EV360: Electric Monowheel

Our team has designed and built a one-wheeled electric motorcycle currently designed to be capable of reaching speeds in excess of 75 mph. Drivetrain upgrades will make the vehicle capable of reaching speeds in excess of 120 mph.  

We're not an official Duke team or organization; we're a group of friends who don't have a garage, established funding sources, or dedicated tools like most motorsports teams. We've built this vehicle just about from the ground up. 

Introduction

During the summer of 2018, I was hanging out with a friend helping him clean up one in one of his labs; on his computer, I saw a window pulled up with a picture of a monowheel. “What’s that?” I asked. After explaining that he had been looking at cool science-fiction style vehicles out of curiosity, I said “let’s build one.” That’s how EV360 was born.

Our Team

Our team consists of Fran Romano, documentarian, Kristine Stanners, Event Planning, Logistics, and Publicity, and four mechanical engineering students: Ahmed Ahmed-Fouad, Carlo Lindner, Jolán von Plutzner, Anuj Thakkar. The team was founded by Anuj Thakkar and Logan Fettes.

Vehicle Systems

The monowheel consists of a series of different physical structures and systems that draw attention. These broad structures and systems are called out, but detailed analysis is not yet provided as the team continues to iterate, design, and refine the vehicle.

Powertrain:

The powertrain consists of the following:
15 hp DC Brushed Motor:

This motor was specified based on estimated power and torque requirements for bringing the vehicle to a speed in excess of 75mph. The particular brushed DC motor was selected over a similar brushless motor of similar power due to an abundance of documentation available for the motor and the team’s comfort with operation of this motor. Future iterations could benefit from a shift to a brushless design.

8″ Custom U-Groove Drive Roller & Ratcheting Freewheel Clutch: 

A Ratcheting Freewheel clutch was selected to serve as an automatic clutch that did not require manual operation and that reduced space by simple integration into the drive wheel itself. A U-Groove drive roller is custom manufactured and loaded against the outer drive wheel with gas-springs. A clutch was required to allow low-resistance continued motion of the vehicle when the vehicle is not being supplied power from the motor. Regenerative braking was not implemented in part for this reason, as well as due to the team’s selection of Lithium Polymer batteries for the power train; uncontrolled charging of these batteries was undesirable from a safety perspective.

Chain & Sprockets:

The gear ratio from motor to drivewheel is 1:1, which, it turns out, approximately optimizes motor and vehicle performance. Alternative configurations would cause the motor to exceed specified RPM / torque limits for desired performance, as specified by dynamics models. The current vehicle consists of ANSI 50 Roller Chain & Sprocket; the team is considering adjustment to the motorcycle 520 standard for chain and sprockets.  A belt drive would not deliver the required power while operating within the physical constraints (space / geometry) of the system. 

Chain Tensioning Mechanism:

A manual tightening friction-based chain tensioning setup is being upgraded to a spring-loaded polyurethane wheel tensioning mechanism.

Mounting Parts: 

Powertrain components are mounted via aluminum and steel components manufactured on a waterjet and CNC mill, as well as via components supplied by McMaster Carr.

Electrical Components

While possible to build into powertrain, electrical systems were approached as a separate system from drive components

72V 22Ah Lithium Polymer, 20C Continuous, 40C Pk Battery Assembly: This battery assembly provided us the best performance at the most competitive price. The battery was assembled via multiple 12V bricks that could be easily configured and adjusted to fit within the frame. The modularity of these bricks allows for large design changes without a significant expense. Lithium-ion configurations were possible, but custom packs with reliable a reliable BMS were cost-prohibitive. The team has been operating on time-constraints provided by stakeholders that would not allow design and implementation of a custom BMS.

Alltrax 500A Programmable Motor Controller:

15 hp Brushed DC Motor:

Throttle:

E-Stop:

Contactor:

Terminals: 

Fusing:

GPS Speedometer:

Accessory Lights:

 

Handle & Seat
Safety (Structures / Materials)
Safety (Equipment) 
Frame & Wheel
Braking
Training Wheels

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Models & Simulations

Fabrication Techniques + Methods Used

Design Elements

coming soon…

Funding

 

Recognition

APPLE: During the early design process, Apple featured the monowheel in a commercial based around the application of their technologies in an educational setting.

RUBENSTEIN ARTS CENTER: After a public display of the monowheel at the Rubenstein Arts Center (Ruby), the Ruby featured the monowheel on the cover of future printed content. 

INNOVATION CO-LAB: After the vehicle’s first public display, Duke University’s Innovation Co-Lab made the vehicle the centerpiece for visitors touring the facility.