|
|
|
 |
|
|
|||
|
Homework at bottom of page
The final will be different for each group and it will be based on the group project, so if you flake on the project you will probably fail the class. Instructor: Dr. Steve Harrington
Students: If you have a project that you want to do, let me know. You should sketch out a project plan and a determine a budget and a timeline.
Goal: To teach students how to approach, plan, and complete an engineering project. The steps below may not apply to all projects and they may not need to be done in the same order. Depending on whether are designing a happy meal toy or a ballistic missile interceptor, the project will follow a different course. Remember that your goal should be to design the best product or system with a given set of constraints and aspects to optimize. If you find yourself doing things just to impress your boss or your coworkers, or run up your hours on a project, it may be time to switch jobs. Step 1. Concept definition and business plan. What are we planning to design? Where will it fit in the market? Will we be able to make a profit selling it? What differentiates our products from others? Why do we think we can do it better than others? Who will buy it? (This may or may not be part of the engineer's job, but it is best to understand why you are designing something) Remember that engineers often think that they are smarter than the marketing people, but they don't make as much money. Step 2. Brainstorm. In this phase, the important thing is to generate ideas on how to solve the problem or design the product. All ideas, no matter how stupid, are put on the blackboard. Input is solicited from everyone. None of the ideas are criticized at this point. Sometimes even the most outlandish ideas can generate better ideas. By looking at the list of ideas, more ideas can be generated. Once the ideas stop, then we can discuss feasibility, how to get started, cost etc. Step 3. Research. Are there other products like the one we are planning to design? What can we copy from them? How do their customers like their products? Can we buy some competitors products and take them apart? Are there any technical articles about the proposed product in technical journals or trade magazines? Are there any patents on this technology? Are there other people that we know who can help us with the design? Can we hire a consultant or contact a professor to get us started on the right path? Be willing to accept the input of others and do not let your pride get in the way of a good design. Step 4. Concept definition (may include more brainstorming). How are we going to solve the problem or design the device? Outline various paths and estimate the risks involved, cost and time to design and build a proof of concept model or prototype, cost and time to test it, to get it into production, etc. Step 5. Engineering calculations. Crack those old books. Calculate how much energy it is likely to use, how strong it has to be, what size pipes, wires batteries etc. Any engineering estimate is better than a guess, so simplify the system until you can calculate something. Use Mathcad, Matlab or a spreadsheet to figure out what the various parameters that influence the design are. Find something to optimize. Minimum weight, minimum cost, maximum efficiency. When optimizing, consider factors such as product lifetime, expected use etc. If your product will be obsolete in 5 years, there is no reason to make it last for 10 years. Step 6. Create a drawing of your proposed device, either with a CAD program or on paper. Sketch out how the parts fit together, estimate how big everything need to be how it will fit together etc. Either go on to step 7a to build a model, or step 7b to create a solid model. Step 6a. Build a proof of concept model. Skip this step if you are building something that is very similar to something that has been made before and you know that it will work as designed with minimum risk. Also, skip this step if the cost of the making or testing the model would be prohibitive. Otherwise, design a model or prototype that involves one or more of the high risk features of your product. If your calculations suggest that it may be marginal in terms of strength, efficiency flow rate etc., then put together the simplest model that will exhibit the feature that you are interested in. Avoid complex custom-machined assemblies if possible. Use off the shelf components, maybe by taking apart competitor's products. The idea is not to make the final product, just to make something that exhibits the features that you are interested in. The goal is to learn something about the product that you are designing, What we are trying to avoid is designing and building a complete product, and then finding out that it gets too hot, vibrates too much, requires too much power, is too loud, falls apart in shipping, does not last, does not work due to a stupid mistake, etc. Step 6b. Build a solid model. If you are building a mechanism or an assembly where the biggest challenge is getting the mechanism figured out or laying out the parts, build a solid model with constrained parts. This will help you see how everything comes together. Don't get too bogged down in making everything perfect. Also build a solid model if the device is too large or expensive to build a proof of concept model. Step 7. Add features to your proof of concept model. If your model works as expected and there are more features that you want to test, add the features to your model and test them as well. You can also begin the optimization process and start designing the final project. Step 8... This will depend on the project. Once you get something that barely works, you may want to patent it, put it in the hands of the end user and see if they have any suggestions on how to modify it to make it more valuable, etc.
We will complete an initial class project that involves designing a check valve for use in liquid oxygen. All students will submit a project proposal and those students who submit the best of those proposals will be selected as group leaders. Then each group will be given a different set of design constraints (flow, pressure, reverse leak rate, closing time, water hammer resistance, weight, size, cost etc.) and the group will design the valve and submit a report. The report will include calculations of flow rate and pressure drop, stress and strain, response time etc. This project will be completed in the first 1/2 of the semester and then the students can start their own projects, hopefully with a better idea of how to complete the project. For information on LOX (liquid oxygen) systems see the NASA Glenn Safety Manual. In the second half of the semester, students will develop a comprehensive project proposal for their own project and submit a proposal. If the project is too hard, too easy etc. or the students are not making progress it may be modified or rejected entirely and replaced with a project from the instructor. The goal is for every student group to have a clear plan for the second semester before the end of the first semester. The project plan will be submitted 2 weeks before the end of the semester and each student will be required to answer questions based on the project during the final.
Check valve is designed to hold against x*100 psi and flow y*10 GPM where x and y are the last two digits of your SSN. If the digit is 0, use 10. i.e. 00 is 1000 psi and 100 GPM. Design specifications: 1000 Cycles, leak rate .1% of flow rate, pressure drop 10 psi at full flow, 5 psi cracking pressure, fits in flat wall of tank, flow going into or out of tank (reversible) tank wall .125 in thick, no trapped contaminants in check valve. Use aluminum or ss, material must have a good strength to weight ratio. May be welded or snapped into place (no welding next to installed seal) You will need to figure out materials, thickness, stress, strain, flow rate, pressure drop, cracking pressure, time to close. You will also need to estimate cost (material cost, machining cost, assembly cost, test cost etc.) The best designs will optimize flow/weight and be reliable Those who submit the 13 best proposals will become group leaders and get to select their groups.
The proposal should include background: why the check valve is needed, what the specs are, etc. It should include a proposed basic design, and the reasons why the design will be lighter in weight than competing check valves of the same pressure and flow capacity. It should also include a method section, how you are going to figure out all the above specs, will you use FEA, or basic stress analysis. Will you use pipe flow and consider the check valve as an orifice or an elbow or consider the drag on the poppett or ball. You should estimate the time to complete the valve design, consider which items should be done first which can be done in parallel etc. Even though you are not going to build or test the valve yourself, it should include a section on how you are going to build and test it. Finally, you should estimate the engineering cost of the valve. Consider that each engineer will cost about $100 per hour when you consider the cost of overhead, office, computer, time wasted talking about last fishing trip, and playing practical jokes on colleagues, etc. (Between $10,000 to $100,000.)
|
||||
|
|
|
|
||
|
||
|
