LUNAR cofounders Jeff Smith and Gerard Furbershaw sought to create a sculpturally oriented bench that provided social interaction opportunities for passersby in outdoor public places and museum and gallery exhibition spaces. People have an innate desire to engage, interact and play, yet there are a limited number of public spaces that enable this. Smith and Furbershaw looked to the playground seesaw for inspiration, as most people have experienced this form of interactive play as children. 

They believed that leveraging the seesaw and enhancing it with a sophisticated design would lead to a compelling experience for people visiting outdoor public places and museum and gallery spaces. Although it is possible to engage in solo play, interacting with another person or persons is oftentimes more rewarding. With that in mind, they named the bench 2toTango after the phrase, "it takes two to tango."

Figure 1: 2ToTango in a public square

Smith and Furbershaw sought to create a sense of magic in how 2ToTango functioned, as if it as if it teeter-tottered about its sharp visual fulcrum corners although that motion would actually be driven by an internal mechanism. The requirement was for the bench to remain horizontal when no one sat on it. When a person sat on one side of it, 2ToTango needed to descend slowly towards the floor or ground and stop within two inches of it to prevent the bench's end corners from being damaged and to ensure it didn't pinch people's feet. When that person left the bench, it needed to return slowly to its horizontal position. If one or two or people sat on both sides at the same time, the bench was to teeter-totter in relation to where they sat and where they might move, depending upon whether and how they chose to interact with each other.

Figure 2: 2ToTango tilted to the side the person is sitting on it.

Figure 3: 2ToTango in a horizontal state of balance with the lighter person on the left farther away from the fulcrum than the heavier person the right.

LUNAR's Engineering Team was tasked with creating a mechanism that achieved the desired motion. Mechanical engineer Bob Lane developed and refined the final mechanism design. It relies on return springs and pneumatic cylinders. When no one is sitting on 2ToTango, return springs keep the bench in a horizontal position. If a person sits on one side of the bench, that side lowers slowly, dampened by the pneumatic cylinder's inlet flow control valve on that side (see Figure 2). If another person sits on the other side, the bench teeter-totters in relation to where they sit and where they might move, depending upon whether and how they choose to interact with each other (see Figures 3 and 5). If both people leave 2toTango, the return springs bring it back to a horizontal state of balance (see Figure 1).

2toTango is fabricated as an 8 foot long welded and ground aluminum monocoque structural skin. A steel base plate embedded into the floor connects to an internal fame. The frame connects the teeter-totter's pivot, the two internal pneumatic cylinders and the two return springs. The outside ends of the pneumatic cylinders and return springs are affixed to the bench's structural skin via structural ribs. Tubing between the pneumatic cylinders maintains equal pressure between them.

Figure 4: Mechanism layout

This teeter-totter design engenders a number of ways of engaging, from beholding its beauty and not interacting with it physically to just sitting, play, and psychological gamesmanship.

Solo State

2ToTango's internal mechanism keeps it horizontal when not in use. When a person sits on either the left or right side, the bench descends slowly to within two inches of the floor (See Figure 2).

Cooperation State

One or more persons sit on both sides of the bench perpendicular to its axis, peripherally aware of the other(s) and how their positions interact to affect the tilt of the bench. Some or all of the individuals seated on one or both sides either move towards or away from the fulcrum to interactively create an imbalanced tilted or balanced horizontal state (See Figures 3, 5 and 6).

Figure 5: The persons on the left and right cooperate by sitting the appropriate distance from the fulcrum to create a horizontal state of balance.

Domination State

One or more persons sit on one side of the bench and move(s) toward or away from the fulcrum to create an imbalanced tilted state between them and an individual or people seated on the other side (See Figure 6).

Figure 6: The two people on the right tilt the bench and lift up the person on the left.

Engaged Interaction State

One or more seated persons straddle the bench while facing an individual or people on the opposite side. The individual or people on both sides move towards or away from the fulcrum to interactively create an imbalanced tilted or balanced horizontal state.

Disengaged Interaction State

One or more people seated on one side of the bench face away from an individual or people seated on the other side. As those seated on either or both sides move towards or away from the fulcrum, they create imbalanced tilted or balanced horizontal states. Although interactions are taking place, they are coincidental and none of those seated are aware that the interactions are occurring with the individual or people seated on the other side.

2ToTango's triangular cross section twists 180 degrees from the left and right sides, which provide flat top surfaces for seating, to a sharp edge in the bottom center to create a visual fulcrum. The resulting rotated form that transforms from the flat seating surfaces on the ends to the teeter-totter fulcrum in the center clearly reflects its function. The triangular cross section on the left and right sides also helps to minimize 2ToTango's visual mass. The four bottom-facing polished aluminum surfaces reflect the floor or ground material, blending the bench into the surrounding environment. This creates a sense of transparency and makes it appear almost as if people seated on it are floating above the ground.

2ToTango enhances the experience of visiting outdoor public places and exhibition spaces by providing functional seating integrated within a piece of striking kinetic sculpture. It also enables passersby to interact with it in a number of ways ranging from simply beholding its beauty to playing, to partaking in psychological gamesmanship. Although engagement in solo play is always an option, it is worth remembering that for the ultimate experience, "it takes two to tango!"