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Keyboard Builders' Digest / Advent Calendar

Glove80: Rethinking split contoured ergonomic keyboard

Co-designer Stephen Cheng reviews the main design and ergonomics decisions of the eight year journey to bring Glove80 split contoured ergonomic keyboard to mass manufacturing.

Stephen Cheng
Published December 13, 2022
This post is part of the KBD.NEWS Advent Calendar 2022. The previous article was: PRK firmware's 2022 by hasumikin. The next post is: 2022 Roundup: the year of EC by Cipulot.

This year is a watershed year for us. Chris Andeae and I took Glove80 to Kickstarter in January and we were amazed by the incredible community support. We are now in the middle of final assembly for batch 1 and with luck we should ship shortly.

Glove80 is not just another ergonomic keyboard. It was an 8 year personal journey for Chris and I. As geeks who were attached to computers from a young age, both of us developed long-term and severe RSI. Many of our friends and colleagues too were in the same boat.

Back in 2014, Chris, a few friends and I decided to make a better contoured keyboard. Lilian Malt’s genius had introduced the world to Maltron and the contoured keywell; the comfort of a contoured keyboard is simply unmatched. Chris was very familiar with the Kinesis Advantage. However we knew a vastly improved contoured keyboard could be built using techniques that were not available to the earlier pioneers. 3D printing had opened the door to further experimentation.

Design goals

Our goals were:

  • To deliver the best ergonomics possible for us: split sides, adjustable tenting, neutral tilt. Neutral tilt was particularly important. Chris had to build a sloping wooden tray for his Kinesis Advantage to achieve a neutral tilt which was essential for his comfort.
  • To work with a wide variety of hand sizes and shapes. I have short pinky fingers, and simply put, I struggle to type anything on Kinesis Advantage with my pinky fingers. We were also told by friends with small hands that there is a lack of ergonomic keyboards that work well for smaller hands.
  • A 6-key thumb cluster whose keys are all easily reachable without stretching.
  • Function keys that are full-sized and easily accessible.
  • Portable. Easy to bring to meetings and take on the road.
  • Extreme customizability.

Superficially Glove80 may look similar to other contoured keyboards such as Maltron, Kinesis Advantage360, or Dactyl Manuform. However behind the casual similarities is a deep rethinking of every aspect of a contoured ergonomic keyboard, which has led to a set of important different design choices.

These design choices were validated by 500+ ergonomic experiments and hardware prototypes, and more than 6 years of long term testing.

This is an account of our eight-year journey and some of the design challenges we faced. We hope that this could provide useful insight for others who are on a similar journey.

Before we go further, here is a Glove80 typing test video:

Scientific data for ergonomic keyboard design

We started off researching hand data and ergonomic information. We thought we could build a digital hand model, and from there determine the perfect ergonomic keyboard.

However once we dug into the scientific literature and academic databases, we were surprised to discover how sparse they were. The best we found were some papers on maximum digit movement with tiny sample sizes, and hand size databases that were limited to a very narrow set of data points such as length and width. However, to build a useful hand model we need far more, at a minimum:

  • The dimensions of each segment of the digits
  • The movement available to each joint for all possible movements

It quickly became obvious that it would be futile to create a hand model, or to design an ergonomic keyboard using such a theoretical method. The required biomechanics data was simply missing.

Scalable hardware prototyping and ergonomic experimentation

Instead we decided to design the ergonomics using empirical methods. That’s a short way of saying "building lots of physical prototypes and doing real ergonomic testing on a wide range of real people".

The biggest challenge is to be able to build physical prototypes. Traditionally, building consumer product prototypes is an extremely time consuming and costly affair. Building a CAD model and making a CNC prototype takes a few thousand dollars and a week minimum per prototype.

Earlier pioneers often used clay models, but clay models have two problems. First, a clay model is simply not accurate enough; 1 degree change in angle or 0.2mm change in position are surprisingly significant in ergonomic design. Secondly, it is practically impossible to reverse engineer from a clay model back into a digital model for manufacturing with sufficient accuracy. Finally, a hand-made model is difficult and time-consuming to make functional, which makes it hard to evaluate ergonomic ideas with real-world typing.

Pic: Imagine what it takes to turn a clay model to a digital model like this, every time you make a new clay model

Imagine what it takes to turn a clay model to a digital model like this, every time you make a new clay model

But in 2014, consumer 3D printing was finally becoming practical, so Chris and I each bought a 3D printer and we started playing. We were blown away by the power of 3D printing, but even so, printing a full keyboard took a full week of printing time.

