First UK-built bamboo bike unveiled
The first UK-built mountain bike made out of bamboo has been unveiled at a major cycling exhibition.
Its designers, from Oxford Brookes University, say the natural material has the strength of steel but the responsiveness of carbon fibre.
They added that it was these properties rather than the plant's environmental credentials that prompted them to build a bamboo frame.
The bikes, built by Yorkshire-based Raw Bikes, will cost from £1,750.
Co-designer James Broughton, head of Brookes' Joining Technology Research Centre, said the idea of using bamboo started out as just a possible exercise for the centre's students to test alternative materials.
"Bamboo has a genuine performance benefit where it has this ability to dampen frequencies quite nicely," he told BBC News.
"In terms of ride quality, we thought that it might have nice characteristics."
Dr Broughton said his colleague and co-designer, Shpend Gerguri, thought the giant grass could offer a different experience for a bike rider from standard frame materials.
"Particularly hard frames like carbon fibre, where the material is so stiff, means you feel everything from the road," he explained.
"This can be very advantageous; you make things stiff because then all the power you put in through your legs goes straight into turning the wheels round, it does not go into bending the frame.
"However, when you go to longer distances then the (frequency) feedbacks that the bike gives to the rider can be quite detrimental as they build up and result in rider fatigue."
Grow your own
The pair decided to test whether a bamboo-framed bike could do what it was supposed to: transmit power, and withstand what a mountain bike rider throws at it.
With the help of their students, the two engineers took the idea from a drawing-board concept to a finished product.
The environmental merits of bamboo as a fast growing, carbon absorbing, sustainable construction material did offer an extra dimension, but it was not the main focus for the project.
But, Dr Broughton added: "Obviously, materials such as wood, timber and other grasses are in vogue at the moment because of the requirements to reduce CO2 emissions."
He explained that one of the main challenges was finding the right sort of bamboo.
"There are very few suppliers of bamboo of the right quality in the UK at the moment.
"You have to be quite specific in what you select, and then be quite thorough when conditioning the bamboo to make sure it dries out and has the right moisture content."
He said that bamboo, as with wood, will expand with moisture and shrink with dryness. Its properties are also inherently much more variable than those of standard frame materials such as steel.
The researchers identified a particular kind of bamboo from the estimated 1,500 species growing on the planet, as well as a certain grade of the harvested grass, that was best for the job.
But they added that they were not at liberty to reveal the details because the information could be used by possible competitors.
The bikes are being commercially produced by Yorkshire-based Raw. Managing director Rachel Hammond said she had been interested in producing bamboo bikes for a number of years.
"As soon as I rode one I realised that they gave such a different ride and I was absolutely hooked," she recalled, ahead of the bike being unveiled to traders at the 2011 Cycle Show at the NEC, Birmingham.
"They were mainly made in North America, and there was no one really importing them."
Ms Hammond explained it took three days to build one bike: "This is because there are various stages when you have to let various resins cure. If you started one on Monday, then you could probably finish it by Wednesday lunchtime."
While the material's strength and durability made it an attractive frame material, she acknowledged that the bamboo bike's starting pricetag of £1,750 meant it would not have mass market appeal.
"It is not aimed at someone who spends no more than a few hundred quid on a bike, it is aimed at someone who really loves cycling."
Dr Broughton said that seeing the bike develop from an idea to being sold in shops was "hugely satisfying".
To put the frame through its paces, he and Dr Gerguri rode two bamboo bikes in this summer's eight-stage TransAlp race, covering 385 miles (620km) from Germany to Italy including 13 miles (21km) of climbs.
"Everywhere we went, people [riding bikes with standard material frames] were having punctures and technical problems. We did not have a single problem with either bike; that was really satisfying."
But, he quickly added: "We don't want to extrapolate that too much and think that the bamboo frame stopped us from having punctures."