bogies for recent commuter trains
mostly use the bolsterless suspension
system. As far as possible, straight side
beams are used for the bogie frame andseamless pipes are used for the cross
beams. Also, conical, laminated rubber,or roll rubber suspension systems are used
for the axle box and also serve as axle
springs. Otherwise, the relatively simple
axle beam suspension type is used. Axle
bearings are generally sealed flanged
cylindrical roller bearings. Unit brakes areused increasingly as part of the ongoing
effort to reduce the number of parts,
thereby lengthening the service life
between inspection and overhaul.

Bogies for express trains
Bogies for express trains have the same
design concepts as bogies for commuter

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Japan Railway & Transport Review 18 • December 1998

Copyright © 1998 EJRCF. All rights reserved.

Figure 16 Roller Type Tilt Systemtrains in terms of simple construction to
cut manufacturing costs and save labour
related to maintenance. However, newbogie designs are required to meet thedemand for higher speeds, thereby cutting travel times and making trains morecompetitive with planes and cars. Narrowgauge lines in Japan are dominated bymany sections with tight curves, and travel
times can be reduced by increasing running speeds on curves instead of increasing maximum speeds. Two types of bogies
have been developed to achieve this aim:
the tilting bogie, which increases runningspeed on curves without affecting ride
comfort, and the steering bogie, which
permits higher speeds on curves by minimizing the lateral force on the rail. They
are described below.
Tilting bogie
When a train runs at a high speed over a
curve, the generated centrifugal force
adversely affects ride comfort by pushingpassengers toward the outside of thecurve. The tilting car has been developed
to minimize lateral forces acting on
passengers by tilting the body toward theinside of the curve, rather like a motorcycle taking a curve. In Japan, the firsttilt railcars (Series 381) were introduced
in 1973 on the western section (Nagoya
to Nagano) of the Chuo Main Line. Figure
16 shows the bogie design concept. The
bogie consists of a body tilting system
supporting the body on two 170-mm
diameter rollers and bow-shaped tilting
beams with a centre of curvature aligned

Test run of roller type controlled tilt system using
Series 381 express EMU. Car body is tilted. (Author)

JR Shikoku used the controlled tilt system in its DMU Series 2000 express train (right) and EMU Series 8000
express train.
(Author)Copyright © 1998 EJRCF. All rights reserved.

Tilt centre(Car)
Tilt angle,±5°Compressed air

Bolster spring
Tilt beam

RollerAir cylinder forcontrolling tilt

Bogie frame

Track
Cant

with the body tilt centre. When the bogie
runs on a curve, centrifugal force acting
on the centre of gravity causes the bodyto tilt up to 5° towards the inside of thecurve. This is called the ‘roller type, natural tilt system’. The Series 381 railcars
were subsequently introduced on otherlines (Kisei and Hakubi Lines), often

Japan Railway & Transport Review 18 • December 1998

59

Technology

Figure 17 Principles of Controlled Tilt System
All curve data transmitted
from CC unit to TC unit
before departure

ATS ground unit
Running direction

50 m
Xm

CC
TC

TC

Beginning of transition curve
Beginning of circular curveTC
A point

Onboard ATS unit

Car tilting started
by command from TC unit

CC unit: Command Controller
TC unit: Tilt Controller

Tilting timing command
sent from CC unit to TC unit
Restoration of tilted car
started by command from TC unit

