This is the first question that always gets asked. Followed by:
“Isn’t it going to break?”
“That must be heavy”
… “What about wood worm?”… “Careful it doesn’t catch on fire”….. and don’t get me started on the wood puns!
To start with, have you ever questioned the ability of a wooden cricket bat to hit very hard balls without denting badly or breaking? Or the ability of a wooden axe handle to avoid dropping a sharpened axe blade on your head as you’re swinging for the next chop? I’m guessing probably not. Cricket bats and axe blades are meant to be made out of wood, right?
The selection of materials for cricket bats and axe handles is just like any other product in that there are plenty of options available and wood meets the job description very well. They each need a material that is strong enough that it won’t break, light enough that you can pick it up and swing it around, flexible enough that it won’t break your wrists when you make the big hit/ chop and resistant enough that you can use it outside for years with minimal upkeep. It is difficult to find a metal equivalent to each of these that could be substituted and still give the same performance at the same price. There is one small caveat to this in that cricket bats are heavily regulated by the ICC and the MCC which tends to put the brakes on any technological development! Also, interestingly, the debate between aluminium vs wooden baseball bats still goes on despite our understanding of the materials and physics of the situation being significantly more advanced than when ash or hickory bats first started to be used.
Each species of wood has slightly different material properties lending them to a very wide range of uses and there is a wood for most applications that will deliver a specific balance of strength, weight, stiffness and durability. In fact cricket bats tend to use willow and axe handles tend to use hickory for the precise reason that those particular woods offer the best material properties for the job. If you used most other wood types then the performance of the bat/ handle would suffer. What about bike frames?
The answers to the first two questions, at the top of the page, are actually very interesting and particularly suprising for most of us that are used to a cycling industry dominated by hi-tech carbon fibre this and ultralight super nano that. Having read the information about the Renovo hardwood frames and their very favourable comparisons to the Cervelo Soloist, I was sceptical. It wasn’t until I armed myself with a pencil, paper, calculator and some research into different hardwood material properties using trusty old Google that I came to the same conclusion that Renovo have – Wood really is a viable alternative for a bike frame. If you’re interested in the finer details of how/ why wood can rival the performance of a more conventional frame i’ve written a discussion on the next page in Let’s talk numbers.
The short answer is that several of the very dense exotic hardwoods offer a very good strength to weight ratio that, when combined with some subtle tweaks to the geometry of a standard bike frame, can give the same or even better characteristics than an aluminium or steel frame.
I’d like to be able to say that my interest in wooden frames came about from a deep rooted desire to save the planet by using more sustainable materials. It didn’t. I think that wooden frames look fantastic and I love the fact that they can be hand crafted using natural materials (ehem, no one mention the power tools and epoxy).
On a more serious note, exotic hardwoods are not the most sustainable form of timber and many of the rare hardwoods are protected species and cannot be used for trade. CITES (Convention on International Trade in Endangered Species of wild flora and fauna) is an international governmental organisation that controls the trade of endangered exotic hardwoods and in conjunction with organisations like the FSC (Forestry Stewardship Council) aim to eradicate unsustainable logging around the world. The nature of very dense hardwoods means that only the oldset trees are cut down and will take decades to replace. This can only be done sustainably on a small scale to avoid the extinction of slow growing species. If sustainability is really of top importance to the wooden frame home builder then something like Bamboo would make a more suitable wood choice. It is very widely available, fast growing and also has decent strangth/ stiffness to weight ratios.
Having said all that, the carbon footprint of a timber bike is minimal compared with a carbon fibre, aluminium or steel frame due to the energy intensive processes used to extract the raw material, convert it to the engineered material and finally produce the finished tubing for a frame. So, whether the particular species of wood used is sustainably sourced or not, any wood type will provide a more ecologically friendly frame than the off the shelf alternative from your local bike shop.
As a footnote, none of this applies to the construction of my 2×4 recumbent which uses the cheapest softwood I could lay my hands on. As a result it is heavy and flexible and fairly unsuitable as bike frame material. It was, however, very cheap, easily available and easy to work with so it did have some benefits over metal, carbon fibre or even hardwood.