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Muffling a Welder/Generator

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  • #16
    Boat exhausts are design intended to work that way there is no other muffler. There are often reverse flow check valves incorperated into the system . (on inboard /outboard ) designs. True outboards often exhaust just at the waterline with the total motor exhaust component vertical above it. Older engines exhaust through the propeller using the water flow to pull the exhaust out creating a higher through flow rate and increasing the power output . The engine -exhaust - waterline relationship is in fact totally controlled by the manufacturer . The installer must select the correct shaft length on the engine and mount the motor correctly or the complete boat - motor package will not work.

    During my high school and early colledge years I worked as a marine mechanic and saw a lot of i/o engines from volvo 4 cyl to chev/ford bigblocks destroyed by problems with the under water exhausts. These companys have learned how to make and install them properly but it took several years before they were really reliable.

    On to general engine useage.

    With the existing muffler in place when you add any extra exhaust components and you must increase the back pressure .
    The manufacturer selects the muffler for lowest cost plus less than maximum allowable back pressure this will give the best silencing for his dollar . All attempts to improve on that without starting by removing the existing muffler and installing a system that allows more silencing without increasing the back pressure put the engine at risk if your actuall operating conditions exceed the back pressure limit.

    Some information. Sound levels are measured in decibels. This is a logarithmic measurement just like the richter scale for earthquakes. 3 db. is the amount of sound level change that is just noticible to the human ear. 3 db is also 1/2 of the available sound energy. That is why the back pressure /exhaust valve temperatures change so much when you add an additional silencing element that makes a very audible difference.

    Engines work by pumping a voulme of air and adding fuel . The combustion process creates a lot of pressure and heat. When the exhaust valve opens the residual energy in the form of hot expanded gass enters the exhaust system ,. The real trick to silencing is to allow the exhaust gasses to cool inside the exhaust system . When they cool they lose energy and velocity untill at ambient the total volume leaving the pipe is the pumped volume of the engine plus the cool created volume from the burnt fuel (about a 7% increase in volume in a properly running engine) .
    Contact cooling and volume reduction is the main reason water mufflers work well if properly designed .

    We often put upside down pails that fit loosly over exhust pipes on standby sets that must have vertical pipes for noise or fume control. . we do this to prevent the wind from opening the flaps and letting rain in as these flaps can stick open . The pails allows a quick visual confermation that the exhaust flapper is indeed closed, I saw a big unit start with a pail jammed on one of its exhaust pipes. blew it about 50 ft into the air,
    Terry

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    • #17
      I think I disagree on one point. I think the manufacturers will compromise many performance parameters in favor of price.

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      • #18
        Originally posted by newtoit
        I think I disagree on one point. I think the manufacturers will compromise many performance parameters in favor of price.
        Yes I suspect so as well but that does not improve the situation . I know that they never spend more than they have to and am charitable enough to give them the benifit of the doubt . If they under spend they generate a situation that shows up as " *** is known for having that problem".

        Terry

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        • #19
          I started an identical thread a year ago, and between it and this one, there is a surprising similarity. No Miller engineers have given an expert opinion. Or do they even log on anymore after the whole thing with Rock?

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          • #20
            Deleteall asked a very simple question about muffling a small welder/gen set. Maybe we could be of more help if we stayed on that issue.

            No need to get **** or defensive.

            I am, however; in awe of those who are jack and master of all trades.

            A water muffler is efficient, cheap and all that is required is a bit of common sense. No college degree necessary... For a demo blow into a glass of water with a straw.

            Be careful when adding mufflers so the back pressure issue doesn't cause problems. There are low tone mufflers available that would fit your need. In fact, your local welding supply can probably fix you up. The one I have on my Bobcat works well.

            Remember this last deleteall, advice is just that. Its your equipment and your money.

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            • #21
              Hey wait a minute, beware the water muffler lest you offend the anti bubble people. You just can't be making a bubbling noise anywhere you want don't you know.

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              • #22
                I have read that a metal barrel sunk in the ground and full of rocks works well.
                What do I know I am just an electronics technician.

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                • #23
                  Yes it does but it is a lot of work to set up for a temporary location .Terry

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                  • #24
                    That would be true.
                    What do I know I am just an electronics technician.

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                    • #25
                      Noise -- Why worry

                      Don't worry about noise from the welder/generator as long as the boom box--ghetto blasters are cruising the streets you won't even know it's running.
                      Baboom, baboom, thud, rattle thud
                      CW
                      Hobart Handler 135
                      MM 210
                      Lincoln AC 225 Buzz Box
                      Lincoln Ranger 10,000
                      Jack of all trades, master of none; therefore Broke!

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                      • #26
                        Thanks for all the responses.

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                        • #27
                          deleteall, I found that somebody's cast off HD dresser muffler works GREAT on my AEAD, actually sounds a bit like a BMW motorcycle....
                          Welded up the appropriate replacement pipes(which were needed anyway) and mounted off the right side of the welder. Gives you a ready exhaust analysis upon start up!!!
                          Last edited by bullmtl; 01-29-2020, 03:40 PM.

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