Jump to content


Senior Members
  • Posts

  • Joined

  • Last visited

Posts posted by Pantaz


    From what I have been reading there is a trade-off between speed(rpm) and torque, and how does an electric motor, starting from zero rpm able to produce the necessary torque to turn the wheels which are standing still. Wouldn't even the electric motor need to be running at certain rpm to produce the torque required to turn the wheels from standstill?


    Electric motors produce maximum torque at zero rpm.

  2. ... solar pane cost is likely 0.70$ per watt.a 500 w solar panel is cost 350$.it's just a dream for a household....


    At 14 years old, using mostly scrap materials, William Kamkwamba built a wind turbine to power his family's home.


    ... He borrowed an 8th grade American textbook called Using Energy, which depicted wind turbines on its cover. He decided to build a windmill to power his family’s home and obviate the need for kerosene, which provided only smoky, flickering, distant and expensive light after dark. First he built a prototype using a radio motor, then his initial 5-meter windmill out of a broken bicycle, tractor fan blade, old shock absorber, and blue gum trees. After hooking the windmill to a car battery for storage, William was able to power four light bulbs and charge neighbors’ mobile phones. This system was even equipped with homemade light switches and a circuit breaker made from nails, wire, and magnets. The windmill was later extended to 12 meters to better catch the wind above the trees. A third windmill pumped grey water for irrigation. ...


    -- http://williamkamkwamba.typepad.com/about.html

  3. John Cuthber,


    I worked for a company for 24 and they no longer required my services and laid me off, killed me, said I was done. I was an "at will" employee to them, but I was reliant on the salary to live. There is a slavery component in there somewhere. More than rhetorical. Much more than rhetorical. I interviewed and was hired back, by the same company 4 months later, in an other department, and am again "subject" to their whims and am required to "take care of" the paying customer. If I were to step out of line, I would be "killed" (rhetorically?). . . .


    Throughout your term of employment you retain the right to choose to work there. A slave has no such choice.

  4. Is there any commercial device used in industry, equivalent to mechanical hysteresis ?

    A device that snaps mechanically or hydraulically, to two states like a toy clicker, or a 'klixon' thermal switch ?


    -A mechanically bistable device like a wall switch, unstable at its center position-


    Yes, but your question is ambiguous.


    Hydraulic systems can use delay valves, so I guess you could consider that a "device" for imparting hysteresis. (Undesired hysteresis is actually a common problem in hydraulics.)


    Mechanical systems would have it built into the design of the mechanism.

  5. Let me see if I can simplify this, from the perspective of someone with no formal scientific education.

    1. Fred, using Newtonian physics, calculates the impact force of an apple striking the ground after falling from a tree.
    2. Jack measures various parameters of an actual apple, falling from an actual tree. He records the results from dozens of apples.
    3. Lisa compares Fred's math with Jack's measurements. The data sets match within acceptable margins of error. (For example, calibration factors within the measurement instrumentation; wind causing some of the apples to fall in a slightly different trajectory.)

    Conclusion: The theory behind Newton's laws, for the purposes of apples falling from trees here on Earth, is demonstrated to be valid.

    For an alternate hypothesis/theory to be accepted, it must also be able to mathematically predict similar results for those same apples falling from those same trees. If the new hypothesis can not correctly make these predictions, then how can you trust it to be accurate about anything else?

  6. From an article at news.discovery.com:

    "The Maya recorded time in a series of cycles, including 400-year chunks called baktuns. It's these baktuns that have led to rumors of an end-of-the-world catastrophe on Dec. 21, 2012 -- on that date, a cycle of 13 baktuns will be complete. But the idea that this means the end of the world is a misconception, Stuart said. In fact,
    Maya experts have known for a long time that the calendar doesn't end after the 13th baktun. It simply begins a new cycle.
    And the calendar encompasses much larger units than the baktun."
  7. Hi! This is my first post. But I'd like to jump into this somewhat stagnant discussion with the following not-so-new news:




    Is anybody reading up on this stuff?

    Note to Panopticon: It's generally considered bad form to post a file link without some description of what it contains.


    I spent a few minutes back-tracing the source of the PDF -- http://www.sede.enea.it/produzione_scientifica/WebTechnology.html

    On that page is the link, titled: "Excess of Power in Deuterium-charged Palladium - Jan 2009 - Vittorio Violante" (The website is in Italian, but this and a few other links are in English.)


    The English-language document is just a four page "technology brief" that discusses ongoing (as of Jan 2009) work building upon Fleishmann & Pons fusion experiments.

