Transmission May 2014
Engineering

Overview

As part of ME 14: Design and Fabrication, students were tasked with creating a single-ratio transmission for a custom bicycle setup.

Transmission assembly CAD

Goal

The goal of this project was to design and fabricate a transmission that would result in the highest rotational speed of the bicycle and require the shortest time for the wheel to reach 250 RPM.

Process

To determine the necessary gear ratio, we did calculations in MATLAB. From there, we evaluated the commercially available options for our gears, taking into consideration the cost of gears and the time it took for parts to ship. We then created a Bill of Materials (BOM) that showed the cost of our parts would be within our budget of $75. After an initial design and a Preliminary Design Review (PDR) with our professor and teaching assistants, we finalized our design.

Transmission CAD

The primary difference between our first and final design was that we decided to extend the length of the channels (there to help align the vertical walls) on the transmission base plate. This design decision was made to make machining easier, as milling a channel across the entire plate would not compromise overall structure.

Transmission base before PDR

Transmission base after PDR

Final Design

Final transmission design

Results

Our transmission operated successfully, reaching a maximum speed of 357.47 RPM and a time of 17.79 seconds to reach 250 RPM. From the 12 transmissions created by our class, the maximum speeds reached ranged from 264.08 RPM to 357.47 RPM. The time to 250 RPM ranged from 16.89 seconds to 44.19 seconds.