What type of wood is best for bike construction?

For my next big project I intend to make a wooden electric bike and for the first article on this subject we are going to look at what type of wood would be best for the project.  To begin, we will look at examples of other wooden bikes and the techniques and materials that were used in their construction. We will then look at specific types of wood in more detail and explore how they might be used in other situations.

Let's first take a look the Rocsie electric bike, the specs of which are as listed below:

Weight of Bike: 6.2 Stone

Battery: 48v 20Ah

Average Speed: 18mph

Top Speed: 28mph

Motor Size: 1000w Hubmotor

Range: 24 miles

The beautiful design of the Rocsie bike takes its inspiration from cafe racer motorcycles. As well as the cafe racer, I also love the Scrambler motorcycles from the 50s and plan to base my designs on these beautiful bikes. The Rocsie is also electric, sporting a huge 2000w hub motor and a battery of 20Ah - a proper beast. Unfortunately it seems the website and social media pages for the bike have been inactive since around 2017 which probably indicates that the venture didn’t work out. However this shall not stop us admiring the beautiful design and incredible amount of work that went into this bike.  

The frame of the bike is made from Beech and shaped using bent wood lamination. Let us take a look at how bent wood lamination works:

When it comes to shaping wood into curves, you have two main options: Steam Bending and Bent Wood Lamination. Solid wood is incredibly strong however this structural strength depends on the integrity of the grain. If you were to cut a curve in a straight-grained piece of wood, you would create areas of extreme weakness in the piece as the curve will cut across the grain. This is why we have to use one of the techniques mentioned above. Both techniques are different, but achieve the same result - allowing the grain to flow with the curved piece rather than cut across. Steam bending involves heating and moisturising the wood with steam until it becomes flexible and can be bent to shape, while bent wood lamination involves gluing thin strips of wood together and clamping them to, or between, a shaped form. Let’s look at this technique in more detail.

The principle for bent wood lamination is simple - thinner strips of wood are easier to bend than thicker ones. When cut, each strip is glued together and clamped to (or sandwiched between) a curved form. When the glue dries, the laminated piece can be removed from the form and it will keep its shape. Laminated bent wood pieces generally hold their shape better than ones that have been steam bent. One of the drawbacks in using this technique however is that when cutting the strips from a solid piece of wood, you lose quite a lot of the material to the kerf of the saw blade. Many suggest a polyurethane, epoxy or resin glue work best for lamination, however standard PVA wood glue is also used by many woodworkers.

Let's take a quick look at steam bending:

Steam bending wood is a process that uses steam to produce moisture and heat which makes the wood become more flexible. The piece is usually left for some hours in a steam chamber and then clamped into a form. Once the wood has dried out, it can be removed from the form and will hold its shape. As the technique usually involves bending a solid piece of wood, the grain pattern will be continuous and there will be no glue lines as with bent wood lamination. This method also creates a lot less waste. Steam bending however is notoriously difficult to get right as you are very much dependent on the quality of the wood. Defects in the grain as well as knots etc can create problems when bending and cause the wood to tear apart or splinter. Steam bent wood is also more likely to lose its shape (a process called creep) than bent wood lamination. When using this technique it is best to find timber with a straight grain as well as cut pieces with no run-out (grain run-out refers to areas in a board where the grain ends along the edge). Air dried stock rather kiln dried is better to use with steam bending. If you are using kiln dried wood, it's a good idea to soak the timber in water for no less than 24hrs before putting it in the steam chamber.

Good video Explaining Steam Bending

Good video Explaining Bent Wood Lamination

Now let us take a closer look at the wood they used for Rocsie - European Beech

European Beech usually has a pale cream color with a tight, straight, grain. The wood becomes darker if exposed to higher drying temperatures or when exposed to steam.  Beech is one of the best woods for steam bending. It is easy to machine and work, however sharp blades must be used to ensure the cut surface does not burn. The Wood Database states “Beech is an important and widely-used hardwood in Europe. Its hardness, wear-resistance, strength, and excellent bending capabilities—coupled with its low price—make this hardwood a mainstay for many European woodworkers.” If Beech is plain sawn the surface tends to be very simple and plain, while quarter sawn pieces have a lovely silvery fleck pattern.  A Beech tree can grow to around 35m in height with diameters ranging from 40-90cm. Toys are often made from beech as it is such a strong and hard wearing wood. I don’t particularly like the appearance of Beech on it’s own, but paired with a warmer, more delicately figured wood will bring out it’s simple beauty. Its extensive use in the cheap furniture market may also have had some influence on my negative feeling towards the wood. It’s straight grain can also make it feel a little too uniform and dull.

