July-13-2019
How are we going to construct the sphere?
The most important detail, we think, is to have a thin and light cover. This ensures that the magnets, holding the head of BB-8 work properly. Therefore we can‘t even use screws of any ferro magnetic material. And, on top of that, it would be difficult to connect those very thin parts with screws or similar things as well.
Our first draft is based on making the sphere out of two parts that are connected via rivets, both made out of the same material: PLA.
In order to make our first experiments, we built some test objects. First of all some boards with knobs and some with fitting, chamfered boreholes. We first heated the knobs with a hot air gun and assembled the rivets with a teaspoon. (Pic. 1). It works, but it is definitely not perfect. The molten material does not bond with the edge of the borehole.
So we build sort of a riveting header using a copper tube and a stopper. (Pic. 2) The problem with this object is, that the PLA tended to stick to the header. We first tried separating agent, normally used to weld steel. It works properly, but smells pretty bad. So we tried baking paper. And we got very good results.
Because of these promising experiments, we made our first design of the parts needed:
Outer sphere (Pic. 3 and 3.1)
Inner sphere (Pic. 4)
Drive pulley (Pic. 5)
Since we initially only had a 25cm x 25cm 3D printer available, we needed to shorten our parts. On the drive pulley we have a clutch to the outer cover and a connection to the motor on the inside of the droid. Once we have riveted the cover, the motor drive could be plugged in easily.
Our first test run:
(Vid. 1)
The parts we will use:
We will publish the stl-files, once they are „finished“.