Into the depths...

This FRLTKL designed by Upas is themed after the three-headed hound that guards the gates of Hades.

Like the creature it is named after, the design of the Cerberus keyboard revolves around 3 major points of interest. An intricately engraved crest, three heads with glowing eyes, and removable sides that can be swapped out for a different colour. Each of these come together to create a keyboard that allows for customisation, staying true to the theme.

The Mounting Style

The Cerberus keyboard and Brutal v2 both use a single-sided gasket mounting structure, where only the bottom case has gaskets. The goal of this structure is to better mimic the sound of top mount keyboards, while also adding some of the benefits of gaskets.

In top mount keyboards, the plate is screwed into the top part of the keyboard, making plate-to-top contact, and does not touch the bottom part of the keyboard. On Cerberus, this plate-to-top contact is present due to the gaskets only existing under the plate, and the top case being designed to touch the top plate.

And by virtue of having gaskets under the plate, there is some bounce present when typing on the board, more similar to a Bakeneko or other gasket mounted board. This provides acoustic isolation between the plate and bottom case - eliminating a confounding factor in trying to achieve that top mount style sound.

The end result is a board that sounds as good as and also feels less stiff than a traditional top mount board (though, in my opinion, plate material will make the most difference in terms of perceived stiffness).

With that in mind - there are still some key differences in the mounting style of Cerberus and the Brutal v2 series. Primarily, the Cerberus covers far less surface area with gaskets than the Brutal v2 did. This results in more bounce, as there are fewer contact points where gaskets need to compress. But I believe the resulting sound is more similar to top mount - on usual top mount boards, the plate to top contact zones are not that large.

The Theme

Since this board is meant to be a bit of a sequel to Chimera - I picked another mythological creature as its theme. I didn’t want to make another Chimera-style board - like a ChimeraTKL or a Chimera75 (though, if people want that, please let me know) - I wanted it to be something new.

Cerberus is a three headed dog from Greek mythology who guarded the gates of Hades. So with the theme of Cerberus, I tried to design around the concept of three. Cerberus has three heads, so the board has three main accent pieces. There are two coloured side pieces, and a bottom crest all sharing an accent colour - for three accent pieces total. And when looking at the bottom of the board, there are three “weights” visible (two brass, one accent piece).

Finally, there’s an engraving of a Cerberus head on the top of the board above the arrow cluster. One piece of feedback I heard about Chimera is that people wished the engraving on the back of the board was mimicked on the front. So I tried to do that here. In addition, the eyes glow with RGB LEDs mounted behind them.

Other Design Considerations

The side profile of the board was designed to be aesthetically pleasing, while still giving users an easy way to pick up the board. One of my personal pet peeves is when a board is hard to pick up - and I try to avoid that in my designs. Many of my previous boards have featured Koala-like curves to enable this, but this time around, I went with a curved back.

For this board, I decided to include wireless functionality. It’s likely not going to be wireless by default, but I wanted to ensure that people who want a wireless board would have an option here for it. The interior of the case has a cavity to hold a battery, and when I tested a ZMK PCB that I designed for Cerberus with an FR4 plate, the wireless worked well. When using the wireless PCB, the RGB LEDs shining through the Cerberus’s eyes also double as status indicators - which I think is a neat little touch.

To reduce the acoustic impact of including this battery cavity, I also included an inner brass weight. This weight spans across the alphas on the board - which has been perceived by hobbyists in the past to improve the sound of the alphas as well. Personally, I do think it makes an impact which I consider an improvement, but if others prefer the sound without the inner weight, that’s totally valid as well.

I also wanted the Cerberus to sit low on a desk. It’s not the lowest keyboard ever designed, but the front of the keyboard is less than 18mm tall (as it sits on a desk), and the case is ~20mm tall at the middle of the first row of keys.The case has a 6.5 degree typing angle, to make it comfortable for most people.

As a result of the design decision to make the keyboard sit low - including three external weights was non-trivial. Parts of the bottom case are entirely cut out to ensure the weights have space to mount. But the acoustic impacts of these cutouts are mitigated by the inner brass weight covering.

There are 4 POM alignment pins included in each unit to help ensure the plate stays centred. The current mounting style does compress the bottom gaskets (which are quite soft) a little, but does not provide nearly enough compression to lock the plate in place. I also don’t use screws to keep the plate in place as you would if you were making a top mount board - so I chose to use alignment pins. I drew inspiration from the Moment keyboard designed by jjw - this was also a single-sided gasket mounted board, with the key difference being that the top case did not touch the plate.

Finally - I wanted to design this board to be price accessible. One of the key reasons why I chose to use an inner weight and three external weights instead of relying on a through weight was to keep costs down. This is a bit counterintuitive - how can more parts be cheaper than one part? But the external weight and inner weight can all be machined from flat stock. Through weights typically have angled features, requiring extra machine time which drives up the cost of keyboards. The inner weight also solved other design problems as well, making the choice even easier.

The Small Details

To provide even compression across the gaskets, and also keep the back curve present on the board, I had to use “internal” screws. There are four screws on the bottom of the board that are necessary to keep the top and bottom case parts together - but there are also 6 screws under the keycaps. The screws that we’ll include for Cerberus will be black screws - at least for these 6 spots - so that the chances of noticing the screws under your keycaps in day to day use is minimised.

And about the four screws on the bottom of the board - we’ve created moulded rubber feet to cover where they sit. If you look at the bottom of the board once fully assembled, you won’t see screw holes. I may modify these to round out the edges to make them less noticeable.

Hearing feedback on prior projects about the big Cannon logo being a polarising feature - I’ve decided to move it to above the USB port for Cerberus. It’s much smaller than it was on a board like Chimera or Balance, and much easier to ignore now if you aren’t a huge fan of it.

The side accent pieces have a small chamfer where they meet the top and bottom cases - which also share this small chamfer. This little design element helps further provide separation between the accent pieces and the top and bottom cases. The top and bottom cases are designed to look seamless.

And the USB port is centred on the back of the board, and features a little hood. This should cover most of the metal bits on most USB cables, so your board will look sleek when used.

I’ve also added little cutouts for force-break specific gaskets.The idea behind force breaking is to break the metal on metal contact of the top case with the bottom case. In my testing, I used soft poron for force breaking, which did make a small change in acoustics. I believe the board already sounds good without force breaking - but this is an extra way that people can tune their boards to match their preference.

I used the same cutouts and gaskets to also provide force-breaking between the plate and top case. Personally, I preferred the acoustics of the board without these installed. Installing them removes the plate-to-top contact which helps the board mimic top-mount acoustics. But they are also there for those who want to experiment and tune their board, or simply prefer a more isolated sound.

Thanks!
Upas

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