Week 6-7 Submission: Project Tramways Stuart Steinfort S3137921
CAD and CNC Model Development At the start of week 7, a scale model was sought after the third iteration CAD model had been completed. After various delays with machining problems, the model was not completed until the Friday after class. This model allowed further development of the form which in turn created another scale model. The first unsuccessful model was milled on the five axis CNC mill to 1/25 scale. Technical problems resulted in the model not finished to a presentation standard. A second model was attempted, this time on the 3 axis router in building 8. This produced two side profiles which needed cutting and finishing to produce an appropriate standard of finish.
fig. 1-3 Unsuccessful CNC Scale Model
The model allowed the form to be seen in a physical sense. This greatly improved the understanding of form through illustrating the positive and negative aspects of the concept. It was felt that the top half of the model did not have enough weight in the curvatures to balance the lower section. Resultantly the curvatures were increased as well as front face pillar. In addition, the inside curvatures that join the roof to the windows were adjusted in order to reduce the sharp curvature and surface transition. This was followed by numerous small changes all over the model in size and proportion.
fig. 4-6 Second attempt at the second scale model,
A significant amount of time was consumed when setting up the files for milling. When saving the file to the igs format, a face went missing for no apparent reason. Through a process of trail and error, a suitable solution was found by exporting the solid model to a new file, scaling and splitting it to the appropriate scale before positioning the file for milling.
fig. 7-8 CAD comparison. Figure 8 is the initial lofted model, with 7 being the evolution.
fig. 9-10 Third scale model under construction
At the point of writing, this third model is being constructed by the CNC mill found in the industrial design workshop. This has allowed a larger model to be produce in order to further understand the form. In the coming week this form will be assembled and used to further develop the concept.
Tram Structure Development Through the development of the various CAD and CNC scale models, the form has influenced the structure of the tram. The design development has created a large side surface that originally had the intention to be completely constructed in glass. This has implications not only in the structure of the tram, but how its internal infrastructure is constructed. The first example (figure 11-13) illustrates the design if a conventional method is chosen for the tram design. Here the panels would be segmented and attached to a box like frame which would comprise the basic construction of the tram. Here the lower and upper panels would be non transparent in order to house the basic infrastructure of the tram; cables, attachments, mechanisms etc.
fig. 11-13 Traditional box like construction
The second proposal (figure 14-16) is inspired by the Barcelona Pavilion (Ludwig Mies van der Rohe, 1929). The building featured a structure supported by internal walls in order to create the illusion of a ‘floating’ building with an exterior predominately faced in glass. Its application within this project is to propose a tram that is internally supported with a number of ‘pillars’. This would allow an exterior that is predominately glass, giving an illusion of a floating structure. The inside of these pillars could house the infrastructure necessary for the tram to operate. Further work needs to be done in the coming week to assess this proposal, especially in terms of the safety found in large panels of glass.
fig. 14-16 Internal Pillar Construction Proposal
fig. 17 Barcelona Pavilion http://upload.wikimedia.org/wikipedia/
Drive Train Development In the last week, further research has been done in the viability of the two drive train proposals. The first, the hydraulic system, comprises of hydraulic motors that would be pressurised from an electric motor. This option allows small, lightweight pumps to be mounted on smaller tram wheels. An added advantage could be to use automated valves within the pumps; this could switch pressure to an electric motor to generate electricity for braking. After completing further research into this proposal, its viability has been lessened by current trends in transport energy use. A current precedent within public transport is the reuse of energy in trains. Current trains servicing Melbourne are being retrofitted with energy recovery systems in order to ease the overall electrical load on the network. In this situation the train’s braking is used to capture electrical energy which is then stored and used to run the on board services such as the heating and cooling. This effort has begun to combat the energy vacuum that occurs when a train accelerates from standstill. Initial research indicates that this is a major restriction on the current timetabled services, whereby between certain sub stations only one train accelerates at a time. This precedent can be applied to the first proposal for a drive train in that the idea was to return excess power to the system. The issue here is that the tram system works off a direct current which is then converted to alternating current by an onboard transformer. This is naturally an essential element because for a direct current tram to operate it would need a live rail to act as an earth; this has obvious safety implications. For this process to be applied, the pressurised fluid that is generated from braking would have to be circulated through a hydraulic motor which would turn an electric generator. This would then generate electricity that would need a secondary transformer in order to produce the direct current required for the network service. This conversion of power in numerous forms has efficiency losses such as through heat and friction. Another option is to mimic the current practises in train development and store the charge for the electric motor or services. This can be done through large capacitors which could be housed in the middle carriage of the tram. Further research will be completed in the coming weeks to ascertain whether it is viable to have a generator which can produce direct current electricity. The second proposal is the use of ‘pancake’ electric motors. This motor offers the possibility of hub mounting, the relevant feature here is that by mounting the motors within the circumference of the wheel space, the interior space can be reduced; effecting overall packaging. This in turn lowers interior intrusion of the drive train. The option has been boosted with the train precedent, in that the motors could be reversed under braking in order to generate electricity for utility use within the tram.
Freight Development In response to the mid semester presentation and studio conversations, the idea of a freight module has been further developed. In this proposal, the module would be carried on a platform which would house the running gear. This gives the option of disconnecting the module onto a waiting vehicle once the tram has arrived in the central business district. The development still allows for the smaller, more accessible items to be unloaded at the tram depot onto other vehicles. This development allows the possibility of the modules to be hired / owned by organisations in order to offer a ‘sealed’ service to mimic the cargo container.
fig. 18 Revised freight module.
Front Faรงade Development The front faรงade of the concept has begun development which can be seen in the illustrations. The initial sketches illustrate the emphasis on incorporating the scallop details of the side profile into the overall design. In the sketches shown, the front windscreen has been scalloped into the surfaces, with large radiuses to form the surfaces transition. Further sketching development will be made in the coming week in order to improve the faรงade so that it incorporates the necessary elements whilst not detracting from the design.
fig. 19 Intial sketches of front facade.
Future Jobs In the coming week the CAD model will again be adjusted and developed as a result of the scale model. In addition the freight module will be commenced in CAD so that a number of prototypes can be produced. In terms of the interior, a number of concepts will be developed around the two structure proposals. Here, emphasis will be given to the themes generated through the participatory action research toolkit. Finally the drive train system will be further researched in order to inform the interior development. As per the initial timetable, I hope to begin engineering the cad model for objet printing in week 9-10, with the eventually aim to print the scale model approximately in week 10-11.
Reflection The past week has again vanished quickly. My main preoccupation for the week was the trouble concerning making the scale models. The difficulty found in producing a presentable model has affected the project in unnecessary time being absorbed. I still feel like the project is falling behind, yet I am working on all areas in a constant manner. Overall, the form is developing well and to schedule. It needs attention on the front faรงade and in the use patterns, such as door location / handles. All areas need further work before the scale model is finalised, so the coming two weeks will involve a significant amount of work.