I want to ride my bicycle… with Simcenter

By Simon Fischer

They are healthy, they are environmental friendly, they are beautiful, but most importantly they are fun! I just love riding a (good) bike. And so the optimum number of bicycles in the garage is always n+1, where n is the current number of bicycles.

In the first place we owe all this pleasure to a guy named Karl Drais, who literally kicked things off in 1817. But clearly, if you look at the Draisine below and compare it to one of the n+1 modern bicycles in my garage it becomes obvious that we’ve come, – or should I say – “rode” a long way. While Drais clearly disrupted the way people are moving with their very own body strength, the question today has shifted from a qualitative how to a quantitative one. Or in other words it’s no longer about walk vs ride, it’s about how to bike best! So we wonder, what makes a “good” bike a “good” bike? Or even a great one, or – wallets aside- the perfect one?

Well, first and foremost the answer depends on what you want to do with it. So the conversation starts, “Look honey, there is gravel, there is asphalt, there is mountains, there is the city, hence, the n+1”. But even then what is the perfect bike also depends on who you ask. For the real bike enthusiast it quickly becomes emotional. Questions like, which is the right component? – Yes you can have philosophic exchanges on the material of a brake lever. Is a gravel bike a legitimate replacement of my road bike? Which is the right brand, anyways? And most recently, is it a crime to ride an e-bike?

Those are the fundamental questions that have destroyed friendships!

Anyways, valid fights aside – I figured out what unites all great bikes and components that offer a faster, safer, further, smoother, quieter, braver ride is one thing: they are a result of great engineering boosted by simulation and rigorous testing.

Therefore, if you still believe only cars and airplanes get a dose of virtual product development and cutting-edge measurement, come ride with me…

Ride faster – Aerodynamics CFD and the power of GPUs

Since the first Draisine a very obvious challenge in the improvement of bicycles was making them faster. Making a bicycle faster means less friction. And less friction means two things: First, lower mechanical friction in the drivetrain and between the wheels and the ground. And second, less air friction aka drag, which translates to better aerodynamics.

And while tight pants (I know you all love them!) can only take us so far, for high performance racing machines, CFD simulation had to conquer the world of bicycle development to make them cut through the air as efficient as possible. And to design a faster bike faster, GPU-native CFD solver technology arrived just in time as Trek Bicycle impressively demonstrated for at the Tour de France 2024.

Ride more – Design space exploration

But meanwhile companies like Trek not just run a one-off CFD simulation to see how a design works and then fiddle around a little with another design. No, they run automated design exploration workflows to explore the performance of hundreds of designs (that’s when cloud-hosted HPC and GPU-accelerated CFD comes in quite handy). To give you an idea of the level of care that goes into today’s optimization of race bike aerodynamics: Trek identified the optimum position of the water bottles to minimize drag, identified the optimum rider position under varying wind conditions and found the optimum drafting configuration four a team of four riders.

On top these optimization studies are no longer only about one performance attribute. Taking it one step further, Trek looked at a multi-attribute optimization of aerodynamic performance and the weight of the frame.

Ride Safer – Helmet impact testing

If you ride fast, you better ride safe. But even if it’s just to pick up the kids from kindergarten or go to the supermarket, when I go out for a quick ride and forget my helmet I immediately feel a bit naked. The great news is that the helmets we are wearing today have significantly improved in terms of safety and comfort compared to the ones our parents forced us to wear in the early days. This is thanks to continuous product improvement, novel materials and smart structural designs driven by homologation for certification and the customer desire for comfortable safety.

As a passionate bike rider I was quite impressed when I realized that we at Siemens are actually performing high-speed video analysis, laser guiding head form positioning, and wireless data acquisition, to provide highly accurate and repeatable helmet testing. Our experts can even evaluate the level of protection a safety helmet can provide against brain injuries generated by critical rotation accelerations. In cooperation with helmet manufacturers, we enter this new era of helmet testing, contributing to the best possible head protection.

