Part.2 - Approaching Autistic Velocity
>>25281
Moving on.
Well, I'll keep this as short as I can. While we were talking about different kinds of gears, I had a thought: Gears are complicated. Is there some way I could remove them from the equation? Would it make things simpler?
As I discovered, the answer isn't that straightforward.
I started off by experimenting with the idea of moving to a purely cable-driven design. In the process, I came to the same wall that kept me from making Orchid fully cable-driven in the first place (you guys didn't see it, but that was my original concept, even well before I had her appearance and name figured out. I'm talking years ago): when you move cables around a joint, the distance between the driving pulley and the end-point changes.
This leads the first design aspect you'll see in these plates. My
theory is that by threading the cables directly through the axis of rotation, the distance between the driving pulley and the driven levers should be the same regardless of the angle of articulation (below 180° at least, which is well within my requirements). Even if it's not identical, it should be
very close.
You'll see this all over {Plate.1}. This is why the hinges are so weird.
But things didn't get better right away. Even though I had more space than most to work with, I found that Orchid's pulleys and motors were getting cluttered.
I experimented with all kinds of wacky designs. Things like planetary pulleys
which I devoted way too much thought to, cyclone drives, the P.O.N.U.T. (Pulleys Operating Neatly Upon a Torus), indexing levers, cable and hook multiplexers, etcetera.
If you really want, I'll sketch these out too.
You've probably never heard of those before because I made them up entirely on my own.
We are officially descending the iceberg of my autism.
Needless to say, things got complicated again.
But I had one saving grace, a tiny, simple little idea that would ultimately lead to the design you see here.
Counterweights.
The trickiest part of a large plushie-bot design is keeping heat low. I haven't touched on this much before, and I was kinda hoping that something would become obvious in the design process, but it became clear that I would have to put more active thought into it.
This is a special concern, because it actually
prevents me from cramming components as close together a physically possible. They'll heat eachother up, and when combined with the fact that
everything is by definition covered by insulation, it leads to dangerous conditions.
So, how do I spread things out without increasing the hard-frame size too much?
The answer came to me when I was revisiting an idea I had previously: using the lateral leg motor as a counterweight to aid in articulating the shoulders.
I won't show you the design, because it was too frail and severely limited the angle of articulation, but I had a better idea just today off the back of that, in the form of a question:
Why does the leg have to start where the torso ends?
Ironically, this came from me thinking about the limitations of the design in the first pic of (
>>25231 ).
This entire time, I've been thinking of the leg as something that is affixed to the side of the torso, when I could have been moving it
into the torso.
There's no law saying I need a rectangular torso, after all. It just needs to
connect to the leg, but how it does that is open to interpretation.
If I may direct your attention to {Plate.1, Fig.1}, you'll see the latest shoulder mechanism. The shoulder/flank frame extends into space previously allocated to the torso, and does so in a way that the motors act as a counterweight.
As I'll explain shortly, the weight of the motors should more than counteract the mechanical disadvantage of swinging a ~36" long multi-jointed lever around. In fact, I was worried that they'd be
too effective as counterweights, thus why I placed one motor on the other side.
In effect, I've moved weight from the torso to the legs, and made that a
good thing. Counterweights are the oldest and most effective way of dealing with mechanical disadvantages after all, and this way prevents me from having to add more weight to the torso.
Now, as you'll see in the other sketches in {Plate.1}, I intend on having the actual legs (aside from the joints, of course) consist entirely of tubes. I noted fiberglass, but PVC or another plastic will do. This brings the weight of the legs (sans shoulder) to the most extreme possible minimum, since materials like that are both light, and strong enough to bear the weight while
also allowing cable passthrough. They're also a dime-a-dozen at the hardware store.