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Mechanical Engineering


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DrD last won the day on May 16

DrD had the most liked content!

About DrD

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  • Location
    Iowa, USA
  • Interests
    Kinematics, dynamics, mechanics of materials, Theory of Machines, machine design, vibrations
  • Present Company
    Machinery Dynamics Research
  • Highest Qualification
  • Engineering Qualification
    Registered Professional Engineer, TX, WI (Ret'd)

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    Consulting work for a variety of industries, particularly in the IC engine related area (Torsional vibration analysis, shaking force analysis, engine cam design, system simulation).

    Author of several books, including one widely used textbook for Theory of Machines.

    Life Member ASME
    Member SAE
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  1. DrD

    What Makes A Ship Move?

    GBH, that is certainly a valid point of view. This article was originally written when I was employed by the US Navy in an electric propulsion research group. I was surrounded by electrical engineers who knew a little bit about electric motors and a whole lot about motor controls. But they had no clue at all as to how that made the ship move. In retrospect, I think the key element that they missed was the interaction at the thrust bearing. They saw no connection between the shaft/propeller rotation and pushing the boat through the water. I was trying to close the loop for them. To suggest a pump turned inside out would have simply blow our all their electrons. DrD
  2. Your numbers disappeared from the problem statement. Please try to fill them in. DrD
  3. As far as the horizontal positioning goes, I think esthetics is probably the main concern. I would suggest supports about 12 inches from each end, but then I'd also make a scale drawing and see if it looks right to you. The bigger question is the vertical support point. You need to look the wall supporting the bottom end of the leg and see where it can best take the loads. Remember that there will be both vertical and horizontal components of the load against the wall. DrD
  4. Dear JAG, Just to be clear, all those pages are from Faires? DrD
  5. I've never really gotten into worm gearing, so I am afraid I am unable to help you. Good luck. DrD
  6. After a little bit more thought, I have one more suggestion (probably the best one yet!). Have you heard of an area of study called "dimensional analysis"? I'm not speaking simply of checking dimensions in your calculations, but a process to help you determine the proper form for an empirical equation. (I would not be at all surprised to learn that the equation you posted is largely empirical.) It is a technique to work from what you think you understand about a process to produce at least the form of the describing equations. One of my own teachers often said that he had made more money as a consultant using dimensional analysis that any other tool. Dimensional Analysis is closely allied with a subject called "Similitude" or "Theory of Models." It is more than I can present at this point, but it is a very powerful engineering tool. Do some web research on -- dimensional analysis -- similitude -- theory of models I think this will get you to the answer, but not without a good bit of work. DrD
  7. You need to ask around to upper classmen, librarians, lab assistants, in addition to the faculty, and the main question is, "How do graduates of this school find jobs? Where do they make the necessary employer contacts?"\I I'd really be surprised if no industry recruiters come to your campus. Most schools encourage this as a way to help their graduates find work. Also, does your school offer a cooperative education (Co-Op) experience? If so, take it. If you don't know, ask in the Dean's Office. My school had one, and I wish I had done it. I had never heard of such a thing, and it was only after I was long gone that I learned that it had existed. Ultimately, you have to find your own way. You know that many have done so before you and others are doing it right now. You cannot afford to be shy; you must put yourself out there, even if you find it difficult. DrD
  8. Great question, and I really wish I could help. Sadly, this is way outside my own expertise. That said, I can offer a few suggestions. 1) If you have the book you referenced, study it really carefully, working through it line by line, equation by equation, doing all of the derivations for yourself. 2) If you do not have that book, make a real effort to get it or something else like it. Here the internet can be a huge help. I'm continually amazed at what I find. And what you find tomorrow will likely be different from what you find today. I'm not sure why this is true, but I've found it to be the case a number of times. 3) You might look in some agricultural engineering books. Tractors and other farm machinery operate on soil, and this is definitely a soil oriented problem. Good luck!1 DrD
  9. What did you most enjoy studying? Did you get a buzz our of thermo and heat transfer? Are you excited by machinery? What do you think you'd like to work on in the future? Your career is what YOU make of it. It can be this, or it can be that, or perhaps it can be the other. YOU have to choose which direction you want to go, and then make the necessary inquiries as to how to get there. Talk to the faculty, talk to any company representatives that come to campus to interview graduates, talk to everyone you can. I have no idea what the opportunities are in your location, but there are folks who do know. Ask them. DrD
  10. With no question, it is not possible to help you. DrD
  11. Posting twice, an hour apart, is a bit of overkill. DrD
  12. I recommend that you choose the area where you think you are best. I know what I would choose, but that is irrelevant to your choice. DrD
  13. You might start by calculating the bending stress for the known case with the load at the middle. Unfortunately, all you know is that this stress is too much. The pipe might also fail with a 90 lb load, but you have no way to know. Consequently, you only know a value too high, but you need the maximum load that does not cause failure. If somehow you come up with a max load that avoids failure, then you can define a failure maximum stress. Then you could calculate the bending stress for the load at an alternate position and compare that to the known max safe value. DrD
  14. That video did not seem to ever get to anything related to the post. As far as the post, get a book that discusses dynamic balancing. Its not the sort of thing easily answered here. DrD
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