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DrD last won the day on April 23

DrD had the most liked content!

About DrD

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Profile Information

  • Gender
  • 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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  • Achievement /recognition/ Certifications
    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
    Member SNAME
  1. JAG: Only a government could keep a straight face and insist this made any sense. Amen, amen, amen!! DrD
  2. The word you want here is "follow," not fallow. To follow is to go with someone or thing, to go where they go. "Fallow" is an adjective that describes a field left for a season to rest without a crop.
  3. I cannot speak for everyone else, but I never discuss perpetual motion! JAG, I just wanted to put some realism into your Ponzi scheme. DrD
  4. To my mind, this quiz focused on mostly the wrong things. These are, for the most part, things that can easily be looked up in a design manual or a handbook. A much more interesting quiz would focus on the understanding and application of idea, the ability to correctly model systems, and the ability to understand and correctly interpret data. DrD
  5. I just completed this quiz. My Score 80/100 My Time 161 seconds  
  6. It is certainly possible that links 2 and 4 have the same length. However, it is not necessary for this to be true. If L2 = L4, that is a special case. Whatever sort of project can you make from this super simple mechanism? DrD
  7. Suresh, I'm glad that you found it interesting. DrD
  8. Hey, JAG!! Let's have a little realism here. You give me a dollar, and I will give the next guy 1/2 dollar. He in turn gives the next person 1/4 dollar, etc. until you get nothing at all back. That's the way the world works. There is no free lunch!! DrD
  9. Sure would be nice if this was in English. I have no idea what it is about. DrD
  10. Quite a few interesting comments on reasons for design failure. Thank you JAG in particular. I would like to tell a story about a failure that I saw once long ago that was somewhat different. It involved a design that had been developed in a government laboratory, manufactured in very small quantities with tight controls for testing, and then put out to industry for mass production. In order to bring the unit price down, the government arbitrarily specified rather loose tolerances, far more loose than anything that had been allowed in the development phase. But then, the government added a performance specification, that the product must function according to design. The result was that the mass production companies were bidding, based on nothing more than the drawings and specifications. It was implicit in the drawing package that a product made according to the drawings was expected to meet the performance specifications, and this was the way the bids were developed. My company was unfortunate enough to win the bid. We found through bitter experience that it was entirely possible to build the product according to the drawings but still fail the performance test at the end. This resulted in massive amounts of rejected products. My job was to show mathematically that this was entirely possible, that the loosened tolerances allowed for performance failure. This was a failure driven by a desire to reduce costs to the purchaser. The result was the destruction of my employer; a company with over 100 years experience in the field was driven to bankruptcy. DrD
  11. Absolutely amazing!! So many people who freely admit that they do not know what they are talking about, but in the next breath, they say they are just sure that this idea will work!! Absolutely stunning!! DrD
  12. For a journal bearing surface, it is obvious that a circular surface is essential; a square section in a square hole would not turn. A square section in a large round hole would have contact at 4 points at most, very little load bearing area. If we are going to use a circular section at a bearing, then there is no point at all to using a square section between the bearings. A square section would be heavier, and only a slight bit more stiff. The square section would require more material for no real benefit. Square or other polygon shapes are used for special situations, but only where the is an evident advantage in doing so. DrD
  13. Your diagram is almost self-explanatory for any one who will think it through. PID stands for Proportional, Integral and Derivative, the three modes of feed back used in the system. Look at the diagram! each one operates on the error signal, and contributes to the eventual control action to minimize the error. DrD
  14. These two concepts are not related the way you evidently think that they are. An aircraft is in accelerated flight when it flies a horizontal circle. That does not cause any increase in lift at all. If you think in terms of straight line flight, then yes, flying faster will produce more lift. If you want to go faster but no higher, you adjust the trim tabs, modifying the airfoil to reduce the increased lift. DrD
  15. Which book he needs depends in part on the purpose for which he is learning this material. Does he want to be a boiler designer? Or does he want to drive a steam locomotive? Or perhaps he wants to be an operating engineer in a steam power plant? Each of these needs to know different aspects of boiler operation, but it is unlikely that any of them know it all. He should go to the library and start researching this topic. DrD