Bicycle frames are often made from metal tubes, generally joined by either brazing or welding. These are the most suitable methods and which one is chosen will depend on a number of factors, including the base metal being used.
At Brompton we braze all our steel frame parts as we feel this is the best process for our product and it allows us to make a light but durable frame; in contrast, the titanium parts are welded as this is the most suitable process for the material.
Welding involves melting two parts to fuse them together. It is common for the component parts to be the same material and a welding rod of similar composition used as a filler to help fuse the parts together under concentrated heat.
Brazing uses a filler metal (brass in our case), which is not the same as the base material and has a lower melting point. The component parts are not melted as with welding. This subjects the frame parts to less heat and reduces distortion, creating less stress and no altering of the physical properties of the materials. Brazing also uses less energy as the amount of heat needed is lower than welding. All this allows us to use thinner steel tubing and components, which would not be possible if we welded the steel parts because the thin material would be prone to extreme distortion or even burning.
This means that each Brompton can be made as light and durable as possible; without needing to add material to the ends of the tubes we end up with lower weight steel frame parts, meaning strong, light bikes.
Want to know why we use steel to make our bikes? We've got the answer for you!