What kind of bicycle rides like steel, dampens like carbon, and is as light as aluminum; yet is none of those?

Answer: Bamboo.

Traditionally, bicycle frames are constructed of composite materials like steel, carbon, and aluminum. Each type has its advantages and disadvantages when it comes to its structural properties. Through modern engineering, the weaknesses of each material can be minimized through innovative design practices, but not entirely nullified.

Enter bamboo. It is naturally balanced, inherently strong, and perfect for building two-wheeled, human-powered vehicles. It’s essentially the ‘greatest hits’ version of bicycle frame material. Of the 1,000 species of bamboo throughout the world, iron bamboo, grown in India and parts of Asia and Latin America, is one of the more ideal species for frame tubing. The stalks, also known as culms, can grow to a height of 50-feet and are approximately three inches in diameter. Anyone who has seen bamboo in the wild can attest that, despite its height, it stands amazingly straight. This can be attributed to the strength of its natural fibers. As one of the fastest growing plants on the planet, bamboo is also a valuable building material, even sometimes used to reinforce concrete instead of steel.

The strength of bamboo is probably its most intriguing property. At first glance, it would be entirely believable that a bamboo bicycle wouldn’t be good for much more than just hanging on a wall. However, it is in fact stronger than steel. The power of bamboo can be quantified by calculating the force required to break something, otherwise known as yield strength. This property is measured in Newtons, the unit of force required to move 1 kilo of mass at one meter per second, per second squared. The yield strength of bamboo is slightly higher than steel: 28,000 compared to 24,000.

Although bamboo is intrinsically strong in its molecular structure, it requires post-harvest processing before it is ready to be used in a bicycle frame. After being cut and dried in the field, it must be heat-treated. Commonly, bamboo tubing is treated with a hand-held blow torch. This process of heating the culm accomplishes two things. First and most importantly, it maximizes the strength of the bamboo by changing the properties in the fibers. While there is no definitive evidence as to how the fibers transform, it is theorized that the process it similar to boiling a sugar syrup. Once dry, the internal ‘juices’ become a stiff, yet pliable substance. And yes, it’s entirely possible that a bicycle built without treating the bamboo would be rideable, but it would unfortunately be very supple. Beyond enhancing strength, heat-treating brings out the natural grain of bamboo, highlighting its highly aesthetic appeal.

As critical as the heat-treating process is, it’s very labor intensive to finish each piece by hand. When you consider that there are seven pieces per bicycle to treat and each takes 20-minutes, you begin to understand that building a bamboo bike is definitely a labor of love. Various manufacturers have tested their own methods for streamlining the heat-treating process. One interesting method requires an oven of sorts to bake the bamboo in sand. Another technique turns the individual pieces on a spit while moving a flame back and forth. Only time will tell of automating the heat-treating process is better than hand craftsmanship.

While the natural strength of material used in building a bicycle is important, so too is how the frame pieces are connected. Bamboo bicycles are usually pieced together in one of two ways: wraps or lugs. Lugs are pre-fabricated fittings that join the various parts of the frame. Currently, steel and carbon fiber are the most common types being used. Alternatively, wrapping involves a strong fabric like carbon, hemp, or bamboo that is wound around the frame joints and reinforced with epoxy. Since bamboo bicycles are still in their infancy there is no evidence to suggest which method is more beneficial.

Bamboo brings a whole new dimension to bicycle manufacturing. It’s exciting to think that sustainable transportation can be built from renewable materials and it’s most definitely a testament to the strength in nature.

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