PUSHING THE BOUNDARIES OF FRAME PRODUCTION

After a seven year sabbatical from the bike industry, Peter took up a 2-year role as GM of the bike division of an additive manufacturing company. His research during this time led him to engage with a number of the world’s most innovative 3D printers, composite designers & manufacturers, as well as several universities.

Encouraged by riders, Peter has relaunched TESCHNER Bikes with a unique range of carbon tubes and additive manufactured lugs. In recent times, 3D printed lugs have become popular in the handcrafted frame market. As a designer, Peter has looked at the materials currently used in the bike frame market – and other materials with potential for use in bike frames.

WHICH FRAME MATERIAL SHOULD YOU CHOOSE?

Steel is an alloy made up of iron with typically a few tenths of a percent of carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Because of its high tensile strength and low cost, steel is used in buildings, infrastructure, tools, ships, trains, cars, machines, electrical appliances sports goods etc Iron is the base metal of steel.

Once upon a time, all bicycles were made from steel, from shopping bikes to Tour de France race bikes. Rapid technological developments over the past few decades have seen lighter materials like aluminium, titanium and carbon fibre push steel out of the spotlight.

Although racing cyclists no longer favour steel, it continues to be the desired frame material for anyone wanting a bike for comfort, distance and durability.

Like other materials, steel has been refined over the years to become lighter and stronger and has remained the material of choice for mass produced, lower priced frames. However, there are numerous bespoke builders that handcraft steel frames of exceptional quality with a price to match.

Some of the reasons to choose steel for bicycle frames are:

  • Availability and price
  • Easy to work with
  • Fabled ride quality
  • Create a fully bespoke custom frame, from geometry to paint finish, right down to every little last detail
  • Durable and very strong
  • Doesn’t become outdated

The discovery of aluminium was announced in 1825 by Danish physicist Hans Christian Ørsted. The first industrial production of aluminium was initiated by French chemist Henri Étienne Sainte-Claire Deville in 1856.

Aluminium is almost always alloyed, which markedly improves its mechanical properties, especially when tempered. For example, the common aluminium foils and beverage cans are alloys of 92% to 99% aluminium. The main alloying agents are copper, zinc, magnesium, manganese, and silicon.

The two principal aluminium alloys used in the bicycle industry are 6061T6 and 7005T6. Both are weldable but this process weakens the weld zone area and must be artificially heat treated to return to the pre-weld state.

Some of the reasons to choose aluminium for bicycle frames are:

  • Price
  • Durability. Aluminium can withstand a hard impact without cracking or failing because it is less brittle
  • Sustainability. Aluminium is highly recyclable (although power consumption in manufacture is significant)
  • You can mount luggage and use your frame for touring
  • Safety. Aluminium is less likely than some materials to fail unexpectedly

First discovered in the 1790s, titanium is named after Titan, the pre-Olympian god. That’s why titanium is sometimes called the metal of the gods.

Titanium is alloyed with aluminium, zirconium, nickel, vanadium and other elements. Titanium alloys have high tensile strength to density ratio, fatigue resistance and high crack resistance.

Titanium is used to manufacture a variety of critical structural components in aircraft. These include fire walls, landing gear, exhaust ducts and hydraulic systems. About two thirds of all titanium metal produced is used in aircraft engines. Frames with Tttanium 6Al-4V alloy accounts for almost 50% of all alloys used in aircraft applications. In fact, around 116 tonnes are used to manufacture the Boeing 787.

Titanium bicycle frames first came to market in the 1960s by Speedwell (England) welded by Lamborghini. Litespeed (USA) brought titanium frames to a broader market in the 1980s. Frames were almost exclusively made with Ti3AL 2.5V and sourced from the aircraft industry.

The 1980s also saw a frame made in Melbourne with CP Titanium with Peter Teschner handcrafting his first TESCHNER Ti 3Al 2.5V frame in 1991.

Why a titanium frame? The most common reasons for choosing titanium are:

  • They’re a sweet ride
  • They’re light and strong
  • They’re long lasting
  • They’re exclusive

Carbon fibre is a polymer sometimes known as graphite fibre. It is a very strong material that is also very lightweight. Carbon fibre dates back to 1879 when Thomas Edison baked cotton threads or bamboo slivers at high temperatures, which carbonised them into an all-carbon fibre filament.

By 1958, high-performance carbon fibres were invented just outside of Cleveland, OH. Although they were inefficient, these fibres contained around 20% carbon and had low strength and stiffness properties.

In 1963 a new manufacturing process was developed at a British research centre, which is where carbon fibre’s strength potential was realized.

