How about a totally different tack. I was thinking about this some and might possibly have an idea (probably not an original one and I'm sure there is good reason it isn't done this way) that could eliminate the need for flexing parts completely. What if you used two outer ring gears of the same diameter one with one fewer teeth. Then have 4 sets of planetaries stacked in pairs. Each pair would be pinned together so they turn as one. The first set would have the teeth aligned so it would be in effect a double thickness gear and would bridge between both ring gears. The 2nd set opposite the double gear would be pinned with the teeth 90dgrees out of phase. And the other two pairs would be pinned together in their respective positions halfway between the other two.
I think these pinned together planetary gears would serve the same purpose as the wave gear/belt in the conventional harmonic drive, with one turn of the carrier advancing the driven ring gear one tooth relative to the fixed ring. You would need to play a little loose with the teeth profiles to make it work though, so I'm not too sure how much backlash that might introduce. And I don't have means to easily model or print it to test. Todd Zuercher P. Graham Dunn Inc. 630 Henry Street Dalton, Ohio 44618 Phone: (330)828-2105ext. 2031 -----Original Message----- From: John Dammeyer <jo...@autoartisans.com> Sent: Thursday, December 02, 2021 2:45 PM To: 'Enhanced Machine Controller (EMC)' <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] Harmonic Drive [EXTERNAL EMAIL] Be sure links are safe. Of course I hit send before I thought it through as the dog is bugging me non stop for a doggy walk. Those darn pivots interfere with each other. Disks can't be larger than the distance from the peak of the ellipse to the pivot point of the other disk. And we're back to a small contact area. John > -----Original Message----- > From: John Dammeyer [mailto:jo...@autoartisans.com] > Sent: December-02-21 11:33 AM > To: 'Enhanced Machine Controller (EMC)' > Subject: Re: [Emc-users] Harmonic Drive > > Half size won't quite work if you want a stub lining up with the cup. > But actually that is an interesting idea. > I'm sure the exact numbers could be determine mathematically but it > was easier to play with dimensions using the drawing tools. If the > disks that slip over the bearings were stacked to interleave then the > attached sketch shows roughly what size you'd need. Any larger and they > exceed the elliptical shape at the smaller diameter. > John > > > > > -----Original Message----- > > From: Chris Albertson [mailto:albertson.ch...@gmail.com] > > Sent: December-02-21 9:41 AM > > To: Enhanced Machine Controller (EMC) > > Subject: Re: [Emc-users] Harmonic Drive > > > > Yes, 16 mm bearing can't help. I think what would be best is to use two > > bearing and make them half the diameter of the inside of the cup. > > That would be the largest possible size that would still fit. > > > > That said, why not make a large size bearing from a small one by > > slipping a plastic disk over you 16mm bearing to make it's effective > > u > > > > Once I thought of slipping a disk over a bearing to make the bearing half > > the diameter of the cup. Then I think "Why can't the diameter of the > > plastic bearing overlap. Cut groves in each disk? (really now it is a > > plastic "tire" mounted on a bearing) You might get a "tire" diameter that > > is 60% of the cup diameter and still use smaller skateboard bearings > > > > > > > > On Wed, Dec 1, 2021 at 9:37 PM John Dammeyer <jo...@autoartisans.com> wrote: > > > > > Broke the first cup. It's possible that a few times I didn't > > > insert it right because the holes didn't line up well so I might > > > well have begun the crack which then escalated. If it's inserted > > > off axis it's hard to get it into position and if it even turns is > > > very rough. Get it right and it's quite smooth. > > > > > > There are several issues. First of all a tiny vertical piece of > > > the root of the tooth broke off. I think that happened first. > > > Then the pressure of the bearings sheared the cup along one of the print > > > layers. > > > > > > So first weak spot of course the print layers and the plastic > > > probably never really bonding past a thin line. I used 0.2mm printing. > > > > > > My smaller 16mm bearing is also a much higher load point than the > > > larger ones used in the belt versions. Even if I'd made the full > > > disk with 10 bearings I don't expect it would have made much of a > > > difference because they just can't get as close together as a real > > > harmonic drive with ball bearings which are also distributing the load > > > over the entire outer race. > > > If anything a larger group of small bearings as close as possible > > > to each other would more accurately duplicate this. > > > > > > https://nam04.safelinks.protection.outlook.com/?url=http%3A%2F%2Fw > > > ww.autoartisans.com%2Fharmonicdrive%2FHarmonicDrive-11.jpg&dat > > > a=04%7C01%7Ctoddz%40pgrahamdunn.com%7C11a6376ee4ce4e304e5608d9b5cc > > > 73b6%7C5758544c573f47cebee96c3e0806fb43%7C0%7C0%7C6377407119840480 > > > 48%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJ > > > BTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=NEzbqfu%2FydNQ1rFP%2B > > > 0RYHX7yzIsz%2ForUrql3LE8r%2BzI%3D&reserved=0 > > > > > > This type of flex cup if not made of metal would be better with a > > > cross hatch carbon fibre in flexible epoxy. > > > > > > John > > > > > > > > > > > > > > > > > > _______________________________________________ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2F > > > lists.sourceforge.net%2Flists%2Flistinfo%2Femc-users&data=04%7 > > > C01%7Ctoddz%40pgrahamdunn.com%7C11a6376ee4ce4e304e5608d9b5cc73b6%7 > > > C5758544c573f47cebee96c3e0806fb43%7C0%7C0%7C637740711984048048%7CU > > > nknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6I > > > k1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=cGqsmIcKaaFXQEuCtM3QjtgdmqZ > > > MqdYhvy%2BmxOEihD0%3D&reserved=0 > > > > > > > > > -- > > > > Chris Albertson > > Redondo Beach, California > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fli > > sts.sourceforge.net%2Flists%2Flistinfo%2Femc-users&data=04%7C01% > > 7Ctoddz%40pgrahamdunn.com%7C11a6376ee4ce4e304e5608d9b5cc73b6%7C57585 > > 44c573f47cebee96c3e0806fb43%7C0%7C0%7C637740711984048048%7CUnknown%7 > > CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJ > > XVCI6Mn0%3D%7C3000&sdata=cGqsmIcKaaFXQEuCtM3QjtgdmqZMqdYhvy%2Bmx > > OEihD0%3D&reserved=0 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
