Arbr bikes are designed, engineered and manufactured in the UK. We use high grade pre impregnated carbon fibre material in both unidirectional and cloth form for the construction of our frames, which are cured in high pressure autoclaves.
The carbon fibre laminate has been optimised to achieve our stringent compliance, strength, impact, and durability targets. A detailed series of analysis using finite element techniques was performed throughout development to carefully define the laminate, dictating ply position, orientation, staggers and overlaps.
“Optimised to achieve our stringent compliance, strength,
impact, and durability targets”
We know every single ply because we defined it and worked with the lay up through manufacture. This is how it should be done, but is commonly not always the case in the industry. The main frame is a true monocoque construction while the swing arm is manufactured as a left hand and right had side before being bonded at the centre bridge.
In order to maintain the highest control on quality and build the bikes will be made in small volumes and as a result the quality and craftsmanship will be experienced by a limited few. The attention applied to our products does not translate to big volume off- shore manufacturing.
“These are limited edition frames, not mass production items. The highest levels of craftsmanship go into each frame at every stage”
The series of plies are pre cut from a roll of material and placed into kits for each frame. Plies are laid against the mould according to the specific sequence defined in the manual. Mould surfaces dictate the basic structural efficiency of the frame, the manual defines the structural integrity which cannot be judged or appreciated looking at the outside surfaces. A huge amount of detail goes into areas that cannot be seen.
The lay up holds the key to much of the frames durability. Plies are positioned to ensure fibre continuity across the frame and reinforcement is added to local areas where required. Key structural features are reinforced with hoop plies, continual plies of fibre running around every bearing bore and mounting lug, each staggered and overlapped from the previous ply. Other internal features include the use of aerospace core materials within the central reinforcing brace and lower downtube, creating sandwich structures that benefit strength and weight ratios.
“Key structural features are reinforced with hoop plies”
This process is intensive and requires high precision from the operators but it is central to the philosophy of the company. The early prototype frames were ridden straight out of the mould with no finishing such is the quality of the raw components. The attention to detail is to the highest degree and the production is meticulous in its approach to precision and process quality. We feel that it is highly appropriate for the performance of our bikes and something we take much pride in.
Our aim is to build exclusive high quality bikes in small controlled batches. This keeps the personal touch in each frame we manufacture, which we aim to transfer to the eventual owner. Our bikes are testament to the passion and experience of a team dedicated to precision, giving unrivalled performance in each one.
The autoclave manufacturing route chosen for our frames uses procedures that follow standards set in the Motorsport and Aerospace Industries. We are not reliant on the commonly used techniques of stacking plies against mandrels which are subsequently placed into moulds. For high volume manufacture other techniques are efficient but the resulting consistency and consolidation cannot match the quality of the autoclave process that we utilise. We prefer to consolidate with direct pressure against the mould surfaces which define the shape of our frames.
“Carbon fibre is pressed into the mould, held under vacuum, then cured in an autoclave at temperature and elevated pressure for 8 hours.”
Each ply of carbon placed into the mould is smoothed and formed to the underlying surface to ensure fibre alignment and structural integrity. Complementing this approach, and offering significant advantages over other techniques, is the application of vacuum, elevated pressure and temperature during cure.
After the laminate has been completed a bag is installed which runs both inside the mould, against the carbon, and outside of the mould surfaces. The bag is sealed and a vacuum line is added to extract air. The presence of a vacuum on the inside of the bag forces the bag against the mould surface, compressing the laminate.
When the mould assembly is moved into the autoclave the force exerted is increased further as the external pressure rises to several times above ambient. Heat is applied and the laminate starts its cure cycle, lasting several hours.
This is the best way of achieving a consolidated laminate, free of voids and wrinkles. The process gives the highest quality structural components, maximising strength from the material and removing requirements to add margin to cover process variability. Simply translated our construction methods ensure minimum variability in frame construction so there is no need to overbuild the frame to compensate.
“This is the best way of achieving a consolidated laminate, free of voids and wrinkles.”
Consolidation is improved further by the use of vacuum and pressure debulks during key stages of laminating. This increases the level of consolidation beyond that achievable during the final autoclave cure alone.