Carbon fibre is made from a process that is part chemical and part mechanical. It starts by drawing long strands of fibres and then heating them to a very high temperature without allowing contact to oxygen to prevent the fibres from burning. This is when the carbonisation takes place, which is when the atoms inside of the fibres vibrate violently, expelling most of the non-carbon atoms. This leaves a fibre composed of long, tightly inter-locked chains of carbon atoms with only a few non-carbon atoms remaining.

A typical sequence used to form carbon fibres from polyacrylonitrile involves spinning, stabilising, carbonising, treating the surface and sizing.

Carbon fibre is five-times stronger than steel and twice as stiff. Though carbon fibre is stronger and stiffer than steel, it is lighter than steel. This makes it the ideal manufacturing material for many parts.
Carbon fibre can be thinner than a strand of human hair and gets its strength when twisted together like yarn. It can be woven together to form cloth. If needed to take a permanent shape, carbon fibre can be laid over a mold and coated in resin or plastic.

Why a carbon frame? The most frequently mentioned benefits are:

  • Lighter weight because the material is stronger and less dense
  • Stiff and responsive, which improves handling
  • More comfortable/better ride quality
  • Carbon frames can last longer because they don’t fatigue
  • Carbon fibre frames can be repaired if they crack
  • More efficient because they are lighter, more aerodynamic and more rigid
  • No corrosion
  • Higher-end and more technologically advanced

Magnesium was first produced by Sir Humphry Davy in England in 1808. He used electrolysis on a mixture of magnesia and mercuric oxide.

Magnesium is the lightest of all metals, being about two-thirds lighter than aluminium. Magnesium is non-toxic, non-magnetic, has high-impact strength and is resistant to denting. Magnesium is too reactive to occur in nature as an element, but its compounds are common. Magnesium is used in super-strong, lightweight materials and alloys. When infused with silicon carbide nanoparticles, it has extremely high specific strength.

In the 1980s, Kirk Precision in the United Kingdom produced magnesium frames, and a few were even used in the Tour de France.

About 20 years later, Pinarello’s experimentation with the metal led to the Dogma, the bike Oscar Pereiro rode to win the 2006 TdF. The benefits of a magnesium alloy frame are:

  • Lightest of all structural materials
  • 33% lighter than aluminium
  • 75% lighter than steel
  • High strength to weight ratio
  • Excellent dimensional stability and repeatability
  • Highest known dampening capacity of any structural metal, including steel and titanium
  • High Impact resistance
  • Large alloy selection
  • Abundant material supply
  • 100% recyclable

This chart shows the mechanical properties of materials used in the bike industry.

MECHANICAL PROPERTIES OF BIKE FRAME MATERIALS
CHARACTERISTICS / MATERIAL CroMo AL 6061 AI 7005 Mag AZ91D Ti3Al2.5V Ti6Al6v Carbon
Young’s Modulus/N/m2x10 205 69 72 45 >90 115 50 – 150
Yield Strength/N/m2 435 260 – 290 <480 160 51.7 880 – 1100 Varies
Tensile Strength/N/m2 670 300 – 320 <540 240-250 621 950 – 1170 250 – 400
Elongation/% 25.5 17 11 3-7 >15 10 2.5
Density/kg/m2 7.8 2.7 2.81 1.81 4.47 4.43 1.8
Weldability & Machinability Excellent Excellent Excellent Excellent Good Fair N/A
3D Print Ability Excellent N/A* N/A* N/A* N/A* Excellent Good**
* No Commercial Power Available ** Research Uni South Australia

TESCHNER Bikes has the exclusive use of XANTULAYR® for our Australian Handcrafted Frames.

Benefits of Xantulayr include:

  • Zero Weight
  • Enhanced Resin Toughness
  • Improved Facture Toughness
  • Improved Composite Fatigue Life
  • Improved Flexural Strength
  • Reduced Ply Delamination

WHAT MATERIAL IS BEST FOR YOUR FRAME?

If beauty is in the eye of the beholder, then the best frame material is in the mind of the rider.

Whilst carbon and titanium seem to reign supreme on their own, there’s an emerging trend in custom build frames that marries 3D printed titanium lugs and carbon tubes.

The properties of titanium 6/4 are known, repeatable and measurable. Peter has explored if a synergy exists where the combined properties of titanium and carbon working together are better than by themselves.

Beyond that, he has researched and tested numerous material inputs, shapes and production methods. These include filament winding, pre-preg, autoclave, out of autoclave, and resin transfer molding.

Is there a definitive perfect combination?

“I am not sure I can answer that as maybe it is not definable. Would 3D printed high strength aluminium, or steel or magnesium lugs or even 3D printed carbon lugs mated to the same carbon tube in each option offer a similar outcome?”

Whilst Peter’s research continues, he believes that the best frame materials will be determined by price and intended use. This is why every TESCHNER frame starts with a conversation between Peter and you, the rider.