A couple of months ago I was contacted by someone who was interested in having me design a desk chair for him. I was in the midst of my Kickstarter campaign at the time, so I only got around to the project this past month. I’ve been really into using bamboo recently and I decided pretty quickly that would be my main material for this project. Bamboo is expensive though, so before plowing ahead I decided I better make a prototype. I started out with the usual sketches, coming up with about five different designs that I liked. One design, though, stuck out above the rest. It would be the trickiest one to make, but it had an instrumental quality to it that I loved. I wasn’t sure if the design was feasible, so I moved on to some more precise drawings.
As with most of my work, the chair employed steel cables under tension as a key feature of the design. The cables, I decided, would hold the seatback in place by pulling it firmly against a single contact point. What made the design so tricky was that I wanted each of the cables to enter and exit the central spine several times and, at certain points, to run through internal channels. I knew that I could design my pieces on the computer and cut them to precision with the Shopbot, but I wasn’t sure if it there would be enough room in the central spine to cut the 20 channels I was hoping for. Additionally, there would be the problem of threading the cables through the channels once the time for assembly came. I knew I would have two use two halves to make up the central spine and, because of the crazy angles involved, I would have to get all the cables in place before gluing the two halves together. I wasn’t sure if it would work, but I decided to give it a go.
Before making the chair out or bamboo, I decided to create a prototype with cheaper regular plywood. To my surprise, everything went pretty smoothly. I designed the different parts on the computer and cut them out with the Shopbot with no problem. The most difficult part, as expected, was the assembly. I had to thread all the cables through their holes and then carefully align each one with the proper channel before gluing the two halves of the central spine together. Gluing the spine was a little difficult since the cables had a tendency to pop out of their channels and block the two halves from coming together, but things went about as smoothly as I could have hoped. After letting the glue set overnight I pulled each cable tight and secured it in a recessed area in the base of the chair. With this process, tension was added to the seatback, thereby locking it in place.
All in all, the prototype turned out really well! The only change I decided to make before moving forward was to the ease angle of the backrest. After sitting in the prototype, I realized that the backrest was much too upright and made several tweaks to my design before moving on to the next iteration
That’s it for now, but check back in a day or two for a post on the finalized bamboo chair.