Now for some sweet sweet eye candy let’s look at a few other Beech wood projects-

Volk Bikes

Volk bikes are based in South Africa and are a small company run by Daniel Hoffman who believes that bikes are an “instrument of freedom" (I definitely agree!). He aims to build wooden bikes which are environmentally friendly and use materials from sustainable sources. The Volk bike is built from a combination of ash (which I think is American White) and Beech which is CNC milled and reinforced with carbon fibre in some areas.

There are also some great behind the scenes pics on his Instagram page:

American White Ash is a hardwood. The sapwood has a white to pale yellow appearance while the heartwood can be light to dark brown. The wood is quite dense and has a straight rather coarse grain, is very strong, shock resistant and if treated with preservative it can be used outdoors. It’s also great for steam bending and is a very stable timber once dry.  

I also want to take a moment to profile the European Ash tree whose wood has been used for centuries in Europe. Its strength, durability and shock absorbent properties make it one of the most popular timbers amongst woodworkers to this day. Ash has been used to make wagon wheels, baseball bats as well as in the creation of The Dandy Horse - a contraption regarded as a precursor to the bicycle. In the book “The Man Who Made Things Out of Trees” Robert Penn explores all the possible things one could make from a single ash tree. I also recently found an article Penn wrote in which he interviews Liam Murray of Woodelo, a company based in Ireland who build bikes from.. You guessed it.. Ash! In talking about the choice of material Murrays says: “Ash timber is used in the manufacture of hurling sticks in Ireland. So we knew about it’s strength, and it’s easy enough to machine. It seemed an obvious choice, so we had a go [...] It’s lovely material to work with. It’s very tactile and we can machine it and strengthen it where we want. But really, we use it because it dampens the road like nothing else. It’s better than a carbon frame in my opinion” Let us take a quick look at some awesome European Ash woodworking projects before looking at Woodelo in more detail.

And how could we forget Bruce Springsteen’s custom Fender with its beautiful ash body and maple neck. The man has good taste. “It still is unique amongst all my guitars the way it sounds [...] For me, when I put it on, I don’t feel like I have a guitar on. It’s such an integral part of me.” - Bruce Springsteen.

Now let us take a look at Woodelo bikes:

Liam Murray who runs Woodelo bikes says that one of the great advantages of using wood is that it allows for such fine tuning of each individual frame, from adding extra material in places where it is needed to changing the direction of the grain, the weight and feel of the bike can be tweaked and refined to suit the individual completely. Woodelo use laminated wood to create the chain-stays which ensures strength while also keeping thickness and weight to a minimum. Murray says he chose to work with the wood as Ash is one of the more flexible hardwoods and is extremely good at absorbing vibration. The selection of the timber they use is one of the most important steps in building a successful bike and they make sure to choose timber with a straight grain, few knots and from a healthy tree. Woodelo also only use the sapwood of the tree to build the frames because “as a tree gets older the heart[wood] develops a browny red timber which has different characteristics and would affect the balance of our frames”. The wood they use is from trees of around 30-40 years old. Apparently in Ireland, such timber is called “Hurley Ash” as wood of this age is also used for making the playing sticks in the Gaelic sport of Hurling. Woodelo also only use quarter sawn planks to construct the frame as they try and maximize the amount of continuous grain that runs through the boards.  

Since we mentioned “Quarter Sawn” lumber, let's take a closer look at what this term actually means and the larger subject of timber production. Unfortunately this is quite a complicated subject and there seems to be as many names and techniques for cutting logs down to lumber as there are tree species, there are also different standards depending on which country you live in. As I’m from the UK I'll be focusing on the techniques we use in this country. But first watch this video from the Woodworkers Guild of America which does a good job in explaining the different techniques and outcomes.

The two main cuts produced by modern machine methods are “Quarter Sawn” and “Plain Sawn”.

Plain sawn boards are cut at a tangent to the growth rings of the tree and this cut produces boards with decorative, elliptical, catedral figures. Quarter sawing produces a board with straight grain where the growth rings are angled at almost 90 degrees to the surface. This cut produces boards which are more structurally strong and stable. Oak is a popular wood to quarter saw as it reveals attractive ribbon like patterns through the wood. In general however, Plain sawn lumber produces the most attractive figure. 

Plain Sawn timber Is the most widely available and cheapest sawn timber to buy. Plain sawing a log is quick and easy and requires the least specialised machinery as the log is just sliced into planks along its length, it is also the least wasteful method. Plain sawn timber however also has its drawbacks which include less structural strength and less stability than quarter sawn timber. Due to the tangential grain of plain sawn timber, when the wood begins to dry the tension of the tangential grain can make the planks cup, twist and bow quite significantly. Plain sawn planks also tend to absorb more water from the air which may cause unwanted movement.

