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  1. #11
    Connecticut CrazyA's Avatar
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    Quote Originally Posted by ph2ocraft View Post
    Something that I have always wondered.
    How is ti that you can use a wrench to change the impeller pitch BUT the water won't change it over time?
    It's because of MA, or Mechanical Advantage. The wrench becomes a lever so-to-speak, one of the six basic tools which are comprised of:

    Lever
    Wheel & Axle
    Pulley
    Inclined Plane
    Wedge
    Screw

    m
    Last edited by CrazyA; 08-07-2008 at 04:09 AM.


  2. #12
    Hi guys, mind if i ask for a copy of the pitch gauge where i can print it? Thanks guys.

  3. #13
    ph2ocraft's Avatar
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    It's in the tech section.

  4. #14
    polarisnut, mind if i ask from you the pattern for the impeller pitch gauge?

  5. #15
    Moderator beerdart's Avatar
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    Last edited by beerdart; 08-09-2008 at 05:31 AM.

  6. #16

  7. #17
    saf's Avatar
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    Quote Originally Posted by ph2ocraft View Post
    Something that I have always wondered.
    How is ti that you can use a wrench to change the impeller pitch BUT the water won't change it over time?
    Ive wondered this aswell.

    The blade of the impeller is cast and its on its own tension. If you bend it, it will surely have some memory to want to spring back and water pressure maybe just that factor to push it back as its now stretched.

    Plus, your pulling it away from the pump on the trailing edge no ?. Clearance same before and after ?.

  8. #18
    PolarisNut's Avatar
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    Quote Originally Posted by saf View Post
    Ive wondered this aswell.

    The blade of the impeller is cast and its on its own tension. If you bend it, it will surely have some memory to want to spring back and water pressure maybe just that factor to push it back as its now stretched.

    Plus, your pulling it away from the pump on the trailing edge no ?. Clearance same before and after ?.
    You have to bend the metal past its yield point, then it will hold. Try bending an impeller once...you wont believe how much effort it actually takes. This isn't spring steel we're talking about here...It doesn't have much memory.

  9. #19
    saf's Avatar
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    Quote Originally Posted by PolarisNut View Post
    You have to bend the metal past its yield point, then it will hold. Try bending an impeller once...you wont believe how much effort it actually takes. This isn't spring steel we're talking about here...It doesn't have much memory.
    Hey there PN, Yes of course i understand this, i am a fabricator of raceparts for imports nowadays and work with stainless, CR-MO, alu, etc every day.

    I realise it doesnt have much memory (some it will have) and i bet its tensile strength would be high in that it would rather snap a blade at a lot of stress than bend, but to bend a casting of sorts, or anything under a lot of tension (ie a wrap around blade) as you say past its yeild point, your stretching the metal on the outside and condensing it on the inside of the bend. Most metals will natrually with opposite resistance/load (water flow) will want to return the stretch under severe load to its former self with much less tensile strength.

    Not that im doubting your method, as ive said, its made me think in the past. I guess you can prove the theory by bending one, feeling the diff .. leaving it and then after your very used to it, go back in with a new prop of the original pitch and see if you now feel the same difference. That would mean under pressure it would hold its corrected pitch.

    But hey, ive not done it, if you say it works, ill buy that. If anything its made discussion

  10. #20

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    they won't bend back by themselves, once it is bent it stays that way unless of course you bend on it again

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