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How to counteract the rotation?

  1. Aug 31, 2010 #1
    Hello,

    I have this question: Imagine a helicopters main rotor. It rotates with some power produced by the engine. But if the tail rotor is not working, the helicopter will start rotating in the oposite direction of the main rotor's rotation. What amount of power is necessary to keep the helicopter still? Compared to the power of the engine that rotates the main rotor. Is it one haft of it (50%)? Or it is less?

    Thanks
     
  2. jcsd
  3. Aug 31, 2010 #2
    You asked "How to counteract", but actually you are asking about the needed power to counteract. The answer is it is much less than the total available power.

    The demanding torque to keep the rotor at a constant given rotating velocity is mainly related to the drag force component generated by the blades, in a nutsell this parasitic force when combined with the rotor diameter will generate a torque that will be counter balanced by the tail rotor.

    The friction generated by the main shaft bearing will also create torque and this number is related to the lift force and bearing size.

    During rotor acceleration, the parasitic torque will also be added by the blades mass inertia, demanding more power from the engine.

    The power to keep a helicopter hovering is just a fraction of the total power available from the engine, as most of the power will be demanded during maximum climb rate and to achieve maximum cruising speed (which is generally limited by stability and not by the engine power).
     
  4. Sep 1, 2010 #3
    Thanks for the reply. What I needed to know is not related to a helicopter but to a compleately different thing. I just made a parallel between that thing and a helicopter. And I received the information needed although it is partial. Thanks!
     
  5. Sep 1, 2010 #4

    Danger

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    It would be best, then, that you explain as exactly as possible what it is that you need. Analogies are fine for trying to get a concept across to someone, but useless when it comes to attempting a design.
     
  6. Sep 1, 2010 #5
    Yes, you are right and I know that but maybe I don't want to share the concept cause someone may steal it.
     
  7. Sep 1, 2010 #6

    Danger

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    Understandable. My suggestion, in that case, is to consult with a patent attorney before proceeding. S/he will be legally bound to non-disclosure, and can advise you as to whether or not your idea is worth pursuing. Good luck with it. :smile:
     
  8. Sep 1, 2010 #7

    Mech_Engineer

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    Talk to an engineer first, so you can see if it's acatually a good idea...
     
  9. Sep 1, 2010 #8

    Danger

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    Good idea as well, but make sure that s/he signs a non-disclosure agreement before the consultation. One can never be too safe.
     
  10. Sep 2, 2010 #9
    All of your suggestions are good and I will consider them. Thank you very much!
     
  11. Sep 2, 2010 #10
    But may I ask you another thing related to that?
    Some time ago I was interested in posting an article in Popular Science about this subject. I tryed to make a contact with the magazine, through the internet of course, but I had no response. Do you know more about this issue?
    And if I decide to do such a thing, do I need to have a pattent first to be sure that the idea won't be stolen by some reader of the magazine?
     
  12. Sep 2, 2010 #11

    Danger

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    Most reputable magazines, as with TV or movie production companies and book publishers, do not accept unsolicited manuscripts.
    Once you send an inquiry outlining your concept and an estimated word-count for the final product, you sit back and wait to see whether or not your target is interested. That inquiry has to be accompanied by a Self Adressed Stamped Envelope. (I used bolding there because it is known industry-wide as an SASE.)
    A preliminary approach is required because they absolutely will not open anything unsolicited for the very reason that you are being secretive about. There are far too many people who think that they're the second coming of Leonardo Da Vinci. If they submit something of their own volition, they are more than eager to scream "plagarism" if that company publishes or produces something that shares a couple of words or even a vague concept that the would-be author submitted. "Nuisance" lawsuits were prevalent until the current policy became the norm. Anything that you send in on your own is automatically returned, unopened, to prove later that the company couldn't have stolen your idea since they never knew about it.
    My strongest recommendation is that you either buy or peruse at your local library a hefty tome entitled "Writers' Market" which is published by Writers' Digest Books. The library is a better approach, since the book is quite expensive. (The last time that I bought one was in '78, and it cost about $45 even back then.)
    There are thousands of entries which provide contact information, overall market health, etc..
    By the bye, unless your contract stipulates otherwise, mags such as PopSci purchase only "first North American serial rights" on a routine basis. That gives them the right to publish (once only) your article in the US, Canada and (I think) Mexico. That means that any subsequent re-printing has to be negotiated with you again.
     
    Last edited: Sep 2, 2010
  13. Sep 2, 2010 #12

    Mech_Engineer

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    In addition, Popular Science is not a technical publication for inventors to publish their ideas. It is an entertainment magazine written by writers and editors in the publisher's employment. My guess is they don't even glance at article ideas written to them unless they include flashy pictures and some real buzz in the industry.

    Individual private inventors are always interested in getting patents on their new and revolutionary idea, but let me add my 2 cents in on that:

    1) The patent office does not evaluate the technical merit of your design (or indeed if it will work at all.) Just because you have a patent doesn't make it a good idea; that's where talking to an engineer who signed an NDA is a good idea.

    2) Patents are expensive to get, and even more expensive to defend. keep in mind the patent office does not defend your patents, that is your responsibility! It's nearly impossible for a private individual to defend a patent from a company that decides they want to use it, and how close a competing design can be is a HUGE gray area... You may spend hundreds of thousands of dollars in court for nothing.

    3) Companies will know exactly how your design works, because your patent becomes public knowledge!

    Your best bet in my opinion if your idea has merit would be to either sell it to a company (or get them to hire you) that deals in your design's area or publish a few papers (a.k.a. technology disclosures) on the subject and chalk it up to a resume booster.
     
    Last edited: Sep 2, 2010
  14. Sep 3, 2010 #13
    Thanks for advising me! Both of your statements sound reasonable.

    What I'd like to achieve by publishing an article is that I'd like to share the idea with other people and here their opinions. Especially of those who are specialists in the field. Not that I'm keen on seeing my name in Popular Science magazine!

    In my opinion the idea should work as I think but I also know that there may be thousands of other aspects that I miss and what I think is compleately wrong. That's why I want to discuse it with other people. But in the same time to maintain the rights over it.

    Is there any way to achieve all these...?
     
  15. Sep 3, 2010 #14

    Danger

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    I can think of only one, and it would be horrendously expensive. That would be to form a company and hire a team of expert consultants to work for you.
     
  16. Sep 7, 2010 #15
    Yeah, I know that too. :)))
     
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