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PROJECT DETAILS ENB 110 – Engineering Statics and Materials Group Project [5 Members] 2012 Semester 1 [1st Year] GRADE High Distinction [7] OVERVIEW Designed, built and tested a cantilevered truss structure to be as light as possible whilst supporting a distributed load of at least 20 kg, but not more than 30 kg.

The objective of this project was to design, build and test a cantilevered truss structure. To achieve a 7, the device was to be: as light as possible; support as distributed load of 20 kg, but not more than 30 kg; withstand a reasonable side load; and deflect less than 10 mm under a 10 kg load. Additionally, the device had to be 920 mm long, 200 mm wide and 40 mm high. Whilst there was no restruction on the material which could be used, the cross-section could not exceed 5 mm X 4 mm. The distributed load was applied by a 150 mm X 400 mm steel plate.

To minimise weight, most groups opted to use balsa wood. Whilst not very dense, balsa is also not very strong and so these groups generally used at least four trusses. We used radiata pine, which reduced the amount of trusses to two and greatly simplifyied the construction process. As the load plate was only 150 mm wide, we also positioned the trusses at the quarter points so that the load would be transferred directly onto the trusses. The timber was glued using a two-part epoxy resin, and to ensure the joints would not fail, we gusseted the joints using cotton-backed timber veneer sheeting.

Our structure failed at 25 kg and weighed approximately 150 grams. The lightest structure that held at least 20 kg was 135 grams. The average weight of structures that held at least 20 kg was 363 grams.

16Thomas Knight | Résumé

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01 OVERVIEW 02 SKILLS & INTERESTS 03 WORK EXPERIENCE 04 EDUCATION 05 PROGRAMS & LANGUAGES 06 REFEREES 07 PROJECTS

VIEWING PLATFORM 17Thomas Knight | Résumé

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Science and Engineering Faculty (SEF) 2012

ENB110 Project Description v2.0 - 2 -

Side view of testing rig with critical dimensions. The model shown here is for illustrative purposes only to indicate important dimensions of the model and its relation to the testing rig. (Not to scale) Plan view of Model. Bracing layout indicative only (Not to scale) DESIGN APPROACH. You will not be given many instructions on how to go about this design. Part of the design process is for your team to research suitable designs. You will investigate in the library, trade journals, books, and on the internet the sorts of truss bridges other people (i.e. practising engineers) have done in previous designs. You should also investigate local structures such as the Story Bridge with respect to load paths. Your research will provide a good amount of information on the best ways to tackle your project. You will also be learning how to work in a group effectively so that the tasks that need to be done are undertaken by different group members, and all team members learn together. You must ensure that tasks allocated to team members are completed within the timeframe specified, so that the work is shared equally. All team members will receive the same grade, unless it is clearly documented and evidenced that other member(s) should receive a lesser grade. It is very important that you get used to using a pencil and paper to sketch down ideas you have in as many ways as possible – it will help illustrate and clarify your ideas and quickly come to a suitable solution. Another important part of the design process is to determine suitable materials for your project though testing and/or research, and to analyse the forces in each structural member of the model. Thus you will need to test the strengths of the materials, glue and fixings you are thinking of using so that you can design the members to take these forces. This way you can properly select the size and number of members and the type glue and fixings you will need. You will need to make samples of the sorts of joints you will be using and test them for strength and see how they fail. Most structures fail at the fixings, so you need to ensure any joints under tension can take the load being applied to the joint with an appropriate factor of safety. This is the way real engineers approach a problem, and one of the purposes of the project is to begin to train you in the normal ways of tackling an engineering problem. Some methods of analysis and design will be discussed in the lecture and project sessions, but you will need to make use of these sessions to ask the sorts of questions you need answers for. You must analyse the truss by the method of joints and method of sections and confirm your analysis at specific structural points with Space Gass software.

60mm

400x150 Loading Plate

Centre pier indicative only

450mm 450mm

150mm wide section of rig holding down the deck end

Truss to be 40mm deep

400x150 Loading Plate