Designing Clock Wheels

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Designing Clock Wheels

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  • #232198
    James Alford
    Participant
      @jamesalford67616

      Rather than hijacking the thread on "First Clock Choice", I thought that I would start a fresh thread.

      A quote from that thread: "James, a 60 tooth wheel will be 48mm diameter at .6 mod and 64mm at .8 mod, the gears just get bigger, take more brass, look a bit large."

      Could someone please explain how the mod size of the cutter relates to the diameter of the gear? From something that I have read elsewhere, a mod 1 cutter used to make to a 60 tooth wheel would have a diameter of 62.76mm (60 X 1) + a constant of 2.76. However, if this is correct, I do not understand how the quote from above is calculated.

      Regards,

      James.

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      #3720
      James Alford
      Participant
        @jamesalford67616
        #232201
        speelwerk
        Participant
          @speelwerk

          This should explain it, **LINK** , Niko

          #232207
          James Alford
          Participant
            @jamesalford67616

            Niko: thank you.

            A quote from a different thread: "James, a 60 tooth wheel will be 48mm diameter at .6 mod and 64mm at .8 mod, the gears just get bigger, take more brass, look a bit large."

            Can anyone explain how the above is calculated? By my understanding of the calculations, I get the following:

            60 tooth wheel 0.6 mod Diameter (60 + 2.76) X 0.6 = 37.66 mm

            60 tooth wheel 0.8 mod Diameter (60 + 2.76) X 0.8 = 50.21 mm

            60 tooth wheel 1 mod Diameter (60 + 2.76) X 0.6 = 62.76 mm

            I am a little confused at present.

            James.

            Edited By James Alford on 29/03/2016 07:47:47

            #232212
            Ian P
            Participant
              @ianp

              Unless I've misunderstood your enquiry the answer is quite simple. The larger the tooth the bigger the wheel and Mod 0.8 is larger than Mod 0.6

              Send off for the HPC (www.hpcgears.com) catalogue, its a mine of useful information and amongst other things shows silhouettes of each gear pitch

              Ian P

              #232213
              John Haine
              Participant
                @johnhaine32865

                To be strictly correct, the modulus is the increment of the pitch circle diameter per extra tooth, so pcd equals no. of teeth times modulus. You then have to add on a bit extra as the pitch circle goes "halfway up" the tooth, which is where the extra 2.76 mm comes from.

                #232215
                JasonB
                Moderator
                  @jasonb

                  Although HPC are good their data is for involute forms not cycloidial, stick with Niko's link for clock and watch gears.

                  Either way I can't see how the figures from the other post were arrived at using either gear form

                  #232216
                  JasonB
                  Moderator
                    @jasonb
                    Posted by John Haine on 29/03/2016 09:25:59:

                    To be strictly correct, the modulus is the increment of the pitch circle diameter per extra tooth, so pcd equals no. of teeth times modulus. You then have to add on a bit extra as the pitch circle goes "halfway up" the tooth, which is where the extra 2.76 mm comes from.

                    "James, a 60 tooth wheel will be 48mm diameter at .6 mod and 64mm at .8 mod"

                    John as those were your figures can you show how you calculated them as they do not come out to what you have just said

                    #232241
                    Ajohnw
                    Participant
                      @ajohnw51620

                      This man may be of help on this and other aspects.

                      **LINK**

                      I didn't check the other link, just assumed it's different. It shows the calculations and a method of doing them.

                      He's removed lots of things from his site since last time I was on it but in terms of cutters it's mostly duplicated elsewhere. Seems he may have more to add at some point.

                      John

                       

                      Edited By Ajohnw on 29/03/2016 11:36:50

                      #232361
                      James Alford
                      Participant
                        @jamesalford67616

                        Thank you for all of the advice and the links: they have made it a lot clearer.

                        Regards,

                        James.

                        Edited By James Alford on 29/03/2016 20:52:08

                        #232377
                        julian atkins
                        Participant
                          @julianatkins58923

                          This is a bit of an aside, but I have in my collection 2 HSS cutters just under 1" dia 1/4" bore marked 34 DP 55-134T, and 42DP 55-134T. As these cutters are now rather expensive I wonder what they would be used for? They came via the late Harry Collett who made some excellent clocks including a Dr J Bradbury Winter Congreve Clock and a very nice Regulator. They all ended up at Bonhams.

                          As Involute cutters I dont know why Harry bought them. It is possible he only used these cutters. He only ever built clocks. The only other gear cutters he had were home made cutters (not fly cutters) for escapement wheels, and very nice they are too which I also have. For pinions he bought old fashioned Pinion Wire.

                          What a very interesting thread! Thank you James for starting it!

                          Cheers,

                          Julian

                          #232385
                          John Haine
                          Participant
                            @johnhaine32865

                            Oops, brain fade I'm afraid Jason! 60 X .6 = 36, 60 X .8 = 48, I should have said. The addendum of 2.76 mm depends on tooth form and that is for cycloidal gears I think. For involute gears the crest circle diameter is (n+2) x modulus for an n tooth gear.

                            #232392
                            James Alford
                            Participant
                              @jamesalford67616

                              John,

                              Thank you for the clarification. I thought that I had misunderstood something.

                              James.

                              #233508
                              Michael Gilligan
                              Participant
                                @michaelgilligan61133

                                Keeping this thread alive:

                                Abbey Clock website has some useful pages about gears

                                … and other items of interest.

                                MichaelG.

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