| CASE STUDIES |
| ADDITION OF PRIMARY SUSPENSION TO SWING MOTION BOGIE (SMB) |
| Background |
| Each vehicle operating over Network Rail incurs
a Track Access Charge (TAC), based on the product
of its gross tonnes, and miles travelled. This
charge is dependent on a number of factors including,
axle load, speed, suspension type and unsprung
mass, and is intended to reflect the track maintenance
cost of the vehicle's passage. One of the factors
having a major influence over the TAC is the unsprung
mass. The 3-piece bogie has many commercial and
track friendly features, but has relatively high
unsprung mass, due in part, to the fact there
is no suspension between the wheelset and the
bogie side frame. |
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| EWSR commissioned ESG to design, test and implement the
installation of a suspension element at this interface. Should
this prove acceptable, a significant reduction in unsprung
mass and TAC's will result. |
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| Project Overview |
| ESG first established, with the help of EWSR, what the
current TAC was for the 3-piece (Swing Motion) bogie, and
to determine what was the most cost-effective way of reducing
the charge. ESG worked with specialist subcontractors to investigate
the effect of varying levels of primary suspension stiffnesses
on unsprung mass. A rubber suspension manufacturer was then
employed to test prototypes and productionise the rubber suspension
element ensuring that they complied with the following criteria: |
- Acceptable spring stiffness (static & dynamic in
all 3 planes) to meet the target TAC reduction, and maintain
vehicle stability
- Acceptable damping levels
- Able to fit in the limited space available
- Easy to fit and required minimal change to the vehicle
and/or bogie
- Compliance to Railway Group Standard requirements (particularly
ride and gauge)
- Acceptable initial cost and service life, giving reduced
vehicle ownership cost overall
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| The project is ongoing, with ESG currently finalising the
Vampire analysis of the new suspension. When this work is
complete and has been approved by a VAB, a number of pre-production
components will be manufactured and fitted for ride and service
evaluation prior to full-fleet fit. It is expected that the
first vehicles will be fitted in early 2005. |
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| Key Features |
- Assessment of commercial viability
- Vampire analysis
- Optimisation of suspension characteristics
- Liaison with regulatory bodies
- Consultation with industry experts
- Design Scrutiny (against Railway Group Standards)
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| Skills Profile |
- Vehicle ride & frequency analysis through Vampire
- Suspension design and analysis
- Project Management
- Risk assessment
- Review and creation of technical documentation
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| Further information contact Robert.Morley@esg-railconsultancy.co.uk |
| Photographs and project detail reproduced by kind permission
of AEAT & EWSR. |
