And this was before I had even begun to look seriously at the electronics. Eventually I decided that the thumb cluster wasn't quite right for a couple of reasons;
1) Your thumb curls inward, not down. It would be pointless to do all the work adjusting for the fingers if the thumb wasn't moving in the optimum motion either, hence the dropped angle not only putting it at a natural resting position but also allowing it to curl in.
Well this is kind of what I mean, and why I say that someone designing a new keyboard should spend some time studying hand anatomy and talking to ergonomics experts. (I’m also not an anatomist or ergonomist or expert: I’ve read some books aimed at laymen and I’ve spent a bunch of time closely inspecting my hand motions, but someone who is e.g. a skilled musical instrument teacher, or a physical therapist, or a professional ergonomics researcher, or a surgeon, etc., will surely have more insight than I do.)
Inre thumb motion: try it! There are 3 joints in the thumb, 2 of which are the main drivers for orienting the thumb relative to a key and pressing it. The distal one of these, the metacarpophalangeal joint, just rotates in one dimension. The proximal one, the carpometacarpal joint, is quite a sophisticated joint, with a bunch of ligagments attached to it, and can move in all kinds of tricky ways, including curling inward [“flexion”/“extension”] (this is aided by the metacarpophalangeal joint usually), and moving up/down [“abduction”/“adduction”], etc. I’m sure this article would be a more useful guide than any summary I can give
http://onlinelibrary.wiley.com/doi/10.1002/jor.1100100319/abstract (seems to be the most cited one on google scholar) or there are surely some others that aren’t paywalled.
A standard keyboard, as well as the ergodox, kinesis, maltron rely mainly on the main direction of carpometacarpal movement. Of these, I haven’t tried a Maltron, but in making prototypes of my own with plastilina and cardboard, and from just holding loose switches in one hand with the other hand sitting in a neutral position and trying to press them, I believe that the Maltron has the best angle for taking advantage of the natural direction of motion for the strongest type of thumb motion. The Kinesis Advantage is in my opinion is a less effective angle, and the ergodox has a still less effective angle.
Oobly’s DIY keyboard, for example, relies on a different, inward movement of the carpometacarpal, plus an assist from the metacarpophalangeal joint. This is in my experience a less easy/powerful joint movement, but he gets away with it by having all the keys very easy to reach, which more than makes up the difference compared to the poor placement of Ergodox thumb keys.
Figuring out the proper height and direction for the thumb to move though, such that (a) the motion takes as little effort as possible using the biggest muscles and aligning with the movement as closely as possible, and (b) reaching all the keys is easy and natural is a quite non-trivial problem. And figuring out something that will work for very large or very small hands is difficult indeed.
2) Adjustability, both for hand size and positioning. This has allowed someone with tiny hands to rest as naturally on the board as my own sizable mitts.
Adjustability is great! Ideally every position and angle could be adjusted, as well as keycap sizes, key spacing, etc. Figuring out just what can be reasonably adjusted and which problems that solves for which hands is pretty tricky. Hopefully the adjustment is both easy and sufficient to match a big range of hands.
On both the ergodox, the little and index columns didn't sit at enough of a height difference I found, and it took a bit of tweaking to find a height that was more comfortable not only to me, but others as well.
Agreed. I find that if the index finger and ring finger keys are level, then the middle finger can use about half a key of stagger, upwards, and the pinky can use at least half a key of stagger, downward. But note, on a standard keyboard, often the best finger to use for a key is not the same as the one advocated by typing teachers / learning materials. As a result, many people have non-standard ways of moving their hands and type keys with other than the recommended fingers. Sometimes people even use different hands to type the 6, Y, or B keys (in QWERTY) depending on which word is being typed. When moving to a matrix or column stagger layout instead, those inconsistencies are going to require a few weeks of getting used to the new layout (maybe sped up by some clever custom character mapping). Even on a column staggered board though, it may not always be ideal to use a separate finger for all the keys in each column (e.g. the pinkies are not going to be easily able to reach up to a number row, so those keys are probably going to be pressed by the ring finger anyway.), which may have some bearing on how much stagger is ideal, depending on how many rows and columns of keys are included.