Conceptual Design

The conceptual design of Eta was based on a set of incremental improvements over Bluenose, the team's previous vehicle used as Eta's benchmark. It was important to refrain from making several radical changes during such a short project timeline. The aerodynamically optimized configuration featured a compact shape designed to reduce drag by eliminating flow separation and preserving stable laminar flow for as long as possible. This resulted in a shell that splits into front and rear "halves" that encase a frame, which can function as a stand-alone bicycle. 

 

Wheelwell

Detailed design and Fabrication

Wheel enclosures were necessary for aerodynamics and rider safety. A challenge the team faced in the past was making wheelwells separable and easy-aligning (to allow for wheel service) while preventing rubbing with the tire. I designed a pin-alignment and latch-tightening mechanism that provided the necessary rigidty and alignment. I modeled the low-clearance profile on Solidworks, from which a male mould was made using a CNC machine. We then laid up the two sets of enclosures using carbon fibre, employing creative modifications to conventional construction methods because of the unique geometry. During this process I learned that foresight is the biggest asset when planning steps in fabrication.

 

 

Power Transmission

Improving power transmission efficiency was the dominating derivative of increasing top speed - it was calculated that each percentage increase in power transmission efficiency from the 92% benchmark would result in a 0.49 km/h increase in top speed. From research I identified the greatest source of loss to be from component wear, followed by chain tensioners due to low radii of curvature. I estimate I improved efficiency by 2% through careful maintenance and design and implementation of a high radii efficient drivechain.

 

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Hub Fabrication

In addition to developing my skill in high precision machining, I learned the prerequisites for effective communication between engineer and machinist when I was tasked with machining the complex hub assembly designed by my colleague. I used a lathe and a mill to convert his drawings into a set of custom wheel hubs that performed exactly as designed. I developed my machining skills including interpreting engineering drawings, planning machining operations, and accurately machining low tolerance areas such as press fits. More importantly as a mechanical engineer in training, I engaged in the fabrication aspect of the process that many mechanical engineers are detached from when they design parts. For instance, I honed my ability to deliberately and efficiently specify tolerances and I learned the importance of "measure twice, cut once" (the hard way). This will allow me to employ a fabrication-conscious approach to my future work.

 

 

World Human Powered Speed Challenge

The target for the entire project was to break the standing human-powered speed record of 133km/h at the World Human Powered Speed Challenge in Battle Mountain, NV. In 2014 we only achieved a speed of 127km/h, but the following year the team returned and smashed the record with an official speed of 139.45km/h, a record that still stands today

 

Video: https://www.youtube.com/watch?v=Y8bbPmn8q6s