Summary:

• Faster to produce
• More affordable
• Displays varied grain patterns & the unique "cathedral" appearance
• Readily available

Quarter Sawn

Quarter sawn timber is much more stable than Plain sawn timber, however more time and advanced equipment  is required to cut a quarter sawn board. A plank which is quarter sawn will have the grain running at almost 90 degrees from the surface making it much less susceptible to warping and cupping and a straight running grain. There is much more waste involved when using this method as not all of the log can be used.

Summary:

• More stable than plain sawn lumber
• Increased moisture resistance
• Less likely to cup, twist & warp
• Beautiful ribbon aka "fleck" patterns are prevalent in species like White Oak & Red Oak
• Less expensive than rift sawn lumber

Rift sawn lumber is the most expensive out of the three as it incurs the most waste and is the hardest to cut. When timber is rift sawn the grain of the wood will be angled at exactly 90 degrees from the surface. This method is best used when you need to maximise the strength of the wood and ensure it has straight grain going all the way through.

As a general rule:

Plain Sawn = Less Expensive, but less stable (prone to warping, expansion and contraction), with more attractive grain patterns

Quarter Sawn = More expensive, but more stable with straight grain.

Here is an example of how quarter sawn and plain sawn timber is affected by the grain orientation.

Now here are some wonderful pictures of the Woodelo bike:

Walnut Road Bike

This magnificent road bike was made by Jake who has very kindly posted an instructable about how he went about making it! It took him around 5 month to complete, but I think you will agree the outcome was definitely worth it. To create the frame he first laminated a total of 8 layers of black walnut of 6mm thickness. The frame is completely made from wood (no carbon fibre inserts), but uses metal for the mechanical components such as the dropouts and bottom bracket. He also used the front forks from his old bike as these will receive a lot of abuse, something I plan to do in my own design. To begin the build he began designing the frame in solidworks, using his old bike as a guide to get the correct dimensions. He stresses that the seat post, steerer and bottom bracket are all important sizes to get right. Once designed he began to cut the strips of wood that would make up the laminated frame of the bike. By layering the wood with the grain facing in different directions, you can create a frame that is incredibly strong and resistant to shock. From what I can understand, he layered the walnut strips at alternate 45 degree angles on top of each other, creating two halves of the frame that would later be glued together. Once he finished laminating both pieces, he hollowed out some areas and then glued them both together to create the finished frame. For the chain stays and seat stays he used the bent wood lamination technique we talked about earlier .

Behind the Scenes.. 

Black walnut is native to eastern North America and is one of the most popular hardwoods amongst american woodworkers. The European walnut is also extremely popular amongst carpenters across the pond, but the wood from this tree tends to be quite a bit lighter. The Black Walnut’s botanical name is the Junglans Nigra and is one of two main species from the Junglans genus, with the other being the European Walnut (called the Juglans Reiga). Interestingly, the origin of the Juglans name comes from the roman god Juipter who was said to have dined on walnuts when he lived on Earth - pretty cool eh? Black walnut is prized for its height and width as well as the impressive strength and durability of the wood. In distinguishing the tree from its European brother, we can look at the bark which is far darker and more heavily ridged. The black walnut also has a greater number of leaves which are far thinner and smaller. In 1629 the tree was introduced to Europe and has thrived in the south of England ever since. The light sapwood of the Black walnut contrasts beautifully with the richly hued heartwood which often features even darker streaks.  

Komar Project - Wooden Low Rider Bike

This guy is very cool. When he began this incredible laminated bent wood bike build, he didn’t know much about bikes, their construction, mechanics or bent wood lamination! But look at what he managed to achieve - a wonderful, organic, flowing bike frame which is completely made from wood. Not only is this feat pretty amazing, he also created a fantastic video documenting the whole process! This is what I love about the online maker community - a place where an almost endless supply of inspiration and knowledge can be found. So, now onto the bike build - The frame is made from laminated strips of walnut and maple which he formed using a series of jigs and many, many clamps. As well as creating the frame from scratch, Komar also made his own custom drop outs and head tubes from sheet metal and tubing. Welding is definitely something I must learn more about. He also built the head forks for the bike combining both steam bending and lamination techniques, though for my bike I think I’ll use metal forks as wooden ones might be a little too fragile (especially as mine is going to be a high powered electric bike).

BTS..

