User:OGgaucho/sandbox/Wooden Bicycle

Wooden Bicycle

Wooden Bicycles are bicycles that are built with hollow or solid wood-based frames, which are usually laminated with epoxy and polyurethane. Wooden frames are sometimes aided by steel or composite lugs to connect the wooden tubes or attach components. Wooden bikes can be made with plywood, hardwoods, or bamboo. A push for more environmentally friendly products, along with the desirable aesthetic qualities of wood have created a growing market for wooden bike frames. Wooden frames can be nearly as light as frames of carbon fiber or expensive metals, and when applied properly wood offers qualities of stiffness and vibration dampening that other materials don't.

Wooden Bicycles can be made cheaply and quickly with plywood for practical, non demanding use. They can also be made slowly with high levels of craftsmanship to compete with frames made of carbon fiber or expensive metals (like titanium and scandium) in both weight and strength. It is important to note that the strength of a wooden bike depends greatly on the wood used and how well designed the frame is, so not all wooden bikes can live up to the standards set by high-end companies. Connor Wood Bikes and Renovo Hardwood Bicycles have become the most prominent high-end wooden bicycle makers, and use hardwoods to build their frames. Erba Cycles is an emerging company that makes their bikes with bamboo at a far lower cost than hardwood bikes, but their bikes are still relatively expensive when compared to steel-framed bikes. As far as cheaper designs go, BSG Bikes, a French company, is an example of a designer that makes more simple wooden frames from layered plywood with steel joints and rear triangles. The cheapest currently available come from a company known as Sandwichbikes which uses plywood as well, and sends you all the parts necessary to assemble your bike for $1,043.

History

Bicycles have changed greatly over time, and while high-quality wooden bikes are relatively new, the first bikes were actually made of wood as well. Bicycles were invented in the 1800s, and it is debated when they were invented and who actually built the first one. However, it is generally accepted that the velocipede, created in 1818 by Nicéphore Niépce, didn't gain the mechanical drive to technically make it a bicycle until 1869. These early bicycles were made with heavy solid wood bodies which did not closely resemble modern bicycles. They typically had very large front wheels, and lacked the characteristic diamond shaped frame of modern bicycles, which didn't become common until the 1900s. The first metal bicycles were built in the late 1800s, and still used solid tubes. It wasn't until the 1920s when monocoque, or hollow, frames began to be made. This monocoque build was only practical for metal at the time, and we lacked the technology to apply it to wooden bicycle frames. It wasn't until we developed modern lamination techniques that monocoque wooden structures became practical. Even with that technology available, it wasn't until after 2000 that this technology began to be applied to bicycles. The first high-quality wooden bicycles that could actually compete with metal and carbon fiber bikes didn't start to sell until after 2000. Since then they have slowly gained more attention, and more companies have begun to produce them.

Structural Benefits of Wood

Strong and Stiff

Wood in itself is a naturally stiff and sturdy material, due to the way it grows over time to resist forces from all directions (think of trees in the wind). Hardwoods are the densest and strongest woods available, while bamboo (technically a grass and not a wood, is accepted as a wood for engineering purposes) displays similar qualities, and though it isn't quite as strong and stiff as hardwood, it is naturally formed into sturdy tubes which work well for bike frames. Plywood is strong as well, but due to the jumbled formation of the fibers in layers, it isn't quite as strong as wood is in its natural state, and is much less stiff.

Absorbs Vibrations

In addition to being very tough, wood has a unique ability to absorb vibrations which is not seen in other bike building materials. When a vibration travels along the wood tube, it will be dampened significantly by the cellulose in the wood before it reaches the rider. This means vibrations transferred from the wheels to the frame are dampened more by wood tubes than they are by carbon fiber or metal tubes. This dampening quality makes wooden bikes ride noticeably smoother.

Wood dampens vibrations better than metal or carbon fiber because it is less dense, and is composed of layers, as seen in the rings of a tree. This alternation between more and less dense layers (dark and light rings, respectively) mean that the different layers vibrate at different frequencies and dampen each other. By vibrating against each other it converts some of the vibrating energy into heat, making the vibration diminish faster than in metal or carbon fiber.

Durable

Being less dense than metal and carbon fiber gives wooden frames an advantage in impact resistance. The lesser density means the tubes of crafted hardwood bikes and tubes of bamboo have thicker walls than a metal or carbon tube of similar strength would. A wooden tube weighs only slightly more, and the thickness makes the tubes stiffer. The coating of epoxy and polyurethane makes the tube even stiffer and gives it a thin, strong, and dense skin. This skin makes it resistant to light impacts and scratches, and the wood underneath provides it the main strength to resist heavy loads and powerful impacts. The thicker walls are much more likely to survive a crash because they are much harder to structurally damage. Instead of a large section of the sidewall deforming into a dent or cracking, as seen in metal and carbon fiber frames, there would be a smaller dent that penetrates only partially into the wooden sidewall. Since this crack or dent doesn't fully penetrate the sidewall, strength along the length of the tube is less impaired. A dent in a metal tube or crack in a carbon tube significantly weakens the tube. Unless they are repaired, the damage will grow from repeated use until the frame finally fails. A dent in a wooden tube can be easily repaired by filling the dent with epoxy and re-laminating, while a damaged metal or carbon tube requires more significant reforming and repair.

