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Everything posted by DrD

  1. Dear Dudley, It would be a real reach for me to "love CFD," but I will agree that those are rather nice simulations. DrD
  2. Dear John, Well, it is really all pretty simple, but only if you know what you are doing. As you evidently believe this is true, it is clear that you do not know. Or, perhaps you do know, and simply wish to scam folks. Either way, keep working on your miraculous inventions and leave real engineering to those who do know what they are about. DrD (Yes, I really do have a PhD in mechanics.)
  3. While this looks like a fairly simply problem on the surface, it has the potential to be quite complex. The fact that the shaft is vertical complicates the situation because it does not offer the stabilizing force of gravity. What you are asking for is professional work, well beyond the scope of the Q&A here at the ME Forum. You should contact a competent Professional Engineer for this assistance. You can send me a PM if you want further help. DrD
  4. You are welcome to disagree, but I will stick by my statement. Numbers may influence emotions, but ultimately it is emotions that drive decisions. DrD
  5. It does not look to me like the red screw will significant change the belt tension which is the source of the brake torque. How do you envision applying/releasing this "brake"? DrD
  6. Unless you are a fully funded research organization, forget the idea of building a rail gun. It is exceedingly dangerous and expensive. That said, why would you want to use such an expensive material for the rails? Are you aware that electrical erosion is a major problem in the rails of a rail gun. A typical rail gun some years back (about 2006) needed new rails about every other shot. Also, while we are at it, what will you use for power? It takes a vast amount of current to drive a rail gun. Force varies with the square of current, but the multiplier is quite low. In the early 2000s, when I was working in this area, we were looking at around 6 mega-amps peak to get a exit velocity of 6 km/s, as I recall. If you can't do better than that, you will be way behind the times. DrD
  7. OK, got it. Now, you need to draw a free body diagram (FBD) for each mass. Show only real forces acting on the masses, no mass x acceleration terms. Do you understand that the force through a dash pot if proportional to the relative velocity of the end points? Once you have the FBDs, you should be able to write the sum of forces on each mass. DrD
  8. This is a strange situation. Why did you stick around to finish an ME degree if none if it interested you? Does that reason, whatever it may be, give you a hint as to what you should do with your life? DrD
  9. You have not given us a system diagram, so we have no way to know how the springs/dampers are connected to the masses (which masses connected to which spring or damper). This is essential information. Please provide it, and we may be able to help you. DrD
  10. Take a look at Post #25 (Feb,, 2016) on the Mechanics Corner blog at this site. You will find a somewhat similar problem worked in some detail. If that is insufficient, send me a message. DrD
  11. Sure, it is certainly possible to find many things regarding this mechanism. But what are b and d? Is it intended that the spring element is perpendicular to the lever? If not, then a better figure would show that it is clearly not perpendicular. This is important. DrD
  12. DrD


    There is a retired SR-71 on display at Eglin AFB, Florida. I was able to walk right up to it and touch the wings; it was pretty scary, even when sitting entirely still. Those of us that never flew still have some appreciation for the astounding engineering that went into these planes. Thanks for your comment, Dudley. DrD
  13. I think you are a bit confused one one of your engineering types. Specifically, I question whether it is appropriate to speak of a "financial engineer." I think that is nonsense. Finance is based on emotions and psychology at least as much as it is on hard science. I also have to ask, why did you make this video? What is the point? I must be missing something. I really did not learn much (other than about the "financial engineer"!) DrD
  14. Dudley, you wrote your "rant" back before the recent catastrophe in Texas and the rest of the south central USA. That even just reinforces what you said about the inadequacy of wind power. It is all "feel good" and not engineering at all. The same can be said of solar. We messed up (IMHO) back in the late '70s (or was it '80s?) when we walked away from nuclear power. By now, it is quite likely we would have solved the waste disposal problem, if we had continued to pursue it. As things stand, we are still on square one. This was a good post. Thanks, Dudley. DrD
  15. And this addresses the question how? DrD
  16. DrD

    Mine Hoist Problem, #54

    Dear Mark, After thinking further about your response, I finally decided that I should tell you more about the situation. The load to be lifted out of the shaft is a massive blob of pure gold, studded with 50 carat diamonds. Your team has been searching for it for months, and now it has been found. Now, do you use the primitive lift described in the problem, or do you place an order for the modern equipment you recommended? Oh, I should also add a couple of other factors that may influence your choice. The action all occurs at a very high altitude (22,000 ft above sea level) in a remote part of the world. There is no electric power available. You could order a diesel generator set along with the rest of your gear, but the diesel might have difficulty producing full power due to the thin atmosphere. As a final consideration, you know that there are at least two "bad guy" teams searching for this treasure, and you've found their tracks in the area. Your gear is not available with Amazon Prime, so delivery may take months. Which lifting rig would you use? DrD
  17. It is far better for you to read the book. I have not done such problems since I taught a course where they were included in the Fall semester, 1969. My memory is a bit fuzzy, and I'd probably mislead you. DrD
  18. DrD

    Mine Hoist Problem, #54

    Thanks for your comments, Mark. If we complicated the problem as you recommend, it would be fa beyond the likelihood of anyone working it. As it is, I am unaware of anyone having work the problem. One of the big points that you evidently missed is the kinematic aspect. I am well aware that slopes that follow exactly parabolic form are exceedingly rare. It was never intended to represent any actual mine, but rather a hypothetical situation intended as an exercise for folks to develop their skills. DrD
  19. Dear Dudley, I'm quite familiar with the soap bubble problem, but there the quantity minimized is the surface energy which is proportional to surface area. I fail to see the connection to the cooling tower problem. Would you elaborate, please? DrD
  20. There is lots of discussion of problems of this sort in Den Hartog's Advance Strength book. DrD
  21. Dudley, I'm still very much here. I'm in the maximum risk group for WuFlu since I'm 80+, but I'm firmly convinced it is just a political fantasy. I never get flu shots, and I don't expect to get the WuFlu either. I have not had a land line for some years now. If you need to reach me for some reason, send me a message through the ME Forum message system. Were you reading TMR? I had no idea anyone was, so I abandoned it after some medical issues slowed me down pretty badly. DrD
  22. If the hands-on stuff is what you are good at and enjoy, why bother with engineering? Become a mechanic (a machine repairman). Engineering is about design, much more than about hands-on operations. It is certainly true that some engineers work more directly with machines in such roles as planning and supervising repairs, but there again, it is more of a guiding role than a hands-on role. DrD
  23. Your hand written work is much too difficult to read. Can you put this into a computer written format, please? DrD
  24. I have never seen such a machine, but it does not look too difficult. Would you not be able to accomplish this with a simple hinge? Imagine a tube running front to back on the machine. It is secured unable to rotate on the rear unit, but allowed to rotate in bearing through some angle on the front unit. Wouldn't this do the e job? I think so. As to fatigue life, that depends upon the specific design details, specifically the loadings and resulting stresses.
  25. It is conceivable, but if will likely be horribly expensive due to the special materials required. Why would you want to do so? Can the cost be justified?
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