I’m in process of brainstorming and blue printing BB-8 from Star Wars. I’ve seen some great replicas online with Canvas cloth and mass produced toys with plastic.
With that in mind, I wanted to push the boundaries and try something bigger and would like advice on torque, motors, and feasibility.
I’m looking to create a 1:1 BB-8, Aluminum body.
It’s specs are:
Height (head and sphere) 670mm
Head ~170mm height
I don’t think the head will be a major concern for me, yet. It’s something to calculate later.
The inside electronics involved are an RC car motor, with the offset center of gravity causing the sphere to move. The BB-8’s top head will remain upright due to large and strong neodymium magnets on the head and the internal propulsion system (which moves with the ball).
500mm Aluminium hemispheres are not easy or cheap to find. They’re running around ~150+ each. Note I am using hemispheres so I can insert electronics without attempting to slice in half a half meter tall ball, but calculations will use an entire hollow sphere.
With a body diameter of 500mm and a thickness of 3mm.
Radius of 250mm, 244mm of it hollow. 4600207.1808mm^3
Weight of Aluminum = 2020.75kg per metre cubed (m^3)
2020.75kg * 0.00460021m^3 = 9.2958743575 kg
For less thick versions;
2mm yields 6.25kg sphere.
1mm yields 3.15kg sphere
Given the Spin master BB-8 (mass manufacture) is around 14-15 lbs (~6.5-7kg) I envision there could be a degree of success with this project.
Would it be feasible or possible to roll such a sphere using an internal weighted motor, or it wouldn’t be prudent due to the weight? Are there any suggestions for an alternative motor/motion system?