Interference between thumb and finger clusters

[nickcoutsos]

Just noticed this but it seems to have been an existing issue. The second column of the finger cluster is intersecting with thumb cluster column support and plate. One option would be shifting the thumb cluster over a tiny bit, but because it's a small corner of the finger column support's bottom side it may be possible to solve this by rounding/chamfering and keeping true to the original thumb cluster implementation.

[7t2]

I think it is very important to keep the thumb cluster in its original spot for ergonomic reasons. So we could either alter the design by cutting the corner of the support off, or we could hand file the problem material away during assembly. I think removing a little bit of material shouldn't be too much of a problem, and needing to own a file would add to the total cost of the keyboard

[nickcoutsos]

Definitely in favour of removing the interference in the design. I want to apply the change generically so I'll need to make sure I'm not removing enough to cause strength issues. Shouldn't be a big problem.

[nickcoutsos]

I've had a closer look. It doesn't take much work to cut off the corner of the columns, but sadly that isn't enough.

Here's the overlap:

Blue is the thumb cluster, red is the finger cluster, and yellow is their intersection. Even cutting a hole into that column of the thumb cluster isn't viable because the intersection goes almost through its entire height.

If I shift the thumb cluster 0.62mm left and 0.62mm forward I can clear it. Here's a couple of images showing the difference:

Staying true to the original Dactyl's measurements was a major design goal for this project, but this is a tough one. If the thumb's column support is in that position and a finger cluster has to sit right next to it then my options are limited.

I tried a longer cut out of the finger cluster's column support which lets it clear the thumb cluster, but it looks incredibly fragile.

That's a rough experiment, but you can see that I'd have to think through how that applies to the profile of other columns. Technically this only has to work for a single column but I'm not too happy with one-off solutions like that.

[7t2]

In my opinion I think that you should definitely stay true to the original Dactyl's measurements and not shift the thumb cluster. I also understand the appeal of wanting to apply the change generically so that you are not making changes to one single column support. I believe that in this situation, it is worth it to apply the change to the single column support, even if it breaks symmetry and requires more code to maintain. In regards to the fragility of the little alignment nub, it would be epoxied to the keycap during assembly, so I do not think that it is much of a problem. The main point of consideration in regards to fragility, is that the bottom of the switch holder is well supported, which it still is.

Either that, or you can just require the person assembling the unit to file off the intersecting corner, keeping as much strength as possible. It is a complicated diy project after all, so requiring a file/sandpaper isn't the end of the world.

[nickcoutsos]

It's not about symmetry so much as the code making sense. More special cases means it's harder to keep track of what's happening and why.

In regards to the fragility of the little alignment nub, it would be epoxied to the keycap during assembly, so I do not think that it is much of a problem.

No, I'm more worried about the end of the column snapping off either during assembly or during regular use. You have these pieces in 2mm acrylic, what's your feeling about those column pieces at their narrowest?

[7t2]

There is plenty of strength in the columns, even when pushing directly on the overhanging corners. But when a switch is installed, the weight of the press is distributed more evenly and it feels like there is plenty of extra strength avaliable to remove material. However, if you wanted to give some extra strength back to the column, you could add some material in a similar method to this

[nickcoutsos]

I'll have to make some other adjustments there so that the columns aren't intersecting the base I'm working on but I should be able to do that as well. Thanks for offering your perspective on this!

[7t2]

Not a problem at all man, thank you for your time and effort!