What's the deal with bamboo bikes?
by Keith Couture
Bamboo, not just the preferred snack
of Panda bears, has long been used to build structures, scaffolding,
water transport systems, flooring material, kitchen utensils, boats,
not to mention its use as a decoration, or even in cuisine alongside water
chestnuts. It didn't take long for someone to conceive of a bicycle
made from bamboo, too. The list of boasts about this wonder-material
grows:
“Bamboo is lighter than aluminum!”
Some say.
“Bamboo has a higher tensile strength
than steel!” Claim others.
“It's sustainable to grow! And can
also grow up to one meter a day!”
“It can be grown locally!” Another
perk.
But, what really is the deal behind
bamboo? Is it all it claims to be? I intend to dispel the myths,
dissect the claims, and provide an objective analysis of this
auspicious bicycle material.
THE WEIGHT:
A bicycle's weight is a major concern
for a lot of consumers. In fact, for many it is the
factor in deciding a bicycle's quality. Could bamboo really be the
super-material that gives millions a race-weight bike at a fraction
of the cost?
Bamboo
is a porous, hollow material, which intrinsically cuts down on
weight. The frame builder Calfee Design (http://calfeedesign.com/products/bamboo/) based out of California has
bamboo frames that weigh anywhere between 1.8 kg to 2.6 kg (around 4
– 5.7 lbs.). Another frame builder called Cognitive Cycle Bamboo
Bikes has frames from 2.4 to 2.6 kg also (about 5.3 – 5.7 pounds).
A relatively new bamboo bike builder called Greenstar Bikes (http://greenstarbikes.com/) makes
single speed bikes which weighs in at 22 lbs for the complete
bicycle.
The Greenstar Eco-Force 1 weighs around 22 lbs
For comparison, an aluminum racing frame could weigh as
little as 2.2 lbs (for an exceptionally
light and expensive bike), more realistically around the 3 to 4 lb
range, sometimes even including the fork. An aluminum bicycle from a
department store, however, could weigh as much as 38 lbs, so material
sometimes has nothing to do with it.
A steel bike can be made to be just as
light or heavier, as well. A steel racing bike from the 80's for
instance would probably weigh around the 19 lb mark for the complete bike,
with a relative frame weight of roughly 4 lbs. Of course, a common
chromoly steel bicycle, vintage or new, would likely come in at
around 6 lbs for the frame, while the complete build could weigh
anywhere between 24 and 30 lbs. A titanium bike or a carbon fiber
bike... well, we're not even going to go there. Those materials can
be used to build frames that are easily under 2 lbs. Of course there
is some variety in the weight of them as well, it depends on the
quality of the carbon fiber or titanium, and likewise for any
material, be it steel, aluminum, or bamboo.
The
point is, there is a great variety in bicycle weights for any
material, and bamboo doesn't have a significant edge over any other.
In fact, the standard deviations of each of these materials' weights
are likely to be very similar. Furthermore, the components chosen for
any given frame and what kind of a build is being done have a great
deal of impact on frame weight as well (a single speed will likely be
much lighter than a bike with thirty gears and big, knobby tires).
So, is bamboo lighter than any other material? It's impossible to
measure with all the variables out there. All the major materials are
capable of creating bicycles of roughly equivalent weights.
THE STRENGTH:
Bicycle
tubing strength has a lot to do with weight actually. If you're using
an intrinsically stronger material you can shave more and more off of
the inside of a bicycle frame's tubes, therefore lowering the weight.
Some bamboo bike manufacturers boast that their bamboo has a higher
tensile strength than steel. I was skeptical, so I really looked into
material strengths. The wikipedia page on ultimate tensile strength
was instrumental for this analysis.
Ultimate tensile strength is the
maximum amount of force a material can withstand (in the case of
tensile strength,
stretching force)
before breaking. Turns out there are a lot of different types of
steel with a wide variety of ultimate tensile strengths. Bamboo has
an ultimate tensile strength of around 350-500 Mpa (Mega Pascals, the
unit used to calculate this type of force). It's possible after the
bamboo has been treated with an epoxy or resin its tensile strength
increases, but considering the ultimate tensile strength of epoxy
adhesive is only 30 Mpa, I doubt it's that much stronger. To compare,
structural ASTM A36 steel has an ultimate tensile strength of 400-550
Mpa. Ah-ha!
