For my final project I am going to build my own custom bicycle frame. While a modern custom frame can range from $2k-10K depending on the material, much of the cost is more for the labor and craftsmanship rather than materials. Custom paints and geometry only add to the cost. By doing all this work individually, I have control of my own aesthetic and function and hope to gain some experience in the process.
My inspiration came when I recently watched a video of early 90’s cycling and was captivated by the colors and flash that riders had back then. All the bikes that they rode were made from steel and had these wonderful paint schemes. Unlike today where there’s a huge variance in bikes just by their shape, steel was unique mostly for their paint and lugs. There’s wonderful craftsmanship to the bikes these guys rode. The riders were shinier, the jerseys were louder, the bikes were flashier, and there was something special in the water.
A lot of modern bicycles are made with high performance space-age materials designed for the sole purpose of speed. Modern machines have become at times too stiff and are known to “beat-up” the rider. For the 2% body fat professional, that’s exactly what they want, but that demographic is a small piece of the cycling pie. For most cyclists, the bike is more about the experience than the speed or quantifiable numbers. To me, that experience comes in two very specific aspects: the ride quality which is how the bike feels in the feedback as you ride and the aesthetic, which is how the bike looks. These last two are my priorities in building my bike.
Bike feel and feedback is largely determined by material choice. For this project I have decided on steel tubes with steel lugs for the forgiving ride qualities that give a real supple feel. Steel has the logistical benefit of being a cheap material and robust to manufacturing mistakes, which is suitable for my first experience. Likewise, manufacturing is straight forward when using lugs and tubes as it has more forgiving tolerances than a from scratch assembly. Make no mistake, using lugs has limited effect on the frame geometry I hope to achieve.
Geometry has an enormous effect on the feel of a bike. Think about the difference between your typical “road” bike and “mountain” bike. Besides the surface differences of tire choice or suspension the difference is largely in the geometry of the frame. Where the road bike is stiff and twitchy, the mountain bike is giving and stable. Among other causes, this difference is brought on by the tube angles of the seat tube and head tube. The different characteristics are described extensively here (http://cyclingtips.com/2011/02/the-geometry-of-bike-handling/), but suffice it to stay that with head tube and seat tube angles, the steeper the angle gives a twitchier more responsive feel, and the more slack angles gives a more stable feel. My design model is more aggressive which is typical for a road bike and suitable to personal preference 72.9 HT and 73.3 ST and matched with the corresponding lugs. Tube lengths were then selected for my personal preference. This was the reason I was drawn to a custom bike. Physiologically I have unique body where my torso is long for my height and prefer a longer rather than taller bike. The result is a 60 cm center-to-center top tube combined with a 58 cm c-c seat tube which is something not commercially available.
Manufacturing dissolves into two parts: prep and welding. Prep will be done with first cutting the tubes per drawing specifications and dryly ensuring they fit into the lugs all together. Filing the adhesion surfaces of the tubes and lugs to remove impurities. I will then apply brass brazing paste to the tube ends. The tube will be placed in the lug and both will be jigged with clamps. Then in a warm environment, I will apply heat with a propane blow torch until the external paste melts and begins to evaporate. Careful to distribute the heat, the flame will warm both the lug and the tube. Once the lug and tube are at sufficient temperature (there’s sufficient glow) I will apply the brass stick. There capillary action will pull the melted brass into the gap between lug and tube. This is applied around the tube until the lug face at the tube is completely filled. More heat is added to remove more braze paste and then allowed to cool. this process will be applied to each connection starting with the front triangle (top tube, down tube, seat tube, head tube) then connecting the seat and chain stays.
The frame will then be painted in the spirit of the glamour days of steel with a retro early 90’s vibrant loud color scheme. My hope is the frame will meet my functional requirements and allow me to apply my own personal aesthetic in additions and paint scheme.