the Stabilizer Problem

🌈 Abstract

The article discusses the long-standing problem of stabilizers in the world of mechanical keyboards, which are critical components that prevent longer keys from seesawing upward when the opposite end is pressed down. The author, who is on a mission to create the "perfect luxury keyboard", embarks on a multi-year journey to solve this problem, going through various design iterations and consulting with experts, in order to develop a stabilizer that eliminates rattle and ticking without the need for lubrication, while also accommodating dimensional variability and providing smooth, binding-free movement.

🙋 Q&A

[01] The Stabilizer Problem

1. What are the main issues with current stabilizer solutions?

• Current stabilizer solutions serve their purpose of preventing longer keys from seesawing, but they all have an undesirable rattling sound.
• Hobbyist modders have to spend a lot of time hand-lubricating and tuning their stabilizers to eliminate the rattle, which is an "ugly hack" and a "concession of defeat" due to poor engineering.

2. What are the author's goals for the stabilizer design?

• Eliminate rattle and ticking without the need for lubrication
• Accommodate dimensional variability across a wide range of keycap stem spacings
• Provide free and smooth movement without any binding
• Not significantly alter the force curve of the switch when used without stabilization
• Be compatible with the author's own capacitive switches
• Allow for tool-free installation and removal of keycaps

3. What are the key challenges the author faces in solving the stabilizer problem?

• Tiny parts are extremely expensive to prototype with accuracy and good surface finishes, making the cost of iterating very high.
• There is a contradiction between the need for the stabilizer mechanism to be "tight" to prevent unwanted sounds, and "loose" to allow for free movement without binding.
• Existing stabilizer designs are kinematically over-constrained, making them highly sensitive to manufacturing variations and prone to binding.

[02] Paradoxes and Contradictions

1. What is the paradox in the design requirements for a stabilizer? The stabilizer mechanism must be "tight" to prevent unwanted sounds (rattle and ticking), but also "loose" to allow for free movement without binding. These two objectives typically require small gaps between mating parts, which are contradictory.

2. How do existing stabilizer designs address this paradox? Existing stabilizer designs seem to favor a key that actually moves up and down (loose fits) over one that is unusable but pleasantly silent (tight fits). This is why they have large gaps and rattle, requiring the "unhappy grease band-aid" solution.

[03] Bearing Ratio and the Binding Paradox

1. What is the relationship between stabilizers and linear bearings? A key stabilizer is essentially a sliding linear bearing, and the geometric constraints of a traditional stabilized key switch are a particularly bad scenario for good linear bearing performance, leading to sensitivity to friction and manufacturing variation, and the accumulation of forces that inevitably leads to binding.

2. How does the author's lack of formal engineering training impact the project? The author's ignorance and "yolo audacity" allowed him to think the stabilizer problem could be an easy one to solve, despite having no formal training in mechanical engineering. This led him to approach the problem through empirical tinkering, rather than a deep understanding of the underlying engineering principles.

[04] Product Development via Dolorosa, in Three Acts

1. What were the author's initial assumptions and design objectives for the stabilizer? The author initially assumed that by prioritizing performance over cost optimizations, he could easily go further than previous solutions. His initial design objectives included eliminating rattle and ticking without lubrication, accommodating dimensional variability, providing smooth movement without binding, and compatibility with his own capacitive switches.

2. What were the key lessons the author learned through the iterative design process? The author learned that tiny parts are extremely expensive to prototype, that there is a contradiction between the need for tight and loose fits, and that existing stabilizer designs are kinematically over-constrained, leading to binding issues.

[05] Act I: Tinkering and Bricolage

1. What were the author's initial attempts to solve the stabilizer problem? The author's first approach was to try using self-lubricating plastic bushings as a linear bearing solution, but this quickly ran into issues with the high cost of prototyping tiny, precise parts. The author also experimented with different materials and a Scotch yoke design, but could not find a solution that eliminated both rattle and binding.

2. What pattern emerged from the author's early experimentation? The author identified three opposed concerns - good acoustics, good mechanical performance, and support for keycap width variations - where optimizing one would always seem to sacrifice the others.

[06] Act II: Kinematic and Tolerance Optimization within the Existing Paradigm

1. How did the author's research into compliant mechanisms influence the project? The author's research into compliant mechanisms led him to realize that they could provide the properties he wanted in a stabilizer, as a single-part design could eliminate the separate parts hitting against each other that cause acoustic issues. However, the complexity and cost of developing a compliant mechanism solution proved to be too risky.

2. What key insight did the author gain from working with the RD8 engineering firm? RD8 introduced the author to the concept of kinematic optimization, which focuses on ensuring that a mechanical system only has the minimum necessary constraints to achieve the desired movements. This allowed them to develop a stabilizer design that was both "tight" and "loose", eliminating over-constraints that lead to binding issues.

[07] Act III: Utopian Reinvention - the Norbauer-type Stabilizer

1. What are the key innovations of the Norbauer-type stabilizer design? The Norbauer-type stabilizer uses a three-dimensional pin joint architecture, rather than a two-dimensional linear slide, to effectively lengthen the bearing and eliminate the issues of bearing ratio and manufacturing tolerances that plagued previous designs. This allows for effectively zero clearance at all interfaces, eliminating both rattle and ticking.

2. What were the major challenges in developing the Norbauer-type stabilizer? The extremely confined work envelope, with the need to fit 21 parts into a 1 cm³ volume, made the design incredibly complex and difficult to engineer. The high part count and need for precision injection molding also significantly increased the cost and tooling requirements compared to previous stabilizer designs.