The simplicity of a hand-built bicycle frame is a quality that conceals all the craft behind each one. For a custom bicycle builder, the dream is to build bikes by hand.
The process of building a custom bicycle
There are only a few steel brands used to build bicycles: Columbus, Dedacciai, Reynolds and Tange. Most frames are built with Columbus and Dedacciai tubing. These two brands offer different models and tube series, which differ in shape and cross-section. The alloys are usually chrome-molybdenum, niobium and other formulas that each brand considers essential. All of them undergo hardening processes so that the walls can be made thinner, with the benefit of reduced weight.
Choosing the tubes
There are different wall thicknesses and butting profiles depending on the family within each brand. Typically, the wall is thinner in the central section of the tube, saving weight in an area that experiences far less stress. At the ends the walls are thicker, since these are the points where the tubes meet and where they must bear the most load. Each tube series has its own butting profile, but they normally range between 0.7 mm at the ends and 0.45 mm in the central sections. Butting can be double or triple depending on the tube type or its function on the bicycle.
Design and construction
The process of building a custom bicycle begins after designing the geometry and making the right choice of tubes.
The mitres where the tubes meet are cut by hand with a file; they must fit perfectly against one another. There must not be the slightest tension.
Once all the tubes are prepared and set into the jig, it’s time to start cleaning. This process is meticulous: the slightest trace of impurities, grease or other substances can contaminate the brazing and create a consequent risk of cracking.
Sandpaper, scouring pad and acetone — the tube must be left completely clean over a fairly wide area, both inside and out.
Fillet brazing
The next step is to tack the tubes together.
This moment is critical: the steps must be followed exactly as the process dictates, because the final result on the alignment table depends on it.
Everything being aligned is key for the frame to work correctly.
Usually, due to the heat applied during brazing, the tubes suffer a slight deviation. That’s what the calibration table is for: at this point, with the help of precision measuring instruments, we align the frame in plane.
Once everything is perfect, the next step arrives: laying the brass fillets to join the tubes permanently.
Once aligned, we determine the brazing process: both the direction the fillet will run (clockwise or anticlockwise) and the exact point where it should start. This is done for every joint.
Thanks to this procedure, once brazed the frame will be fully aligned. In the process of building a custom bicycle there should be no stress, which is why it’s considered a methodical, hand-built process where craftsmanship comes first.
Final frame details
Once we’ve finished brazing, we check again that everything is perfectly aligned and consider this step complete.
Next, we braze the cable mounts and the seat clamp slot, then carry out the reaming in the head tube, seat tube and bottom bracket shell.
Now it’s time to clean up the fillets: jeweller’s work, where there must be a perfect union between the tubes and the braze. Once painted, you shouldn’t be able to tell they are two tubes joined together.
Several weeks of sanding and precision file work.
The personality of the bicycle
Everything is finished, but the process of building a custom bicycle doesn’t end here. After carrying out the relevant checks, it’s time for the final touch. The frame is sent to the paint shop, where a bicycle frame paint specialist will give it the desired finish.
Once it’s back from the paint shop, it’s time to build up the bicycle. A point where all the work we’ve done over these weeks will come together.
The bicycle can then be built up by its owner, ready to be enjoyed.
With every bicycle I hand over to my clients, seeing the satisfaction on their faces and the excitement with which they ride it is motivation enough to get to work on the next project.