Ym

End of circular curve
End of transition curve

Figure 18 Link-Type Forced Steering Bogie

Tilt beam
Car tilt control cylinder
Tilt control cylinder

Bolster anchor

Control
valve

Steering beam

Axle box
Cushion rubber
Steering link
Steering lever
Steering link
Axle box

60

Cushion rubber

Japan Railway & Transport Review 18 • December 1998

contributing greatly to reduced travel
times and improved riding comfort. However, they were not a success on sections
with many frequent tight curves where
body tilting was either delayed or occurred too abruptly.
To ensure smooth tilting in these circumstances, the ‘controlled tilt system’ (Fig.
17) was developed. This system incorporates air cylinders into the body tilting
system. An onboard controller stores data
about all curves on the section where thetrain operates, including curve radius,alignment, elevation, distance between
ATS (Automatic Train Stop) ground units
and starting point of transition curves,
lengths of transition curves and circular
curves, etc. The controller is activatedby ATS ground units and controls thetiming and degree of body tilting 30 to 40
m before entering curves by referring to
the stored curve data and computing therunning distance to the curve using theaxle revolutions from the nearest ATS
ground unit.
The controlled tilt system was first introduced in 1989 on JR Shikoku DMU Series 2000 express trains. It was soon
introduced by all other JR companies due
to its good reputation including ride comfort.
In fact, the controlled tilt system increased
running speeds over curves with a radiusof 300 to 600 m from 80–110 km/h
achieved by the natural tilt system to 85–
120 km/h.
In addition, the body tilting system was
modified to reduce tilt resistance byusing a large number of smaller bearings,
in place of the conventional rollers,
thereby achieving a smaller lighter bearing guide type tilting mechanism, which
is used in recent tilt cars.
Steering bogie
As a train runs on a curve at high speed,
the wheels exert high lateral force on therails causing wear and tear of wheel
flanges and rails, and resulting in derailing in extreme cases. This lateral force

Copyright © 1998 EJRCF. All rights reserved.

Figure 19 Alignment of Link-Type Forced Steering Bogie on Curved Section
Bogie frame

Steering beam (equivalent to carbody)

Ra

di

us

of

cu

rv

at

ur

e

Steering lever and linkage

Centre of curvature

Figure 20 Lateral Forces of Link-Type Forced Steering Bogie and NonSteering Bogie on Rails
Radius of curvature = 302
Cant = 105

60

Maximum lateral force (kN)can be reduced by various methods,
including use of self-steering bogies.
As shown in Fig. 1, normal wheels arepress-fitted onto the axle and have a tread
gradient. This gradient provides somedegree of steering over a curve by allowing the centre of the axle to move towards
the outside of the curve as a result of thecentrifugal force. The steering bogie isdesigned to make the most of this ability
by reducing the stiffness of the axle box
suspension and increasing the tread
gradient to maximize the difference indiameter between left and right wheelson the same axle. These features allow
the wheels and axle to move more freely
without sacrificing running stability. This
concept is used in most recent bogie
designs, ranging from those for commuter
trains to express trains. Nevertheless, withthis self-steering design, care should betaken to avoid excess reduction of stiffness of the axle box suspension and excessive tread gradients. These concepts
may be effective in reducing lateral force
on the rail, but they can adversely affectrunning stability due either to smallchanges in tread gradient caused by wear
and tear, or to slight play in the wheelsuspension, both of which risk generating wheelset hunting.
To deal with the drawbacks of the selfsteering bogie, the link-type forced steering bogie has been developed (Fig. 18)
and is currently used on JR Hokkaido
Series 283 DMU express trains. The
operating principle is to transmit rotational displacement of the bogie relative tothe body to the axle via a linkage, so theaxle centre line is aligned on the radiusof curvature (Fig. 19). This mechanism
cuts lateral force on the rail to one half or
one third that of conventional bogie
designs (Fig. 20).
■

Non-steering bogie
outside rail

50

lateral force

10kN

40

10kN

inside rail30

Link-type forced steering bogie
20

outside rail

lateral force
5kN

10kN

10
10kN

0
50

60

70

80

90

100

inside rail

-5kN

110

Running speed (km/h)
Steering bogie
Non-steering bogie

Unit: mmKanji Wako
Mr Kanji Wako is Director in Charge of Research and Development at RTRI. He joined JNR in 1961 after graduating inengineering from Tohoku University. He is the supervising editor for this series on Railway Technology Today.

Isao Okamoto
Mr Okamoto is General Manager of the Vehicle Technology Development Division of the JR Railway
Technical Research Institute. He joined JNR in 1972 after obtaining a masters in mechanicalengineering from the graduate school of Waseda University. He worked in the Rolling Stock Design
Office of JNR before transferring to RTRI.

Copyright © 1998 EJRCF. All rights reserved.

Japan Railway & Transport Review 18 • December 1998

61