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Re: 23hp B&S [90 deg belt drives]

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  • Kev A
    Oil feed on a stock camshaft Briggs has two advantages, one is low compression in the first few turns, second is no sparks until 250 rpm. Reckon oil feed is
    Message 1 of 58 , Apr 2, 2012
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      Oil feed on a stock camshaft Briggs has two advantages, one is low compression in the first few turns, second is no sparks until 250 rpm. Reckon oil feed is round the bearings by the time it fires?

      Rotax keen owners spin with ignition off until oil pressure shows on the gauge, my Vanguard will spinup with a fresh battery cold, but once warm it fires so quickly that it kicks back and stalls the starter, so now am shorting out the mags until the engine is turning enough to carry it over compression.

      This is with no decompressor on the cam, higher compression at 9.5:1 and eight degrees advance more than standard, so not surprising that startup has to be 'managed' a little.

      My fave way to use the vertical shaft would be a PTO adapter off the flywheel to a shaft drive and surplus outboard gearbox, low mounted engine, high mounted prop, make a great trike unit and those gears are built for tons of horsepower. They even have a shearpin or cush drive if you roll it over or strike the prop.

      Cheers
      Kev
    • woody king
      I agree, totally different animals. Have you seen the gears in a OMC 150 foot? They are huge compared to what is in a rotax redrive, even the 912/914. It would
      Message 58 of 58 , Apr 2, 2012
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        I agree, totally different animals. Have you seen the gears in a OMC 150 foot? They are huge compared to what is in a rotax redrive, even the 912/914. It would have to have some hard hours on a test bed to have trust in it, one that could move to give it gyro loads. Even using a 250 or 300 hp foot wouldn't be out of the question, but they are huge and heavy.

        --- On Mon, 4/2/12, Rick Martin <ricknsharons@...> wrote:


        From: Rick Martin <ricknsharons@...>
        Subject: Re: [Small4-strokeEngines] Re: 23hp B&S [90 deg belt drives]
        To: Small4-strokeEngines@yahoogroups.com
        Date: Monday, April 2, 2012, 6:02 PM



         



        Be careful here, totally different harmonics. I see gearbox failure happening very quickly. If we didn't have the power pulses to deal with it would be easy, but you have a constant back-n-forth vibration to deal with. Swinging that large diameter prop in free air is totally different than a small diameter prop in water. Also compare the differences between a four cylinder, two cycle outboard vs. your two cylinder four cycle engine. That is four power pulses per revolution vs. one.

        Rick
        Palmyra, WI

        ----- Original Message -----
        From: woody king
        To: Small4-strokeEngines@yahoogroups.com
        Sent: Monday, April 02, 2012 04:40
        Subject: Re: [Small4-strokeEngines] Re: 23hp B&S [90 deg belt drives]

        I like the idea of using a boat foot for the 90 degree turn!!! Something like a 100-150 hp would hold up for sure, and they are made for constant load. I think you'd have to extend the prop shaft and that would weaken it considerably as far as gyro loads. Another bearing holder could be mounted easy enough, though. Great thought!

        I have a buddy who mounted a 1 hp electric motor onto an old dead outboard foot, he runs a generator for his fishing lights anyway, so he has super smooth propulsion when bow fishing, and can "bump" it. He has a fan motor also, as well as the main 150 outboard. Quite a setup.

        --- On Mon, 4/2/12, Kev A <kevin@...> wrote:

        From: Kev A <kevin@...>
        Subject: [Small4-strokeEngines] Re: 23hp B&S [90 deg belt drives]
        To: Small4-strokeEngines@yahoogroups.com
        Date: Monday, April 2, 2012, 5:29 PM

        Oil feed on a stock camshaft Briggs has two advantages, one is low compression in the first few turns, second is no sparks until 250 rpm. Reckon oil feed is round the bearings by the time it fires?

        Rotax keen owners spin with ignition off until oil pressure shows on the gauge, my Vanguard will spinup with a fresh battery cold, but once warm it fires so quickly that it kicks back and stalls the starter, so now am shorting out the mags until the engine is turning enough to carry it over compression.

        This is with no decompressor on the cam, higher compression at 9.5:1 and eight degrees advance more than standard, so not surprising that startup has to be 'managed' a little.

        My fave way to use the vertical shaft would be a PTO adapter off the flywheel to a shaft drive and surplus outboard gearbox, low mounted engine, high mounted prop, make a great trike unit and those gears are built for tons of horsepower. They even have a shearpin or cush drive if you roll it over or strike the prop.

        Cheers
        Kev

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