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Discussion in 'Electronic Design' started by John Larkin, Jan 12, 2008.

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  1. BobW

    BobW Guest

  2. Rich Grise

    Rich Grise Guest

    My client is bidding on one of these:

    And I get to design the tooling fixtures that will hold the sticks
    in place while we build the trusses. I haven't drawn in the
    circumferential struts yet; I envision them shipping the hub
    and 16 trusses and a whole pile of struts to the site, and bolting
    it together the way the carnies do a roller coaster. :)

    It's not electronics, except for the signals it reflects to the
    feed horn; I honestly don't know if it's for satellite comm or
    a radio telescope, a la the VLA. I'm sure that as soon as we get
    the PO, I'll find out. :)


  3. John Fields

    John Fields Guest

  4. John Larkin

    John Larkin Guest

    Only a very minor role. They have installed about 60 RTDs in various
    parts of the structure to measure temperature, to adjust for thermal
    growth. We're going to supply the data acquisition stuff for the RTDs.
    They need about 0.1 C longterm accuracy.

    This is an impressive dish. It works to 100 GHz and has an adaptive
    surface to keep a near-perfect shape. One of the antennas is a
    64-pixel imager, sort of like a real optical telescope. I'd never
    heard of a radio telescope that had more than a simple antenna at the
    prime focus.

    Great pics on the web site.

  5. John Larkin

    John Larkin Guest

    How big?

  6. Phil Hobbs

    Phil Hobbs Guest

    Cool--that's some crystal set they've got there: 80-275 GHz! MM waves
    can tell you a lot of things about the interstellar medium, because
    that's where the thermal emission of cold interstellar objects peaks.

    I had an undergraduate research assistantship back in 1980-81, doing
    some simulations for millimeter-wave (110-115 GHz) imaging of carbon
    monoxide in interstellar giant molecular clouds. My professor, Bill
    Shuter, had a mm-wave telescope of about 5m diameter, with a filter-bank
    signal processor and cooled parametric amplifier front end. They never
    let me touch any of the neat electronics. :(


    Phil Hobbs
  7. john jardine

    john jardine Guest

    Even more impressive is that beanpole crane. Seems held down just by 4 bolts
    on a 6' square, yet manages to soar upwards forever. There's no way it
    should stay up, never mind do any actual work.
  8. Rich Grise

    Rich Grise Guest

    42' 4" diameter. We can only fit one truss at a time in our shop.

    The hub is about 3' in diameter, so each truss is a little over
    20 feet long; and if oriented orthogonally, over 10' tall. Of
    course, we'll design our fixture so that it's kind of tilted,
    both for balance and to save space, albeit that makes it closer
    to 25' long and about 7' or 8' high.

    Say, John, you're a gazillionaire - if you need any precision
    fab done, we're only an email away!

    That's richardgrise[at], but elide ard. ;-)

  9. John Larkin

    John Larkin Guest

    I'll keep that in mind, but we avoid serious machining, because it's
    too expensive. We prefer punched/folded sheet metal and laser-cut
    plastic stuff.

    We just decided to do a new line of small-box (7x5x2.25 inches)
    products and looked over the usual suppliers of enclosures... Hammond,
    Bud, Buckeye, Rose, like that. Everything was too expensive or not
    quite right mechanically, or had grounding/thermal problems, so we
    designed our own. Turns out you can generally have a sheet-metal shop
    run off a batch of custom enclosures cheaper than you can buy+modify
    the standard stuff.

    I'll post some pics of our design. A bunch of people had good ideas,
    so it's cheap, very versatile, and should look good.

    Buckeye does have one interesting process. They nc machine flat pieces
    of plastic and then heat-bend them into very clever interlocking
    snap-together shapes, with all the device and mounting holes,
    standoffs, and lettering done at once. They can even do copperclad
    plastic for intenal shielding.

  10. John Larkin

    John Larkin Guest

    I can't imagine how they got all this gear up onto a 15,000 foot
    mountain peak in rural Mexico. One of the guys told us how, for the
    first few hours, people get merely exhausted, and then the serious
    altitude problems start to kick in.

  11. According to the accompanying book, they built a 20 km access road up
    the mountain.
  12. Jim Thompson

    Jim Thompson Guest

    Plot, plot, plot away. Here in AZ we're systematically doing away
    with unions. Multiple suits in Federal courts against them for
    creating fake non-profit corporations that spread falsehoods about
    anyone they're trying to unionize.


    ...Jim Thompson
  13. Eeyore

    Eeyore Guest

    When does AZ bring back slavery ?


  14. After Obama becomes president, and a race based civil war splits
    the US in N and S again.

  15. You're both fucking retarded.

    It would be funny to see the donkey with a bunch of gear strapped to
    his back, braying as someone in a cowboy hat whips his ass with a crop to
    get him moving down the trail.

    Then, he might actually be able to claim to have been a productive
    member of society... as a pack mule.
  16. Mr BorEd,
    one of the reasons slavery was abandoned, is that machines became available.
    Now with the current deficit, oil payed for in Euros and gold perhaps,
    China and Japan withdrawing dollars, you may well soon have to resort to
    human resources again.
    The joke you make on long ear, may well become your destiny.
    Imagine you, pulling your (tank empty) car, uphill, no taxicabs,
    whats it called 'ricksha'?
    No, you would not get bored, no time for that.

  17. MooseFET

    MooseFET Guest

    The split if it happens won't be that clean. There is a move underway
    to return Texas to Mexico now that all the oil has been pumped out.
  18. John Larkin

    John Larkin Guest

    I'm mildly anti-union for what I think are valid reasons, not to
    mention that I'm too irritable and too disorganized to join
    *anything*. The co-founder of my company was once an international
    organizer for the Teamsters.
    Well, don't show up before 9:45, because I probably won't be there.
    Around noon is good, because I could take you to Zuni for lunch.
    We like crispy whites or light reds, pinots or merlots or whatever.
    Those "big" tannic zins and stuff are too much for us. Nothing fancy,
    just stuff that's easy to drink.

    But your real proplem will be to find the place. The intersection is a
    nightmare, and most people miss it the first try. Email me and I'll
    send you the directions, a mere 3 megabyte PDF file.

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