The humble stem isn’t typically the most exciting part of a bicycle. That is unless you’re Escape Collective member Jamie Hough and you’ve just created your own (stunning) aluminium stem for an industrial design course at university.
In this fascinating story, Jamie explains the why and how of his Honours degree project, from design, through manufacturing, to the finished product, explaining what he learned along the way. And as you’ll soon see, the result of Jamie’s work is quite spectacular.
The term ‘CNC’ gets thrown around a lot in the bike industry, typically as a nonchalant descriptor for a product that seemingly creates a point of difference from other products. CNC is an acronym for ‘computer numerical control’ which by itself doesn’t mean much; it simply describes the automated control of something by computers. However, when someone says ‘CNC’ they usually mean CNC-machining, which describes the computer control of a tool via coded instructions (programs). The tool in question can come in many forms: drills, lathes, mills, routers, and 3D printers, to name a few.
As an aspiring industrial designer, the CNC is one of the coolest bits of technology associated with advanced manufacturing and prototyping. Equal (but opposite in approach) to 3D printing, it allows you to translate a digital model into a physical item with relative ease compared to traditional forms of manufacturing.
OK, that might be a slight oversimplification of the work required. Perhaps a better way to understand it could be to follow along as I share with you my experience of designing and making a custom CNC’d road bike stem completed in 2023 as part of my industrial design studies at university.
So, strap yourself onto the proverbial saddle and follow along as I attempt to channel Romian and Trelorian storytelling techniques toward the making of a bike stem and the underlying factors that make this project more than just a hunk of aluminium chiselled into something somewhat nice to behold.
2SS stem
Let’s start at the end. This is the stem. It is a 100 mm-long, -17º road bike stem with a 31.8 mm handlebar clamp and a 1 1/8″ steerer bore. It weighs a relatively stout 228 grams with bolts and a top cap (not shown). It is machined out of 6061-T6 Aluminium alloy, then anodized and laser engraved and finally fitted together with prototypical bolts (more on that later).
A bit about me
The stem is affectionately known as the 2SS stem – or ‘2 second starts’ – it was my attempt at being clever through a double entendre. Here’s how I argue this name: The stem is functionally and aesthetically that good (my opinion, naturally) that you will be faster if you use it. I have no research or testing to back up my claim, but the sheer electric glow of the anodized blue finish and the engraved graphics may temporarily blind/distract/entrance a fellow rider or car driver a nominal amount of time at a stop that you can take off unbeknownst to them. Let’s call it a two second (head)start. It’s a stretch, but I think it works?
The stem also showcases how close I am to being ready to practice as an industrial designer. 2024 is my final year of this degree, after which I will be able to struggle as a 35-year-old trying to recapture the childlike imagination and creativity that has been lost to maturity and the realities of adult life and channel it into designing ‘things’. The real challenge is shortly upon me, but this new career path fills me with joy and excitement compared to my former life doing mundane, repetitive office-work. Here’s to second starts! (Better?)
If we go back just a little further in time, you may understand just how important this stem is to me. Before going back to university in 2020 I worked for six years in another industry and over time I became more anxious, depressed, and apathetic toward my career as it progressed down a path I was not enjoying. What I didn’t tap into as a young adult was my own self interests and drivers. My attitude in these years stemmed from an initial disinterest in studying coupled with a lack of direction in what I wanted to do.
Around 2015 I got into cycling, first for transport and then for sport. You can thank Escape Collective’s very own Andy van Bergen for my first road bike – a 2006-ish alloy Colnago Dream purchased from Facebook Marketplace. The intervening years, between taking up cycling and starting a new degree, saw me rapidly build fitness and skill. Every Tuesday I would ride a shoppie through Kew, Melbourne, striving for a sub-10-minute Yarra Southbound time. This gave me purpose and drive for a few years outside of my working life. Getting up at 5am became the norm and more riding ensued as it became a way of life, second only to drinking more coffee and eating croissants.
