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Shared Three Week Plan and Vision
By the end of week 9 we hope to have delivered the following project components:
- Finalized Concept Proposal
- Preliminary CAD files including and focusing on animations showing use scenarios and system level components
- Beginnings of Bill of Materials
- Continuing Feasibility analysis
What progress and deliverables Team 15741 plans to provide by the end of Week 12:
- Feasibility Analyses of individual subsystems (Specifically Lifting component selection, Rotational System, Finalized Gripping System)
- An updated pricing list of parts required by design
- List of individual part parameters as per approved analysis
- A beginning draft of the developer's safe operation and construction manual.
The following tasks and engineering questions will need to be addressed in order to achieve the above.
Budget and Tentative Parts Listing
Updated Constraints List
Updated System Proposal
After benchmarking the Vere optical breadboard hoist found at http://www.vere.com/html/table_hoist.html. It is clear that our base concept is viable as it is very similar to another already commercially available product. The Vere system has many interesting and useful features. The base of each lifting end is attached to the other through a central bar while in use. This prevents twisting between ends of the lifting mechanism. The clamping heads are removable and designed to be attached to the table and then have the lifting mechanism brought to the table afterward.
However, the system we previously proposed in comparison to the Vere system has some features our customers would like addressed.
- The clamping frame is too large. They would prefer we minimize the size of that system.
- The customer also asked that we look into using the 1/4-20 bolt pattern on the tables as a method to secure them to the lifting system.
- The jaw system will also be much smaller than shown in the design sketches for the week 6 review.
- A structural analysis of minimum material needed to supply necessary rigidness will determine the needed thickness of the plates.
Model Development and Method of OperationAs mentioned in the systems design review, the maintaining size constraints are very crucial in developing an effective solution. A CAD model of proposed design and simple size feasibility representation demonstrate our design's features.
Use Scenarios for Safety Analysis
An interactive table has been provided that will generate a use-scenario chart for the user. The operator or client must simply input key factors of their desired task and a use-scenario flow chart will be generated that explains the specific transport process.
The design of our concept requires that a removable plate with an array of screws be present as part of the clamping head. These screws are used as interface to secure the table within the clamp by inserting all screws in the clamp into the fitted pattern on the table. Once secured, the screws will experience tensile and shearing forces as the table rotated and supported by said array of screws. An analysis has been completed for the case of not overtightening the screws on the table. All tensile forces in the initial analysis are therefore generated by the table mass. The excel table shown below provides our analysis of the forces, handbook ratings, and safety requirements in using this method to secure optical breadboards. All data for safe loads and stresses taken from Mark's Mechanical Engineering Handbook 6th Edition.
The screw analysis was completed using basic stress equations using the following free body diagrams
To accurately determine the number of screws that will be needed for the full design and go beyond proving feasibility preload and angled cases will need to be taken into consideration. Preload was calculated by using the SAE torque tightening standards found at http://www.engineersedge.com/torque_table_sae.htm. These gave a preload rating of 900lb tension. This analysis will be completed during weeks 10-12.
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