of the world, while being low cost and easy to construct. Two years later I was introduced to the work of Buckminster Fuller through Jay Baldwin’s book “Bucky Works.” I saw in that book the answer to the housing construction method diagramed by the drawings and photographs of the octet truss.

The octet truss is at the heart of Buckminster Fuller’s “Explorations in the Geometry of Thinking.” In section 200.03 he states that “Energetic geometry employs 60-degree coordination because that is nature’s way to closest- pack spheres.” Bucky suggested that the 60-degree coordinate system was “Nature’s own most economical coordinate system,” and this coordinate system is defined by the isotropic vector matrix. “When the centers of equiradius spheres in closest packing are joined by most economical lines, i.e., by geodesic vectorial lines, an isotropic vector matrix is disclosed.” The isotropic vector matrix “corresponds with the comprehensive coordination of nature’s most economical, most comfortable, structural interrelationships employing 60-degree association and disassociation. Remove the spheres and leave the vectors, and you have the octahedron-tetrahedron complex, the octet truss, the isotropic vector matrix.” (sec. 420.01)

I have examined the various methods people have developed over the years for building octet truss and other space frame structures and found them all to be expensive and limited in their ability to handle modifications (image 1). Having played with Tinker Toys and LEGOS, I wanted a building set capable of building functional structures that would at minimum equal the adaptability of these toys. I wanted a building set capable of building octet truss structures that would utilize quick connect/disconnect hubs and allow for structural members to be added to or removed from any hub in an assembled structure. I recognized that in order for struts to be removed from an assembled structure they must be able to slide inside one hub so they could be pulled clear from the assembly by the other end. Having manufacturing experience I realized that the cheapest way to make large numbers of parts is to set up an injection molding process. With these considerations in mind and access to the solid modeling software Solidworks, I developed what I anticipate to be the solution to the broad scale application of the octet truss. I have shared these ideas with my other team members who are working with me to anticipate and solve design problems and to develop a full implementation plan for realizing the potential of my work.

The solution consists of four interlocking rings that assemble into a spherical hub into which struts or other components can be securely fastened. Each of the four rings is uniquely grooved so that in a specific order they slide over and lock together (image 2). By using collar assemblies designed to fit into either the holes where two rings intersect, or into the spaces in between the rings, struts or component parts can be attached to the hub in 26 different radial directions. The radial directions defined by the locations of the ring intersection holes correspond to the twelve vertices of the isotropic vector matrix. Connecting struts to these locations allow for the hub to be used for the construction of octet truss structures. All of the parts for the hub can be manufactured in an injection molding process. The rings are molded in two halves by splitting them circumferentially down the middle (image 2&4). Standard diameter pipes NPT threaded on both ends can be used for connecting struts. We believe this design will prove to be the simplest and cheapest hub for building octet truss structures.

The unique ring based hub design extends its usefulness beyond the basic octet truss. Using a part that fits into the square shaped space in between all four rings enables the hub to be used for building right angled structures (image 3). The triangular space in between three rings will accommodate component parts used for holding eventual floor, wall and ceiling panels (images 3&4).

This design has the added benefit of shipping in a compact form. All of the connecting struts can be packed inside a stack of rings (image 4). Structures can be assembled either on land or water without prior foundation by unskilled labor. Structures can be modified or disassembled at any time. With the proper material selection, the structures will be UV tolerant, rust resistant, mold and mildew resistant, and capable of handling extreme loads. These structures will be well suited for flood and earthquake prone regions, and can serve a wide variety of needs.

As the parts are currently designed, the rings have a 200mm outside diameter and 152mm inside diameter. They are designed to use standard ½” pipe (0.84 inch OD). The four rings have a combined volume of about 1500 cc. This translates to a total material cost for the hub assembly of less than $4 using 30% glass fiber reinforced engineering grade nylon. Depending on the structural needs, any material of standard diameter pipe can be used for the strut members. For light duty purposes, schedule 80 PVC pipe can be used. Medium duty needs can use aluminum pipe, and heavy duty needs can use either structural grade galvanized steel or coated carbon steel pipes. The finite element analyses I’ve completed (image 5) suggest that a single tetrahedral assembly using PVC pipe for the strut members can handle loads exceeding one ton. By changing the material for the struts to galvanized steel, the same assembly can handle loads in excess of six tons. And like a geodesic dome, the octet truss assembly’s strength will get proportionally stronger with additional members.

We want to oversee the manufacturing of a complete building kit based on these four ring hubs. Our plan is to begin by manufacturing a small number of components to work with the hubs to build “niche market” utility structures like car ports and work and storage spaces. With some capital flow we will increase the number of component parts available with the kit to increase its functionality. A likely next area of development will be in agricultural needs such as green houses, grain and hay storage, animal housing and irrigation systems. With eventual public acceptance and proof of concept, we’ll move into broader market areas with a major focus on addressing the problems that generated my interest in the beginning, to provide reasonably priced housing needs for people living in poverty.

The basic design phase is essentially complete and we have submitted a provisional patent application to protect the development process. The next stage of development for this idea is a single prototype made by a rapid-prototyping process. This will be self financed and completed by January, 2008. This will demonstrate the feasibility of the design. Based on any design concerns raised by the first prototype, a second single hub prototype will be completed by the spring of 2008 and again be self financed. Simultaneous with the hub prototype development, initial designs for a structural anchoring system and method for covering eventual assemblies will be developed. At this point (approximately June, 2008) we will need to build and demonstrate a working prototype structure to attract potential investment for setting up manufacturing and initial operating expenses. Additionally we will be seeking material and manufacturing consultation for eventual production. We intend to use a low-volume injection molding process to manufacture the working prototype hubs, while cutting and threading the strut members by hand. These last two steps are the areas where we’d like to apply the potential Challenge grant money. With this support we believe it is realistic to be able to construct a full scale prototype structure by September of 2008.

Team leader Dan Stearns is a graduate of Brown University engineering who has worked on projects in Guatemala and Dominica. He has worked for CACI in logistics and the National Academy of Public Administration on federal government geographic information coordination. He has also worked in home and building construction. Dr. Robert Stearns is a retired member of the federal government's Senior Executive Service and PhD economist with over 30 years experience as policy advisor and analyst primarily for the federal government. From 1989-1995, he was Deputy Assistant Secretary (Project Management), Department of the Army (Civil Works). John Longan is a plastics engineer who over the last 15 years has provided engineering consultation for product development from idea conception through manufacturing.