Monday, November 18, 2013

Model: Rocking Chair

So this post is about version 2 of the rocking chair. It should be noted that I haven't yet really spent enough time refining the shape and size of the back of this chair. The most important part for now was the join between the back and the seat and the join between the back and the legs. Later I'll probably sculpt the back of the chair more and determine a good height for the back based on anthropometric data and some ergonomic research.

So on with the show. First here's the sketch from which the parts rough shapes and relative sizes were determined. I've changed the type of joint shown in the sketch below though may review that. The joint shown in the sketch below is similar to the wedge system used in an old device called a spanish luthiers rack. While it's incredibly adept at clamping pieces together for short periods of time I think something more substantial needs to be used for a piece of long lasting furniture.

I began the model by creating the back and the seat. These were then fitted together. While balsa is not the nicest material to attempt to carve, as the grain rips out very easily, I was more confident as I recent;y got a nice set of small carving chisels just for this purpose. The "ass groove" on this chair should resemble something close to what I achieved on this model though it would be a bit more refined before being made full scale.

Also shown below is the wedge joint underneath the seat that joins the back and seat together. If this is the type of joint I settle on the wedge would be flared slightly on one side then pushed through the mortice, split on the far end with a chisel and have a wedge inserted to flare the end that has been pushed through. I hope all that makes sense. It does in my head, which I suppose is important for now.

Below is the model assembled for fit with the legs, rockers, back and seat checked for fit. The brace between the two rockers has not been added at this stage. The gimlets were used to drill the holes for the leg posts to go through the seat, back and rockers and much of the contouring on the underside of the seat was done with the small carving chisel on the right.

Now just a few posed shots of the assembled chair

Side Profile

Underside With Seat/Back Joint

Front View (before the brace was put in)

Rear View (back/leg joints are slightly misaligned)

Shot with Rocking Stool and Miniature Anglepoise Reading Light

The Two Rocking Models To Date

So again I was glad to get these models built and learned a few important aspects from them. Firstly for the legs to be straight the brace between them should be carefully built to exact length and placed close to equal from the front and rear legs. For the rockers to splay they can be placed a bit further forward. The precise positioning of the rear legs is important as the slight misalignment in this small scale model produced a lot of other issues throughout the assembly. The grain on the seat might be better orientated front to back rather than sideways to avoid tearout during carving. Finally and most importantly the joint between the back and seat appears quite rigid even in this soft material and small scale. A promising sign for a larger version to come.

John O'Shea

No comments: