Thursday, October 2, 2014

Auto-Regulator Chapter 2: Below the Waist

I couldn't help myself when it came to naming this entry. The irony is that in this case, everything below the waist isn't where the real action is.

 A note on process: I started this project with a commission to build 2 cases. One in walnut, one in curly maple. So, you'll see parts here for 2 different cases. As I went through these parts, I decided that I would separate the two cases when I went on to build the movement case. The walnut case would be the prototype, (the one where I made my mistakes) and the maple would be the first official 'production' case. Walnut's a little more forgiving to work with than maple, both in the working of it, and in the fact that minor discrepancies are more easily covered up.

The case is divided up into three basic parts: The movement case, the pedestal, and the base. The movement case is what it sounds like. The waist separates the movement case from the pedestal, and the pedestal sits in the base. The base gets leveled before everything else goes up. The pedestal sits on the base, and houses the power supply for the clock. The waist is part of the pedestal, and all of the cables that connect the power supply to the movement pass through the waist, and up behind the rear panel in the movement case.

The base is nothing more than a mitered box. There are grooves inside, and some plywood parts that fit into those grooves, to reinforce the base from inside. Basically, it's a splining technique, but it also allows me to help with mounting the feet. The top of the base is rabbeted to receive the pedestal.

The pedestal is actually rabbeted around the bottom edge, because I wanted the joint line to be horizontal. This is intended to be a production case, and this joint will not be glued. So, in the event of any gaps between the base and the pedestal, I didn't want those gaps to be visible. So, the pedestal lips slightly over the base, and seats solidly in.

The pedestal is, at heart, basically a mitered box, too. The panels that miter together to form that box are mitered frame and panel pieces, that all come together to give the appearance of a three-way miter on the top front corners. It was important to make sure that the vertical pieces are oriented properly, as the grain is continuous with the pieces that will frame the movement case. It's a subtle detail that will probably be lost on most folks, but it's that kind of supporting detail that really makes the difference, and helps to unite the entire piece. (I find that the supporting details, when properly executed, become invisible. But when they're not there, or when they're not done right, they stand out.) The panels that fill the frames have book-matched or 4-way veneer patterns.

Like the base, there are internal plywood frames to reinforce the structure from inside. The bottom frame is open to allow access to the adjustable feet in the base, if needed. That way, if anything settles, the clock can be leveled without having to take it all apart. (That's the theory, anyway.) The top frame is open to allow cables to pass through, and go up into the movement case. The solid wood, mitered top of the pedestal is glued to this frame, and the waist is glued to it, too.

Because the plywood frame is glued into a groove that cuts across the vertical members of each panel, the miters won't actually be supporting the weight of the case, and the movement. The vertical load of the clock will sit on the waist, which sits on top of the plywood frame, which sits in dados that lock that frame directly into the vertical members. So, while it looks like the miter joints are supporting everything, they're not. The load actually hooks into the structure just south of that top mitered panel.

So, as I said, below the waist, the case structure is fairly straightforward. That's not where the real action is.

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