We are exclusively using the highest grade carbon prepregs with specific properties for the requirements for our rims and adapt our production processes specifically to the demands of the material in use in order to thus be able to fully exploit the potential of the raw material. That way we are using high-grade, high-tensile fiber types with a specific resin system with long curing times and adapt our processes accordingly. Whilst a rim in mass production is hardly ever allowed more than 30 minutes, our first curing cycle accounts to a whopping 2 1/2 hours and in addition features very flat temperature and pressure gain slopes. This is in order to guarantee a resin flow as optimal as possible and to ideally net the laminate layers as well as to offer enough time to press out even the smallest gas bubble in between the laminate layers. With faster curing times however the danger of even generating additional gas bubbles in the system increases due to the fast and high rising temperature. These would not be visible with the naked eye - so do not differ in quality optically - but will yield vastly worse mechanical properties; a not be taken lightly price of a quantity driven mass production.
As material we are using a specific resin sytem from motorsports that offers the highest heat tolerance and mechanical robustness and there predominantly is being utilized for the thermally and mechanically highly stressed brake exhausts of Formula 1 cars.
This no enough and especially important for rim brake rims: In addition to the actual curing all our in effect already finished rim brake rims run through another heat cycle in a separate heating oven. During this so called "tempering" the rims are being gradually brought to their glass transition temperature (T_g) in order to prepare them for extreme thermal stresses, such as dragging brakes of a heavy rider in alpine territory. In this cycle the resin crystals re-orientate and this way ensure the highest possible safety.
The production of a single ax rim takes 7 1/2 hours in order to get the maximum out of the material and to be able to offer you the best possible quality and performance - a span of time that was unthinkable in mass production!
Over and over we are confronted with the question if we could not produce or offer our rims as well in UD.
Thanks to the exclusive in-house production in our own manufacture and therewith short reaction times and the option to serve custom demands as well as the constant availability of different fiber types, cloths and fabrics in-house with us, technically this would of course not be any challenge.
Howsoever at the same time an execution in UD will impact the quality of the rims and both lower the mechanical as well as thermal resistance of the rims.
There are two main factors that hold responsibility:
That we produce our rims in contrast to current trends solely in cloth instead of UD has mere functional reasons. Whilst UD fabric is very well suited for long, bending-loaded components (examples: handlebar, seatpost), they are in comparison to cloth less favorable for dynamically loaded components such as the case with rims, as the latter is able to cope with different load directions whilst UD is only able to do so in one direction, alongside the fiber. These advantages especially bears fruit in case of exterior impacts. The cloth net keeps the surface together and can cope with impacts much better than UD layers that tend to delaminate. That way the rims can be build lighter with the same level of safety and stability.
A classic, abstracted example on the same basis by the way is the well-known issue of tearing off pieces of carbon upon (tubular) tire removal from the rim. Here as well forces contrary to the high-tensile direction of the unidirectionally orientated fibers occur - issues, that would not have been present with cloth..
A further disadvantage of UD fabric is especially relevant in case of rim brake rims: The induced heat from the friction of the brake pads at the brake track can only be dissipated in direction of the fiber, the resin in between the laminate layers acts insulating. With unidirectional fabric (UD) the occurring heat can thus only be dissipated into one direction. Due to the rotation and the medium air (wind) as coolant as well as the possibly large rim surface this is mostly just enough to sufficiently cool down the rim, yet cloth yields not to be ignored advantages here as it can dissipate the heat onto a much larger surface that firstly (and in compliance with simple physical considerations) is able to cool down much faster and moreover also effectively eliminates the for the laminate dangerous "hot spots". A key benefit when approaching the limit(s)!
Upon production individually casted and moulded as well as according to the occuring load specifically reinforced spoke holes eliminate the need for a post-processing, machining or subsequent drilling and therewith a weakening of the structure. In particular the area of the spoke nipples is the highest stressed part of the rim: A drilling and therewith cutting of the fiber in this respect technically makes even less sense, but is an accommodation to mass production (in regards to time and labour) respectively simply due to a technology-transfer of well-known manufacturing techniques from metal rims without paying respect to the specific requirements and properties of fiber reinforced materials.
The moulded nipple seats yield perfectly orientated nipples. As a result our rims do not carry any spoke tension limit. Stress tests at an independant university test laboratory attested a nipple pull-through resistance of 5t - much more than any spoke, nipple or hub body would ever be able to bear. Us ourselves we use a spoke tension of 1300 N for our wheelsets, and for that purpose are being supplied with specifically reinforced hub bodies from our hub suppliers that are able to cope with the high tension.
The rim hooks of our clincher rims are material-specific individually casted and moulded. In contrast to the industry-typical standard a subsequent machining and weakening of the laminate is herewith evaded.
This extremely time- and labour intensive process forms the basis for the extraordinary resistivity and stability of our rims.
The rim hooks are being individually casted by hand upon production of the rim and then manually laminated into the rim to then be cured as one piece composite thanks to specialized, adapted tools.
Inside of the rim hook there is a carbon roving, the fibers around it on the outside run continuously in one piece, undisrupted and material-specific around the rim hook. In contrast to mechanical machined and fly-cut rim hooks, that tend to delaminate rapidly upon impact due to the blunt outwards directed laminate layers, our rims can cope with impacts a lot better as they are distributed and spread onto a much larger surface area - the loading capacity is incomparably higher than with competing products!
Moreover deeply pronounced hooks provide a secure seat also with low tire pressures as well as heavily flexing tires. Increased safety as well as the option to ride with lower pressures and therewith a plus in comfort or grip as benefit!
From the carbon fork to the carbon handlebar to the complete carbon racing bike: ax-lightness from Upper Franconia, Germany is the number one manufacturer of lightweight bicycles and components thanks to the company's wide range of carbon products. Why carbon? The individual components of carbon bicycles offer ultimate stability with superior performance and are extremely lightweight. Page through the website to discover the amazing diversity of carbon bicycles from ax-lightness.
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