Groove for round belt pulleys

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Groove for round belt pulleys

Home Forums General Questions Groove for round belt pulleys

Viewing 25 posts - 1 through 25 (of 27 total)
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  • #208526
    Rainbows
    Participant
      @rainbows

      Anyone know if there is a specific shape I should machine a pulley to accept polyutethan round belts?

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      #24172
      Rainbows
      Participant
        @rainbows
        #208530
        Roderick Jenkins
        Participant
          @roderickjenkins93242

          "Our" Tubal Cain reckons 30-35 degree V up to 1/4" / 6mm, depth 1.25 x cord diameter.

          HTH

          Rod

          #208531
          Michael Gilligan
          Participant
            @michaelgilligan61133

            That's interesting, Rod

            GHT [for the Universal PillarTool] started at 50° included angle, and revised that to 40°

            Looks like it's not too critical.

            MichaelG.

            #208565
            Ian S C
            Participant
              @iansc

              I use 60* for the 3 mm fused belts that I use on my hot air engines, I make the top of the groove about 4 mm.

              Ian S C

              #208566
              Michael Gilligan
              Participant
                @michaelgilligan61133

                Returning to the original question … I think we are all agreed that [except for idler pulleys] the best basic shape is vee groove, truncated if you wish, with an included angle somewhere in the range 30-60 degrees.

                Any advance on that ?

                MichaelG.

                #208589
                Ajohnw
                Participant
                  @ajohnw51620

                  I have seen a round profile at the bottom of the V on older stuff but the modern belts are pretty compressible so it may be tricky to get it right. I think there is info in older copies of Machinery's.

                  As pressure on the belt needs to increase under load I think Tubal Cain's figures make sense. A more acute angle will help with that.

                  One thing I do know is that round belt into a old L1 (light 1) profile as on my Pultra is pretty useless for anything other than very light work on rather small diameters – what ever diameter goes into it.

                  John

                  #208594
                  Michael Gilligan
                  Participant
                    @michaelgilligan61133
                    Posted by John W1 on 20/10/2015 10:57:57:

                    I have seen a round profile at the bottom of the V on older stuff but the modern belts are pretty compressible so it may be tricky to get it right. I think there is info in older copies of Machinery's.

                    .

                    I'm happy to be corrected, but: I think that 'round profile' is just a tidy alternative to truncating the vee [i.e. I believe that the belt is intended to ride on the flanks of the vee, and not touch the profiled bottom]. Idler pulleys, such as those on the BCA are, of course, a different matter; in those, the radius of the belt is smaller than that in the pulley groove, to accomodate some mis-alignment.

                    MichaelG.

                    #208600
                    Gordon W
                    Participant
                      @gordonw

                      Old round belt pulleys were round bottomed, I think that was because they used round leather belts, a higher co. of friction. Modern plastic belting works better with a V groove, I don't know that the angle makes a lot of difference. Last I made was using a threading tool 60 deg. works well, but not high power.

                      #208602
                      Ajohnw
                      Participant
                        @ajohnw51620

                        I think I'll just leave people to figure out what happens when these systems are used under load.

                        ropepulleys.jpg

                        I have seen something similar for leather belting but can't remember where. These are for manilla rope.

                        Anyway it would be tricky to work out on belts with different rates of compression with load but going on the above I would try the English one with no chance of it bottoming. On the other hand the belt coming out of the V may be "sticky"  of the angle is too acute.

                        John

                        Edited By John W1 on 20/10/2015 12:19:41

                        #208603
                        Michael Gilligan
                        Participant
                          @michaelgilligan61133

                          Useful illustration, John

                          Thanks for posting it.

                          MichaelG.

                          .

                          P.S.  I was [slightly] amused to see that both drawings dimension the Radius at the bottom of the groove as a decimal fraction of the Diameter of the rope … Practical, I suppose, but it does seem odd draughting.

                          P.P.S. … More importantly, I note that both varieties have curved faces to the vee.

                          Edited By Michael Gilligan on 20/10/2015 13:12:08

                          #208606
                          Roderick Jenkins
                          Participant
                            @roderickjenkins93242

                            I seem to remember from my old leather belt driven Hobbies fretsaw that the belt tended to mould itself into a V shape. Presumably the same happens with a rope drive. Plastic belts are much more elastic, which may account for some differences in recommended groove profiles.

                            Rod

                            #208608
                            Michael Gilligan
                            Participant
                              @michaelgilligan61133

                              I know what you mean, Rod … but isn't the English language frustrating sometimes !!

                              Plastic belts are much more elastic [and therefore don't exhibit plastic deformation]

                              dont know

                              MichaelG.

                              #208615
                              Ajohnw
                              Participant
                                @ajohnw51620

                                I'd guess TC obtained his views from the English version. Neither are supposed to bottom but I find that hard to believe on the American one.

                                It also mentions that some think curved faces are undesirable.

                                Personally I feel for anything home made that could use a V belt the smaller width ones that SimplyBearings sell are preferable. There are also sewing machine belts of a similar design to these in polyurethane but the drive doesn't seem so strong and the top of the belts are noticeably wider than the top of the V.

                                John

                                Edited By John W1 on 20/10/2015 15:27:50

                                #208623
                                Roderick Jenkins
                                Participant
                                  @roderickjenkins93242
                                  Posted by Michael Gilligan on 20/10/2015 13:42:48:

                                  I know what you mean, Rod … but isn't the English language frustrating sometimes !!

                                  Plastic belts are much more elastic [and therefore don't exhibit plastic deformation]

                                  dont know

                                  MichaelG.

                                  Touché. The decisions about mixing technical English with everyday usage can be sometimes be quite tough. wink

                                  Cheers,

                                  Rod

                                  #208624
                                  Neil Wyatt
                                  Moderator
                                    @neilwyatt

                                    I recall that TC specified the reduced angle because the more own vees were prone to slipping with synthetic belts. It's a problem I anticipate with the Adept when turning large-diameter titanium and tough stainless.

                                    Neil

                                    #208632
                                    Ajohnw
                                    Participant
                                      @ajohnw51620

                                      You can run then really tight Neal. That's why I think it's best to give them a miss, cause unless they are getting towards that they slip with very little load on them.

                                      V belts tend to tighten with load but I do wonder if that happens on the miniature types.

                                      John

                                      #208671
                                      Ajohnw
                                      Participant
                                        @ajohnw51620

                                        I knew I had seen round grooved pulleys some where – HPC catalogue. Specially for polyurethane belting.

                                        John

                                        #208674
                                        Michael Gilligan
                                        Participant
                                          @michaelgilligan61133
                                          Posted by John W1 on 20/10/2015 22:42:36:

                                          I knew I had seen round grooved pulleys some where – HPC catalogue. Specially for polyurethane belting.

                                          .

                                          Thanks, John … I didn't know they did those

                                          Shame about the prices though. surprise

                                          MichaelG.

                                          #208704
                                          Ian S C
                                          Participant
                                            @iansc

                                            Went out to the workshop and had a quick look at the Super Adept, the angle of the Vs on the pulleys ranges from about 90* on the lathe, to about 75* on the jack shaft, I know the motor pulley is 60*, because I made that one, I run 5 mm polyurethane belts.

                                            Ian S C

                                            #221847
                                            Roderick Jenkins
                                            Participant
                                              @roderickjenkins93242
                                              Posted by Michael Gilligan on 20/10/2015 13:42:48:

                                              I know what you mean, Rod … but isn't the English language frustrating sometimes !!

                                              Plastic belts are much more elastic [and therefore don't exhibit plastic deformation]

                                              BBC website today **LINK**

                                              smiley

                                              Rod

                                              #221848
                                              Michael Gilligan
                                              Participant
                                                @michaelgilligan61133

                                                Cheers, Rod

                                                MichaelG.

                                                .

                                                P.S. … The closing line is a little unfortunate, because most 'plastic forks' are made from polystyrene [or similar], which can't be remelted. 

                                                Edited By Michael Gilligan on 20/01/2016 12:05:06

                                                #221863
                                                Jeff Dayman
                                                Participant
                                                  @jeffdayman43397

                                                  Ah, polystyrene most certainly CAN be remelted, as can all thermoplastics. Thermosets are the ones that can not be remelted, such as phenolics ( Tufnol is one brand) and epoxy. JD

                                                  #221867
                                                  Michael Gilligan
                                                  Participant
                                                    @michaelgilligan61133
                                                    Posted by Jeff Dayman on 20/01/2016 14:11:48:

                                                    Ah, polystyrene most certainly CAN be remelted, as can all thermoplastics. Thermosets are the ones that can not be remelted, such as phenolics ( Tufnol is one brand) and epoxy. JD

                                                    .

                                                    Apologies, Jeff

                                                    Thanks for the correction.

                                                    blush MichaelG.

                                                    #221872
                                                    Chris Evans 6
                                                    Participant
                                                      @chrisevans6

                                                      My 1933 copy of "Fowlers" machinists handbook states. "There is no drive as efficient as a rope drive"

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