BB-8 want-to-build thread (apparently I'm calling him BB-8)

[kresty]

I'm a bit concerned about the sphere. I had to redo the bloody model 3x because I messed up the inner surface. I finally have something that the parts tool says'll be about 6.3 kilos, BEFORE adding the weight of glue. Also I'm considering an inner ABS printed surface for further rigidity/smooth surface for the hamster, which I imagine must be another kg or two. In other words around 15lbs.

I'm concerned because the thin walls cause several small bricks in the construction, and places where it's "only" 3 plates thick. I know it's a sphere, but 15lbs seems like a lot to put on that frame.

So, I chatted with a local Lego Master Builder (former, Lego charges artists to use the title). He's done spheres before and thinks it should work, even without glue. I sure hope so. The 2nd opinion helps a bit....

Another problem is that a 15lb ball means that I need a significant hamster weight to move it. Given that it needs batteries and motors and speakers & stuff I was probably already looking at 7-10lb there, so I guess that's OK. 22-25lb total for the sphere & hamster then.

Also thought about the hamster/head a bit more. I have too much Lego, so I'm thinking that the magnet approach is unrealistic. That means that what I probably need is both a hamster and balancing head. Weight is again a huge factor here. Lego head is also not going to be "light". It's way smaller than the sphere, but probably still a few lb of lego. And of course a couple lb of motors/controllers.

It's be nice if I can keep it to 5lb or so, but that's about what one of L3-G0's feet weighs, so that might not be possible. The biggest problem with a heavy head is that it'll move the CG of the entire system when it runs around, causing the ball to move. Not enough to roll like the UK builder, but enough to wobble. 5lb head and 25lb body should be OK for the "peering" effect, but if it ends up being a 10lb head, the body may want to move too much.

Of course I could mitigate that somewhat by having the hamster move opposite the head to keep the sphere balanced, but they probably won't talk to each other, so that may be tricky. Hmm, maybe BOTH need gyros? Though then they'd want to fight each other. Should be interesting anyway.