Ride cooler – Helmet aerodynamics and thermal comfort CFD

Safety is one thing, but if you are on a long ride (thermal) comfort is another. But just like with vehicles, when it comes to helmets there is this constant fight between aerodynamics and cooling. Luckily, todays engineers have advanced CFD simulation at their fingertips. Below are just a few examples of how fluid dynamics combined with heat transfer enable insights to find optimum solutions in the trade-off between thermal comfort and low drag of helmets.

Ride further – System simulation for ultra-lightweight hydraulic transmission

When it comes to bicycles I am still one of those stubborn purists admittedly. No e-bike made it into my garage (yet). However, I have to admit I can see the appeal (maybe that’s exactly why I try to stay away from them in the first place. Once hooked-up, it turns out to go back is impossible is what I keep hearing).

Whatever my personal feelings, the success of e-bikes is actually great news. For human beings, for this planet. A lot of people who would probably have never taken the bike, would have taken their car even for short distances, would have claimed they would have been sweated all-wet, had it not been for the development of the electric bicycle to change their minds. Above all the success of the e-bike was driven by innovation in battery technology. But also the electric motor design and even rethinking transmission systems made the e-bike an interesting playground for engineers.

And thanks to holistic system simulation the journey for a longer ride has only just begun, as this interesting thesis on Ultra-lightweight vehicle hydraulic transmission and concept development shows.

Ride quieter – Harnessing Simcenter for testing e-bike acoustics

Hey. psst. you? yeah, you. Can you hear that? No?

Well, I can’t either. Because when it comes to e-bikes range is by far not the only thing in scope of engineers. Noise is equally. And as you cannot just make an e-bike dead silent it’s about creating acoustic comfort for the rider. And guess what, leading companies are heavily investing into these acoustic experiences. Take Trek Bicycles again, they are pioneering the concept of putting sound quality on the e-mountain bike metric map as it continues to be a hot topic in the industry. Likewise, MAHLE, who use Simcenter testing solutions to streamline e-bike drivetrain noise-vibration-harshness (NVH) analysis and for end-of-line testing. And of course my colleague Frank, who – after putting some Simcenter SCADAS XS on a snowboard in wintertime – repeated the same NVH test for a bunch of electric bicycles last summer.

Ride smoother- The grandfather of all comfort

Talking about vibration, we can’t miss out on this one: It is probably the most underrated part on almost any modern bicycle. Just a little bit more than an inch long, this tiny little piece has saved billions of bicyler’s a#*s over the last 130 years. If it wasn’t for Scotsman Dunlop with his tiny little invention we would probably still be riding harsh full rubber tires. But thanks to the invention of the Dunlop bicycle valve from 1891 (US patent US455899), we can now happily inflate our tires and enjoy the pleasure of air damping. Now, if you claim to be a bike enthusiast, can you explain how such a valve actually works? No? Well, here’s a little Fluid-structure interaction simulation that may give you some insights you will remember the next time you have to pump it…

Ride braver – Simcenter for a safe low-drag monocoque wheel

Ok let’s shift gears again. And in cycling shifting gears always means let’s talk Carbon. In the competitive world of cycling, innovative engineering plays a crucial role. At the edge of technology marginal gains can be the difference between winning and losing. That’s the playing field for Radiate Engineering & Design AG. Radiate’s collaboration with Scott Sports led to developing the Syncros Capital SL, a wheelset that makes every bike enthusiast go quiet in awe.

The standout feature: “The Capital SL is a one-piece, or what we call monocoque, construction, meaning the rim and the spokes are fused together into a single piece,” says Frederic Poppenhäger, a partner at Radiate. This design enhances structural integrity and reduces rotational inertia, leading to better power transmission and substantial speed gains for riders. By running simulations, Radiate evaluated various rim shapes and geometries, optimizing for aerodynamics and structural performance without the immediate need for physical models. While Radiate reduced drag by 7 percent they also improved rider confidence and safety by ensuring greater stability in crosswinds. To enable a braver ride.