These pages document a part of my project to create my version of the wearable PC. For more information about the project in general, go to the project's main page. This part of the project is both the computer's keyboard and its mouse (although I may add some other pointing device later). It is a Chordite keyboard as described by John McKown on his website, but I have made some improvements to the mechanical design (or at least I think they're improvements -- Mr. McKown and others are of course entitled to their own opinions on the matter). What follows is partly a description/instructions on how to build one of these for anyone who wants to duplicate (or improve upon) this design, and partly an account of my experience in building this keyboard. I strongly recommend that you first download Mr. McKown's information kit and read at least the instructions.html file. Because my design is only a relatively minor (but to me important) variation on Mr. McKown's design, this document just builds on what he has already written about his design, and I assume that you are already familiar with the basic concepts of a chordite keyboard.

First, a technical note on the pictures. Most of the pictures on these pages can be clicked for an enlarged and/or higher quality image (those that can't have the text "(no enlargement)" in the caption). The pictures here in the text are 400 pixels wide unless the original was less than 400 pixels wide. The enlargements are the original images and vary in size from no bigger than the pictures in the text up to 1280 pixels wide (although your browser may "zoom out" to fit larger images in your window). The original pictures were all taken with the same camera set on its one megapixel mode. They vary in size because I have cropped the pictures to only show the objects of interest. In some cases, the "enlargements" are barely any wider or taller (in a couple of cases they're the same size), but the enlargements are higher quality images. I did this to make the JPEG files embedded in the text smaller, improving the loading time of these pages. For those who are interested in such things, here's how I went about it. The small images are all at least 85% quality (according to The Gimp, which is the image editing software I used). If the file size was under 50KB at 85% quality, I raised the quality until the size went over 50KB, then stepped back to the maximum quality under 50KB (or just went all the way to 100% if that was still under 50KB). Similarly for the big images, except that they are 95% or better quality up to 300KB.

As I said, this keyboard is based upon Mr. McKown's latest (at time of writing) design, but I've replaced the kingpin from his design with a pair of offcuts of "deck track" meant for model yachts mounted on a small block of wood. The deck track is just a kind of miniature T-slot/T-track or runner.

One end of a piece of deck track.

An "overhead" view.

A cross-sectional view
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my two pieces side-by-side with bolts
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As you can see from the last picture above, the idea is that a nut is held "semi-captive" inside the deck track, and tighened in place against a washer on top of the track. The track I used is made by SAILSetc (see Products | Fittings | Hull) and is available from various hobby shops and the like. It's aluminium, so it's very lightweight. I got mine from Radio Yacht Supplies Australia, who were very nice to deal with, but their online ordering is a bit "primitive" with no secure credit card facilities. The deck track is available in 150, 330, and 500mm lengths. One 330mm piece should be enough for one keyboard, but I bought two 330mm lengths so I'd have some spare in case things didn't go to plan (and also because it looks like it might come in handy for some future project). This way I also saved a little time cutting off the required lengths because I could do both pieces at once.

It is quite possible that this design would work well with just a single length of deck track. I opted for two pieces because I was concerned that the keyswitch mountings would have a tendency to rotate around a single fixing-point. Since the deck track and nuts and bolts are all very cheap, the only real reason to use a single track would be to save a little weight (although I suppose it would also make assembly a little quicker and easier).

For reasons best known to model yachtsmen, the deck track comes with sloped ends. For our purposes we want to be able to run our bolts right up to the end, so the sloping part has got to go. I just sawed it off with a hacksaw. One of the major benefits of this design is that it allows the positions of the keyswitches to be adjusted to fit any width of palm. For this reason I cut my deck track pieces quite a bit longer than the width of my palm. Even if your keyboard doesn't need that much adjustability, I would recommend cutting your pieces a couple of centimetres (or about an inch) longer than the width of your palm to give yourself a bit of "slack". In addition, if you have small or narrow hands then you may need to make the tracks longer than your palm width in order to fit all eight bolts in each track. This design allows the keyswitch mounts to be angled in or out a little, but I doubt that it could easily be made to fit a small child's hand, for example.

Next you will need something on which to mount the deck track and the rest of the frame. I just used an offcut of pine I had lying around, cut to the same length as the deck track. Note that whatever you use will need to be thick enough to mount the braces for the back of your hand, your thumb joint, and the heel of your hand as well as the deck track (but you needn't necessarily mount these the same way that I did). On the other hand, the block does not need to be thick enough to lift the deck track to the correct height above your palm -- the other parts of the frame should do that. My block is probably a little on the thick side (it does actually touch my palm), but I'm happy with it so I'm not going to fiddle about planing it down or anything.

The deck track comes with it's own little mounting bolts and nuts. I initially thought it would be easier to use some small wood screws to mount my track pieces to my wood block until I discovered that the heads of the screws wouldn't fit between the lips of the deck track. (I did later use such screws to mount an extra piece of track for the heel brace -- more on that later).

The complete assembly viewed from the thumb end...

...and from the underside, showing the sunk-in nuts of the deck track mountings