I assume the wood Komar used was Hard Maple as opposed to Soft Maple. Hard Maple is around 25% harder than soft maple and also has a higher density and is the type most used to make furniture and instruments. A good way to tell the two types apart is the color, though both are a light cream, Hard Maple tends to be much lighter and uniform in color, while Soft Maple is much darker and varied, with tones of red, brown and grey. Hard maple also grows at a much slower pace than soft maple, so the growth rings will be much closer together. Both Hard and Soft maple are the most common hardwoods found in North America. Hard Maple is quite easy to work with, though due to its high density it can be a little tough on tools, it may also burn if high-speed cutters are used. The wood is commonly used for flooring, as well as furniture, baseball bats and instruments. In tree form, Hard Maple is often referred to as the “Sugar Maple” which is the tree most often harvested for Maple Syrup. Hard Maple wood is often sort out for its “Birdseye” grain pattern which is actually a product of difficult growing conditions - the tree attempts to grow more buds to maximize its light intake, but with poor growing conditions, the tree does not have enough strength and the buds die, leaving the birdseye knot pattern in the wood.

Now let's take a look at a few more Maple wood projects:

Now that we’ve looked at some examples of the wood used to build specific bikes, I’ll just list a few more popular hardwoods that could also be used for the construction of my bike.

Oak is the most widely used wood for furniture, it’s strength, resistance to rot, workability and economical price has ensured its popular use amongst woodworkers. There are two main types of Oak: Red and White Oak, with the latter being most popular for fine woodwork as it is thought to have a more attractive figure. A good way to tell the two apart is to look at the endgrain, Red oak has larger, visibly open pores, while the pores of the white oak will be sealed. Due to this fact, white oak is also more moisture resistant and is the variety of choice for boat building. When taking a sample from the white oak, be sure to take it from the heartwood as the sapwood pores are generally not sealed. Another way to tell is by looking at the rays on the surface of a board (rays carry nutrients perpendicular to the growth rings). White oak has much longer rays than Red. If quarter sawn, White oak will reveal lovely ribbon patterns throughout the surface. The wood of the White oak is extremely strong and heavy with a light to medium brown heartwood and olive tinge while the sapwood can be whitish to light brown. It is a ring porous wood (meaning that it has larger pores in the earlywood and smaller pores in the latewood) which gives the wood quite a coarse texture and prominent grain.  

White Oak                          Red Oak 

Now let's take a look at Hickory

One of the reasons I’ve chosen to look at this wood next is that I heard Nick Offerman (*the most famous celebrity woodworker***besides Harrison Ford***) mention it quite a bit in his interviews/books. Other than this, I don’t know much about Hickory, so let's take a look:

Hickory is known as the hardest of hardwoods, so hard in fact that after the Battle of New Orleans in 1815, General Andrew Jackson was nicknamed “Old Hickory” by his soldiers as he had fought so tenaciously. Historically, Hickory was used by the Native Indians for bows and baskets and was also used to build the wheel spokes of the first automobiles! North America is home to some 16 species of Hickory, but the one most commercially available is the Shagbark Hickory. The sapwood is white to cream colored while the heartwood is a tannish red brown. There is a stark contrast between the sapwood and heartwood which visually sets it apart from other hardwoods, this characteristic is popular with furniture makers and pieces are often designed to showcase this particular trait. Hickory is regarded as stronger, denser and harder than both White Oak and Hard Maple and is often used in situations where strength and shock-resistance are needed. The wood takes stain and oil very well as it is so dry, but this also means it can split quite easily. The hardness of Hickory makes it a tough wood to work and can blunt machine tools very quickly - carbide tips are a must. It’s grain is coarse and straight. Hickory has a slow growth rate and can take up to 200 years to mature.

Cherry (Cherry Sweet Caroline)

The Cherry we are talking about here is the North American kind, also called Black Cherry. In Europe we have Sweet Cherry, but the wood from this tree is only usually sold in smaller sizes or veneer. The fruit of the black cherry is small and bitter and is used to flavour jelly and drinks, though commercially its grown mostly for its lumber. Cherry is one of the most popular hardwoods and is known for its good all-around workability. The grain is straight with a fine, uniform texture and machines well, but it does have a tendency  to burn so best to use carbide tipped blades. The heartwood is a light, pinkish brown when first cut, but with aging and exposure to sunlight this changes to a dark orange-red (not too dissimilar to Mahogany). The sapwood is a light cream color which never changes to match the dark heartwood. Though Black Cherry is lighter and less hard than Maple, it still matches in strength and stability. Cherry takes glue well, though one must take care to minimize squeeze-out as it can marr a clear finish.

There are many other beautiful hardwoods (and softwoods) to explore, but they shall have to wait for another time. The next topic I’m going to tackle will be “The Anatomy of Wood”

Thanks for reading!