Hammerhead Karoo Product Development Series: Chapter 7 — Mechanical Engineering
This is the next retrospective installment of our story of bringing Karoo to life. Following on from Chapters 5 and 6, a factory has been chosen and the Karoo is prototyped— so let’s just start cranking out Karoos, right? Not at all. In a way, we needed to design it all over again…
The process of engineering Karoo has resulted in more than 900 pages of documentation and decision-making. Our team of electrical and mechanical specialists has worked exhaustively to both engineer Karoo — a device unlike anything else they’d ever seen — and the completely separate process of producing it on a large scale.
Our VP of Hardware, Rob, has been in charge of this entire process since day one. Him, myself, and almost every other member of the product team has crossed the night into the pre-dawn twilight hours many times, in order to ensure every part of this project reaches its proper end state. This continues — even intensifies — as we move towards the final chapters of our story, and certainly as you, the patient and expectant two-wheeled traveler, read these words.
To recap and give a rough outline of the development story we’ve told so far: We identified a market need, realized by the passion of our team of cyclists and technologists. We conceptualized a product, and used competitive analysis and market trends to specify the product. We then sorted both constraints and possibilities based on current technology, conducted industrial design, engineering, detailed specification processes, and factory vetting. Here we made tradeoffs between form and function. Make it rugged, smaller, smoother, darker, waterproof, ergonomic, polarized, UV resistant, washable, wipeable, responsive, vibration resistant. We throw these adjectives and more into a pot, and much stirring later, we end up with Karoo.
Once we finish the industrial design phase, a totally new challenge presents itself: mechanical design, and the large-scale production of the device. Hand-making a few prototypes is one thing — it’s slow, expensive, and really just for proof of design and function basics. The process of working with a manufacturing facility, however, to design every individual component in such a way that it can be reliably and consistently made, over and over again, economically, in conjunction with myriad others, is almost like starting over.
And yet, before we can even start that process, we need to work with the factory to test (and potentially re-engineer) almost every component individually, to make sure we should be building it on a large scale to begin with — or, for example, if a certain element needs to be reconsidered. Each part of Karoo has been compiled and tested by a thorough investigation long enough to write a book. Here are just a few examples of what drove our decisions and (some of) how the validation of these parts occurred:
The Screen
The fundamentals of a screen are the illumination type, aspect ratio, pixel density, power use, and luminous intensity. Most smartphones’ screens are hyped with extensive marketing on pixel density, clarity, and size. It’s certainly a race in which we’re not trying to involve ourselves. Most of these screens are aggressive battery hogs, too, especially when trying to fight the sun. Some OLED technology is starting to change things, but it’s currently cost-prohibitive. The existing head-unit market is hovering around a screen size of 2.5–3 inches — too small to display a good map experience, meaningful training data, or to house a keyboard to actually input information — and often monochrome or relatively low-contrast.
Reflective, monochrome screens are great for contrast but less effective for differentiating information. The Karoo screen had to be full color but somehow still hold its own in high-light conditions, but then we run into an efficiency problem. The Karoo needed to maintain a high contrast ratio in direct sunlight while not sacrificing battery life of at least 10 hours and ideally 15+ with optimizations. To understand this more technically: you need at least 600 millicandelas have any sense of readability in direct sunlight. Your standard transmissive LCD screen or off the shelf OLED was not going to be able to meet this without enormously increasing power requirements of the final device. While OLED is getting there with efficiency it is still not mature enough for our market.
Also necessary was to develop capacitive touch into this screen that was “intelligent” enough to deal with the many types of accidental input it could receive during use, from blunt gloves to water or dirt and mud, without being too complex. We’ve all used devices that cut corners in rendering these screens for production (slow to respond, if they respond at all, or sometimes responding to a button you clearly didn’t press), but that wasn’t going to be acceptable for Karoo. The user interface required responsiveness seen in smartphones.
