Here's a bit of an addendum with respect to the HGD_EWG version. The wheels are mounted on an ellipse and as close as possible to each other. http://www.autoartisans.com/harmonicdrive/HarmonicDrive-29.jpg They are just close enough to create zero backlash across the opposite wheels which hold the cup in the ellipse form. The center gear (100T 1.25 module) is fixed to the frame and doesn't turn. The center shaft is fixed to the cup and runs in 1" ID tapered trailer bearings. Eventually this will be metal.
The motor drives the outer cup which holds the bearings and you can see that the pressure on the cup is now on the shallow part of the ellipse rather than the peak resulting in way less tension on the cup. It's formed around the gear in the same way a drive belt goes around a toothed pulley. So proper involute teeth can be used or even rubber belt teeth forms. The outer cup is located with bearings located in the output shaft so it all stays concentric. Compared to the smaller internal wave generator which has some resistance to turning this one can have the bearing cup spun with a finger tip and you still can't hold back the output shaft. Ratio is 36:1 with the 70 and 72T forms and direction is the same as the motor. This also turns more easily than Todds dual ring gear and triple pulley but to be fair, I don't have any ball bearings or support structure on that one yet. John > From: John Dammeyer [mailto:jo...@autoartisans.com] > What I also found was that with the cup, (don't know about the belts), is > that even a very thin cup flexes in a way that only the 3 > bearings at the top of the ellipse contact the cup. The other two are > redundant and the reason they are there is because the original > designer I don't think knew any better. > > So although I printed a wave generator that used all the wheels I did some > detailed inspection and I cannot see them ever > contacting. The cup is different from the belt perhaps? Maybe the belt > could be held in place by the extra wheels but the cup is way > too stiff for that. > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
