On 7/15/22 02:46, mikeonenine@web.de wrote: > Eureka! Sweet! But I wonder how long the belt would last in the real world. > > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org Cheers, Gene Heskett. -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author, 1940) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/>

Very nicely done! On 7/15/2022 2:42 AM, mikeonenine@web.de wrote: > > Eureka! > > > > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org

On Fri, Jul 15, 2022 9:52 AM gene heskett wrote: Sweet! But I wonder how long the belt would last in the real world. On Fri, Jul 15, 2022 10:19 AM jon wrote: Very nicely done! Thank you for the kind words! And I was never any good at maths and have no programming background. But such knowledge would only have been a hindrance, because when you cross a toothed belt, you find yourself in a topsy-turvey world where familiar rules no longer apply and nothing is as it seems. If you set both radii to, say r=50, you get one curve with r=50 and the other with about r=80. So what do you do? Divide the second one by 1.6, right? WRONG! Silly boy (slap on the wrist). Outch! You MULTIPLY it by 1.6! And if you want both curves with r=30, what do you do? Er, multiply the bigger one by 1.6, right? WRONG AGAIN! Silly boy (another slap on the same wrist). Outch\*2! You multiply by THREE POINT ONE! Above r=75, however, things are a bit more normal, though still not completely so. Should you innocently decide to adjust the length of the straight runs, everything will go all over the place and you will have to start again from scratch. The program is severely challenged by a crossed belt. Getting different things to move at the right speed requires judicious application of the Stradivarius\* factor to $t in each case and to related parameters. Though there are considerable constraints on the available possibilities, it is nevertheless possible to get a worthwhile animation. In the real world, a crossed belt would of course benefit from something that separates the runs where they cross – a metal plate or, better still, a pair of needle rollers. Belts usually require a tensioner, too. \* Remember Stradivarius, the greatest maker of fiddles of all time?

Actually what you should really do for a different geometry is work out the math for the new geometry. That model was not designed to make a crossed belt, so I'm a little surprised you were able to trick it into doing so. On Fri, Jul 15, 2022 at 6:26 PM <mikeonenine@web.de> wrote: > > On Fri, Jul 15, 2022 9:52 AM gene heskett wrote: > > Sweet! But I wonder how long the belt would last in the real world. > > > On Fri, Jul 15, 2022 10:19 AM jon wrote: > > Very nicely done! > > > Thank you for the kind words! > > And I was never any good at maths and have no programming background. But such knowledge would only have been a hindrance, because when you cross a toothed belt, you find yourself in a topsy-turvey world where familiar rules no longer apply and nothing is as it seems. If you set both radii to, say r=50, you get one curve with r=50 and the other with about r=80. > > So what do you do? > > Divide the second one by 1.6, right? > > WRONG! Silly boy (slap on the wrist). > > Outch! > > You MULTIPLY it by 1.6! And if you want both curves with r=30, what do you do? > > Er, multiply the bigger one by 1.6, right? > > WRONG AGAIN! Silly boy (another slap on the same wrist). > > Outch*2! > > You multiply by THREE POINT ONE! > > Above r=75, however, things are a bit more normal, though still not completely so. > > Should you innocently decide to adjust the length of the straight runs, everything will go all over the place and you will have to start again from scratch. The program is severely challenged by a crossed belt. > > Getting different things to move at the right speed requires judicious application of the Stradivarius* factor to $t in each case and to related parameters. Though there are considerable constraints on the available possibilities, it is nevertheless possible to get a worthwhile animation. > > In the real world, a crossed belt would of course benefit from something that separates the runs where they cross – a metal plate or, better still, a pair of needle rollers. Belts usually require a tensioner, too. > > * Remember Stradivarius, the greatest maker of fiddles of all time? > > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org

Adrian Mariano wrote: > Actually what you should really do for a different geometry is work > out the math for the new geometry. That model was not designed to > make a crossed belt, so I'm a little surprised you were able to trick > it into doing so. . . . and tidy it up so that “center = true”. Which language does the script use? Maybe I can get on a crash course. No trickery is involved, just a parameter: angle. The tricky bit is sorting out the mess afterwards.