Starting in October 2014 and completed the following spring, this 100+ hour project was conceived as a scholarship project in my high school drafting class. Combining my passion for design and biking, this is definitely one of my favourite projects to date.
The early stages involved lots of research, as I had next to no knowledge about suspension design, geometry, or bike standards. After a research phase spent uncovering the merits and drawbacks of various suspension designs, I decided to base my design around the Split Pivot or ABP design. This involves placing the seat-stay to chain-stay pivot concentric with the rear axle. Shortly after, I finalized the geometry for the bike based on trends observed across multiple race-proven downhill bikes. With this in mind, my first prototype consisted of a high main pivot placement and near-horizontal shock placement. Upon further iteration this design was abandoned due to its large chain growth and digressive leverage ratio.
Learning from the mistakes of the first prototype, I sought to keep the chain growth low and give the bike a linear leverage ratio with a progressive end stroke. To do this, the main pivot was moved closer to the bottom bracket and the shock adopted a more vertical placement. The bike now had a rearward axle path at the start of the travel, and a nice linearity to the leverage ratio curve. With the suspension design out of the way, I started working on the aesthetics and structure of the frame.
This part of the project was definitely the most challenging part of the project from a 3D modeling perspective. The entire project was done using Solid Edge modeling program. The frame consists almost entirely of swept features, as surface modeling was beyond my skill level at the time. I also modeled all of the bike’s components at this stage in the development, which was relatively easy but took a long time. In the end there were over 50 unique parts that were included in the final assembly.
