On Thursday, December 16, 2021 5:03:12 PM EST Todd Zuercher wrote: > The pinion pairs are 1 tooth different in size (40 and 41). I think If I > were printing them I would print them as one piece instead of screwing them > together. All three sets of pinions on the triple pinion design, would use > the same angular offsets so all 3 pairs of pinion gears would be identical. > All of the gears use the same module. As to the overall size it is 6" > diameter and less than 2" tall. Other changes I would incorporate would be > adding a ball bearing between the carrier shafts and the pinions.
Definitely on the todo list but it raises the cost considerably. What I have now can be duped if it breaks, for around a tenner, Only bearings are crosman BB's with printed races. $17 for a big 6000 count bottle. PETG at $22/kg roll. By using a 3 phase motor that comes with an 8mm shaft I grind for a much bigger Dflat, no metallic hub, just drive it onto the motor shaft, done. > I have no idea how much scaling down would affect the strength of it. Or > even the overall strength of printed gear sets in general. So which tends > to be stronger printed in plastic larger or smaller gear teeth. I'm in that same boat called curious. Scaling the teeth down also puts more of then in contact so I suspect its probably a wash, Using an eccentric armature idealizes the contact impact by having double the teeth in contact at the same time which should also lengthen the service life. The weak point there is the outer race that transfers the eccentricity of the armature to the inside, smooth face of the loose belt, the wave generator in this parlance. I'm using a loose belt with 60 splines, and my internal gears are 60 and 62 teeth, So my gear ratio is 30/-1. I have code in my hal file which can measure the scale to about 2 places right of the decimal point so I can drive it to about 3 arc-minutes of accuracy, And so far I have used triangles as the splines with a height of around 3mm because they render fairly accurately on my printer. That probably results in a higher wear rate than a true involute gear due to the increased sliding. Its good to clip the tips about 10% to keep them from bottoming against the fillet the printer leaves behind where two triangle bases meet. OTOH one of those has now been running at about 300 revs input speed since the last week of september, sitting on the kitchen counter. No load because I knocked the output gear loose trying to make a fixed length belt work with one too many teeth. This A drive has no provision to move either shaft to tighten the belt, and not enough room to add a tensioning idler. So I'm going to see if there is a magic combo of teeth that will result in a tight enough belt. 23 on the drive and 83 on the chuck axle leaves quite a bit of backlash, but a 24 tooth on the drive was torn out. If push comes to shove, at 60 teeth on the load pulley it will be some smaller, and I will then have room to build an idler pulley & bracket to tighten the belt to just right.. With the 3 or 4 pinion model I think I'd make the pinion carrier in two pieces in order to brace the tops of the posts better since they will want to put the two rings out of phase so some sort of a pillar to lock the top and bottom rings together should be printed to join the rings in the outer gap between the pinions. That would hold the pinion axles vertical even when its loaded to near its breaking point. The pinion carrier itself should float between the sun and outer rings, no bearings except maybe a axial thrust washer/spacer, some sort of a greased fiber. enough to contain any axial thrust and keep the outside edges of the rings from dragging on the housings, > Also different numbers of teeth are possible and still work out to mesh > correctly and can change the overall output ratio. I did a layout with > 1.00 module gears 125/126 tooth rings and 50/51 tooth pinions and it all > meshes the same and is the same overall dimensions as the version that John > printed. This change increased the output ratio to 84:1. > I'm very curious how strong this actually is and where the weak points might > be. Some guesses, possibly wrong, above. Take care and stay well, Todd. > Todd Zuercher > P. Graham Dunn Inc. > 630 Henry Street > Dalton, Ohio 44618 > Phone: (330)828-2105ext. 2031 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/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
