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.

More random project updates

I tried to finish the wheelmotor side plates at the Almighty Dale’s yesterday. Keyword is tried – I thought I would be able to get both done in about three hours. The details don’t matter much, but in the end, I barely got one carved out and that one might need redoing.

The side plates have a little taper on the outer edges to mate with the tapered inner rim of the scooter wheel. It’s a tire bead, if you may call it that. The problem is, it’s a somewhat odd angle (about 40 degrees). So the toolpost on the lathe had to be readjusted to cut it.

Well, after cutting the taper, something was either missed on the realignment or something wasn’t tightened down enough, but the cutoff tool ended up cutting at an angle. That’s weird, it went in straight enough!

Either way, the side plate is slightly concave. The ring structure also indicates “oops, something got loose”.

There’s a 55% chance I might scrap this part too. The 45% “don’t scrap” comes from the fact that most of the dimensions are extremely close to the design – by about .002 or so.

It sucks that I might have to redo something that got this close. Next time, there will be a change of strategy regarding the final cutoff – I’ll probably part it a bit long, turn it around, face cut to the proper length, then cut the taper. Even if I have to do it with a file to not disturb the alignment of everything else!

Lesson? Don’t trust the machine to be perfectly aligned even if it looks like it. It’s a fallacy of luxury that something which looks and runs better requires less brainwork to operate.

Same can be said for soccer moms in plushy SUVs. Oh well.

In TB4.5MCESP1 news, more stuff came.

Drive motors! Since I was going to be running an elevated voltage this time around, I went looking for some slower motors. There are plenty of moderately hot-wound 550 motors on the surplus channels, but not as many with a Kv of around 1000 to 1500 – that is, 12000 to 18000 RPM at 12 volts. That was the “sweet spot” for TB this time around. Fortunately, AllElectronics came to the rescue with some surplus Power Wheels motors. You can never go wrong with Power Wheels motors.

What’s more fun, though? NEW CHARGER! Up until now I haven’t ever had a “real” charger – one that actually follows battery chemistry charging curves and wasn’t a dumb wall wart. The move to Lipolies sort of necessitates my upgrade, since you can’t plug a Li battery into a wall without some fun explosions.

The “good charger” did not get struck off the list, since I can use it for so much more than just TB. This should cover most of my electrochemical needs – 27 Ni cells, 8 Li of various subtypes, and even lead-acid.

The battery in question. This should fit snugly between the Ebay plates of TB. Some additional standoffs make sure it doesn’t fly around inside the bot. TB should never need the full 25C of this pack – if it is drawing 80 amps for any reason, something has gone terribly wrong.

I intend to make an “integrated charge connector” which combines the balancing port with the main battery lines. This way I don’t have to have 2 cables coming out of the bot.

What I particularly love about United Hobbies / Hobbycity is that they make absolutely no attempt to hide the fact that yes, everything on the site is Chinese in some way. This includes full broken English manuals, which I find quite funny. Often, they express things in such a manner that you get what is being conveyed, but wouldn’t ever find it in a real English manual.

Check out my awesome quad-reflection. I mean, come on, what charger besides the most kickass and awesome has a WASTE TIME function?!

Anyways, it’s currently working on the 4-cell Lipoly and I have the new cutting fence set up on the miter saw, so I should get some chassis work done before I have to fly back to the Northern Wastelands.

Oh, and Jesus welcomes you.