The tour de force of cycling for fitness, sport, and social purposes was a great distraction from my career, or lack thereof, but I inevitably burned out and became disinterested in riding altogether. I seemingly have a real ability to get bored and shut off from something that was otherwise my passion, which I am sure was a major factor in my career trajectory to date. My working life became my focus again, and travelling and getting married could only provide temporary relief.
At the start of 2020 I decided enough was enough and with the support of my wife I quit my job with no prospects lined up. If your mind is itching at what happened in 2020, it was COVID. People from Victoria experienced some of the worst lockdown conditions around the world and for a lot of people that was hell – but for me, someone with a lot of time on their hands, it was the impetus I needed to explore further study. I narrowed down my interest to industrial design and decided to enrol in a degree commencing in July of that year. After all, there is a significant learning curve to design – it’s not just the software and fabrication skills, but an understanding of how to design.
Back to the stem
OK, so now you know why this stem means so much to me. Let’s get back to the good stuff.
The stem was designed and fabricated as part of an ‘advanced prototyping’ class. In this class you are to use, you guessed it, advanced manufacturing techniques to bring a design to life. What could be better than to use a CNC machine to achieve this. Well, one thing: using the capabilities of a university to construct a one-off design for a fraction of the cost of going through a professional business (it somewhat offsets my new debt!).
Below is an amazing sketch of my idea. There is nothing groundbreaking here. I have a beautifully designed Kumo road bike [Kumo is an Australian steel framebuilder – ed.] with a horizontal top tube, and I wanted a stem that complemented it. 17º stems are not as commonplace as they once were. And ones designed by me even less so.
When you think of a stem fabricated on a CNC machine you may picture something angular and sharp, or with features on it that lend itself to the machining process. Think of the Paul Components Boxcar stem. Or you may expect to see machining marks from the tool left on it as a unique aesthetic, a la Hope Tech XC stems from the 2010s. I wanted a smooth finish to my stem, something you would typically gain from casting the part. It was supposed to be a challenge after all.
I cannot go any further without first acknowledging the incredible talent of the machinist, the chief fabricator-extraordinaire, Tristan Janle. I did what I could in the fabrication space, but learning to operate a CNC without breaking it or its tools that can cost upwards of $1,000 (I’m being conservative) is something I was simply not allowed to do. It was a blessing in disguise as raising a child really limits how much time you can put into things.
Oh, did I mention the only CNC available was one with only three-axis capabilities? This type of CNC is severely hampered by a stationary workpiece that the cutting head rotates around. This means the workpiece needed to be removed and relocated multiple times to cut different features, as opposed to a five+-axis CNC machine where the workpiece can be rotated along with the cutting head to access most features. It may sound simple enough – you take the stem out, rotate it and put it back in the machine, done. The reality is much different, and this is why I think CNC machinists, and machinists in general are incredibly smart (and why I would like to get into this field).
I may butcher this with my incomplete knowledge but let me try and explain. When you first place the block of material (that will eventually become the stem) in the machine, you create an origin point within a coordinate system (the cartesian coordinate system of X, Y, Z, all with perpendicular axes), where X,Y,Z = 0,0,0. The billet of material first needs to be squared up (all six sides perpendicular to one another) and these become reference planes existing somewhere within an X,Y,Z coordinate that all future operations are measured against. Operations are the cutting of features into the stem, such as a bore hole or trimming of a surface to give it a rounded corner.
For my design, there were hundreds of cutting operations. As soon as you cut the first one, the remainder need to be aware of where they are in space to ensure subsequent cuts follow the design. If you remove the workpiece, there needs to be a point of reference that can be fed back into the machine so it knows how the workpiece is oriented and where it exists in the X, Y, Z space. This needs to be done without displacing the origin, otherwise future machining operations may cut more or less material than desired.
