[Flexy + Aero] Handlebar Stem System by Canyon

In this article, we’ll be discussing a Handlebar Stem System by Canyon, US publication 20210061400. The publication date is March 4th, 2021 and the filing date is Aug 25th, 2020. This patent has not been granted, yet.

This one appears to associate with this article I wrote a while back, about a flexible stem system.  These patent releases are impeccably timed, because Canyon have been in the news lately for their ‘stop ride’ thing.

This was released at the exact same time as the flexy/aero seat post, so it appears Canyon are working hard on their race bike compliance and aerodynamic systems.  

There was also a third patent for racing handlebars, but there’s just not enough content in that one to justify an entire article. The image to the left shows how the bar can be shaped, among other shape-items of note. How are they going to enforce this one? No idea.

Intro

Canyon are introducing a new type of stem attachment system, similar to the last article I wrote (above), where there is a long stem tube that travels inside the steerer tube and head tube. The stem tube bolts to the steerer tube from the front of the steerer tube and the stem then attaches to the top of the stem tube. Canyon state this system will allow for more aerodynamic design flexibility and for a compliant stem system, in one package. If this system works, there could be some noticeable racing advantages.

Intended Novelty

The explicit intended novelty here is that the stem tube attaches to the fork through an ‘insertion opening’. The insertion opening is not the opening in the head tube; it’s the opening in the actual steerer tube. Remember, this patent has not been granted yet, so the language of the intended novelty could change if the attorneys are required to add limitations based on prior art.

Why

Canyon state the typical stem attachment system, where the stem bolts to the top of the steerer with a protruding steerer tube, has it’s disadvantages.   

Known handlebar stem tube systems have the disadvantage that at least parts of the clamping means are arranged above the fork tube or the head tube of the bicycle frame, respectively. Thus, particularly the design possibilities in this area are limited.

Canyon state a very explicit reason for this design, relating to the aerodynamics of the stem.

A particular advantage of the [invention] is that the area above the steerer tube, in which the handlebar stem is arranged, can be more freely designed and that particularly aerodynamic configuration are possible. The handlebar stem can particularly be designed such that it does not protrude beyond the top tube of the bicycle frame. Furthermore, lower handlebar positions and/or other configurations of the overall frame design are thereby possible.

They’re also doing this for a compliant stem system.

…it is possible to provide a flexible handlebar steerer tube which can be flexibly formed within the steerer tube.

What

Figure 1 shows an assembled system based on this invention. Component 16 is the stem tube, which attaches to a stem. The little image in the bottom left is from the previous patent, which this one is clearly referencing. Notice how the stem tube travels inside the stem itself. The steerer tube has an opening for the bolt 20. There are also clamping elements 30 and 32 that apply the actual pressure to stem tube.

3/10 edit: I’ve been wracking my brain as to how this system is going to be vertically adjustable. The images and text are unclear but I finally found it. Component 36 is a vertical slot, which is the same width as the bolt. Just loosen the bolt and slide the stem up and down. Retighten, and you’re good to go.

stem tube 16 comprises an opening 36 which is particularly designed as an oblong hole… [therefore] it is easily possible to adjust the height of the handlebar stem tube and thus of the handlebar stem or the handlebar… simply loosing screw 20 and displacing the handlebar stem tube in longitudinal direction 38… simply tightening screw 20 and thus by clampingly holding handlebar stem tube 16 in steerer tube 10 via the two intermediate elements 30, 32

Figures 2 shows the system from the top. Note the stem tube is not circular, it’s rectangular. This shape allows for the tube to flex or bend, which gives the handlebars some level of compliance. This whole concept is outlined in the previous article mentioned above. Below is an excerpt, from this patent, on the intention about the cross-sectional shape of the stem tube.

…the cross-sectional shape of the handlebar stem tube differs from the cross-sectional shape of the steerer tube…. a non-circular handlebar stem tube can be arranged in a… circular steerer tube… [therefore] it is possible to provide a flexible handlebar steerer tube, for example, which can be flexibly formed within the steerer tube, in particular for damping shocks… the handlebar stem tube comprises a cross-section whose dimensions in the mounted state are smaller in the direction of the travel than the dimensions transverse to the direction of travel. The handlebar stem tube is particularly formed horizontally oval. Such a wide handlebar stem tube has the advantage that a bending or flexing in the direction of travel is possible. Said bending or flexing is particularly carried out within the steerer tube in the direction of travel. Traverse to the direction of travel, such a handlebar stem tube has a higher stiffness. The travelling comfort can be significantly improved by such a designed handlebar stem tube since particularly shocks are well absorbed or damped, respectively.

Canyon state that a preferred design would be to add a small hole to the front of the steerer tube to access this bolt without removing the actual fork. And yes, the opening will be pluggable with plug 44, in Figure 3 below.

… it is preferred in a particularly preferred development of the disclosure that an access opening is provided in the fork tube or the head tube… The opening can be closable by a plug or the like in order to avoid penetration of moisture.

Lastly, we should address the preload, because it’s not clear how the actual stem and fork apply pressure to keep the system from wiggling around. The reality is, is the stem will float, which means you can’t preload the system. If you could preload it, then that sweet, sweet compliance would never materialize.

Conclusion

I have my reservations about this one, especially removing/loosening a bolt on the inside of the steerer tube from the outside. I would hope the bolt is long enough to not fall down the head tube. Additionally, the two clamping elements would seem to be very difficult to keep lined up with the stem tub bolt holes when you insert the whole system into the steerer tube. Those little things would keep moving or falling down the steerer.

I feel for the mechanics on this one. Moving the entire stem/fork attachment system into the steerer tube sounds like a huge headache for people working on these bikes. But, racing doesn’t give a shit about anything but the clock, so if Canyon can shave some clicks of drag with a more complicated design, more power to them.

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