[14:05] Now that I've got some way of splicing some loops, I can start printing out a concept so that I can obtain the correct tension required. One of the drawbacks of this design is that there isn't any way of adjusting chain tension and ball-chains themselves would be rather inflexible. I can only assume a 3rd pulley, connected via a flexure of some kind, would allow for looser tolerances in this regard.

The first print attempt is currently being printed as I type.

[18:00] So I used tape to hold the ball chain onto the print without even needing to splice anything. Looking back, I probably should've tried this weeks ago. 

The good news is that it looks like the renders and it seems to work well with my fingernails; I actually have grip instead of the ice skating my fingers have to contest with on keyboards. Finger5, which seems to approach at an angle almost 45 degrees from the normal, seems to have rather good grip.

If slippage does occur, I think it feels more comfortable than a GT2 belt. The chain does sit inside the sprocket, but I think I'm near the limit before I need to add another tooth. Additionally, it seems that the chain doesn't leave the track when this Tetrinsic mockup is in varying orientations, such as upside-down. When my eyes are closed, it's easy enough to feel where the center of the chains are.

The bad news is that it seems that the chain won't make the 8mm diameter pulley bend without significantly lifting from the track (see below), as well as the understandable fact that the difference between tensioned and loose seems to be on the order of fractions of a milimeter.

I can't tell if I've engineered myself into a corner or if someone else designing a motorised, pressure sensitive linear slider would come to the same general design (e.g. a computer mouse having at least a left / right click button and a scroll wheel). The main requirement really is that Tetent works for me, not the other way around, thus that's the reason why a tangible requirement for Tetrinsic was natural fingernail compatibility; I didn't want to meticulously trim them (and lose out on their benefits in day-to-day life) just so I can type.

It doesn't help that the current best option for splicing is a £90 tool, but if Tetrinsic ever got popular enough, there'd be some AliExpress seller selling prespliced chains and so the tool cost would be a non-issue. I'm not sure if the issues discovered are showstoppers or not, but until I have something manufacturable, having to restart from square 1 is still a possibility.