Cluster 1: Sommerville system – edge based

Using an aggregation system based on regular Sommerville-tetra cells, bike frame clusters can be connected along edges.

Edge extension

Two bike frames could be positioned inside a cell with one of the bike’s main profiles aligning with the edge in between faces connected at a right angle. The two frames touch to form a connection that would have to be welded. To compensate the bike’s asymmetrical position along the tetra-edge, an extension profile is attached.

The resulting structures are much denser (and cell size smaller) than in the previous study.

Unmodified bike cluster

When bike frame geometry is allowed to exceed the cell container, bike frames can be positioned in type-18 configuration.

This system has the benefit of avoiding additional extension profiles, and it requires only minimal editing/trimming of bike frames – parts are connected along profiles, producing bundle joints at the shared edges. In stochastic aggregation, allowing all possible combinations of connection rules, collisions appear in some locations due to geometry exceeding cells. This could possibly be overcome by restricting the set of allowed connection rules.

In space-filling aggregations with regular Sommerville-tetrahedrons connected at face centers, the aggregation graph shows two types of cells – square and hexagon – visualizing the connection topology of parts. This pattern is also called the dual graph of the tetrahedron network.

Aggregation with connection graph (green lines) with a hexagonal connection graph cell at the image center
Edge-based parts connected along hexagon connection graph, the yellow polyline highlights continuously connected profiles (structural loop)

Around the larger (hexagon) cell, the edge-based parts form loops, that are relatively large producing weak areas in an assumed structural framework (space-truss-like system).

Attempting to overcome this, a variation of the type18-part in different orientations (right) is introduced as an additional part as well as a new connection part (below) which is designed to create structural short-cuts.

While solving the problem in some locations (to some extent), the aggregations become very complicated very quickly – putting in question the approach of introducing a connection part (purple).

Edge-trim combination

When clipping the extending geometry, a part is created that combines both, edge-connections and plate joints. The disadvantage of this system is the amount of extra material needed for the large plates to join the trimmed ends.

Global form finding

When positioning one bike frame to connect the main tetrahedron edges, a single frame part can be created without modifying (cutting) bike frames. This, however, only works for bikes with a vertical steering axis. With this part type aggregations can be formed by only utilizing the standardized joints that already exist in the source object.

If the axes at which parts are connected are defined as hinges, allowing rotational movement along those axes, aggregations could be deformed globally to adjust to an overall load case scenario similar to experiments from our previous research project. Such global form-finding methods have the potential to utilize not only the discrete parts themselves but also activate global geometry for structural performance. This approach will be further investigated in future studies.