You can program the machining tool paths (i.e. cartesian coordinates; G-code) in the machine as separate operations to allow for removal of the workpiece, so long that these reference planes are intact. For the machining of this stem, given its limited by the three-axis, there was a lot of removal of the workpiece as different operations were called for, such as manual boring on an end-mill and EDM wire cutting of the rear slot (yes, really, an EDM machine was used for this operation!).
It all sounds fine and dandy, but it wasn’t. There was a programming error early on that lead to the tool paths crossing over a previously machined part; one that wasn’t supposed to be touched again, save for sanding and polishing. Luckily, this was early in the process and there was enough material in the stock billet to reprogram the previously completed operations to cut a few millimetres down from their previous position, which eliminated all the gouges.
The bulk of the stem body and faceplate were completed in two machining processes, involving one flip of the workpiece to facilitate access to the underside. There were a few more instances of wayward tool paths during this process that were manually cleaned up later with a file.
It is incredible that the fabrication of this stem comes down to a measure of microns (millionths of a metre) between a good and bad aesthetic outcome and fitment with other parts, namely the handlebar and steering tube of the bikes fork, but also the bolts that fix them together.
If you recall I noted prototypical bolts were included in this project. I’m trying to be clever again. It is a bit of a play on words for the prototype stem bolts generously donated by Lindsay from Prototipo Works.
I reached out to Lindsay at the very start of the project to see if he would like to collaborate on a design for some fancy stem bolts to complement my project. To my surprise he was already testing some and offered them to me to use throughout the project. This may sound like a nice gesture, but I’d like to stress just how generous he is – Lindsay entrusted me with his intellectual property (IP) for an as-yet unreleased product. Needless to say, I will continue to protect his IP. What I will say is that these are exquisite. Who would have thought you could make a utilitarian fixing so appealing? Prototipo Works can.
The Prototipo Works bolts were designed into the stem from the very beginning and were intended to be seen in the final product. Keen observers may notice the roughing on the face of the stem shows the bolts going into the stem body on an angle. I leveraged the aesthetic of the Ritchey C220 stem that wraps over the midway point of a 31.8 mm handlebar but inverted the bolts so that they screw down into the body of the stem through blind threaded holes.
This looks really cool but also adds additional complexity to the project. If you design a hole that is perpendicular to one of the reference faces, then the operation is simple, but if the boring surface is a few degrees off that plane, an additional reference point is needed, in this case a series of laser-cut metal jigs that reposition the stem to allow for straight bores. Did I mention how talented Tristan Janle is as a machinist? I overcomplicated this project massively and he fabricated it to perfection. It was a learning experience for me as a designer to think about how to make something that looks great but is also cost- and time-efficient.
Manual labour and further work
At the completion of the machining phase of the project, the stem could be considered finished. That is, if you like to see the handiwork of the CNC machine present on the surface of the work. For me, I wanted a smooth, polished surface, so sanding and polishing was a must. Sanding is the arduous process of removing material from the surface of the part in directional passes of sequential sandpaper ‘grits’ (a measure of the size of abrasive materials on the sandpaper) to even out the surface and remove imperfections.
I started with 400 grit to remove machining marks and progressed through to 1,200 before buffing to a mirror shine. After buffing I noticed some marks I wasn’t happy with, so I decided to sand again, this time from 400 through to 2,000 grit. For most of the sanding process the faceplate was still attached to the stem body, which made sanding and buffing easier (and aligning grain as well as surface mating). The rear reference block was also still attached to the stem, which serves as a handling and clamping body to avoid marring the stem. Things start to get nerve-wracking when you are so close to a finished product that any mistake could ruin the surface quality.
It would be perfectly reasonable to polish the stem to a high shine and call it a day. There is nothing quite as striking as high-polished aluminium bicycle components glimmering in the sun. At this point the stem would arguably strike a balance between modern fabrication techniques and the vintage flair of retro parts that received the polished treatment (bring back the polished aluminium parts!) However, I was keen to elevate this stem and give it the best treatment, which in this case is an anodic treatment.
