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Pully-to-pulley distance varies by step

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  • upand_at_them
    My Delta 4x6 has pulleys that result in different pulley-to-pulley distances based on the speed selected. Not really a problem since the tensioner takes up
    Message 1 of 11 , Jun 4 7:38 PM
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      My Delta 4x6 has pulleys that result in different pulley-to-pulley distances based on the speed selected. Not really a problem since the tensioner takes up the slack.

      But are all saws like this?

      I was thinking of some quick-release tensioner mechanism, but it would only work if the step distances are the same. So I'd have to machine a new pulley.

      Mike
    • Joe R
      Mike The pulleys on my red HF saw are the same (bores are different though). That allows the belt to be slipped between the different grooves. Joe R ... From:
      Message 2 of 11 , Jun 5 3:12 AM
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        Mike

        The pulleys on my red HF saw are the same (bores are different though). That
        allows the belt to be slipped between the different grooves.

        Joe R

        ----- Original Message -----
        From: "upand_at_them" <upand_at_them@...>
        To: <4x6bandsaw@yahoogroups.com>
        Sent: Friday, June 04, 2010 10:38 PM
        Subject: [4x6bandsaw] Pully-to-pulley distance varies by step


        > My Delta 4x6 has pulleys that result in different pulley-to-pulley
        > distances based on the speed selected. Not really a problem since the
        > tensioner takes up the slack.
        >
        > But are all saws like this?
        >
        > I was thinking of some quick-release tensioner mechanism, but it would
        > only work if the step distances are the same. So I'd have to machine a
        > new pulley.
        >
        > Mike
        >
        >
        >
        >
        > ------------------------------------
        >
        > Yahoo! Groups Links
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        >
        >
        >
        >
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        >
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      • upand_at_them
        Hmm...Now that I think about it...Even if the pulleys are the same there s no guarantee of equal lengths. Steps 1 and 3, yes, because that s X-Y and Y-X. But
        Message 3 of 11 , Jun 5 7:54 AM
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          Hmm...Now that I think about it...Even if the pulleys are the same there's no guarantee of equal lengths. Steps 1 and 3, yes, because that's X-Y and Y-X. But step 2, that could have a different circumference from the others.

          Time to take some measurements and fire up the Excel.

          One reason I'm complaining about this aspect of my saw is that the motor doesn't always sit in the same place for each speed and I often have a helluva time using that tensioner bolt...It hits the motor casing.

          --- In 4x6bandsaw@yahoogroups.com, "Joe R" <jromas@...> wrote:
          >
          > Mike
          >
          > The pulleys on my red HF saw are the same (bores are different though). That
          > allows the belt to be slipped between the different grooves.
        • Joe R
          The 3 speeds give 80, 120 and 200 Feet Per Minute on my HF saw are if that s any help. Joe ... From: upand_at_them To:
          Message 4 of 11 , Jun 5 1:56 PM
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            The 3 speeds give 80, 120 and 200 Feet Per Minute on my HF saw are if
            that's any help.

            Joe

            ----- Original Message -----
            From: "upand_at_them" <upand_at_them@...>
            To: <4x6bandsaw@yahoogroups.com>
            Sent: Saturday, June 05, 2010 10:54 AM
            Subject: [4x6bandsaw] Re: Pully-to-pulley distance varies by step


            > Hmm...Now that I think about it...Even if the pulleys are the same there's
            > no guarantee of equal lengths. Steps 1 and 3, yes, because that's X-Y and
            > Y-X. But step 2, that could have a different circumference from the
            > others.
            >
            > Time to take some measurements and fire up the Excel.
            >
            > One reason I'm complaining about this aspect of my saw is that the motor
            > doesn't always sit in the same place for each speed and I often have a
            > helluva time using that tensioner bolt...It hits the motor casing.
            >
            > --- In 4x6bandsaw@yahoogroups.com, "Joe R" <jromas@...> wrote:
            >>
            >> Mike
            >>
            >> The pulleys on my red HF saw are the same (bores are different though).
            >> That
            >> allows the belt to be slipped between the different grooves.
            >
            >
            >
            >
            > ------------------------------------
            >
            > Yahoo! Groups Links
            >
            >
            >
            >
            >
            >
            >
            > =======
            > Email scanned by PC Tools - No viruses or spyware found.
            > (Email Guard: 7.0.0.18, Virus/Spyware Database: 6.15150)
            > http://www.pctools.com/
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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 5 of 11 , Jul 3, 2010
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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 6 of 11 , Jul 5, 2010
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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 7 of 11 , Jul 5, 2010
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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 8 of 11 , Jul 6, 2010
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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 9 of 11 , Jul 6, 2010
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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 10 of 11 , Jul 6, 2010
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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 11 of 11 , Jul 6, 2010
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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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