American M3 Grant Tank

Tower Builder: Caterpillar Tracks

One problem with designs of the Tower Builder up until now have been its limited range, and bulk. Solutions have been variations on the theme of a telescopic tower that rises to a maximum height. It rises either through a crosshatch of bars or levers that rises when compressed, or levels of segments that rise when ligaments or cords are tightened, or when motorised wheels roll up segmented bars.

All of these design solutions require an internal structural element within which the Builder climbs or is pushed as it extrudes the outer shell of the substrate tower. The thinking behind this was an assumption that the substrate would not be strong (either because it was damp, weak or simply that the tower would rise unevenly and result in an unbalanced, wonky structure), and that it would therefore need additional support to keep it stable.

I have decided to re-think an idea that I had prior to these structural solutions, and return to a design that imagines the Builder as autonomous within its tower – building and moving with nothing additional between it and the substrate. For this phase of development I am going to use wax (or chocolate) instead of substrate – something that melts and solidifies easily.

The design of the Builder that I am working on now (actual prototype, not just drawing board) is a small cylindrical unit with a motor facing out at each end. One motor drives caterpillar tracks, the other motor distributes substrate in a gradual spiral that rises as the Builder rises. Small teeth on the tracks grip the inside of the wax tower and stop the builder from sliding or falling.

Another feature of this design is that substrate is now delivered to the Builder by a dripping mechanism from directly above the tower. A block of wax is held above a funnel with heated filaments pushing through it. Periodically the wax is released and falls down into a splashback-proof head that sits atop the Builder. The Builder reheats the wax and mixes pigment before pushing it out to the substrate tower wall.

So its basically modeled on a tank, although it has tracks on 3 or 4 sides (since it is climbing inside a tube not rolling across mud). It receives the substrate from above rather than carrying it up from the base. And it is designed with a wax structure in mind – which will set sold quickly, and will be pretty strong in a cool environment.


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