Anodising is once again having its day in cycling, and I wanted a taste of the possibilities. What I didn’t know was the process of anodising removes a lot of the lustre of aluminium due to the chemical preparation processes involved. The only way to keep a high shine is to use a process known as ‘bright dipping’, but that is quite toxic and not commonly practiced in Australia (at least for small anodising companies).
It hurts a little bit to see your hard work polishing and prepping a surface taken back a few rungs. That said, a 2,000-grit polish leaves a very smooth surface for anodizing and since anodizing amplifies surface impurities, the result would not be possible without polishing to a high degree in the first place. I would like to give a big shoutout to Collins Anodic in Blackburn, Victoria for the exceptional job.
To really complete this project, I needed something that identified this stem as mine, beyond the obvious blue colour. How about laser engraving? Quadtec in Moorabbin was the place to go. They are experienced with other bike parts and did an exceptional job of engraving small, detailed logos into the stem on flat and curved surfaces, revealing some of that high-shine aluminium underneath.
So that’s it: machining, anodising, and engraving across a period of about two months. A few errors here and there, a million reconsiderations of the design and a few doubts that it would all come together, but it did.
Infilled with acrylic paint (for now).
Engraving on flat and curved surfaces.
This is just a prototype
Remember, this is just a prototype for class. The stem may look finished, but it isn’t.
Firstly, the material is regular 6061 alloy; it has not been heat-treated for strength. You are probably wondering if I use it. I don’t. I probably could take it out on a bike ride without issue, but as such a critical piece of control on a bike I don’t want to risk it failing on me (did I mention I have a child to think about now?)
The stem is also overbuilt – at over 200 g it is portly when compared to other CNC’d stems, like the Darimo IX2AL Stem (approx. 90 g). Since its function is to sit on my shelf, I wasn’t concerned about the weight of the stem’s 4 mm wall thickness, but if I were to design these for use, I would continue to iteratively reduce the weight through rounds of designing and stress simulation and testing.
A note on testing. I am no engineer (I have barely touched mathematics since graduating school) but for the design I needed to simulate the forces acting upon the stem to see if it would survive. I found a study on the forces acting upon a stem and handlebar from Olympic track cyclists – 200 Nm exerted. This is a good start!
I conducted Finite Element Analysis (FEA) on a range of conditions that the stem will be subject to – twisting of the shaft during pulling/pushing, downward pressure from the rider leaning over it, and remote force of the hands resting on the bars at a distance from the centre point of the stem clamp. The idea of a ‘safety factor’ comes into play when simulating these forces. This is the ratio of the stem’s strength against the intended loads placed upon it. The stem achieved a safety factor of three across the board. This is good, but it also means there is plenty of room to shave grams and maintain strength.
If I were to remove myself from the warm embrace of student life and enter the uncompromising world of being a designer who, ironically, would need to compromise to produce a competitive outcome, I would probably have designed the stem very differently in order to minimise the time on the CNC machine as well as the extra operations required to complete some of the features, such as the number of laser-cut jigs required to bore the stem holes and the rigorous sanding activity.
With that said, the university where I study is embracing change (next year … when I’m gone!) and shifting their industrial design model away from a mass-manufacturing focus to an advanced manufacturing focus. This is a smart move in a local environment where we have almost no mass-manufacturing, but a lot of advanced design and manufacturing abilities (think Bastion and Prova and their slew of 3D-printed titanium parts).
What’s next?
I am in the second half of my Honour’s year project. I am designing yet another bicycle part; this time a fork designed for the adventure/gravel crowd. The idea is to improve the functionality of the front end of the bike through mountable modules and adjustable geometry.
This is but a teaser of what I am doing in the final three months of my second (and final!) university degree. I don’t know if I’ll be able to produce something as great as the stem. I also have a second child due at the same time as I am supposed to finish. This time I know what I am in for, so I’ve already started to pare back and realign my focus to my family. Watch this space for how it all goes.
What did you think of this story?