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  • ration question on sprockets

    I need to transform 400 rpm's of a 50mm sprocket down to roughly 8 rpm's.

    I think I will need to do it in two stages. Is it better to try to match the ratio's over the two stages or do one larger ratio and one smaller? I would like to use 1/2 " pitch X 5/16's roller chain.

    So if I start with my 50mm sprocket what size sprockets would you use for the other three?
    Location: The Black Forest in Germany

    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

  • #2
    400 rpm in and roughly 8 rpm out translates to 50:1 reduction.

    2" small sprocket (+/- 12 teeth at 1/2 pitch) and 14" (84 teeth at 1/2" pitch) large sprockets will give 7:1 reduction each

    7x7=49 or "roughly" 50:1

    The next question is what is available from your supplier. Sprockets selection with more than 50 teeth at my supplier seem to be a bit sparse...
    Design to 0.0001", measure to 1/32", cut with an axe, grind to fit

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    • #3
      I considered changing my V belt drive system on my bandsaw to a chain & sprocket. After I looked at the necessary sprockets & chain along with the required modifications and costs I also looked at a reduction gear box. It turned out this was the less expensive and simplest modification. In addition it is quieter and does not need the guarding a chain & sprocket system should have. In the long term it also requires a lot less maintenance.

      You may want to look at https://www.surpluscenter.com/home.asp for either your sprockets or a gear box.

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      • #4
        I can get almost any size I need.

        Readily available is a sprocket 313mm and 385mm in the pitch and width I need.

        I ordered the switch I need to control the motor today. Ouch. It is a two pedal momentary switch. left pedal runs the motor ccw, right pedal runs the motor cw.

        I think when I test this on a live sheep I will use my neighbors sheep! Or do any of you know where I can buy a blow up sheep?
        Location: The Black Forest in Germany

        How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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        • #5
          FWIW, a vee belt reduction can serve as a torque limiter as well as one of the reduction steps...
          Design to 0.0001", measure to 1/32", cut with an axe, grind to fit

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          • #6
            This motor and reduction is for the pivot arm of my leg restraints on my sheep shearing machine. The motor will only have to run very intermittently and turn the pivot arm from perpendicular 90 degree's each direction. Definitely going to need some limit switches. I don't want my sheep coming of the machine looking like corksrews!
            Location: The Black Forest in Germany

            How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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            • #7
              Originally posted by Black Forest
              Definitely going to need some limit switches. I don't want my sheep coming of the machine looking like corksrews!

              that one would be for sunday supper i would guess. . . . .

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              • #8
                Originally posted by Black Forest
                I Or do any of you know where I can buy a blow up sheep?
                I am sure Australians would have some of those!

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                • #9
                  Blackforest---I hope you bought a gearmotor with an internal brake like I suggested. Those gearmotors coast a lot. You may end up with pretzel-sheep.
                  Brian Rupnow

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                  • #10
                    Originally posted by The Artful Bodger
                    I am sure Australians would have some of those!
                    Oh the irony

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                    • #11
                      Brian, I took your suggestion and bought a motor with a brake!
                      Location: The Black Forest in Germany

                      How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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