Why a wood and carbon bike?

As designers and engineers we are fascinated by materials and our pallete of material tools here at Coh&Co Copenhagen is quite broad. We began as carbonfiber/ composite specialists in the marine industry and have since gained considerable experience in the design and manufacturing of different projects, utilizing everything from aluminium to stone.

Given this background it is therefore not surprising that we at Coh&Co often get asked why we have chosen wood for our WOOCA bikes when we are so clearly open to other materials. Many assume that it is for aesthetic reasons, and although we are flattered by the complement, we believe that the beauty here is far more than skin deep. The beauty is in the ride.


Wood as a structural material

Wood is one of nature’s most fantastic engineering materials. It’s tough and resilient and it has an incredible ability to withstand cyclic fatigue that is very difficult to match. It also has some really great harmonic characteristics that lend themselves to bicycle design. Wood cannot be discounted as an engineering material – lets face it, trees tower up to 100 meters into the air and do so borne by foot prints which are proportionally smaller than that of the highest skyscrapers. Trees last for centuries and in extreme cases millennia (some Sequoias have been shown to live for 3,500 years and reach over 100 meters into the air), while regularly surviving storms, earthquakes, rot and even in some cases, forest fires – this is a formidable structural material. Wood also has a harmonic range that is very compatible with the human machine. There is something warm and natural about wood that is almost mystical, but it is possible to substantiate it.


The human machine harmonises with wood

We humans are living organisms and we respond to the environment around us. One of the things we respond to is vibration. Holding a vibrating tool or instrument (even lightly) will affect blood flow to the hands (or whatever region is in contact with the vibration) thus reducing blood flow. This means that less oxygen reaches the cells and ultimately muscle performance and power become exhausted. As it happens, “road noise” – or vibrations transmitted from the road surface through the bicycle to the riders hands, feet and groin – provokes a condition where the body systematically reduces blood supply to the areas affected by vibration and we lose power… In extreme cases the body can reduce blood flow by as much as 20 or 30%. One of wood’s great strengths as a frame building material, is that it is incredibly good at absorbing these “road-noise” frequencies that are in the irritating part of the spectrum, without giving up on strength or flexing. This means that we can produce a frame with an unparalleled ride experience utilizing wood to absorb the unpleasant harmonic disturbances from the road – without the need for all the fancy gadgets and design gymnastics required when designing with other frame building materials.


A wood and carbon hybrid frame = stiffness

However, one of the characteristics that makes trees so incredible is the resilient nature of wood and although this may make trees really tough and very strong, it is not usually associated with extreme stiffness. Stiffness is part of what we need for power transfer.  This is why we have chosen to combine wood with carbon. As is the case in any successful composite structure the choice and marriage of  the right materials can augment the performance of the individual contributors.

WOOCA technology does just that. It utilizes the strengths of both the wood and carbon and allows them to do what they are good at. Our forward triangle is a wooden box construction which is locally reinforced with internal structure for specific loads such as the bottom bracket, headtube  or the forward derailleur attachments.
Stiffness is an inarguable ingredient in the power transmission equation and is needed to provide a fast ride. Unfortunately, as with almost anything else this is not a simple job of selecting the stiffest material available. First off, stiffness is primarily governed by section modulus which is really to say that a mediocrely stiff material can be made to perform with great stiffness by increasing tube size.  Some materials and geometries will transmit road noise and give a very dead feel despite having a theoretical optimal power transfer. This is why aluminium frames can be phenomenally stiff but are generally lacking in ride quality.
WOOCA allows us to stiffen the backend of the bike as much as we like without deadening the ride – the wood toughens up the structure and keeps absorbing all the excessive road noise.

Frame flex

Material stiffness as we can see is only one part of the power transmission equation. Another is global frame flex. Although we may think of frame flex as a bad thing, frame flex is an important part of the power transfer equation. It defines how we transfer our power to the wheels. A frame with the proper materials is a sort of a spring that helps to store the energy of the rider and return it at the bottom of each stroke thus providing a more even power curve. Different materials return energy differently and our WOOCA composite frames do this incredibly efficiently resulting in the snappiest ride out there.

Production technology

Coh & Co’s box construction for the forward triangle of our frames lends itself quite well to being built up with thin veneers. There are 14 laminated base components cut and joined to produce each frame. Each of these components is moulded in a high pressure moulding process to insure maximum bond performance and a minimum of resin. Some components are interleaved with carbon fiber during lamination – fibers are oriented to compensate load scenarios specific to each individual components function on the frame. One of the unique features of this construction technique is that there are no finger joints or individual wood joints in the corners – wood fibers run unfettered and unbroken around the load paths of forward triangle and the rear assembly.

The beauty is in the ride

WOOCA produces a very dynamic frame building technology and provides an unparalleled ride experience. This experience is marked by power transfer mechanics that augment our performance abilities in manners previously unseen with traditional build materials (carbon included). Finished bike weights are down around ICU minimum where sub 7 kilo ride ready bikes are available with high end stock components (Tour De France weights).

As we said, these bikes may look great, but the beauty is in the ride.