[M] Hurdle hit for harmonic drive

A project log for T^2 Tiles [gd0095]

If a competing company produced a home-use version of Aperture Laboratories Panels.

kelvinakelvinA 05/28/2023 at 11:490 Comments

Yesterday, I was thinking "I know how to model this" and started researching and modelling the new harmonic drive and looking for the components I want to use. I thought 14:1 was a good reduction, and it's coincidental because if I can get over 70% efficiency, I'd get a 10X multiplier of torque. 

It then kind of turned into a goal to:

  1. Only use the same amount of tubes as the amount of teeth a traditional harmonic drive would use.
    1. That means 28 + 26 = 54 tubes, as opposed to the 3D printed designs (mine included) that had both input, flexspline and output teeth. This would be 28 + 26 + 26 = 80 tubes.
  2. Get as many of the high wear or precision contacts to be metal-on-metal as possible. If this is not possible, see if UHMW tape can be applied to the surface.
  3. Only use 2 deep-groove ball bearings.
  4. Ensure flex-spline durability.

Part of these goals were because I did some planning and thought that I could obtain a solution where the tubes slid over a single, solid wave generator:

Here, I was going for a tube-to-tube angle of 30 degrees (which is 60 degrees if you thing of the entire V angle) or less so that there was more resistance to torsional loads. This just so happened to be just-about 25mm, which is an available deep-groove ball bearing inner diameter.

I was still kind of clueless as to how I was going to actually model the design, so I drew up a sketch:

Now, knowing how I needed to model, I started, taking advantages of the coincidence that the Nema14 bump is 22mm, the tube is 1.5mm and the inner diameter of the 6705-2RS is 25mm.

This is where I've been for hours now, because I'm mentally doing simulations and one thing or another isn't working out.

I'll have to do more thinking. I'm both trying to figure out what won't work just as much as what does, because that makes all mental simulations more accurate.