Research
Brief
Technology transfer for reducing mass
Overview
Why are trains getting heavier? With railway industry concern over the
increasing mass of railway vehicles, the Vehicle/Vehicle Systems Interface
Committee (V/V SIC) held a seminar in November 2005 entitled "Reducing
Vehicle Mass" to see what could be done to investigate and, hopefully, reverse
this trend. During the seminar several potential work-streams were identified,
among them "Better engineering of trains", which focused on new or
transferable technologies and how they could be used to improve British trains.
Figure 1 shows the proportion of total train mass that is represented by each
sub-system for a typical train.
Figure 1: Typical train mass distribution
The concept put forward was to examine existing trains from other countries and
also technologies from other industries with the aim of adopting best solutions
and best practice to reduce vehicle mass for British trains. Reduced mass would
benefit the operating company in terms of lower fuel and energy bills and brake
pad/disc wear. It would also benefit the infrastructure controller by reducing
track maintenance costs, as rolling stock weight is related to track wear.
T688
February 2008
RSSB Research and Development Programme
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www.rssb.co.uk/research/index.asp
From the rail sector, the number one ranked priority was found to be a reduction
in un-sprung mass. Among technologies from outside the rail industry, four
items were equally ranked as high priority considerations: dual function
structural elements, dry transformers, integrated systems, and LED lighting.
The five greatest contributors to overall train mass are quite similar, and there is
no one area that would provide a significant contribution on its own. However,
by addressing all areas it should be feasible to reduce overall vehicle mass by
up to 20%.
Aims
Following on from the 2005 seminar, the V/V SIC asked RSSB to pursue its
conclusions and commission a research review. ESR Technology Ltd with
Interfleet Technology Ltd were commissioned to perform this review, to highlight
technology areas for further investigation that have the potential for reducing
vehicle mass.
The aim of the research was to identify existing technologies that could
potentially be adopted by Britain's rail industry to reduce vehicle mass per
passenger carried and also to consider their likelihood of success for Britain's
railways. Any further work that might be needed was to be identified. worldwide
sources were used from within the rail industry and from other industrial sectors.
Method
Several technology areas have been considered within the scope of the
research review. These areas are summarised as follows, together with a brief
clarification:
Integrated structural design
Can the use of multi-functional designs reduce
part count and number of sub-system structures?
Dual function structural elementsCan one structural element fulfil dual roles?
Un-sprung mass
Can the un-sprung mass be reduced through
lightweight materials or re-design?
Articulated bogies
Can re-design of the bogie by including
articulation reduce weight?
Inboard bearing bogies
Do inboard bearing bogies reduce weight cost
effectively?
Bogie-less designs
Axles and suspension directly connected to
carriage body using a lightweight novel
suspension.
Braking
Are there technologies that can be transferred?
Integrated control design
Solid-state devices as opposed to relays and
wiring.
Optical control
Can this replace copper wires?
LED lighting
Can this replace incandescent and fluorescent
items?
Dry transformers
Can heavy liquid cooling systems be removed?
Hot super-conductor technologyCan this give smaller, lighter motors,
transformers, and generators?
New energy
What is scope for solar power, energy storage
systems, and fuel cells?
Integrated system
How do British and Japanese Standards on
crashworthiness and fire safety compare? What
are the safety implications?
Materials technology
Can lightweight, high strength materials from other
industrial sectors be adopted?
Environmental toilets
Can they be smaller with lighter storage tanks by
re-using waste water?
All electric vehicles
Can air compressors, dryers, pipework, etc. be
eliminated?
Double deck trains
Mass per seat is better but can they be
accommodated on the GB network?
One per coach instead of twoCan vestibules, doors and energy absorption
devices be shared across two coaches?
Reduced vehicle life
Is this a cost effective solution?
A structured matrix approach to the research was used to identify and assess
the potential of each technology. The ranking (or scoring) was applied to each
technology as according to the criteria defined in Table 1. The lower the score,
the greater its potential. The technology was ranked in terms of its:
•
•
•
•
•
Potential (has it been used before?)
