| CASE STUDIES |
| REDESIGNED GEARBOX SUB FRAME FOR MBA WAGON |
| Background |
| During 2006 EWS started noticing problems with the parking brake on a number of their MBA wagons. MBA wagons are large box wagons which are often used for carrying scrap metal for customers. |
The design of the wagon is such that the gearbox for the parking brake is supported by a bracket which hangs from the floors struts. The input for the parking brake is applied by hand from either side of the wagon and the application torque is transferred by a shaft which passes through a tube in the centre sill, the central load bearing strut on the wagon. Unfortunately as a result of heavy scrap being dropped from considerable height, some of the wagon floors have become gradually indented leading to lowering of the gearbox relative to the tube through the centre sill. This has caused the cross-shaft to rub on the tube (see photo opposite) which makes the parking brake harder to apply.
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| EWS Railway asked ESG to provide a bracket which would be independent of the wagon floor. |
| Project Overview |
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Initially ESG performed an investigation to accumulate further information on the current bracket design, wagon layout, forces encountered and maintenance and installation factors which may affect fitment of any new bracket. This enabled a full understanding of the customer’s requirement prior to commencement of design work and ensured ESG were well positioned to create an optimised solution.
As a result of the investigation ESG were able to offer EWS a solution to directly meet their request whilst providing other options for lower cost solution for wagons in service.
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Autodesk Inventor CAD software was used to model the appropriate wagon section with the existing bracket (see 3D CAD model opposite).
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| Then a new bracket was modelled that spanned from the sole bar to the centre sill (see 3D CAD model below right). This had the result that the gearbox was suspended independently of the wagon floor, therefore preventing indentation from causing damage to the parking brake system. |
| In order to ensure that the new bracket was fit for purpose the design was then analysed using ANSYS finite element analysis software (see FEA model opposite) to ensure that fatigue and proof stress levels were compliant with railway group standards. |
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| In addition, ESG presented EWS Railway with a proposal for an alternative solution to combat the problems on current wagons in service. The alternative solution involved keeping the existing bracket while reinforcing the floor structure and providing a greater allowance for the gearbox misalignment. This has the benefit of reduced material and manufacturing costs as well as the fitting time required, it also reduced the risks and resources associated with the removal and handling of the gearbox and current bracket. |
| Key Features |
- Systematic investigation to understand problem
- Monitoring of customers expectations and requirements
- Innovative solutions through lateral approach
- Design scrutiny (to Railway Group Standards)
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| Skills Profile |
- On-site investigation
- Computer Aided 3D Design and Modelling
- Finite element stress analysis
- Project Management
- Review and technical documentation
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| Further information contact Thomas.Whitfield@esg-railconsultancy.co.uk |
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