Long Fatigue Life

File:Fatigue Life of Materials Used in Building.jpg

This graph shows the loss in strength over time of various materials used in frame building.

Fatigue is progressive damage and weakening of a material due to cyclical loading. In other words, when a material regularly experiences a deforming force it becomes weaker over time and is less likely to endure the same force without breaking. The fatigue life of a material is how long it takes for it to fatigue to the point that it cannot survive the forces it was designed to withstand. Wood has a very long fatigue life, and its strength decreases much more slowly over time when compared to metals and carbon fiber. It rivals carbon fiber in its fatigue life, and it maintains its initial strength longer than everything except aluminum. This means a wooden bike frame lasts a long time without needing to be replaced. This long fatigue life is due to the natural strength of wood as well as the lamination. The lamination protects the wood from natural deterioration and helps the tube maintain its shape and chemical structure.

Issues with Wood

The first big issue with wooden bicycles is preventing the wood from deteriorating, which is one reason for their high prices. Since wood is an organic compound it is vulnerable to the effects of decay and deterioration, and steps must be taken to protect the frame. Wood can be damaged by fungi, insects, bacteria, water, oxidization, and UV light. To protect the wood from decay, wooden frames must first go through drying processes and get expensive coatings of epoxy and polyurethane. The drying process is done in a kiln, and the wood is dried to a low moisture content that still allows some flexibility and minimizes the possibility of decay. The coating of epoxy and polyurethane seals the wood and protects it from oxidizing effects of air, external moisture, organisms, and UV light. While this process effectively preserves the wooden frame, it is very expensive and the coating must remain intact. Scratches and dents must be resealed quickly to prevent moisture from entering the wood and to block deteriorating UV light.

The other major issue with wood is that it is much more time consuming to build a wooden frame. Metal frames can be shaped with hydroforming, which uses pressurized water to shape the tubes, which is much cheaper. Carbon fiber frames can be built by layering strips of carbon fibers on a removable core, which is more expensive than making a metal frame, but cheaper than wood. Wood requires lots of work to be done by hand, and there are the added steps of prepping the wood and finishing the completed frame. This makes the wooden frame impractical for mass-production at this time, and since they involve more time and skilled work they costs a lot more than their competitors.

Styles of Wooden Bikes

Hardwood

Hardwood bicycles tend to be the most expensive, but strongest and most durable type of wooden bikes. They are made with hardwoods such as maple, hickory, ash, walnut, and a multitude of rainforest hardwoods, and sealed by an epoxy and polyurethane coating. They offer more stiffness than steel by weight and can be made with solid or hollow tubes. These different designs have different strengths and weaknesses. In general hollow tubed frames are lighter, and stiffer due do the increased diameter of the tubes. With both types of frames, the wood must be kiln dried to a certain moisture content for the desired amount of flexibility and to prevent decomposition. After being dried, the wood must then be shaped to make the frame. Hollow frames are made by hollowing out and rounding two halves. Then they glue and seal together the two halves of the frame with epoxy. Solid wooden frames are generally made by steam bending the wood to form each piece of the frame. These solid pieces are shaped at the ends to be flush with the others, and are then glued together with epoxy. These joints are often strengthened with kevlar when the frame is laminated to prevent separation. Metal inserts are typically added to hardwood bikes at the bottom bracket and in the head tube to prevent wear on the wood. The rest of the components can be attached just as they would be to a metal or carbon frame.

Bamboo

Bamboo bikes are the second strongest style of wooden bicycles. They cost less than hardwood bikes, but are still relatively expensive since they must be hand made. They are made with laminated bamboo shoots and composite or steel lugs. First the shoots must be kiln dried to a specific moisture content to allow a certain amount of flexibility and prevent decomposition. The shoots are cut down to the appropriate length, laminated with epoxy and polyurethane, and glued into the lugs at the joints. These connections are then sealed with epoxy and polyurethane to ensure a strong hold and prevent moisture from entering the joint. Then the frame is complete and components can be attached the same way as any other lugged bike frames. These bikes much simpler to build than hardwood frames and can be made much faster. That along with the fact that bamboo is less expensive than hardwood makes these bikes much more affordable.

Plywood

Plywood bikes are the cheapest but weakest style of wooden bicycle. They use laminated plywood and steel lugs to build the frame. The plywood can be easily cut into the shape of the frame, which allows them to be made very quickly. Most plywood bikes then laminate a few layers of plywood together to make a somewhat typical frame, which is then laminated with epoxy and polyurethane like other wooden bicycle designs. At this point lugs are attached at the bottom bracket and head tube. Unlike most lugs which hold together the joint, these lugs just add strength to the corners(the frame is a single piece with no joints) of the frame. More importantly they house the bearings for the fork and cranks. After the lugs are attached components can be attached to the frame or the lugs. Sandwich bikes use a slightly different approach by using two laminated pieces of plywood separated by metal spacers. This build is lighter but much weaker, built only for low impact riding on roads. At the bottom bracket and head tube, metal components are housed in between the sheets of plywood. These frames rely on more metal pieces than other wooden frames because of their unique 'sandwich' design. Since plywood bikes require the least craftsmanship and use more metal parts which can be made cheaply, they are much cheaper than other wooden bicycles. Sandwich bikes are the cheapest of all because unlike other plywood bikes, they require self-assembly.

External links

• example.com