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Re: Pully-to-pulley distance varies by step

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  • upand_at_them
    Okay, a little followup... First, thanks for posting that, Joe. Haven t used the RPMs yet, but probably will soon. Here s my problem again: I m looking to
    Message 1 of 11 , Jul 3 3:53 PM
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      Okay, a little followup...

      First, thanks for posting that, Joe. Haven't used the RPMs yet, but probably will soon.

      Here's my problem again:

      I'm looking to make some sort of quick-release for speed changes. I usually use the same speed all the time because of the hassle of changing it. The swivel bolt bumps into the motor, depending on the speed selected, making it difficult to loosen/tighten.

      I measured the pulley circumference for each step on each pulley and took half the circumference of one plus half the circumference of the other. Distance should be the same (or close) for each of the three speeds. I measured at the outer diameter where the outside of the belt sits.

      _______Driven pulley Drive pulley half circum + half circum
      Step 1 3.702" 1.886" 8.777"
      Step 2 2.914" 2.200" 8.033"
      Step 3 2.168" 2.594" 7.480"

      So this explains why the motor doesn't sit in the same place for each speed setting. I bet the pulleys were originally machined to a spec, but Chinese copies were just cast and then cleaned up on the lathe.

      Mike


      --- In 4x6bandsaw@yahoogroups.com, "Joe R" <jromas@...> wrote:
      >
      > The 3 speeds give 80, 120 and 200 Feet Per Minute on my HF saw are if
      > that's any help.
      >
      > Joe
    • Joe R
      Mike. Interesting! I measured my pulley diameter sizes, outer most area of the flanges, and found the pulleys are not like also. They may not be completely
      Message 2 of 11 , Jul 5 5:00 PM
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        Mike.

        Interesting! I measured my pulley diameter sizes, outer most area of the
        flanges, and found the pulleys are not like also. They may not be completely
        accurate but close (I didn't remove the guard)

        Motor
        1.65"
        2.09"
        2.53"

        Driven
        2.06"
        2.60"
        2.99"

        However one thing I remember is the original belt didn't fit and I bought a
        3L220 and it works perfectly One tension setting and there's enough "give"
        in the mount that all three steps are ok.

        As I remember with the original belt the motor would not swing close enough
        in the slot in the rear of the belt guard to put the belt on and it was
        roughly one inch shorter then the 22" one I put on. I bought one later for
        my son and had no problem?????

        Joe

        ----- Original Message -----
        From: "upand_at_them" <upand_at_them@...>
        To: <4x6bandsaw@yahoogroups.com>
        Sent: Saturday, July 03, 2010 6:53 PM
        Subject: [4x6bandsaw] Re: Pully-to-pulley distance varies by step


        > Okay, a little followup...
        >
        > First, thanks for posting that, Joe. Haven't used the RPMs yet, but
        > probably will soon.
        >
        > Here's my problem again:
        >
        > I'm looking to make some sort of quick-release for speed changes. I
        > usually use the same speed all the time because of the hassle of changing
        > it. The swivel bolt bumps into the motor, depending on the speed
        > selected, making it difficult to loosen/tighten.
        >
        > I measured the pulley circumference for each step on each pulley and took
        > half the circumference of one plus half the circumference of the other.
        > Distance should be the same (or close) for each of the three speeds. I
        > measured at the outer diameter where the outside of the belt sits.
        >
        > _______Driven pulley Drive pulley half circum + half circum
        > Step 1 3.702" 1.886" 8.777"
        > Step 2 2.914" 2.200" 8.033"
        > Step 3 2.168" 2.594" 7.480"
        >
        > So this explains why the motor doesn't sit in the same place for each
        > speed setting. I bet the pulleys were originally machined to a spec, but
        > Chinese copies were just cast and then cleaned up on the lathe.
        >
        > Mike
        >
        >
        > --- In 4x6bandsaw@yahoogroups.com, "Joe R" <jromas@...> wrote:
        >>
        >> The 3 speeds give 80, 120 and 200 Feet Per Minute on my HF saw are if
        >> that's any help.
        >>
        >> Joe








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      • upand_at_them
        Yes, interesting. I did your half circumference calculations and yours is nearly identical for each step: 7.288 7.366 7.209 Total variance of only
        Message 3 of 11 , Jul 5 6:17 PM
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          Yes, interesting. I did your "half circumference" calculations and yours is nearly identical for each step:

          7.288"
          7.366"
          7.209"

          Total variance of only 0.157". Mine is 1.297". Wow, the Chinese did a better job on yours than Delta did with mine.

