The missing piece is that the trackball doesn't click, and this seems to be the case in general with trackballs on the market.
Does anyone know why trackballs don't click? I'm imagining a casing that would allow the entire ball to drop by a few millimeters to trigger a click. One potential reason is that it's hard to click without moving the mouse on screen, but I'm unsure of how much of an issue that is in reality.
I build keyboards/mice for a living and also think a trackball with tap to click would be great. Intuitively I see why this would be complex to build. I would say the major paths are a physical switch or touch sensor. I see the physical switch as similar to a mouse wheel which lets you middle click it;- disassemble a mouse and see it's really quite complex to have this whole electronic component move up and down hitting lever. Now imagine trying to mount a similar system below a trackball with 3 far apart touch points and continuous movement of the ball rather than the discrete movement of the mouse wheel which can absorb some rotation (as you mention). I think a touch sensor would be a really interesting way to go, you could probably pass conduction through the right ball and sensor touching the ball, A force feedback vibration motor might also be possible.
The angle of your thumb on the ball will change and turn the ball unless the press is perfect parallel to the axis of the switch at the point exactly opposing the switch on the ball.
I saw the mod that Kevin Christensen wrote on ZSA's site: https://blog.zsa.io/diy-moonlander-trackball/
The missing piece is that the trackball doesn't click, and this seems to be the case in general with trackballs on the market.
Does anyone know why trackballs don't click? I'm imagining a casing that would allow the entire ball to drop by a few millimeters to trigger a click. One potential reason is that it's hard to click without moving the mouse on screen, but I'm unsure of how much of an issue that is in reality.