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  1. Boothby171

    Do Engineers have a (Weird) Sense of Humor

    "Four, minus 4 over three, plus 4 over 5, minus 4 over seven. Dad!?! How many frikkin' terms do I have to bring this out to?" "With a mouth like that...20." "Aw! Jesus frikkin' Christ!" "Thirty, then!" Ah...memories. I shall enjoy them! --Boothby "The biggest cause of trouble in the...
  2. Boothby171

    Do Engineers have a (Weird) Sense of Humor

    Oh, goodness....you're one of those. --Boothby "The biggest cause of trouble in the world today is that the stupid people are so sure about things and the intelligent folks are so full of doubts." - Bertrand Russell
  3. Boothby171

    Do Engineers have a (Weird) Sense of Humor

    I did once attempt to punish my daughter (then 10) for something by making her sit in the corner and counting backwards from "pi". Being as big as geek as I, she did: "Three, point one four one five nine two...Hey!!!! --Boothby "The biggest cause of trouble in the world today is that the...
  4. Boothby171

    Odd response running load combinations...

    JAE, Thanks for taking a look! It's definitely a load-sensitive instability, but I don't think I have any slenderness issues with my elements. I DO think it's related to relative spring stiffness issues, since increasing the spring rate of the tension and compression springs seems to have...
  5. Boothby171

    Odd response running load combinations...

    Mike, Fair question ("Make sure that the computer is plugged in?" and "First, can you make sure your friend is really dead") that I have asked people myself many times before! Yes; the DL is non-zero. I have since upped the TS and CS values by a factor of 5, and I got the Load Combination...
  6. Boothby171

    Odd response running load combinations...

    Add to that: The model DOES have Tension-Only Springs and Compression-Only Springs. I'm focusing my attention there... --Boothby "The biggest cause of trouble in the world today is that the stupid people are so sure about things and the intelligent folks are so full of doubts." - Bertrand Russell
  7. Boothby171

    Odd response running load combinations...

    I have a relatively simple model in RISA-3D. No "tension only" members. No "Euler Buckling" members. Spring constraints and some RIGID members, though. It's got a few HUNDRED load combinations, and I'm trying to run ONE, using the "Solve Current Combination" command. So far, so good...
  8. Boothby171

    Buckling in telescoping hydraulic cylinders

    The telescoping cylinder itsself will never see tension. It's purely a compression column. But as I picture it, the cylinder walls NEVER see any axial compression! (Except maybe the top-most stage) Even the bottom-most stage doesn't carry any axial load--it's all hoop stress from the opil...
  9. Boothby171

    Buckling in telescoping hydraulic cylinders

    I started to examine a multi-stage telescoping hydraulic cylinder for Euler buckling (it actually is rigidly mounted at its base stage, and has side loads as well, so there are interaction equations to be dealt with), when I realised something important. My "d'oh" moment of the day. The walls...
  10. Boothby171

    Study Material for PE Exam

    Unless they've improved it (and I hope they have), AVOID the ASME study materials at all costs. I bought their books & videos to study for the Mechanical ENgineering PE exam in NY. The ASME books were full of the same sort of errors that the Kaplan books were accused of having....missing...
  11. Boothby171

    Your Thought On "Planners"

    Palm-based PDA's can also run a great little HP Calculator emulator. There's one less thing (again!) you have to carry. But all the info you can store on these things is amazing! Plus phone. Plus Outlook. Plus Excel & Word & (so-so) PDF reading, Camera, Video, Dictionary, Avantgo (so you...
  12. Boothby171

    What is the best engineering advice you ever received?

    My boss told me something the other day that I thought was very helpful in being successful at whatever engineering job you have: "Stop spending so much ^&%$%^&@ time on the Internet, and get some of your ^&%$%^&@ work done!" :)
  13. Boothby171

    new vehicles and factory rustproofing

    Simple cost calculation, I would think: cost of rustproofing vs. cost of multiple car washes (only count the "extra" washes after those snowstorms), measured out over the duration of the warrantee...
  14. Boothby171

    Space Elevator

    Has anyone ever done an ADAMS or other physics simulator simulation of all this, all the secondary (etc.) effects, loss of cable responses, etc? Or are we all discussing how many angels can dance on the head of a pin?
  15. Boothby171

    Space Elevator

    Stupid Question: Assume (for the moment) that you have no drag or wind or standing or travelling waves on your cable. It's just a straight cable, running from the surface of the earth out to a geostationary satellite. Where the cable starts, on the surface of the earth, is also a...
  16. Boothby171

    What is the best engineering advice you ever received?

    "The biggest problems are always at the interface..." --Me
  17. Boothby171

    Alternative of drive dogs to push the chain in overhead conveyor

    But you CAN push chain. It, um, called...PUSH CHAIN! Go look up a company called SERAPID
  18. Boothby171

    Minotaur from Vandenburg flys over LA (pics)

    ...but why does it say, "Surrender Dorothy" ??
  19. Boothby171

    Position = FUNCTION(VELOCITY, ACCELERATION, JERK)

    Nothing, really. If I sat down and did it, it would have taken me less than an hour. In trying to find the solution already "out there," I've probably spent twice that amount! The problem is keeping track of "time" during the various time-spans (step functions based on threshholds (t-t3))...
  20. Boothby171

    Position = FUNCTION(VELOCITY, ACCELERATION, JERK)

    nbucs, and not to forget that a=a0 + integral(j*dt) I need the overall equation of motion (position as a function of...) given: @ t=0 x=0 v=0 a=0 j=0 @ t=t1 x1=integral(integral(integral(j))) v1=integral(integral(j)) a1=integral(j) j1=jmax (j has gone from j=0 at t=0, to j=jmax at t=t1)...

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