We had a shortlist of 24 screen manufacturers, from companies like Mitsubishi, Sony, Kyocera, Sharp, Casio, OSD, Tianma, TPK, Samsung, Hydis, Kingtech, Ampire, and more. During testing of various screen technologies from these companies that were economically and technically viable for Karoo’s production, we measured the power draw, varied ambient light conditions, temperature fluctuation tolerances, contrast ratios, saturation, and more. Ultimately, we narrowed it down to one, and moved forward with determining how to protect and house it.
A host of details had to be sorted to protect the screen itself. We picked glass to have a better touch screen and to protect our display. Corning Gorilla glass 4 tested well for rigidity, impact, and scratch resistance. However, we also needed to protect the edges, so we designed a protective bezel, and at the same time, optimized it for enough offset to protect the top of the glass if you were to put it face-down on a flat surface.
Over the summer, Caffery, our Director of Communications, hit a major pothole on busy Canal Street in Manhattan riding home from the office one evening, sending his early Karoo prototype (and this bezel design) flying at around 30mph. It smashed into the tarmac, tumbled a bit, then skid face-down over the road the for at least 50 feet, with traffic swirling all around it. In a bit of a miracle, Caffery was able to grab it before any vehicles could hit it. While the prototype’s bracket foot had failed and sent the unit flying (note: it’s been heavily updated since), the screen and bezel design was handily proven effective.
This anecdote, and many more, in addition to lots of controlled in-house testing, left us confident in finalizing the screen design as a whole for production.
Sealing Out the Elements
A lot of our mechanical design considered the unique needs of a mountain biker or long-distance tourer. We knew if we could meet their needs, on-road requirements should be relatively easy. With this in mind, Karoo needed to be waterproof and dustproof to supreme degrees. We set out sites on certifying it to the IP67 waterproofing standard.
We chose the most-effective sealing method that is generally employed across ruggedized devices, an O-ring in a U-channel, with compression is provided by eight equally spaced screws, each of which have their own O-rings. The USB port is waterproof in its construction, as well, while it locks into the housing with an O-ring. This layout was superfluous by some standards, and adding a bit of cost and complexity which some facility engineers advised us wouldn’t be necessary for production, but we’d preferred to err on the side of assuming people will do things to this device we can’t even imagine.
Housing Assembly
The engineering of the housing’s form and production had to account for the durability we’d benchmarked, and the beautiful lines that Julio had penned, without costing a fortune. We considered various renderings of this shape and different variables therein — should the screws be exposed, for example, or hidden? If they’re exposed, are there risks? If they’re hidden, would assembly or repair processes of the device be compromised? Do we even need to use screws everywhere to assemble the housing, or are there superior fixing mechanisms for different, specific applications therein? What types of screws may be best for Karoo’s mission, anyway? And all of these screw-related questions and more came from just one of the dozens of dimensions of Karoo’s housing paradigm.
Many answers later, both the housing and the structural skeleton of Karoo are something I will admit to being proud of! An incredibly complicated but efficient aluminum-titanium framework provides superb rigidity while also affording the surface area necessary for all mounting points for all key electronics and other hardware components on the interior. The whole structure comes together in three parts, where the buttons are all isolated from the outside world under what I call “trampoline seals,” or basically silicone membranes that flex as the buttons are depressed. They are immensely satisfying to use.
On that subject, it’s hard to overstate the deceptiveness of the complication of button selection (the touchscreen is central to Karoo’s functioning, but it’s not standalone — the buttons are for use when the screen may just be too dirty or your gloves are too thick). We spent much time testing different buttons for actuation depth, actuation force, and overall size. The outer shell holds the four button caps and clips on nice and snug.
Inside the housing, linking those buttons are connectors between various switches, sub-assemblies, antennas, the screen, the battery, and other parts of the PCB to the aforementioned skeleton. Many types of tests would need to be conducted to ensure that all of it would stay connected.
All of this is really just a small percentage of the insight we could share into the process of prepping Karoo for mass production. This chapter is shorter than I would have liked right now, but we can perhaps expand on it later.
Next time, I want to share a bit more of the processes that went into proving that it all could work as planned. It was a crucial step to ensuring Karoo would live up to the promises we’ve made.
Thanks, as always, for following along. More to come soon!
Written by Caffery Garff and Laurence Wattrus.
Click here to read Chapter 8 of this series.
