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About to give up on my tachometer.

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  • #16
    A trick to using the cheap photo-tach from harbor freight.

    I was getting odd readings while looking at the chuck while it spun. I put a piece a black tape all the way around the chuck with just a 1/2 inch gap. I got very good readings from that point. Once I marked the dials I put the tach away and have not used it since.

    Dan
    At the end of the project, there is a profound difference between spare parts and extra parts.

    Location: SF East Bay.

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    • #17
      [QUOTE=gr8life]Cheap from LMS-accurate checked it w/ a really good strobe tach-easy to install

      Ummm, if something were to happen to you ......Can I have your stuff? please?

      just kidding, I seen those pictures and well, physicologial changes came about and my wife thought I was looking at porn!!!!!
      I got Nuthin' to sell, Got no fancy machines, just an old G4015 (can't even afford the "Z" at the end) and a willingness to learn and have some fun!

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      • #18
        Easiest if you insist on doing it yourself is to just count 1 pulse per rev and use that to gate a 555 timer that is producing a high frequency pulse stream. Set the counter to count down and then you can make it produce a direct rpm readout by adjusting the 555 pulse rate
        I have a Franken-bandsaw project in the works which involves the frame from a 14 in. woodworking bandsaw and a variable speed drive system. In this case I don't so much care about R.P.M. as F.P.M., and I figured I'd do something along these lines but adapt it to read that.
        "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

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        • #19
          The circuit above is the complete unit and by adjusting the pot on the first 555 it will read in any units you wish from an incoming pulse stream. It's good into the megahertz.

          Add a zero to the number shown.

          Free software for calculating bolt circles and similar: Click Here

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          • #20
            I know the peope at the motor repair shop I been doing business with them for 32 years. I have a small 6 cylinder radial engine that I built I tried my tackometer but could not get a good reading. I took the engine to the motor shop they put a black spot on the flywheel with a black marker then the electronic type tachometer looks at that black spot as it goes past the tach. When the tach read 30,000. RPMs. I freaked out.........that can not be right. They said, yes it is. They double checked by testing a 1725 RPM motor and 3400 RPM motor to prove it was reading right. So we tested my motor again this time 30,110. RPMs.

            Buy one of those new electronic tack gizmos they work great.

            Here is the video.

            http://www.youtube.com/watch?v=1d33uTjTXW8
            Last edited by gary350; 12-18-2010, 10:24 PM.

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            • #21
              The nice thing about the LMS unit is it's ability to read out in sfm, so when reducing large dia. pieces you can keep a constant sfm as the dia. reduces.
              thanks
              ed
              do what works 4u

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