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DrD last won the day on June 4

DrD had the most liked content!

About DrD

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  • 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
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  1. What aspect did you not understand? It looks pretty straight forward. DrD
  2. DrD

    Linear actuator

    There are many ways that such a device can be made, and what Jek says may be the way this one works. It can also be done with a ball screw powered by a small electric motor. Without more details, no one will be able to say with certainty how t this one works. DrD
  3. Pete Wills has the right idea. By "off the shelf" if the right equipment exists, but don't buy the wrong equipment just because it is "off the shelf." You will get what yo pay for. DrD
  4. DrD


    Friction eventually imposes a limit. If there were no friction, you could just add pulleys ad infinitum, but in reality, each new pulley adds friction to the system. Eventually you would get to a point of diminishing returns. DrD
  5. Sure, all you need is the appropriate set of gears from each of A,B, and C to D. DrD
  6. I would hardly call looking for a job suffering. I presume no one is beating you or otherwise torturing you, so I don't see any real suffering involved. DrD
  7. Looks like you have the dimensions of the channels (10 x 15.3). Do you know if those are inside dimension, outside dimension, or what? I would suggest you go to a steel design book which will probably give you I for the section. The loading diagram indicates that w = w(x), a variable loading, so you will need to express that mathematically and then integrate twice to get the moment, M(x). From there on, it should be easy. DrD
  8. JAG - If the units do not work, there has to be a dimensional constant (a constant that has dimensions, not a pure number) involved. This is not uncommon with empirical relationships, but it means that the whole equation is only valid in the original system of units. DrD
  9. I'm not familiar with that process (I've seen it, but never really analyzed it). You can bet that if the units do not work, the expression is not correct. Where did you get this? DrD
  10. There is no simple formula for the force you are asking about. It depends upon the nature of the motions involved. If you would like to post a drawing of your machine (or send it to me by PM), then perhaps I can help you. DrD
  11. Cracks do not grow by themselves. Most cracking is due to fatigue, and that requires motion. A motionless car will not crack. DrD
  12. Many years ago, I was involved as an expert in a legal dispute. My company was suing the US Army in a contract dispute. I got a very bad taste for lawyers as a result. An Army facility had designed a mechanical system and put out drawings for the system as the basis for suppliers to bid on building the system. There were five major suppliers bidding to build these devices for the Army, and the bidding was extremely competitive. Being higher by half a cent ($0.005) per unit would mean losing the bid. My employer had the misfortune to win the bidding, and we were building this rather complicated mechanical system (around 200 parts) for about $15 per unit with many 1000s to be built. Each week's production would be declared to be a "lot," typically around 20,000 units. The inspectors would draw a random sample for testing, and if all tests were passed, the lot was accepted and the company was paid for the material. If any tests were failed (and there were about a dozen different tests), the lot was rejected and the company received no payment. Dimensional tolerances were extremely critical, and the company had taken then into account in the bidding. In suing the Army, my employer was alleging that the tolerances had been deliberately set loose for the bidding while the Army knew that closer tolerances were required in order to consistently meet all the specifications and pass the tests. The Army denied this. My job for 18 months was to demonstrate mathematically that there were dimensional combinations within the allowed tolerances that would fail some of the tests, and therefore that the Army had misled the bidders in the original contract negotiations. I did this quite fully, showing that some combinations would work while others would not, even though all were within the specifications on the drawings. I was completely disgusted by the attitudes of the lawyers on both sides. The had ZERO interest in the truth; they only care about winning the argument. They were only interested in information that supported their side of the case. If a part of my study did not support my employer's case, our attorneys ordered me to destroy that paper work and to deny that I had ever done it if asked. I refused to do that; the truth is the truth. Most of my encounters with lawyers since that time has supported my early evaluation; they are evil men (and women) intent only on winning. Truth means nothing to a lawyer! DrD
  13. Backlash depends upon clearances at the joints. You will have to specify all of these, and then look at the various possible combinations to find the worst case. It is a long, tedious process. DrD
  14. Mechanics Corner A Journal of Applied Mechanics and Mathematics by DrD, #48-B Correction To Mass On Multiple Spring Supports Correction The previous post, #48 titled Mass on Multiple Spring Supports had several typographical errors. Strangely, they are all in the brief introductory example regarding the loads on the four legs of a table, at least these are the only ones that have been called to my attention. As many of you know, I am older than dirt, and my typing skill is degrading; this leads to errors at times. I apologize for misleading anyone. Fortunately, one reader notified me that there were errors. MassOnMultipleSpringMountsB.pdf
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