TIG welding (Tungsten Inert Gas), also known as Gas Tungsten Arc Welding (GTAW), was first developed by the aerospace industry in the 1940s. We chose this technique for the high quality, clean welds it produces. And the exceptional precision it allows in hard-to-reach places.
TIG Welding requires a high level of skill and coordination between hand, foot and eye. Even the most experienced welders need time and intense focus. We use this process when building our ultralight T Line bikes.
How does it work?
It's all in the name - Tungsten Inert Gas.
Our welders use a tungsten electrode (it looks a bit like a pen) to create an electric arc that produces intense heat. They manually guide the electrode along the join between the titanium pieces.
As the pieces start to melt, the welders introduce a commercially pure titanium wire rod to the mix. A molten pool of titanium is created. Once cooled, it forms a strong bond.
The skill of the welder here is to perfectly balance the pool of molten filler with the heat of the torch and the pace or motion of their hand.
What about inert gas?
When you heat titanium to high temperatures, it chemically reacts with the oxygen and nitrogen in the air, compromising the strength of the weld. To get around this problem, we create an inert gas environment around the weld pool. Inert gases (Argon in this case) don't react under high heat – so you get a strong, clean weld as intended.
It's not just oxygen and nitrogen that compromise the strength of a weld, even the tiniest bit of dirt contamination causes problems. Before building the frames, we meticulously clean every titanium tube with acetone to make sure it's free of dust particles and fingerprints.
Every joint of the frame is welded at a precise angle - there's no room for error as this dictates the final geometry of the bike. To achieve the designed angles, our tooling engineering and manufacturing teams work together to develop and build bespoke jigs for each section of the frame. These jigs hold the parts of the bike at the perfect angle while allowing the welder to move around and get up close.
The beauty of the weld
TIG welded titanium joints have a silvery bead; at times it almost appears to have a mirror finish. Every TIG welder has a signature style making each weld unique.
All Brompton titanium framesets start their life as a set of tubes in our specialist TIG welding factory in Sheffield, 300km north of our London Factory. We built this dedicated space as titanium requires different skills, machinery, and process than steel. The city of Sheffield has a rich history and legacy of expertise in metalworking.
Brompton T Line
The entirely re-engineered T Line titanium frame weighs 37% less than our original all-steel equivalent and is just as strong. At 7.45kg in total, the T Line is comparable to a carbon road bike. Yet, it can be comfortably ridden by a 110kg rugby player. And withstand the punishing impact of the city.