Boat

Discussion in 'General Electronics Chat' started by kammenos, Jun 3, 2009.

  1. kammenos

    Thread Starter Active Member

    Aug 3, 2008
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    I am making a boat, 1 meter long (approx)

    For propeller i want to use a semi-merged (arneson-like) 6 fin surface propulsion system. I gave this fancy title to the hacked 50mm fan that i will use for this reason not to sound "cheap".

    But i need a motor. A 9-12V (better 12V). DC around 1100rpm would be nice.
    Any vendor?

    Thanks
     
  2. Externet

    AAC Fanatic!

    Nov 29, 2005
    758
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    A heater blower fan from an automobile wreckyard should work fine. With reduction gear, an electric window lifter motor. Or a radiator cooling fan...
    Even a 120VAC vacuum cleaner salvaged motor will be fine for low rpm at 12V; or a rechargeable drill; it has reduction gears or even speed control. There is always one with dead batteries somewhere waiting for you. A 12V car vacuum cleaner...
    Many, many cheap sources.
    Miguel
     
  3. kammenos

    Thread Starter Active Member

    Aug 3, 2008
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    lol! Thanks!
     
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    How much power do you need? Model aircraft / model cars, have wide variety of electric motors available, in brush or brushless, 80+-W to 2200W, straight or gear reduced, from ?$20 to cant afford. With push toward brushless, might find used brush type at a hobby store.
    Example: www.maxxprod.com ;E-fliteRC.com
     
    Last edited: Jun 11, 2009
  5. beenthere

    Retired Moderator

    Apr 20, 2004
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    1100 RPM will cavitate like crazy. The bubbles will eat the blades off. Propellers in water are limited to lower speeds, but I'm not sure of the limit for small blades. Think more like 300 - 350 RPM.
     
  6. kammenos

    Thread Starter Active Member

    Aug 3, 2008
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    300-350? That low rpm? Wow! I Knew that cavitation is a problem but i thought that a model 45cm propeller would not have problem with this.

    I checked some at ebay but i found water cooled ship motors and air cooled plane motors. Water cooled are out of the question. The air cooled motors (that have very high rpm) is possible to work for the ship? I mean, is there a problem if they do not have tons of air flowing from the plane nose?

    Bernard: I do not know how to calculate the power that i will need. It's a ship, not heavier than 3-4 kilos (due to the batteries), not longer than 1 meter, not wider than 35-40cm.
     
  7. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    Edmund Scientific sells a "bag of motors" for about 5 bucks.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Gee, Beenthere - I think you're thinking about propellers for aircraft carriers or battleships, in which case you'd likely be right.

    Dad's old Evinrude 25HP outboard would spin the prop at up to 5,500 RPM (max @ WOT).

    Some model gas (fuel) engines run at up around 30,000 RPM, and people use them with a direct drive. :eek:

    Just a guess here, but I think the major limiting factor is the speed of the prop tips, with blades being razor-sharp a close 2nd.

    This page has some useful tips: http://findarticles.com/p/articles/mi_qa3918/is_200012/ai_n8912069/
     
  9. kammenos

    Thread Starter Active Member

    Aug 3, 2008
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    Golly! I thought that the prop would be the easiest. Actually, i did not think of it at all.
     
    Last edited by a moderator: Jun 12, 2009
  10. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Guestimate on motor power: My Pitman Panther Mod. 9001B model boat motor maesures about 15W, was for a 24 in. submarine[1961], wild guess 50- 75W would do. Your boat sounds like a tug, or shrimper? Not planning on getting it up on a step?? Battery motorcycle 12V lead-acid, 5Ahr?? Was looking in Am. Sci & Surpluss, www.sciplus.com where I [10 years ago ] found a neat Johnson, Chicom, 12V ,4A motor, and see windshield wiper motor, 12V @ 3.5A, about right size. [2005 cat.]
     
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