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DrD

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Everything posted by DrD

  1. Perhaps you might start on a research problem, and when you think you have something publishable, look for a "sponsor" to co-author with you? This "sponsor" might be a faculty member or a working engineer, but someone who already has some publications and knows the process. As I read your original request, you are asking another person to identify a promising research problem and then let you do a part of the work to get your name on the paper. The big problem with that, as I see it, is the very limited value of your contribution. Suppose for example that I propose a problem that I'm working on. I will have to expend considerable time and effort to simply communicate the problem to you. With that same amount of effort, I could probably simply finish the problem and write the paper. It would not likely be worth it to me (or any other researcher) to bring you on board. You are only of value if you can do something that I cannot do, and right now, I don't know what that would be. This is why I suggest you propose a problem, do the preliminary research to get yourself familiar with the problem, and then look for a co-author to help with finishing the publication. DrD
  2. You say that you are a ME student working on a bachelor's degree. If you are already in college, why are you seeking a scholarship? Are you trying to change universities? DrD
  3. Everything JAG said is correct. Further, you have not allowed for wheel slippage, varying load weight, wet or slippery rails, etc. Not a great idea. DrD
  4. So, are you looking to get your name on a published paper? Is that the point here? It is pretty rare for undergraduates to publish papers, and I don't think I've ever seen such required for university admission. Perhaps you might tell us more about what you have in mind here. DrD
  5. Why not just do your own analysis and write your own code? This is cheap, gives you complete control, and let's you analyze any device you can understand. Take a look at my book, Mechanics of Machines, Ver. 2.1, available here at ME Forum without cost, for the way to do these things. DrD
  6. Mechanics Corner, #53 A Journal of Applied Mechanics and Mathematics by DrD A Hoisting Problem for Engineers A Learning Experience in Machine Design There is a document available on the Internet at several locations with the title 2.003 Problem Archive by MIT Professor David Trumper, Last Updated April 19, 2005. It is a collection of engineering problems, some with Matlab solutions. One thing that particularly caught my eye is 4.4 Hoisting Problem for Engineers, found on pp. 27-28. The source document does not provide a solution for this problem. The thing that caught my attention is that I thought that there was a better way to build such a machine. Below we will first analyze the machine as Trumper presented it, and then look at an alternative using the same hardware. It turns out that, in some senses, both are correct, but we must explore that below. HoistProb53.pdf
  7. Still cannot open any of your pdf files. Your claim to increase both speed and torque implies that you are increasing total power output = speed x torque. Where is the extra energy coming from? DrD
  8. Is there a guide or surface supporting the bar AB? This is a poorly stated question. DrD
  9. I cannot open your picture files. What is the .rar format? A PDF would be a lot better idea. DrD
  10. Is any information given about friction with the wall at the right side? DrD
  11. Timothy, it seems to me that your idea violates the essential idea of the railroad track, namely to have a flanged wheel to assure that it stays on the tract. The flange is only there as a backup; the wheel is actually conical and will tend to stay centered with no flange, providing there is no disturbance. It sounds like you want the front truck to reach sideways to an adjoining track and then leap over. Woul all the trailing wheels be required to follow the same sidewise leap? DrD
  12. It might help if you would tell us what HLP means. Asking questions that involve riddles helps no one. DrD
  13. Before you can publish a paper, you need to do something new. From the sound of your question, its all new to you, but that does not make it new to experienced folks. Find something you are interested it, read up on it and see what others have done and are currently working on. Then you can start to think about research on your own, but not before. DrD
  14. And this has what to do with cigarette machines? DrD
  15. The previous post on this topic was certainly acceptable for engineering purposes, but there was one small oversight in the model. Many would actually prefer that oversight because it makes the algebra quite a bit less complex. Even so, it is not quite correct, so this revised post is offered to correct the oversight. There are also a few additional comments that may be of interest, and a final question for the readers to consider. DrD LiftedBar_Revised.pdf
  16. Dear Negar, Sure, you can re-post the solution anywhere you want with the proper citation. I would appreciate it if you would post a comment on the blog regarding the solution. I think it helps encourage others to read the blog if they see that someone has already left a comment. DrD
  17. DrD

    What Makes A Ship Move?

    That's one reason photography is often not allowed in classified areas. DrD
  18. DrD

    What Makes A Ship Move?

    thedoctorD -- Seems you rather missed the point, but thank you for a review of elementary fluid mechanics (even with a mention of cavitation! wow!!). How many readers do you think have access to the propeller details of to US aircraft? DrD
  19. DrD

    What Makes A Ship Move?

    Very good! You know Archimedes Principle!! That's what enables the boat to float, so that it does not sink. What do you think that has to do with making it move? Why do you think boats have oars, sails, or propellers? DrD
  20. DrD

    What Makes A Ship Move?

    Why would you think that an upward force makes a ship move forward? That really does not follow. DrD
  21. Dear Sir, I have posted a solution for this problem over at my blog, Mechanics Corner. Please take a look at that and see if you agree. DrD
  22. DrD

    Suddenly Lifted Bar

    Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD, # 51 © 4 July, 2020 Suddenly Lifted Bar Introduction In the Forum section, under the Machine Dynamics and Design Considerations heading, Mr. Negar Rahbar has posted a topic, Bending Moment. It is a problem he found in an older textbook (one that I might have studied back in my college days, although in this case, I did not), a book titled Theory and Problems of Machine Design by Allen S. Hall, 1961. It is an excellent problem, and I thank him for posting it for us. The problem statement from the textbook is shown in the PDF that follows. The questioner says that the book provides an answer for the maximum bending moments as 592 in-lb. He is confused because he sees the system as unconstrained and asks for help understanding the solution. This is a great problem, one that really requires us to think about the dynamics of the system. Before attempting to calculate anything, it is well to simply think through the expected sequence of events. Initially the bar is lying undisturbed on the table top, presumably in intimate contact at every point along the length. When the force P is suddenly applied, the bar acting as a rigid body begins to lift. Contact between the bar and the table top is ended at every point along the length, except at the left end. The left end remains in contact, and an upward force R on the bar develops at that location. Now we are only interested in the first instant after the bar lifts off the table, so the geometry is essential the same as it was before except that the bar is now supported by two point forces, unknown force R at the left end and known force P at the right end. It is a uniform bar, so the weight of the bar acts at the middle of the length. What can we say about the motion? The questioner says that the book provides an answer for the maximum bending moments as 592 in-lb. He is confused because he sees the system as unconstrained and asks for help understanding the solution. This is a great problem, one that really requires us to think about the dynamics of the system. Before attempting to calculate anything, it is well to simply think through the expected sequence of events. Initially the bar is lying undisturbed on the table top, presumably in intimate contact at every point along the length. When the force P is suddenly applied, the bar acting as a rigid body begins to lift. Contact between the bar and the table top is ended at every point along the length, except at the left end. The left end remains in contact, and an upward force R on the bar develops at that location. Now we are only interested in the first instant after the bar lifts off the table, so the geometry is essential the same as it was before except that the bar is now supported by two point forces, unknown force R at the left end and known force P at the right end. It is a uniform bar, so the weight of the bar acts at the middle of the length. What can we say about the motion? LiftedBar.pdf
  23. 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
  24. Your numbers disappeared from the problem statement. Please try to fill them in. DrD
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