Being software engineers and compiler writers who lived with optimizations day-in day-out, we quickly realized we could take our software experience into hardware engineering:

  • Modular architecture: similar to software design, we needed a modular architecture that allowed us to easily replace portions of the hardware prototype. This enabled us to cut the printing time required to make a change from a week to as short as 15 minutes.
  • Parametric design: When we first started this journey, we had no idea how sensitive fingers and hands are. We didn’t expect that 1 degree or 0.2mm change would be perceptible, let alone matter ergonomically. Unfortunately, that meant we needed to make many variants to optimize any particular parameter. The amount of time it took to update the CAD model quickly became overwhelming. This is where parametric design came in: by creating a parametric model, we could generate a whole series of variations for about the same effort.
  • A/B testing: We extensively relied on comparative side-by-side evaluation of two or more variants, inspired by the A/B testing method popularized by web application developers and game developers. By swapping out individual modular pieces, we could quickly iterate through a set of variations to determine the optimum. To achieve this, we had to make sure that the printable modules were fully functional, and could be quickly swapped into a working keyboard without PCB redesign or resoldering.

The goal was to build an ergonomic test jig that could work just like a real keyboard for extended long-term testing, while allowing us to easily optimize ergonomics.

Pic: An early fully-functional prototype, showing the replaceable end plates, caddies, thumb cluster and palm rest

An early fully-functional prototype, showing the replaceable end plates, caddies, thumb cluster and palm rest

Overall the ergonomic test equipment is composed of:

  • Individual key caddies for each column of keys. Each column is a separate caddy, which defines the shape of that column’s arc.
  • Two end plates, which determine the rotation angle, up/down position, left/right position, and north/south position of each caddy. The caddies clip into the end plates. This alone provides 4 degrees of freedom for each column. With 6 columns, there are a total of 24 degrees of freedom.
  • A mounting region for thumb panels, so that different thumb panel designs can be easily swapped in..
  • A contoured top cover, including the palm rest, which similarly can be easily replaced.
  • The ideal columnar arc: circular arc vs golden ratio

    Our first attempt in designing a key column was a perfect circular arc. Circles are simple to draw, and there is beauty in their simplicity and regularity.

    However, after five minutes of typing on the first prototype we realized our mistake. The human finger is composed of 3 separate segments which all bend together: with three pivot points, the finger tip moves in a shape very unlike a perfect circular arc. In fact the finger’s “natural” arc is much closer to the golden ratio spiral.

    Pic:

    After this realization, the exercise became a long quest to find the perfect arc shape for each finger. The pinky was especially tricky due to the huge variance of pinky lengths between people. After much experimentation, we found an arc shape that works for long pinkies and short pinkies alike. The resulting shape of that arc is nothing like a circle:

    Pic: A small subset of the pinky finger caddies we experimented with. Each caddy has a unique code identifying the experiment.

    A small subset of the pinky finger caddies we experimented with. Each caddy has a unique code identifying the experiment.

    This design isn’t universal among contoured keyboards: for example, Dactyl and Dactyl Manuform have opted to use circular arcs, while Kinesis Advantage largely defines the shape of its arcs using the contours of the keycap surfaces rather than the angle of the switches themselves.

    Curved two-row thumb cluster

    We tried many different thumb clusters. At first we had no idea what would work at all. We tried different block-style thumb clusters like Maltron and Kinesis Advantage.

    We then tried two rows of 1u keycaps in various configurations. They worked fairly well, if the block is oriented so that it’s perpendicular to the thumb. However, our tests showed that the thumb either tended to bump into the upper row middle key, or alternatively the outer keys were hard to reach.

    Pic: An early experimental 2 + 3 two-row thumb cluster, that we could easily move and rotate to explore the best position

    An early experimental 2 + 3 two-row thumb cluster, that we could easily move and rotate to explore the best position

    The configuration that worked best was two rows of 3 keys each. Trying to figure out why, we realized it is all about the sweeping motion of the thumb. The two-row 3+3 block works well because it can be positioned so that the thumb can reach each of the bottom row keys by sweeping out a nearly-straightened thumb without moving the palm.

    Once we understood how the two-row thumb cluster works, the next steps for improvements were clear:

    • First we identified the bottom joint of the thumb (also known as the CMC joint) as the center point.
    • Then, we drew a circular arc with the thumb CMC joint as the center and the length of the thumb as the radius.
    • We placed two rows of keys along that arc, with an inner row just inside the arc and an outer row just outside it.
    • We made the outer row easier to press without interference by raising its height compared to the inner row.

    This forms the basis of the Glove80 curved two-row thumb cluster, which was then further refined by lots more empirical testing. Some particular aspects that took a lot of iteration to get right were the spacing and tilt for each row, and the amount of staggering between the top and bottom rows.

    Interdependence of ergonomic factors: Palm rest design

    At the beginning of the Glove80 journey, we tried to design each ergonomic element independently. We ended up with what seemed like a comfortable keywell and a curved two-row thumb cluster. Then we decided to add the palm rest. A surprise awaited us.

    The first palm rest gave us wrist pain after a second day of use. We were surprised, as we did not expect the palm rest design to be complicated. We continued to iterate on the design, and the palm rest progressively became more comfortable.

    Pic: Just how hard can it be to design a palm rest?

    Just how hard can it be to design a palm rest?

    However, it soon became obvious that the keywell design that was comfortable without the palm rest was suboptimal with palm rests. With the change in hand position and angle from the improved palm rest, keys were no longer as easily accessible as they had been from the original simple palm rest. We had to re-optimize many elements of the keywell design.

