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Re: Next prop question

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  • Johnny
    Hi Dave: I think compositing is a suitable alternative to metal casting, but in many cases, without proper training an neophyte caster would be setting himself
    Message 1 of 21 , Apr 30, 2013
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      Hi Dave:

      I think compositing is a suitable alternative to metal casting, but in many cases, without proper training an neophyte caster would be setting himself up for failure and lots of wasted materials.

      If adding material is the goal, I would recommend a fibrous nonmetallic product such as fiberglass, carbon fibre, or in a worse case scenario, even certain plant fibers (bamboo?) for short term use.

      Even suspending a framework/latticework of common chicken wire could add additional strength without detracting from the necessary flexibility in the application of this sort.

      John W

      --- In multimachine@yahoogroups.com, "David G. LeVine" <dlevine@...> wrote:
      >
      > On 04/29/2013 09:50 PM, Johnny wrote:
      > > I would suggest that you determine the appropriate pitch, diameter, shaft size, etc, and find a locally available aluminum screw and make a duplicate mold out of silicone, and send it along with casting resin so that the screws could be duplicated hundreds of times, perhaps even creating several boats of this type for this guy's village.
      > >
      > > Reynolds casting materials is a good place to start, they're on the Internet and located in Los Angeles, CA.
      > >
      > > John W
      >
      > John, would it also be wise to consider reinforced composited, like
      > bronze or stainless wool?
      >
      > Dave 8{)
      >
      > --
      >
      >
      > /"Among the many misdeeds of British rule in India, history will look
      > upon the Act of depriving a whole nation of arms as the blackest."/
      >
      > Mohandus Ghandi, An Autobiography, Page 446.
      >
    • Pat
      Hi Barge Pis did not get through (thanks Yahoo!!) Please open a photo folder (let us know which one) and try to upload them there. Very anxious to see them, I
      Message 2 of 21 , Apr 30, 2013
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        Hi Barge

        Pis did not get through (thanks Yahoo!!)

        Please open a photo folder (let us know which one) and try to upload them there.

        Very anxious to see them, I got a Chinese 125cc m/c manual today which did not help much except to learn that most are Honda or Suzuki copies and that some are water cooled.

        Pat

        --- In multimachine@yahoogroups.com, michael broadbent <bargemaster24@...> wrote:
        >
        > Hi Pat,
        >             Trying to send some pictures one shows the mounting boss for power unit
        >
        >
        > ________________________________
        > From: Pat Delany <rigmatch@...>
        > To: "multimachine@yahoogroups.com" <multimachine@yahoogroups.com>
        > Sent: Tuesday, 30 April 2013, 4:00
        > Subject: Re: [multimachine] Re: Next prop question
        >
        >
        >
        >
        >
        >
        > Good points all!!
        >
        > The prop I am going to try to buy (along with the engine to shaft adapter) is the one Thai boat racers use on their 150cc motorcycle engine, long tail boats. I know the pitch will be wrong but 100mph performance is nothing to sneeze at for a motor this small.
        >
        > Pat 
        >
        >
        > ________________________________
        > From: Shannon DeWolfe <sdewolfe@...>
        > To: multimachine@yahoogroups.com
        > Sent: Monday, April 29, 2013 9:03 PM
        > Subject: Re: [multimachine] Re: Next prop question
        >
        >
        >
        >  
        > Pat and all,
        >
        > I have read all the posts concerning the motor and prop design for
        > Jeremmy to try. This is probably the most ambitious project he could
        > possibly tackle. The propeller design is crucial to the success of the plan.
        >
        > I know very little about propellers. But I do know a few things about
        > engines.
        >
        > The 4stroke engine shown in the demo video early-on in this thread has a
        > wide flat torque curve and is governed to about 3200 RPM. A 2stroke
        > scooter motor rated to the same HP will have a very narrow powerband,
        > probably peaking somewhere north of 6000 RPM. The strength of a 2stroke
        > is the ability to rev. You can make a lot of HP from a small motor if
        > you can spin it very fast. But the trade off is no power down low in the
        > RPM range.
        >
        > A prop that works on a 5HP 4stroke will not work on a 2stroke rated at
        > 5HP. The pitch will be too coarse for the scooter motor to overcome. It
        > will not get up to speed to utilize the narrow powerband. If the motor
        > actually gets to it's powerband, the prop will likely cavitate.
        >
        > Will the boat move? Yes. But it will have high fuel consumption and very
        > high wear on the motor.
        >
        > What I am trying to say is, don't copy a prop used on a 4stroke engine.
        > Better to use a prop off of an older 2stroke outboard motor as a
        > starting point -- if one can be found. I haven't seen a small 2stroke
        > outboard motor in a long time. But, if memory serves, the prop pitch was
        > much finer than the prop in the video of the 4stroke on a stick.
        >
        > Of course, if Jeremmy has access to 4stroke scooters this post was
        > useless. ;-)
        >
        > Mr. Shannon DeWolfe
        > --I've taken to using Mr. because my name misleads folks on the WWW. I am a 57 year old fat man.
        >
        > On 4/29/2013 8:50 PM, Johnny wrote:
        > > I would suggest that you determine the appropriate pitch, diameter,
        > > shaft size, etc, and find a locally available aluminum screw
        >
      • David G. LeVine
        ... Whatever else you do, USE A HEAT EXCHANGER with a water cooled engine, do not use raw river water. Dave 8{) -- A word to the wise ain t necessary - it s
        Message 3 of 21 , May 1, 2013
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          On 04/30/2013 10:52 PM, Pat wrote:
          > Very anxious to see them, I got a Chinese 125cc m/c manual today which did not help much except to learn that most are Honda or Suzuki copies and that some are water cooled.

          Whatever else you do, USE A HEAT EXCHANGER with a water cooled engine,
          do not use raw river water.

          Dave 8{)

          --

          "A word to the wise ain't necessary - it's the stupid ones that need the
          advice."

          Bill Cosby
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