Kettenreaktion Bikes | Zell unter Aichelberg, Germany

Southern German manufacturer builds high-tech bicycles on a stainless-steel tube frame with milled components: Kettenreaktion Bikes, that is fairly new to the scene, offers a high-quality, custom-built gravel bike that is made in Germany and equipped with a lightweight, stainless-steel tube frame and milled components. This includes the stem, derailleur hanger, BB shell, chain wheel and brake discs. The company employs state-of-the-art 5-axis machinery and the hyperMILL® CAD/CAM system from OPEN MIND in its milling operations.

Isn’t a bike with a stainless-steel frame far too heavy? “No, not at all,” says Marc Gölz, seeking to dispel the misconception that steel frames are heavy. “You can build a racing or gravel bike that weighs about eight to nine kilograms on a stainless-steel frame that also absorbs shocks and jolts better than a carbon frame. That is really important for ambitious, health-conscious recreational cyclists.”
Marc Gölz is an expert when it comes to bikes. In the 2000s, he was a professional biker, riding with Team T-Mobile Mountainbik. Hestill maintains close ties with the cycling world to this day. He had long dreamed of designing and building a bike of his own: “Marc Schneider, who’s been both a friend and cycling partner since I was young, and I had this idea over ten years ago.”

There are several reasons why the two decided at this time to develop a high-quality gravel bike built on a steel frame. Bicycle expert Gölz explains: “First of all, stainless steel is gaining more and more fans in the world of cycling. That’s in part due to the retro trend, because, at the turn of the millennium, all the top riders in the Tour de France used bikes with a stainless-steel frame. Sustainability also plays a role here as steel parts are rather easy to modify, repair, and recycle. Beyond that, modern manufacturing techniques give us more options than we would have had 25 years ago when it comes to designing stainless-steel bikes.”

That brings us to the second reason why they decided to set up the company: Marc Schneider is the owner and Managing Director of a company that offers machining services in and around special tools, equipment, prototypes, and models. Ten years ago, he founded Precimo GmbH & Co. KG in Zell unter Aichelberg, Germany, taking over the former Pferdt Werkzeugbau GmbH along with its staff, machinery, and customer base. “We specialize in the high-precision milling of complex components made of aluminum, Inconel, and various types of steel,” states Schneider, who holds a degree in engineering. “We are also happy to develop products for our customers, an area I was able to gain a lot of experience in my previous job as head of testing and development.”

This stem is milled from aluminum, while the optimized NC program was generated by the programmers at Precimo/Kettenreaktion Bikes using the hyperMILL® CAM system from OPEN MIND.

hyperMILL® CAD/CAM system and 5-axis milling centers

Precimo is a small, successful company. Schneider and his three skilled employees can rely on state-of-the-art equipment, including one 3-axis and two 5-axis milling centers along with several eroding machines, cutting-edge CAD software, and the hyperMILL® CAM system from OPEN MIND. “I think it is the best software for 5-axis milling,” reports Marc Schneider. “We already had a hyperMILL® license when we acquired Pferdt GmbH. Since then, we’ve purchased a second workstation, additional 5-axis modules, and hyperMILL® MAXX Machining, which has allowed us to speed up roughing operations markedly.” Using the roughing strategies available in the hyperMILL® MAXX Machining performance package, the two programmers working at Precimo create trochoidal toolpaths that maximize stock removal rates and utilize the full length of the tool’s cutting edge.

Schneider and his colleagues feel that the feature and macro technology available in hyperMILL® helps to greatly reduce programming times: “It lets us use existing geometry and colour data available in CAD – on holes and surfaces; for example – for automated CAM programming and define typical, recurring geometries as macros. hyperMILL® then generates the matching NC program.

hyperMILL® – the right strategy for every machining application

Precimo can meet a wide range of requirements. “For customers in the cleanroom equipment space, for example, we have to meet the highest standards in terms of surface quality,” explains Schneider. “This is also true for press molds used to produce fibre optics that then make their way into dental tools.” hyperMILL® delivers the optimum milling strategy needed in applications like this. Marc Maier, OPEN MIND’s regional technical sales manager who oversees the Precimo account, mentions the “Soft Overlap” function, which greatly improves surface quality in transition areas.

