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A little gear help please

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  • #16
    I'm not sure about this particular case but often you can move one of the gears in one axis to get the proper center distance. For example, a camshaft must be directly under the lifter, but the vertical distance could be changed to suit a particular gear set.

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    • #17
      Originally posted by J Tiers View Post

      Bented, what you say appears to be wrong, if I am understanding your statements. You appear to be confusing the OD and the Pitch Diameter.
      Both OD and PD are a function of DP and number of teeth.
      As Machinery's Handbook tells us.

      The PD = # of teeth/the DP
      OD is (# of teeth + 2)/ the DP

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      • #18
        Originally posted by Bented View Post

        Both OD and PD are a function of DP and number of teeth.
        As Machinery's Handbook tells us.

        The PD = # of teeth/the DP
        OD is (# of teeth + 2)/ the DP
        OK.... so what? Nobody is arguing that. Previously you related tooth form to PD, apparently suggesting that they are not proportional, since you said "unfortunately", as if the statement invalidated info in prior postings.

        The OD will not scale exactly, but the PD does, so the C-C distance will only vary depending on the clearance given. The OD for a higher DP will actually be smaller, since the addendum is less.

        In other words, ther is basically no downside other than tooth strength, to doubling the DP and tooth count. The minor C-C issue of clearance is just that, minor.

        Originally posted by Bented View Post
        Unfortunately the pitch diameter is fixed by the tooth form.
        .........
        2801 3147 6749 8779 4900 4900 4900

        Keep eye on ball.
        Hashim Khan


        It's just a box of rain, I don't know who put it there.

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        • #19
          Unfortunately one can not produce any PD required using standard DP's.
          As mentioned by the OP many have 32 DP tooling which will not produce a 1.041 PD with a whole number of teeth.

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          • #20
            Originally posted by johansen View Post
            Modulous 2 gears are an exact fit for your needs. 13 and 26 teeth
            I caught this. Nobody else did?

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            • #21
              There was really nothing to catch.

              The gear module is 1/DP, so a module of 2 mm/tooth is the same as a diametral pitch (DP) of 25.4 (mm/in)/(2mm/tooth) = 12.7 teeth/in

              The OP's center-to-center distance is 1-9/16" with a 2:1 ratio, so the number of teeth on the pinion is N_P = (25/24)*DP

              Using module 2mm/tooth gives the number of teeth on the pinion is (25/24)*12.7 = 13.23 - not gonna work.

              Another way to look at it... the center/center distance is
              (N_G + N_P)/(2*DP) = (N_G + N_P)*mod/2 = (13+26)*(2 mm)/2 = 39 mm = 1.535"... which is not 1.563"
              Last edited by DrMike; 02-12-2021, 10:33 AM.

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              • #22
                Originally posted by Bented View Post
                Unfortunately one can not produce any PD required using standard DP's.
                As mentioned by the OP many have 32 DP tooling which will not produce a 1.041 PD with a whole number of teeth.
                Show me the equation that includes the tooth form.....

                The OP did not mention that. What Brian said is that many have a different DP cutter set available. The 32 is not gonna work, we know that. But starting from 24 DP, the 48 WILL work.

                If you want to preserve every detail, the tooth count, the spacing etc, then you must use the same DP. That's not what is happening here. The DP and tooth count can be doubled. That leaves the C-C distance.

                The spacing is related to the PD and the backlash allowance. The same spacing with a double tooth count and DP will mesh, just not with the same allowance, because the teeth are smaller. The C-C distance might have to change a few thou.

                I think you are just "poking the bear", here. Your "objections" lack any explanation of their basis, and seem to ignore the statements made.
                2801 3147 6749 8779 4900 4900 4900

                Keep eye on ball.
                Hashim Khan


                It's just a box of rain, I don't know who put it there.

                Comment


                • #23
                  Originally posted by brian Rupnow View Post
                  My gear cutters are 24DP. Many people want to build my engines, but have 32 dp or 48 dp gear cutters. If my engine plans call for a 2:1 ratio and 1.563" center distance, this works out fine using a 25 tooth gear and a 50 tooth 24 dp gear. Are there combinations of other gear sets that will still give 2:1 ratio and 1.563" center distance?----Brian
                  Brian you can use 32DP cutters to make 66 and 33 tooth gears if you increase the OD on each gear by 0.0145" using OD's of 2.1396" and 1.1083" respectively. The tooth form changes very little and you gain half a thou clearance between the gears.

                  That is for 20 degree pressure angle gears if you use 14.5 degree gears increase by 0.0137" instead of 0.0145"
                  Peter - novice home machinist, modern motorcycle enthusiast.

                  Denford Viceroy 280 Synchro (11 x 24)
                  Herbert 0V adapted to R8 by 'Sir John'.
                  Monarch 10EE 1942

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                  • #24
                    Originally posted by J Tiers View Post

                    I think you are just "poking the bear", here. Your "objections" lack any explanation of their basis, and seem to ignore the statements made.
                    In the northern hemisphere the published tool and part dimensions work nicely together, if producing gears south of 0° an Equatorial Deviance must be used, .0000001 is close.

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                    • #25
                      Originally posted by DrMike View Post
                      There was really nothing to catch.

                      The gear module is 1/DP, so a module of 2 mm/tooth is the same as a diametral pitch (DP) of 25.4 (mm/in)/(2mm/tooth) = 12.7 teeth/in

                      The OP's center-to-center distance is 1-9/16" with a 2:1 ratio, so the number of teeth on the pinion is N_P = (25/24)*DP

                      Using module 2mm/tooth gives the number of teeth on the pinion is (25/24)*12.7 = 13.23 - not gonna work.

                      Another way to look at it... the center/center distance is
                      (N_G + N_P)/(2*DP) = (N_G + N_P)*mod/2 = (13+26)*(2 mm)/2 = 39 mm = 1.535"... which is not 1.563"
                      It would work if the center distance was 39mm and the gears are perfect. They arent. Backlash is needed.

                      Op asked for a solution. Mod 2 gears are off the shelf and will be functional.

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                      • #26
                        Originally posted by johansen View Post

                        It would work if the center distance was 39mm and the gears are perfect. They arent. Backlash is needed.

                        Op asked for a solution. Mod 2 gears are off the shelf and will be functional.
                        OP asked for a solution for 32DP and 48DP cutters, not Mod 2 cutters. If the end users are going to buy gears, they can just buy the specified gears

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