Rockwheel gearing -- how does it work?

[Daan]

I would like to learn how a 'geared' EUC works. I believe the Gotway' Rockwheel's have gearing right? Does anyone have pictures or a video that shows how this works on the inside?

Thanks!

[esaj]

I think older Gotway MTens were geared, but all other (including newer Mtens) are direct-drive. Rockwheel has geared motors in at least 16" and maybe 14" or 12", others are direct-drive (I think). Never seen a tear down of any geared wheel, so hard to tell exatcly how it works (is the gearing inside the motor or is the motor outside the tire hub?).

Here's a cutaway-picture of some planetary geared brushless DC, but I guess the gearing can be done in multiple different ways:

The upside of gearing seems to be that the motor can have vastly larger RPM-range, like up to 3000RPM or more (direct-drives are what, up to 400-500RPM?). The gearing is then used to "transform" the high-RPM, low-torque motor output into lower RPM, higher torque output at the tire, I've understood that in terms of performance, geared motors surpass direct drive in wheels (16" Rockwheel goes what, 30-35km/h?). Vee also told me that he hasn't found a hill that the 16" Rockwheel cannot go up (so high torque also). The downside is that the motors wear out faster (maybe)?

 

[Daan]

Thanks ‌@esaj, I mixed up Gotway and Rockwheel

Anyway, my secret quest is to build my own open-source EUC but somehow under 8kg.... I think to reach such low weight we need:

1. Redesign the standard BLDC direct-drive motors; they are just too heavy now. I wonder if we can convince a manufacturer to build one where for example the outer shell plates are done from strong polyester instead of the heavy metal shells. I couldn't find any lightweight direct-drive motor though...
2. Use geared motors: this way one can use a small high-rpm electric motor to still drive the wheel efficiently. This seems most promising. I looked at e-bike motors, like the small Tongxin 250W engine but most of these are either under-powered or still quite heavy....
3. Use a geared motor based on basically a small RC motor and use that to drive the wheel (somewhat like the Solowheel Orbit or Firewheel 'Ring'). Unfortunately, that comes with its own problems of dealing with outside conditions like wetness or rocks getting in. This is really troublesome for an eWheel where we really need to have a trustworthy drive that will not slip or fail unexpectedly.

Just some initial thoughts  If anyone finds info about lightweight electric motors please post here