So, if some really
strong bamboo at 500 Mpa went toe-to-toe with some of that steel that
managed to top out at 400 Mpa, then yes, bamboo is stronger than
steel. However, what are bicycles commonly made out of? These days,
chromoly or perhaps during the peak of American and Japanese road
bikes in the 80's a different mixture such as manganese-molybdenum.
In either case, the UTS of these types of steel are between 700-900
Mpa, well over bamboo. Some steel bicycles are made from steel with
strengths up to 2050 Mpa!
6061 Aluminum
comes in at 325 Mpa, slightly under bamboo. Obviously aluminum is
commonly used in bicycles, so these are strengths which make it
perfectly safe to use as a frame material. Bamboo bicycle
manufacturers are likely using the few exceptions when their material
is stronger than steel to help market their product. Nothing wrong
with that! It is vague enough to not be fiction.
THE SUSTAINABILITY:
One of the reasons
bamboo has surged forward as a viable material to build bikes with is
because of its suspected sustainability. Nowadays, stamp something
with a sticker that says “sustainably harvested,” or
“eco-friendly,” or “humanely produced” and it'll sell. Bamboo
has those stickers written all over it. It has always been true that
the mining industry is one that tends to exploit and abuse the
laborers who produce the raw materials for metals (be they steel,
aluminum, or otherwise). Some bamboo manufacturers tout the hardiness
of bamboo and its ability to be grown in various climates, but the
majority of this bamboo is nevertheless harvested from Thailand,
Vietnam, and the rest of southeast Asia where it is abundant. There's
nothing wrong with that of course. It's likely that the coal that
goes into making steel for bikes comes from the same place, and the
workers there are likely experiencing much worse conditions. Bamboo
definitely seems to have the advantage in regard to the humanitarian
aspect of production. What about the environmental impact?
A more traditional looking bamboo bicycle (photo by Flavio Deslandes)
Again,
mining coal and other metals is terribly destructive to the planet.
Growing bicycles sounds like the kind of idyllic fantasy that you'd
come across after landing on a square in Candyland. However, if that
bamboo is coming from across the ocean, there's the carbon footprint
of that transportation to consider. Not to mention, bamboo does have
to undergo a process of treatment which involves using epoxy to join
tubes and lugs together (be they aluminum, hemp, steel, carbon fiber,
or titanium). The majority of industrial epoxy is derived from
petroleum. As a result, the process of making a bamboo bicycle still
depends on mining and drilling. There are a growing number of epoxies
that are plant based, however. Calfee Designs explains that they use
hemp binding along with an eco-resin to construct their bikes, which
seems like a step up. However, they also finish the frames off with a
satin polyurethane, so there seems to be no escaping the use of
petroleum products.
THE VERDICT:
Bamboo bicycles
are clearly the next great thing in bike-building that we should all
pay attention to. As with any material, it can be done well, made
lightweight, strong, and dependable. It can also be used, just like
any other material to build a bike that is a cheap, single speed with
knock-off components to keep the price down. It all depends on what
goes into the bike. My advice would be the same advice I'd give to
any bicycle shopper; do your research, make sure it's comfortable for
you, make sure you like how it looks, make sure you can afford it,
and you will end up with a fine bicycle. I think even if bamboo
doesn't surpass the other materials used in framebuilding, it is at least equivalent in its capabilities. We can
safely add it to the pantheon of bicycle framebuilding methods.
More generally
speaking, I think the fact that bamboo bicycles are popular at all is
an encouraging trend in and of itself. That we would look to this
material for bikes suggests, to me, that we as consumers are becoming
more aware of the commodity chain that links us to the people that
make our things—bikes or otherwise. The more knowledge we have of
how these wonderful machines are produced, the more connected we will
be to the people that make them possible, and the more connected we
are to those people, the more we have a stake in their well-being,
which is extremely important if we want to keep the wheels of the
world rolling.
For more info on a few different bamboo bicycle manufacturers check out:
