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Plotting involute curves

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  • "Insulting people isn't generally regarded as a mark of high intelligence"

    Horse$hit! That's just a myth started by insultees who didn't have a clever comeback to hurl at the insultor.

    A cleverly crafted insult indicates a high degree of intelligence.

    Some of my favorites are attributed to Sir Winston Churchill. I try to remember to recall some of those when I need a laugh.
    Lynn (Huntsville, AL)

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    • Originally posted by lynnl
      *** A cleverly crafted insult indicates a high degree of intelligence. Some of my favorites are attributed to Sir Winston Churchill. ***
      No, the preludes to his insults were mere sophistry. It is a shame that the Knight could not seem to wield his intelligence in a more gentlemanly manner toward the Lady.

      The nature of a man's character, whether beneficent or malicious, determines whether his intelligence is worthy of respect. Whether lewdly propositioning a Lady, or discussing involutes, how we treat others matters.

      Bob

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      • Absolutely! Not all intelligence, nor maybe even most, is worthy of respect.

        In fact, some intelligent people provide a compelling case for post-birth abortion.
        Lynn (Huntsville, AL)

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        • Originally posted by Bob Farr
          ....how we treat others matters.

          Bob
          I make it a point to stay far, far away from contentious threads but I just had to comment on your statement Bob.

          Them there's some words to live by. Should be a Golden Rule or sumthin'.
          Milton

          "Accuracy is the sum total of your compensating mistakes."

          "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

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          • Originally posted by philbur
            So the minimum number of teeth on a gear must be zero

            Phil
            0 tooth gears are the only kind i am good at making.
            North Central Arkansas

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            • I did some more personal experimenting on this since it is very interesting. The gears are quite correctly called spiral gears since they are not a helix. The gears are a 3 dimensional involute curve that run in quadrature, sine against cosine. That forces them to stay in phase as that is the only way the mating angles share the same line of contact.

              The spiral as seen from above is clearly an involute. I didn't make it long enough as it appears that they are actually more than one turn. They have also been modified from a true involute since the section must return to the axis.

              The reason they cannot be considered a helix is because a helix always cuts the axis at the same angle. A 3D involute does not. It is however still a screw since the definition of screw is not specific in that regard.



              Last edited by Evan; 10-22-2010, 04:32 PM.
              Free software for calculating bolt circles and similar: Click Here

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              • Originally posted by Evan
                I did some more personal experimenting on this since it is very interesting. The gears are quite correctly called spiral gears

                It is however still a screw
                Make your fücking mind up.
                They can't be gears some Yeti from the backwoods said so.

                End of the day lowest number of teeth is one regardless of what golden bollocks says

                .
                .

                Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                • You also need to call the patent office and inform them of their mistake.
                  Free software for calculating bolt circles and similar: Click Here

                  Comment


                  • Poor reading comprehension? I even spelled it out in one post. IPC stands for International Patent Classification. Call your patent office.
                    I think my reading comprehensions are better than yours. Because I did not complain about the IPC, about the US-patent offices and their poor quality.

                    But you just had to hit somewhere with your hammer. Aiming is not among your skills, nor hitting the target.

                    So one more nice try and one more failure.

                    Now back to the video:
                    http://www.youtube.com/watch?v=0yVngc21q9A

                    What you came up with, Even, is a funny misunderstanding. You tried to fix it by just making half a turn. Draw your construction with say 3 turns and post it for our amusement. Compare your result with the video.
                    Furthermore, your gear transmits power only by friction. Not exactly what a gear is. Also a nice property is the fact that the angular speed changes.

                    Ah well ...


                    Nick

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                    • For further amusement, this shows how the one-toothed gear works and how John's posted gear can be derived from it. Again, at least one full turn of the helix is essential.

                      Here, you can find the author of the videos.

                      Note how he called the gear (in the YouTube comment).



                      Nick

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                      • Barrington's script, #4

                        A few more weeks pass and there's enough to play with now. I see some problems - sometimes the base circle falls below the root, and sometimes the tooth tips are short of the OD. Feel free to tell me why this is and we'll fix it.

                        Again, Perl is needed to run this. You get it from activestate.com, version 5.10 I believe has the Tk libraries.

                        You'll also need ghostscript, pstoedit, and might as well get Qcad too (if you're needing a basic CAD program). These come from sourceforge.net. Free stuff, no strings.

                        Once again, Barrington's script is at uploading.com. Sorry about that. http://uploading.com/files/cb335c17/Barringtons-04.pl/

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                        • Lodsb - you seem to be expecting rather a lot from a very basic script - if I might quote myself : "Lodsb - Don't get too excited - this is all just 'stream of consciousness' programming - a very long way from decent code or anything useful" ... this wasn't false modesty - it really is very crude !

                          As you've found, a great deal more work would be required to deal with the variations of root/fillet conditions.
                          I see some problems - sometimes the base circle falls below the root
                          Well yes..., but the script was just to give you some ideas and get you started - it didn't cover anywhere near all conditions. - e.g. for a 20؛ pressure angle the base circle will be inside the root circle for gears with more than 40 (I think) teeth. You will need to do the appropriate calculations and also make some decisions on the fillet form you require. This is a 'designed' form rather than 'generated' so it's not written in stone.
                          sometimes the tooth tips are short of the OD.
                          Can't say why this is - might depend on what time is 'sometime'...

                          Cheers

                          .
                          Last edited by Barrington; 11-01-2010, 02:13 PM.

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                          • The fillet is down in the clearance area and since I haven't found any formal rules it will be addressed in be another development phase - probably asking the user to eyeball things, unless there's a real method to use.

                            I'm still looking for dedendum factors to suit 30 degree angles, guessed at it, and thinking that's where I noticed the problem of the tips falling below the OD. You can lean on the spinners and watch the drawing change shape on the fly. The script needs more of them.

                            There are sections in the code defining various dedendum factors based upon pressure angles. I should not have the PA set in a spinbox because that allows one to select odd values like 17.2 degrees, but the code defaults to factors for 20 degrees when it finds angles like that. I'll be changing it.

                            As to the tooth count over 40 causing the base circle to drop below the root diameter, is that normal in the real world? I don't think it's a problem in the math, but more of boundary checking than anything else, eh?

                            The green line here is the base circle in question, for those following along. It "normally" rides a bit higher. You can see the odd wanderings in the root as the script tries to comply:
                            Last edited by Lodsb; 11-01-2010, 04:02 PM.

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