Driven: from concept to reality
The remarkable behind-the-scenes story of the development of CeramicSpeed’s ultra-efficient chainless drivetrain system, with Project Lead and CTO Jason Smith
CeramicSpeed’s low-friction shaft drivetrain design, Driven, has turned heads and started countless conversations and debates since the public prototype was first unveiled in the summer of 2018. A radical design, it hit its aggressive primary goal of achieving 99% drivetrain efficiency – but the 2018 model didn’t shift gears, and a new engineering challenge was on.
Drawing slack-jawed admirers, head-scratching enquirers and the inevitable pursed-lipped nay-sayers in apparently equal measure, the development program continued at pace.
The next crucial phase of the process was not just to deliver a model that shifted gears with ease, accuracy and speed, but also to ensure that it retained that unprecedented 99% efficiency.
A little more than a year later, in the summer of 2019, Driven V2 saw the unveiling of a series of updated working, shifting models – Hero, Venge and Lux together highlighting the shifting process, the aerodynamic prowess and the opportunities for application beyond asphalt and into the world of full-suspension.
A lot of time, effort and meeting of mathematical minds went into that 1% gain. It’s an impressive feat, and at its heart is a reliance on the super-efficiency of the highest level of ceramic bearings. But a lot more went into proving that it works – well, reliably, and across a range of types of bikes – and takes it from an impressive exercise to what might just prove to be the biggest, most significant ‘1% improvement’ the cycling industry has ever seen. If the first phase was a technological leap, the second stage may be a paradigm shift.
Driven V2 has attracted a huge amount of interest, not least from the leading cycling media – CyclingTips, BikeRadar as well as the off-road PinkBike amongst them – with the design concepts, technology and advantages digested and well explained. Along with the skeptics who keep us on our toes, we won a lot of fans and the discussion forums have been ablaze. But here, for the first time, is the behind-the-scenes tale of the latest phase of the Driven adventure with the Project Lead, Jason Smith, revealing his insight into the inspiration, process and emotions as much as the tech itself.
Boulder-based Smith is – apologies – driven. He has boundless energy and enthusiasm for this project that’s tempered with a healthy dose of pragmatic realism. Within an agreed brief, budget and a timescale in line with agreed access to his project allies – a team from the University of Colorado Boulder’s Mechanical Engineering Department coming back on board for a second academic year – the starting place was an open route to achieving the goals of first 99% efficiency, then slick-shifting prowess. And it turns out that the significant aerodynamic advantages of the Driven V2 system over conventional drivetrains are something of a serendipitous bonus!
Original goal: the chase for 99%
The 98% efficiency that can be achieved by CeramicSpeed components sets a high bar yet it’s an understandable compulsion for a racer and a product developer to chase more. But at the start of the Driven project, why set a goal of 1% more?
“We needed to set a quantitative goal. As with many technical challenges, simply saying, ‘I’m going to do the best I can’ isn’t always the most effective approach. A goal with a specific end result typically translates to a higher success rate.
“We looked at where we were with drivetrain efficiency. A high-end stock drivetrain can achieve about 97%, and upgraded with off-the-shelf CeramicSpeed components can push the efficiency to about 98%. We obviously wanted to get better, but by how much? The theoretical upper limit of drivetrain efficiency would be 99.999…%. A 100% efficient drivetrain is theoretically impossible; it would be perpetual motion. We were also aware of the principles of diminishing returns: it’s more difficult to achieve incremental efficiency gains as the efficiency approaches 100%."
So the team looked at the goal of 99%. “That’s a 50% reduction in friction on the path from 98% to 100%,” says Jason. “Many people might feel going from 98% to 99% is not too inspiring, it’s easy to say, ‘it’s only 1%’. But when the friction decreases are viewed from an absolute wattage number, 99% is a 50% decrease in friction from 98%, which is a huge jump, especially considering we are already at 98% with the most advanced go-fast products.
“By setting the goal at 99%, we knew it would not be easy, and more likely than not, would require a completely different way of looking at the bicycle drivetrain.”
Initial renderings of Driven - team archive
The shape of the process
With the initial goal clear, and a collaboration on the cards, what was the shape of the process?
“We worked together with the University of Colorado Mechanical Engineering Department on the challenge. The goal of 99% was set internally ahead of the collaboration. Then, in conjunction with the university, we set to work on how that 99% was going to be achieved. We had two years of great engineering teams working with us, creative young minds, plus access to the university facilities.”
For Driven V1, the CeramicSpeed team worked within the University’s 2017-18 academic year. Likewise, for Driven V2, which focused on shifting, the timeframe was the 2018-19 academic year. The defined project end dates “kept us moving, very quickly!” says Jason.
“The process was more problem solving, brainstorming, theorizing, and experimentation. We pretty much figured from day one that it would be easier to start with a blank sheet of paper to develop a 99% drivetrain, rather than to ‘fix’ the weak points of the present chain/rear derailleur-style drivetrain.
“So we threw out the present-day drivetrain and started from scratch with a clean slate. Our roadmap was to brainstorm on new power delivery systems suitable for a bicycle and get to work with prototyping and experimentation. But of course it wasn’t that simple... the Driven V1 brainstorming sessions alone took about two months.”
Jason recounted how there were around five possible, plausible solutions. Each were presented on a big screen over a pizza and beers evening, with theoretical designs explained and math attached. One was “a belt drive… but not as you know it,” teases Jason. Apparently these concepts still exist, but will they ever see the light of day again? We’ll come back to you on that!
“We analyzed and picked the concept which we felt would hit 99%, and, of course, fit onto a bike. After that, it was purely trial and error, prototyping, testing, iteration, more testing, more fine-tuning, until we hit that 99% number.”
