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Sunday, September 5, 2010

9/5/10 Motor Update

Good news: I took the sensor board out and tested it with a small magnet. The sensors were fine, they just weren't close enough to the magnets/coils. So I'm going to stick them in the slots of the stator and get rid of the sensor board. Even though they won't have the same angular separation as on the board, it will be a combination of slots that works, such as A(sensor)aAB(sensor)bBC(sensor)cCAaABbBCcC. I'm pretty sure I did a previous post on calculating hall effect sensor positions, or it's in my design review for this project, so look that up if you want to know where to place hall effect sensors. Anyways, this means that the sensor board cannot be adjusted, which is nice to have if you want to mess with timing. Oh well.

picture added 8/20/11

picture added 8/20/11

Bad news: Chips of the polycarbonate hub caps/spacers fell out. However, it wasn't the total disintegration I thought it would be. In fact, it's salvageable, so I may just put them back together the way they were. (I'll at least do one to test the sensors in the slots idea.) On the other hand, sidewalk cracks and other bumps might finish the disintegration process, which would be really bad while riding.

Another option is to make new hubcaps/spacers out of aluminum, but it wouldn't be see-through anymore. :(
I could waterjet new polycarb spacers and hubcaps, but I really don't want to deal with that again. Especially because it'll be impossible to get rid of every little molecule of loctite.

Another option is to shove the rotor into an aluminum pipe and make aluminum hub caps for the pipe, eliminating the spacers. Something like this:
I got this idea from Charles if you can't tell.
Cool. The cylinder in the background is the tire.

The holes are filled with glued or pressed-in polycarbonate disks. I really like the way this looks, and I think it'll be much stronger than the current design (though the current design is plenty strong...). The larger diameter will give a slightly higher topspeed. One draw back with this is that the outer edge of the hub cap is now an important surface and has to be a very close fit for weather-proofing. In fact, the hubcap-outer tube interfaces would probably have to be sealed with silicon. Drilling radial holes is no easy task, and getting it apart would also be a pain.

Here's a combination of the above two options:

 Aluminum hubcaps with polycarbonate inserts in the outer-side one. Keeps the current bolt pattern. Scraps the useless o-ring seal (explained in an earlier post). This allows partial see-through without the draw backs of polycarbonate (can't loctite, not as stiff).

I'm leaning towards the last one.


  1. I like the idea of the aluminum hubcaps! Can't wait to see the end result.

    So you motor will be press fit into the tire?

  2. Chrome Rims:
    McMaster 7872K14 / 7872K15

  3. No, the tire is going to be made out of a strip of urethane rubber rolled around the outside of the wheel and glued in place with urethane glue.

    Nice scooter btw.