          I may have a go at turning a new pulley, or remachining one, to get better center-to-center distances.

          --- In 4x6bandsaw@yahoogroups.com, "Joe R" <jromas@...> wrote:
          >
          > Mike.
          >
          > Interesting! I measured my pulley diameter sizes, outer most area of the
          > flanges, and found the pulleys are not like also. They may not be completely
          > accurate but close (I didn't remove the guard)
          >
          > Motor
          > 1.65"
          > 2.09"
          > 2.53"
          >
          > Driven
          > 2.06"
          > 2.60"
          > 2.99"
          >
          > However one thing I remember is the original belt didn't fit and I bought a
          > 3L220 and it works perfectly One tension setting and there's enough "give"
          > in the mount that all three steps are ok.
          >
          > As I remember with the original belt the motor would not swing close enough
          > in the slot in the rear of the belt guard to put the belt on and it was
          > roughly one inch shorter then the 22" one I put on. I bought one later for
          > my son and had no problem?????
          >
          > Joe
        • zero_kay
          @upand_at_them: not to pick nits, but you ve calculated the total range (max - min), not the variance. by variance , you probably meant variability, or more
          Message 4 of 11 , Jul 6 8:34 AM
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            @upand_at_them:
            not to pick nits, but you've calculated the total range (max - min), not the variance.
            by "variance", you probably meant variability, or more specifically total range. but in mathematical/statistical terms, variance has a different & distinct meaning. the variance of a group of numbers is a measure of central tendency/dispersion, and is the standard deviation squared. the standard deviation is the root mean square of the deviations of each number from the arithmetic mean of the group.
            the variance of the group of 3 numbers given is 0.006".
            cheers,
            -z
            --- In 4x6bandsaw@yahoogroups.com, "upand_at_them" <upand_at_them@...> wrote:
            >
            > Yes, interesting. I did your "half circumference" calculations and yours is nearly identical for each step:
            >
            > 7.288"
            > 7.366"
            > 7.209"
            >
            > Total variance of only 0.157". Mine is 1.297". Wow, the Chinese did a better job on yours than Delta did with mine.
            >
            > I may have a go at turning a new pulley, or remachining one, to get better center-to-center distances.
            >
            > --- In 4x6bandsaw@yahoogroups.com, "Joe R" <jromas@> wrote:
            > >
            > > Mike.
            > >
            > > Interesting! I measured my pulley diameter sizes, outer most area of the
            > > flanges, and found the pulleys are not like also. They may not be completely
            > > accurate but close (I didn't remove the guard)
            > >
            > > Motor
            > > 1.65"
            > > 2.09"
            > > 2.53"
            > >
            > > Driven
            > > 2.06"
            > > 2.60"
            > > 2.99"
            > >
            > > However one thing I remember is the original belt didn't fit and I bought a
            > > 3L220 and it works perfectly One tension setting and there's enough "give"
            > > in the mount that all three steps are ok.
            > >
            > > As I remember with the original belt the motor would not swing close enough
            > > in the slot in the rear of the belt guard to put the belt on and it was
            > > roughly one inch shorter then the 22" one I put on. I bought one later for
            > > my son and had no problem?????
            > >
            > > Joe
            >
          • Kurt Laughlin
            You guys seem to be judging quality based upon the lengths of the belt perimeters. What leads you to believe that they were *meant* to be exactly the same in
            Message 5 of 11 , Jul 6 4:53 PM
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              You guys seem to be judging quality based upon the lengths of the belt
              perimeters. What leads you to believe that they were *meant* to be exactly
              the same in all three positions? If the design goal was for the three steps
              to have nice "round" RPMs as outputs, they would almost certainly all be
              different. So long as there is enough range in the tensioning adjustment to
              cover the manufacturing tolerances in the pulleys and standard belts, along
              with a reasonable amount of stretch, what difference does it make? (I
              understand this all came about because of a planned mod. The fact that the
              saw doesn't support that is no reason to say that it is a quality issue.)

