The Grand Plan

As you can imagine the gearing became the first big challenge.  Getting a simple clock with a ratio of 1:12 is easy enough, but that wasn’t what I was after.  My original design had just casually included ratios for tides (Auckland has two harbours, so both of them), moon phase, and moon position that were really not straightforward when converted into the integer-only ratios of a bike cluster.  It took a lot of working, lots of geeking out with spreadsheets and code, and an entire pad of refill paper over the course of about six months, but I got there in the end (these drawings here ended up not being the final design – they don’t show the coaxial drive for the moon phase).

Of course, geekiness had a vital place, but my design was further limited by the availability of scrap parts.  I spent a lot of my spare time going around bike repair shops and digging through their rubbish for parts, scrubbing them out with toothbrushes and turpentine, lamenting how hard it is to cut stainless steel, and arranging them so they could be mounted and connected properly.  No mean – and certainly no clean – feat!  Several different iterations were needed because I couldn’t get the right cogs, and to make sure that the cogs I could get could be physically placed in the grander scheme of things.  This meant going back to the drawing board a few times, but that’s all part of the fun, right?

In the end I had an eight-layered design, with acrylic rods mounted between perspex sheets and set into ball bearings to help them turn easily.

It’s intended to be driven by a motor timed off a minute hand, mostly because with all the other complications I couldn’t be bothered making my original design of pendulum and escapement!  And also, because of its physical size (600x600x200mm) and weight, it would be difficult to suspend to enable it to be pendulum-driven. And also, I’m chickening out.

So far it’s been a lot of fun. And maybe one day I’ll consider finishing it.

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