Ze Chair. A Chair Design that Failed.

I designed and built Ze Chair in the Spring semester of 1980 while in college. It won first place in the quick assembly category of the 1980 IWF Design Emphasis Student Furniture Design Competition. With padded seat and back it was very comfortable to sit in. 

Ze Chair

"Ze Chair" was an obvious name for the zig zagging frame of this chair design. "Gravizy" was my second choice. It is gravity that holds the design in its Z shape. The design bolts together and can be taken apart for compact storage, packaging, and shipping. It can also be unfolded, although when stretched out flat the length is impractical to hang or store. 

The back of Z pivots to meet the back of the occupant at whatever angle is most comfortable. This meant that most who sat in it, no matter their posture, found it comfortable. 

I made two prototypes of this design.  The first had thinner parts and was made from locust.  The wood split at the bolted half lap joints when first put under load. This should have been a clue. I (temporally) solved that problem by increasing the part size and using red oak instead. My second prototype survived a competition (where it won 1st place) and 2 years of use before failing the same way the first prototype had.  It eventually started to split at the half lap corners. 

I also won an award for the poster design I designed for Ze Chair. It was a first place award from the National Association of Furniture Manufacturers, 1980 local student furniture design competition / poster division. Sadly I no longer have this poster or any record of it.   

I often revisit this design with the hope of finding a way to reproduce it without the potential flaws. I know now far more about joinery, the forces involved, and production methods for making the parts. The chair doesn't need to unfold, and that it did made it a challenge to pick up. That it can be quickly put together and taken apart is a nice feature though which I'd like to keep.

I've thought about trying this design one more time.  One idea is to trim away 3mm from each side of the half-lap corner joints and glue in a piece of 3mm Baltic birch plywood.  The plywood shouldn't split. Glued to the oak it should help keep the oak from splitting.  I can even pocket out a recess for the plywood so it doesn't show when the joint is together. First task would be to find/buy material to make the parts.  

If this was an initial design of a student of mine I would encourage them to keep iterating, perhaps toward some triangulation in the design that would remove splitting stress on the folding corners.   The bottom piece running from front to back could be eliminated and a rear leg could run up and connect to the angling front leg, seat rail and the arm rest for example. That would triangulate the structure and lock all the pieces together.

Questions and comments are encouraged!

4D