              I guess more to the point, would you pay more for a saw with identical belt
              perimeters that used 50% of the adjustment range (under all possible
              conditions) than you would for one that used 75%?

              KL


              ----- Original Message -----
              From: upand_at_them

              Yes, interesting. I did your "half circumference" calculations and yours is
              nearly identical for each step:

              7.288"
              7.366"
              7.209"

              Total variance of only 0.157". Mine is 1.297". Wow, the Chinese did a better
              job on yours than Delta did with mine.

              I may have a go at turning a new pulley, or remachining one, to get better
              center-to-center distances.
            • upand_at_them
              True, but are round RPMs necessary? They certainly didn t end up round the way it is. And I would think they would shoot for close so that they actually do
              Message 6 of 11 , Jul 6 7:54 PM
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                True, but are round RPMs necessary? They certainly didn't end up round the way it is.

                And I would think they would shoot for close so that they actually do fall within the range of the adjustment bolt. Mine's on the border of being unacceptable, since bolt hits the motor on two of the speeds.

                I'm just looking to get them close so that I can work on a quick-release, which needs them all close.

                --- In 4x6bandsaw@yahoogroups.com, "Kurt Laughlin" <fleeta@...> wrote:
                >
                > You guys seem to be judging quality based upon the lengths of the belt
                > perimeters. What leads you to believe that they were *meant* to be exactly
                > the same in all three positions? If the design goal was for the three steps
                > to have nice "round" RPMs as outputs, they would almost certainly all be
                > different. So long as there is enough range in the tensioning adjustment to
                > cover the manufacturing tolerances in the pulleys and standard belts, along
                > with a reasonable amount of stretch, what difference does it make? (I
                > understand this all came about because of a planned mod. The fact that the
                > saw doesn't support that is no reason to say that it is a quality issue.)
                >
                > I guess more to the point, would you pay more for a saw with identical belt
                > perimeters that used 50% of the adjustment range (under all possible
                > conditions) than you would for one that used 75%?
                >
                > KL
              • Larwyn
                I ve never found it to be a problem myself.  My saw earned it s keep today on some 4x3x1/4 angle iron.  For what I paid, I do not expect more. ... From:
                Message 7 of 11 , Jul 6 8:24 PM
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                  I've never found it to be a problem myself.  My saw earned it's keep today on some 4x3x1/4" angle iron.  For what I paid, I do not expect more.

                  --- On Tue, 7/6/10, upand_at_them <upand_at_them@...> wrote:

                  From: upand_at_them <upand_at_them@...>
                  Subject: [4x6bandsaw] Re: Pully-to-pulley distance varies by step
                  To: 4x6bandsaw@yahoogroups.com
                  Date: Tuesday, July 6, 2010, 9:54 PM

                   

                  True, but are round RPMs necessary? They certainly didn't end up round the way it is.

                  And I would think they would shoot for close so that they actually do fall within the range of the adjustment bolt. Mine's on the border of being unacceptable, since bolt hits the motor on two of the speeds.

                  I'm just looking to get them close so that I can work on a quick-release, which needs them all close.

                  --- In 4x6bandsaw@yahoogroups.com, "Kurt Laughlin" <fleeta@...> wrote:
                  >
                  > You guys seem to be judging quality based upon the lengths of the belt
                  > perimeters. What leads you to believe that they were *meant* to be exactly
                  > the same in all three positions? If the design goal was for the three steps
                  > to have nice "round" RPMs as outputs, they would almost certainly all be
                  > different. So long as there is enough range in the tensioning adjustment to
                  > cover the manufacturing tolerances in the pulleys and standard belts, along
                  > with a reasonable amount of stretch, what difference does it make? (I
                  > understand this all came about because of a planned mod. The fact that the
                  > saw doesn't support that is no reason to say that it is a quality issue.)
                  >
                  > I guess more to the point, would you pay more for a saw with identical belt
                  > perimeters that used 50% of the adjustment range (under all possible
                  > conditions) than you would for one that used 75%?
                  >
                  > KL


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