yes, the hourglass shaped worm would only fit an infinitesmally thin disk of a gear exactly. from my research, such fitting scheme is practiced in conventional worm gear mesh to make alingment of the two rotation axes less critical: an over large radius is used on the gear tooth form with respect to the rotational radius of the mating worm thread. so for an hourglass shaped worm, the contact areas would be maximized at the ends of the worm. that seems okay for a ball worm scheme too.
would the rate of travel of the bearings through a spiral circuit lead to sliding instead of rolling at some point between the large and small diameters of the worm? i want to say no, because the balls are in an idle position between the worm and the stationary track around it. ..the worm would have to have an harmonically varying pitch along its axis. the flexible wave drive has a design advantage of constraning the motion to a plane. --- On Mon, 5/14/12, andy pugh <bodge...@gmail.com> wrote: > From: andy pugh <bodge...@gmail.com> > Subject: Re: [Emc-users] Some advice needed > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Date: Monday, May 14, 2012, 3:11 AM > On 14 May 2012 06:00, charles green > <xxzzb...@yahoo.com> > wrote: > > > i wonder, in the ball worm mechanism, why not make the > worm engagement happen over more like a quarter of the > diameter of the gear. > > This can be done, to an extent, with conventional worms, but > it gets a > bit difficult as eventually you have to teleport the parts > into mesh, > or lose the advantage of increased engagement. (ie, assembly > becomes > impossible). > They are called "enveloping" or "hourglass" worms. I think > David Brown > hold the patents, and market as "Cone Drive" > http://www.directindustry.com/prod/cone-drive-gearing-solutions/worm-gears-16379-491012.html > > I believe that there are drives which use half of the > hourglass to > make assembly easier. > > The ball-worm has an advantage there, as you can put the > balls in > second, and so there isn't the same shape-locking problem. > Where I do > see an issue is in the required tooth profile in the wheel, > which > needs to be correct both at the large ends and small middle > of the > hourglass. My feeling is that the helix angle varies, which > might make > things difficult. (Maybe the angle doesn't change, as the > track > becomes tangential) > > -- > atp > If you can't fix it, you don't own it. > http://www.ifixit.com/Manifesto > > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's > security and > threat landscape has changed and how IT managers can > respond. Discussions > will include endpoint security, mobile security and the > latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
