Top 5 Specifications and Top 5 Constraints: Custom Bicycle Frame

My final project for this course will consist of documenting the design process and aesthetic decisions that have gone into making my own custom bicycle frame. I have been working on this project as a part of an independent study course at CU. With this in mind, I have several design specifications and constraints.

My first specification for this frame is that it will be a street trials frame that is made for larger riders. Historically, street trials frames do not have different sizes and they do not cater to larger riders. Furthermore, the frame itself will be made from steel because it is a material that is commonly used for bicycle frames that I am comfortable welding. Next, the frame will accommodate 24″ wheels. This is an important specification to have because it will drive the bike’s geometry and it is important to consider for rear wheel clearance. Next, the frame will need to accommodate standard bicycle components. Because of this, I outsourced a bottom bracket, head tube, rear dropouts, and rear brake mount since these are critical components that accept standard components. Finally, for the sake of this class, the frame will be aesthetically pleasing. I plan on following an industrial aesthetic by clear coating the frame to keep the color of the steel and the welds exposed to give the frame a hand-made appearance keeping with the theme of the project.

Street Trials Bicycle (1)

As for my constraints, there are several considerations that will make this project difficult. One constraint from a welding standpoint is the fact that the steel tubing used is thin-walled. The wall thickness of the tubing varies between .049 and .035 inches which can make the material difficult to weld. This means that it will be necessary to use a TIG welder to control the applied heat and prevent holes from being blown in the frame. I also have a time constraint for this project. In the midst of Senior Design and other course work I want to have the welding of the frame done by the middle of April to not interfere with my Senior Design responsibilities. I am also constrained by the resources I have. I am lucky that I get to work with James Bleakley at Black Sheep Bicycles to have the frame jigs, bending tools, and mitering tools that I need to make the frame but that is what I am limited to. I also believe the the appearance of my frame is constrained by my welding skills. By choosing to clear-coat my frame to show the raw appearance of the steel I am also subjecting myself to my own amateur welding abilities. I am not a professional welder so it is possible so it is possible that my frame will not look as good as it could if I were a better welder. I hope that the heat-treated area of the welds will add some discoloration to the frame and I trust in my abilities to weld a strange frame but not necessarily a pretty one. Furthermore, I am constrained by my budget so I will be saving some money by using linseed oil to clear coat the frame instead of paint. I have never tried this before but it will work well to accommodate my budget.

Sources:

1. https://www.webcyclery.com/product/inspired-hex-team-26-bike-14112.htm