  8. Nearness means something like:


    The word "school" and the word "Skool" might be 70% near or alike.

    I would consider "skool" a misspelling, rather than a comparative word.


    For many words, you must also consider usage. Using your example:


    Main Entry: school


    Part of Speech: noun

    Definition: place, system for educating

    Synonyms: academy, alma mater, blackboard, college, department, discipline, establishment, faculty, hall, halls of ivy, institute, institution, schoolhouse, seminary, university


    Part of Speech: noun

    Definition: body of philosophy on subject

    Synonyms: belief, creed, faith, outlook, persuasion, school of thought, stamp, way, way of life


    Part of Speech: verb

    Definition: teach

    Synonyms: advance, coach, control, cultivate, direct, discipline, drill, educate, guide, indoctrinate, inform, instruct, lead, manage, prepare, prime, show, train, tutor, verse


    - Source:

  9. ... A tapered roller bearing would probably suffice for the radial and axial loads -- but I don't think it would be too happy doing so at 20_000 RPM. ...

    We used matched-pair angular contact ball bearings in superchargers spinning >35000 rpm. That was more than twenty years ago, and I don't have any of the engineering data, but I know the lateral shaft load was significant (using "multi-v" belt drive).


    When you get all of your data together, just call the technical department at one of the bearing manufacturers. They will help you determine the best solution.

  10. ... Is such a reversal possible? ...

    The Wiki page covers it pretty extensively, including numerous citations:


    "The Earth's field has alternated between periods of normal polarity, in which the direction of the field was the same as the present direction, and reverse polarity, in which the field was the opposite. These periods are called chrons. The time spans of chrons are randomly distributed with most being between 0.1 and 1 million years with an average of 450,000 years. Most reversals are estimated to take between 1,000 and 10,000 years. The latest one, the Brunhes–Matuyama reversal, occurred 780,000 years ago. ..."


  11. What are playing word games now? Or are you seriously asserting that the outer building structure as observed through numerous video recordings, did no decent at freefall acceleration for any period of its collapse?

    If you are responding to swansont's last post, he referred specifically to the "initial collapse" described in the NIST report. As previously posted, the NIST report states that a 2.25 second period of free fall occurred between two periods of "acceleration less than that of gravity":


    The analyses of the video (both the estimation of the instant the roofline began to descend and the calculated velocity and acceleration of a point on the roofline) revealed three distinct stages characterizing the 5.4 seconds of collapse:

    • Stage 1 (0 to 1.75 seconds): acceleration less than that of gravity (i.e., slower than free fall).
    • Stage 2 (1.75 to 4.0 seconds): gravitational acceleration (free fall)
    • Stage 3 (4.0 to 5.4 seconds): decreased acceleration, again less than that of gravity

    - Section 11, FAQs - NIST WTC 7 Investigation



    is it possible for an object to begin decent, and during a measured period to accelerate at free-fall speed, while simultaneously during this period moving downward through a pathway that is occupied by considerable mass? ie, a pool ball landing on another without losing momentum? ...


    When you added "simultaneously" you have indeed proffered a false premise. The report specifically states the measured free fall occurred prior to contacting additional material. Certainly, some portions of nearly any collapsing structure will experience brief periods of "free fall" between the instances of contacting/impacting neighboring debris.



    ... Because if I understand the agreed upon measurements of the first several stories of collapse of that building, as equal to free-fall acceleration, wouldn't that mean that had I jumped off the building at the moment the collapse began, and videotaped my twin standing on the edge of roof, that we would have both remained at the same elevation, even though I had nothing but air beneath me, yet my twin had a vertical wall of construction material directly beneath him? Am I wrong to see this specific part of the collapse as a issue of basic physics? If incorrect, why?


    The initial 1.75 seconds were determined to be less than gravitational acceleration. Per your analogy, you would fall 15 meters before your twin achieved "free fall". Bear in mind, at that 1.75 second mark, you have reached a velocity of 17.15 meters per second (and continuing to accelerate), but your twin has been accelerating more slowly, so he has fallen a lesser distance and is traveling at something less than 17 m/s. Your velocity will never match that of your twin at any given time after zero.


    As a (very rough) example, let's imagine that your twin's initial acceleration is 8 m/s^2 (free fall being 9.8 m/s^2). At 1.75 seconds, he has fallen only 12.25 meters (2.75 meters less than you) and is traveling at only 14 meters per second.


    (Note: I understand that the initial 1.75 seconds is a period of increasing acceleration for the twin, so the velocity and distance traveled will be somewhat greater than my example, but I don't know how to do the calculations.)

  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.