That’s a big ‘funnel moment’ in the project, but from then on, it still wasn’t a linear model. Fixing or improving one element made ripples and created new challenges in other areas.
“The project was riddled with compromises. We’d have a great idea on paper, then put it on the test stand, only to find our great idea was negatively affecting something else. This was sometimes disappointing, but when revolutionary concepts, in general, are developed, these occurrences are par for the course.
“We actually could have made the drivetrain even more efficient than it presently is, but we had to always consider the physical form factor of the frame, wheel, bottom bracket, etc. We had several different and great concepts for the shifting mechanism, but some of the concepts we found caused a decrease in the overall efficiency of the drivetrain. Those had to be scrapped until we found a concept which provided an elegant shifting method, and did not negatively affect the efficiency.”
Ideas from initial brainstorming sessions - team's archive
Whiskey Tango Foxtrot
“For Driven V1, we were really close to hitting the 99% mark, but not quite there,” says Jason. “We had to do several tooth shape and pitch iterations and tons of testing, before we nailed it. It was frustrating because we were often dealing with miniscule changes with each iteration, and only realizing fractions of a watt – sometimes a new iteration produced slower results. It was a tremendous amount of trial and error. Each iteration was more design, more 3D printing, and often more prototypes being fabricated by the machine shop.
“We didn’t have any setbacks in which we found problems with the fundamental design, thank goodness. But we did have plenty of ‘Oh shoot, how did we miss this?’ surprises. We called them ‘Whiskey Tango Moments’.”
Renderings from initial prototype - team's archive
“Driven V1 used machined flat-plate rear multi-speed cogs. When we developed the shifting mechanism as part of the Driven V2 program, most of the prototyping was done on the test stand, which also used a flat rear cog. When it was time to build the drivetrain on the actual bike, guess what? We designed and fabricated a beautifully complex – and expensive! – 13-speed flat rear cog. As we were building the bike in preparation for EuroBike [the bike show where the Driven V2 bikes were set to be unveiled], we immediately determined that the beautiful flat rear cog was useless, because the shifting mech came in at an angle as it followed the chainstay forward…
We all looked at each other and scratched our heads. ‘How the heck did we miss this super-obvious design requirement? This was a huge oversight! We were down to the wire for the Eurobike show, and weren’t sure if we could do the redesign and fabrication of a new rear cog in time for the show. But with some scrambling and long evenings, we got it done.”
The project had its breakthroughs, like the moment the team “crammed everything inside the driveshaft” – the motor, gearbox, drum, wireless electronics, sensors, batteries – “It fitted, and it worked!” Jason thinks the single biggest ‘eureka’ moment was the successful development of the internal shifting drum.
“It’s a novel slotted and gated design, with a unique leader-follower feature. This patent-pending single drum saved us from using multiple motors/actuators and a ton of moving parts to actuate the shifting pinions.”
Wins like the internal shifting drum keep the team spirit right on track. Seemingly impassible obstacles being negotiated. Silencing those nay-sayers.
“We had the standard haters. Maybe even to a greater extent for us, because this drivetrain is so revolutionary. We were like a naysayer magnet. ‘It won’t hold load’, ‘It’ll never shift’, ‘It’s a marketing stunt’, and on and on. I wonder where those naysayers are now, given we hit 45kph on the test bike, and we came up with an ingenious shifting method!
“We never let negative comments deter us. We stuck to our goal and stayed focused.”
The team of students from University of Colorado - personal archive
Driven – V1 and V2 – had initially clear goals: the low-friction drivetrain system and proof of concept with shifting. But there were other benefits that, if not overtly targeted, came about through the ‘open ideas’ brainstorming, and the trial-and-error honing, not least the aerodynamic efficiency. Aerodynamic performance was always “at the back of the mind” but the outcome, as and when Driven appears on a bike you can buy, is huge.
“With the Driven system, the aero efficiency gains are similar in magnitude to the friction reduction on an optimized drivetrain,” explains Jason. “I say ‘similar’ because there are several variables at play, such as the bike itself, the original drivetrain under comparison, among others.
“Driven V2’s drivetrain drag reduction is greater than aero gains if compared to a lower-tier, and subsequently slower, drivetrain. This is because the aero differences are negligible between traditional rear-derailleur-style drivetrains, whether it’s a high end or low-end groupset. When compared to a stock low-end drivetrain, Driven’s friction advantages are much more than the aero advantages.”
But when we move to a high-end stock drivetrain, the gap closes.
“Then, compare it to a CeramicSpeed optimized 98% drivetrain, and the friction and aero advantages are getting to similar savings. But the really cool thing is that aero and friction are additive. The aero advantages and friction reduction advantages can be combined for a substantial total watt-savings.”
But this aero advantage wasn’t a stated goal in those initial brainstorming sessions and the beer-and-pizza nights. “To some extent we got lucky,” says Jason.
Jason's reaction when he was told by the Specialized team the aero test results in the Win Tunnel.
We’re not done yet
Jason doesn’t hesitate in identifying shifting speed as the area where there’s ‘more to get’.
“We’re at a point with shifting speed, which in order to make it faster, would require advanced custom electronics boards, custom motor, custom battery pack and other custom internals. For a larger company with unlimited resources, custom internals would not be as big of an issue. It’s not a big technical challenge to get a faster shift time, it’s a bigger financial proposition, which is frustrating.
“With limited resources, we pushed the project through the idea stage, into proof of concept, and now prototyping. A larger team and budget would put Driven that much closer to production.”
What’s next? “I like technical challenges. Doing something that hasn’t been done before, or doing something which people say can’t be done.
“100% is impossible. Maybe the next goal will be 99.5%. Then 99.9%? All of the above. It’s often more about the journey than the destination…”