Barriers to implementation
Timescale to implementation
Cost to implementation
Benefits in terms of mass saving
Table 1: Scoring criteria for the evaluation of potential technologies
Technology
evaluation
(score)
1
2
3
4
Potential
Previous rail
applcation
Other industry
application
Emerging
technology
Not suitable
Barriers
None
apparent
Timescale
Costs
Benefits
Non-compliant
Significant
Compliant
with
introduction of
with
Standards
risk
Standards, but
not
recognised
industry best
practice
<12 months
12 months <
2 years
2 years <
5 years
> 5 years
< £1M
£1M < £10M
£10M <
£100M
> £100M
High
Medium
Low
Not Applicable
The scoring system was intended to balance the benefit of mass reduction
against, for example, the cost and time to implement the technology. Therefore
the lowest ranked technologies may not automatically result in the largest
potential mass saving.
Findings
Having researched the technologies outlined in the method detailed above, the
ranking methodology was applied separately for rail sector and non-rail sector
technologies.
Rail sector
For rail technologies, the results are summarised in Table 2.
From the worldwide rail sector assessment, some technologies were identified
for further consideration in terms of potential for their mass reduction. These are
discussed individually below with estimates of the potential mass saving. By way
of example, the estimates have been made based on a 4-car multiple unit, a very
prevalent type of train used on Britain's railways. This allowed the potential mass
reduction estimates to be assessed in a consistent manner.
Table 2: Overall technology ranking for rail sector
Rail Sector Perspective
Ranking
Technology
Score
1
Un-sprung mass
5
2
Inboard bearing bogies
6
Environmental toilets
3
Integrated system
7
Articulated bogies
4
Bogie-less designs
8
Integrated control design
LED lighting
Materials technology
One per coach instead of two
5
Integrated structural design
9
Braking
6
Dual function structural elements
10
Dry transformers
New energy
7
Optical control
11
All electric vehicles
8
Double deck trains
12
Reduced vehicle life
9
Hot super conductor technology
14
Un-sprung mass could lead to a mass saving estimated to be 1,300kg for a 4car unit. This is largely achieved through use of hollow axles and could be
implemented immediately on new train designs. The potential for further
reduction would depend on increasing the allowable stress levels for wheels and
axles (i.e. smaller wheels and axles).
Inboard bearing bogies could lead to a mass saving estimated to be 10,000kg
for a 4-car unit and could be implemented immediately on new train designs as
demonstrated by existing technology, though there is a cost premium. It is
recommended that investigations to see how incentives can be established to
deliver a strong business case for a broader implementation.
Environmental toilets may lead to a mass saving estimated to be 200kg for a 4car unit. This is achieved through recent developments in toilet systems but with
increased complexity and can be implemented immediately for new train
designs. More detailed results on the potential for mass reduction are expected
as part of RSSB's research project T692 (Water recycling technology for train
toilets).
Non-rail sector
From the non-rail sector assessment, the technologies identified for further
consideration in terms of potential by the ranking process for mass reduction are
summarised in Table 3.
Table 3: Overall technology ranking for non-rail sector
Ranking
1
Technology
Dual function structural elements
Score
9
Dry transformers
Integrated system
LED lighting
2
Increased noise and vibration
10
Integrated control design
Optical control
Materials technology
3
Integrated structural design
11
New energy
All electric vehicles
4
Un-sprung mass
12
Environmental toilets
Reduced vehicle life
5
Braking
13
6
Hot super conductor technology
14
Looking at some of the highest ranking technologies in a little more detail:
• Dual function structural elements could lead to a mass saving estimated to
be 800kg for a 4-car unit. This can be achieved by considering elements of
the vehicle construction as adding to structural strength instead of ignoring
them as at present. It is not current technology and would take a small
number of years to implement on new vehicles. The relationship between
the increased cost for design and the saving in mass should be investigated.