It really is a small world. Like Marc Gölz, CAM specialist Marc Maier hails from Weilheim an der Teck. He has been a good friend of Marc Gölz’s for over 25 years, is also a passionate cyclist and tinkerer, and knows Marc Schneider “from back in the day,” so the three of them have more in common than just sharing the same first name.

Custom-made, one-of-a-kind bikes with components sourced from the region

Let’s return to Kettenreaktion Bikes, as Gölz and Schneider have called their manufacturing venture, which will launch more than 20 custom-developed bikes to meet its customers’ needs this year. The two founders point out that “our company sources 95 percent of all semi-finished parts and components from Germany and Italy. In cooperation with Precimo, we also manufacture as many parts as possible in-house, milled from stainless steel and aluminum.” Given the current supply chain issues, Gölz and Schneider believe they are on the right track.

The prototype for the Kettenreaktion bike has been finished for some time. Gravel Bike No. 1, a custom-made bicycle for Marc Gölz, is also ready, which the former professional mountain biker is now putting through its paces. “I really love the stainless-steel frame. With this fully rigid bike, the steel absorbs some of the harsh impacts from the surface below, which is good, especially for the rider’s spine.”

Optimized in 3D CAD and programmed in hyperMILL®

Marc Gölz, who trained as an industrial mechanic before setting out on his professional career, explains: “We buy tubes that are forged from one block and double butted, meaning that they are roughly 0.9mm thick at the ends and only 0.4mm in the middle. Thanks to the high compaction of the microstructures, the material has a tensile strength of just under 1000N/mm2, so it can take any type of stress or strain.”

In the 3D CAD system, the bike specialists adapt the stainless-steel frame to the customer’s body. Ideally, data from an ergonomics analysis that can be imported into CAD should be available. The length of the tubes is then adjusted based on the length of the cyclist’s legs and arms, the seat position, and so forth. “This is not possible with high-end carbon bikes, since the frame is always produced in fixed shapes,” reports Marc Gölz.

The stainless-steel tubes are cut to length by machines and contoured for (manual) brazing with the tube diameter. “It's a relatively straightforward process,” says Marc Schneider. “Components like the stem are much more difficult to manufacture. We have designed and built it as a milled aluminum part. We manufacture the stem using 5-axis technology in two clamping operations on our Hermle C 22 high-performance machining center. Needless to say, we created the accompanying NC program in hyperMILL®.”

Milled from solid stock as a mark of quality

In addition to the stem, there are many other components that Kettenreaktion Bikes produces in-house, including the derailleur hanger. This is the aluminum part between the frame and the rear derailleur, which has a predefined breaking point to protect the derailleur and frame in the event of a fall or hard impact.

Marc Gölz is particularly proud of it: “I haven’t worked as an industrial mechanic, which is the trade I learned, for years. However, what we have planned with Kettenreaktion Bikes inspired me to take courses to learn how to operate the machines and CAD/CAM system. After a one-week online course on hyperMILL®, I was able to program the derailleur hanger. Among other things, the simple, intuitive user interface was a real help, making milling on the Hermle C 22 a breeze.”

Other components developed by Kettenreaktion Bikes and milled at Precimo include the dropouts, the notches on the frame used to mount the wheel’s axle onto the bike, as well as the BB shell, crank, seat clamp, chainring and brake disc. Marc Schneider points out that the parts are designed by Kettenreaktion Bikes and that they are not cast but milled from solid stock. “It is a mark of quality that we really focus on. And it’s also why the surfaces we created on certain components could, in a sense, be seen as a design element.” hyperMILL® makes this possible because it lets each milling path be defined individually. Out of this came a special service, as Marc Schneider goes on to describe: “On request, we engrave the customer’s signature on the stem.”

All this means that Kettenreaktion components cannot be copied in any garage workshop. That is very important for Gölz and Schneider since they intend to sell the components, which can be used on most gravel, mountain, racing, and touring bikes as standalone parts as well. Customers can then use them to upgrade and customize their current bikes.

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