    This is a good illustration of how good ergonomics needs a holistic approach, and how each ergonomic factor interacts with all others, sometimes in surprising ways.

    Keyboard height and neutral tilt

    One of the most important ergonomic factors for keyboards is the position of the arms and wrists. The common advice is that the forearm be held roughly horizontally, and never tilting upwards, and the wrist should not be bent backwards, since this limits the blood flow and is a common cause of wrist pain.

    Most keyboards, including many ergonomic keyboards, make this position difficult to achieve: they have a positive tilt, which forces the wrist to bend upwards. This is something that we refused to compromise on with our Glove80 prototype: we designed it with a neutral tilt, so that the wrist is neither bent upwards nor downwards when typing.

    To allow for both a horizontal arm position and neutral wrist position, the keyboard – specifically the top of the keycaps – needs to be low enough. Unfortunately, the amount of space between your hands and your thigh is extremely limited – and that space needs to accommodate the table, the keyboard and still leave enough wriggle room for your legs. This was a problem for the Glove80 prototype. Its neutral tilt was very comfortable to type on, but it was simply too tall to use on most non-adjustable office tables.

    Pic: Height comparison of the MX-switch Glove80 prototype and the production Choc-switch Glove80

    Height comparison of the MX-switch Glove80 prototype and the production Choc-switch Glove80

    Pic: Height comparison of Glove80 and Kinesis Advantage

    Height comparison of Glove80 and Kinesis Advantage

    We came to the conclusion that to keep the neutral tilt on Glove80, we needed to do everything possible to minimize the keyboard height:

    • Switching to a construction method where the switches are directly mounted on the case rather than on a separate plate
    • Switching from standard MX mechanical switches to the low-profile Kailh Choc mechanical switch
    • Selecting a short low profile keycap.

    This required drastic re-engineering of the whole keyboard, while retaining exactly the same ergonomics. The lowest keys are the home row keys for the middle fingers: ‘D’ and ‘K’ for a qwerty layout. After the redesign, the top of the keycaps of these two keys is a mere 20 mm above the desk (including keycaps, keyswitch, case and feet). For reference, an MX key switch with no key cap is 19mm alone.

    Keycap profile and MCC keycap

    We all have different hand sizes, different typing habits and we use different applications. Glove80 celebrates customizability and with the ZMK firmware made it easy to customize the keyboard layout on the software level. To accommodate this on the hardware level, we decided to use a uniform keycap profile that allows the keycaps to be easily rearranged to match custom layouts, i.e. every key uses the same shape of keycap.

    The MBK keycaps we started with were nice for the main keywell, but did not work well for the Glove80 thumb keys. They cut into the thumb, so what we needed was a cylindrical profile. That's why we ended up designing our own keycap profile: MoErgo Choc Cylindrical (MCC).

    Pic: Glove80 knows how to party too

    Glove80 knows how to party too

    We wanted a minimal look for the production Glove80, so we decided to hide the LED indicators behind the keyswitches. To achieve this, we made our MCC keycaps using translucent POM material. This also allowed us to easily extend our plans for a few indicator LEDs into support for full RGB backlighting. Like with the keyboard itself, it took many iterations to get the POM material just right with translucency and ability to laser mark legends, but POM’s wonderful buttery-smooth typing feel is absolutely worth it.

    Conclusion and looking forward

    With the first mass manufacturing batch of Glove80 at the final assembly stage, our Kickstarter backers will soon be receiving their Glove80s. We started our Glove80 journey wanting to democratize keyboard ergonomics, and we are immensely grateful to our backers for making this dream real. With mass manufacturing, we are hopeful we can make top-notch keyboard ergonomics accessible to anyone who types a lot.

    Looking forward, Chris and I have many extension ideas to make Glove80 even more comfortable and useful. Glove80 is designed to be extensible, with a GPIO extension header and various mounting points for accessories. We will be working on some of these ideas, and we expect our users to come up with many cool solutions too.

    Pic: Template sidecar expansion module to attach to Glove80. You can add switches, dial indicators, display, touchpad or whatever you fancy

    Template sidecar expansion module to attach to Glove80. You can add switches, dial indicators, display, touchpad or whatever you fancy

    Special mounting is another area that we will focus on. Although Glove80 already supports many mounting methods, we believe there is much further to go. Wireless, split and custom mounting is a potent combo that could further ergonomics.

    Pic: Glove80 mounted on an office chair

    Glove80 mounted on an office chair

    Resources

    Stephen Cheng


    @moergo_keeb / MoErgo
    LocationWellington, New Zealand
    OccupationInventor at heart; serial entrepreneur by necessity
    OutlookHolistic thinking is the foundation of good solutions
    Other inventionsTessellated origami furniture, OO-refactoring optimizing compilers, cross language compilers for the mobile industry, high availability middleware, harvesting equipment to boost life-cycle land-use efficiency
    Linksmoergo.com

    Published on Tue 13th Dec 2022. Featured in KBD #107.


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