carbon frame construction (1)

The construction techniques of the carbon tubes are fundamental and make a difference in the frame quality. These complex techniques resulted from many tests and the experience we gained since 2001 when we started producing our first carbon fibre frames.

Inside a carbon tube

In constructing the tubes, we use various diagonals of the unidirectional carbon fibres to maximize rigidity, resistance and balance the tensions during road / off-road use of the frame. The tubes of the frame’s front triangle have – depending on the model and type – asymmetrical reinforcements and symmetrically arranged canvases. Pipes generally work in flexion and flexion-torsion: to counteract the tensions, the lay-up of the carbon fibres is arranged radially and at 45° longitudinally. Tubings are made with High Modulus carbon to have very high stiffness and resistance and High Resistance carbon module to increase the tenacity and resistance to breakage due to fragmentation. The fibres, made of carbon Toray T 700 and T800 type, laminated in triple thickness, are pre-impregnated with appropriate resins. Externally, tubings are finished with Plain 3K. The outer fabric also contributes to the resistance of the tube itself. Internally there are various types of fabric and lay-up.

The stratification technique

The production process using high-pressure Mandrel Wrapping in an Autoclave guarantees the best final resistance of the material by reducing to zero voids for gas or air. In addition, the distribution of the resin evenly throughout the tissue is essential. This slightly increases the specific weight but guarantees an increase in resistance for the same material section and permits the thickness reduction to the minimum value. Finally, the stratification technique consists in adding sheets of carbon fibre alternating with sheets of Kevlar, and mixing them with the resin. Kevlar gives a touch of elasticity to the structure. This makes the frame more robust and able to better absorb impact shocks due to falls, but also the roughness of the road or off-road terrain.

Carbon fibres and high temperatures

The sun will hardly damage a frame in composite material if the resins and paints are of high quality. There are two external factors that can damage a carbon product: UV rays and high temperatures. Ultraviolet rays are capable of damaging only a very superficial layer, of a few microns, of the resin of a raw compound. The transparent polyurethane varnish forms a protective layer which completely eliminates the UV risk. As for heat, the resins we use for our carbon frames have a transition temperature above 120°C. However, there are many manufacturers who use cheaper resins, with transition temperatures slightly above 60°C. If the transition temperature is exceeded, there could be irreparable damage, as the resin would undergo a vitrification process, with complete loss of the resistance characteristics.
carbon fiber and hot temperatures

Carbon frame assembly techniques

In order to assemble the frame, the carbon tubes must be cut to the desired length and then joined together with a touch of glue, just to give shape and the right angles to the frame. Once the tubes are joined together, they are then reinforced with additional layers of carbon fibre and resin to increase strength and rigidity. This process is called “tube-to-tube”, in which the fibres are woven together to create a strong, lightweight connection. It is more costly but produces a stronger and more durable frame. And also it allows to build a real custom-made frame, calibrating every single millimetre of the geometry.

carbon frame inside

Costs and results

The tubetotube carbon frame construction technique definitely costs more. It asks a lot more time than building an inmould frame. But the criteria for choosing the carbon fibres and how they are used in the processing convey the final result one step ahead. The tubestotubes building technique gives the frame a high level of precision and stiffness, allowing for better control and handling of the bike. It also enables better absorption of the vibrations that come from the terrain. It also increases the strength of the frame while reducing its weight.

 

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