Back to the lab again…

chorl

I’m back at the Massachvsetts Bay Colony Institvte of the Technologickal Arts. Rejoice! Time to get back into the swing of things. Interesting occurrences along the way:

  • It started snowing on the way to the airport and was getting a bit heavy right before departure. Snow in Atlanta? Wow, that’s almost as rare as rain. I was afraid of getting delayed. That, fortunately, did not happen.
  • The luggage half-full of robot parts and electronic parts somehow made it past screening. I was expecting armed security guards as soon as I landed.
  • On the subway ride back, a random black guy boarded train section I was in with a boombox and proceeded to breakdance for the passengers. That ranks as the most innovative panhandling I have witnessed to date. Certainly better than the bad karaoke that goes on in Beijing subways.
  • 50 pound suitcase 5 stories up the stairs.

So now I’m in the same place I was 3.5 weeks ago. TB4.5 (SP0) will undergo disassembly soon. First, though, I have to finish making all the UHMW parts and get some machining done, probably at MITERS.

Bawt on!

OMG LÉ WHEELMOTEUR

chorl

It’s done! Structurally, anyways. And it’s really shiny. Besides being shiny, it actually stands a chance of working.

…because I’m fairly certain it has the same center of rotation throughout. If it does not, the discrepancy is too small to see or feel. The outer holes will be countersunk when I can get a sample of a 4-40 flathead cap screw.

Outer plates of 6061 aluminum, can of steel.

The insides. Getting the stator onto the internal hub was a bit of an adventure, and it got a bit mangled in the process. If I were to do this again with appropriate funding, the stator will be a professionally made part. I bet that even if it works, the efficiency will be horrendous since the stator laminations are “insulated” with wood lacquer and made of hot rolled sheet steel, the stuff usually used for odd sculptures, not the cores of high performance electric motors.

With a wheel. The only thing that wobbles now is this wheel, which is most likely a quality issue. The wobble isn’t much at all – a hundredth or two at most. What sort of annoys me is that the tire profile is so tall, which means the motor has to have a relatively small diameter compared to the whole wheel. If I could go completely balls-out custom on this, the motor would be much larger and the tire custom-cast from urethane with a lower profile.

The downside to a lower profile tire is less shock absorbtion, which could impact motor lifetime. That’s a matter of IRL testing.

The magnets and magnet wire are still back in my dorm room, so I’ll finish this motor up when I return.

I also took the opportunity to trim down this gear for TB4.5’s arm geartrain. It will drive the rear link through a pin.

Since I’ll be back on campus on Wednesday, I’m going to order some materials that will have parts cut out of them with various large machines. Some half-inch aluminum for the arm and frame bits, some quater-inch aluminum sheet for the wedges, Garolite for the top and bottom plates, and polycarbonate for the internal EBay components.