• Dry transformers could lead to a mass saving estimated to be up to 600kg
per transformer. This can be achieved though development of methods such
as air cooling and improved insulation. This technology could be
implemented within two years for new vehicles. It is recommended that
investigations are undertaken into what equipment is available to meet the
requirements for rail use and to establish mass savings.
• LED lighting could lead to a mass saving of 200kg for a 4-car unit which is
small but also offers electrical energy saving. This could be implemented
immediately. The business case for implementation should be investigated.
Alternative philosophies
Several alternative philosophies in terms of design or operation were identified
from other rail sectors or industries which could offer the potential for mass
reduction. If significant mass reduction is to be achieved then fundamental
changes in design and/or operating philosophy by the complete rail sector would
have to be adopted. Of the identified philosophies the following are considered
to have significant potential:
• Japanese crashworthiness philosophy; whilst significant weight saving could
be made by the adoption of this philosophy, ie lower standards than those
applied in Britain, it is likely to result in an increase to the risk of passenger
injury in an accident, unless rigorous controls on reducing collision risk are
adopted.
• Metro-train philosophy; by focusing on key areas with strict mass targets
and by removing non-essential equipment this can be implemented
immediately on new train designs. An investigation into the incentives for
raising the significance of vehicle mass in the selection criteria for new build
trains, including the effect on passengers of lowered standards of amenities
on trains for short journeys would be required.
• Performance based specification: to establish the potential for this
philosophy it is recommended that investigations into the effect in other
industries that performance based specifications have on mass reduction.
This philosophy has a close link to the metro-train philosophy.
Conclusions
This short review has not permitted a fully exhaustive analysis to be performed
and the results of the review should therefore be considered as a coarse, first
pass ranking assessment of the technologies.
Because of the balanced ranking approach used, some technologies were rated
highly because they have either been applied elsewhere, could be readily
implemented or have a limited cost of implementation, not because their
application would lead to significant mass reductions.
The initial study identified five technologies and three philosophies which if
adopted could lead to significant mass savings. The aim of the study was not to
quantify the potential savings but to identify them. However, estimates have
been made as was necessary for the ranking process.
The breakdown in mass of a typical multiple unit vehicle was presented as being
roughly evenly split between five key areas; bogies, bodyshell, interiors,
propulsion equipment and other. Therefore, even if the best identified
technology was adopted, on its own in one of the key areas, it would be unlikely
to yield a total mass reduction of more than 10% of the total vehicle mass.
It was identified that significant mass savings will only be achieved by adopting
several of the identified technologies simultaneously. It is suggested that a
potential mass saving on current vehicles of the order of 20% is realistic.
However, the incentive for the developer of the technology and manufacturer of
the vehicle has to be commensurate with the added cost of the development to
ensure that adoption of available mass reducing technologies are employed.
Some of the technologies are already in use to a limited extent in Britain. This
study has highlighted that with incentives they could be adopted in short
timescales and uised to a much greater extent.
Two anomalies were identified in the results, these being environmental toilets
and LED lighting. Although they scored near to the top of the list, the mass
saving is not large but the technology already exists, so they can be easily
implemented. The real benefit would be in energy savings from operation
onboard the train.
Next Steps
The review and assessment was only an initial pass of the technologies and
therefore the recommendations can only be that identified technologies or
philosophies should be looked at in greater detail to quantify their potential. Only
crude quantitative estimates were made of the potential for mass savings.
In order for there to be take up of any technology that leads to mass reduction
there needs to be a clear incentive for the developer of the technology. One of
the major aims of reducing mass is to reduce the damage caused to the track
infrastructure. To encourage technology driven developments, a financial
rewards scheme (eg reduced track charges) at least commensurate with the
development costs is recommended.
The V/V SIC has considered the findings from this study and will test the
recommendations in detail by using the Rolling Stock Whole Life Cost Model
(RSSB research project 'T676 Produce a rolling stock whole life cost model (RSWLCM)') that is being developed following the Reducing Mass seminar. This
model will be used to identify further detailed work streams to follow on from this
study.
Contact
Head of Engineering Research
R&D Programme
Rail Safety and Standards Board
research@rssb.co.uk