Project Overview

Problem:

As part of a term-long project at Dartmouth, three teammates and I were tasked with using a $500 budget and parts from two scrap bikes to build a diwheel. The diwheel had to be able to complete four laps around a curvy racecourse as quickly as possible, while switching drivers each lap.

Solution:

While we based the overall design of our diwheel on the previous year’s state of the art model, my team and I optimized multiple key features to create a superior vehicle. Our novel features included an open cockpit for quick entry and exit, enhanced steering, braking, and differential gear systems, an optimally located drive wheel, a stable yet flexible drive chain construct, and an adjustable seat length to accommodate many sizes of riders. During the annual diwheel race at the conclusion of the term, our vehicle outperformed xx others to win the race and earn us the 1st place award for best fabrication and design.

Product Details

High-Level Structure

The large hoops joined by the differential steering system were tested in previous years of this class, and validated as a feasible structure for the vehicle. Beyond those basic components, we constructed the additional mechanisms and features of the diwheel.

Braking System

A brake system was salvaged from our scrap bikes to facilitate steering, in conjunction with the differential. Braking one side prevented the hoop from rotating, allowing the vehicle to turn in that direction.

Spur Gear Differential

The differential allows independent turning of each hoop, so the braking mechanism from the salvaged bike can turn the diwheel by braking one side and not the other.

Wire Brush

We originally added a wire brush in front of the drive wheel to clean the hoop of debris and subsequently ensure a good contact. Upon testing, we realized it added too much friction so we removed it from the final product.

Cockpit & Seat

The open design of the cockpit allows the driver to enter and exit quickly, saving time during the four required driver switches of the relay race.

We constructed the seat of the vehicle out of carbonfiber. This material reduces weight, and positions the driver so his or her center of gravity easily balances the diwheel.

Drive Chain

One of the subassemblies that I was responsible for was the drive chain. I needed to ensure that our chain stayed on during the race, and ensure that the gearing was ideal. I designed and machined a chain tensioner to keep the chain taught, and I also designed and fabricated a chain positioner that would allow us to adjust the gearing of the diwheel.

Chain Tensioner

As part of the drive chain construct, this tensioner keeps the chain tightly around the bike gears to ensure that it doesn’t derail. Instead of welding it in place, I designed it to move along the bar so that it could align with the different gears on the bike gear hub.

Chain Positioner

The chain positioner keeps the chain in place and on the correct gear. It was designed to move along the bar so that it could align the chain with the different gears on the bike gear cassette. This allowed us to fine tune the gear ratio once the diwheel was assembled to ensure optimal efficiency.

Diwheel