Shell Eco-marathon Project - Chassis Group
Sponsor Company: Shell
Team Members: Robert Chang
Dipnil Chowdhury
Chongwon Shin
Kira Witwer
Project Sponsor: Dr. John Lamancusa
Faculty Advisor: Dr. Eric Mockensturm
Date: Spring 2007
Executive Summary:
The Shell eco-marathon is an event created for individuals to design and compete vehicles for the highest mileage per gallon of fuel. Penn State is planning to compete in the 2008 eco-marathon, with the design of the chassis and planning for the continuation of the project taking place in the spring of 2007.1 The Shell Eco-marathon website may be found by clicking on the following Shell Eco-marathon picture, while the rules may be downloaded at the link below.
The chassis of an eco-marathon vehicle involves several design decisions for various systems, such as the frame layout, engine placement, wheel design, wheel size, and steering system. Due to the greater simplicity and the lower cost, rolling resistance, and weight, a three wheeled layout was decided as the best option. The mid engine layout was found superior to front and rear engine layouts since it provides good weight distribution, front and rear traction, good stability, visibility and simplicity.
The wheel size also accounts for stability, traction, drive train losses, and rolling resistance. Decreases in rolling resistance come with larger diameters; however, keeping in mind simplicity, clearance, and weight, 18 inch diameter wheels were decided as the best option. Also, a recirculating ball type steering was selected for its stability, balance, driver feedback, and relatively inexpensive components.
As for the frame structure itself, a sit up space frame is the best option considering the strength to weight ratio, structural rigidity, driver visibility, and shell mounting points. The material best suited for this vehicle is 6061 aluminum based upon low cost, weight, and material properties to maximize performance. Using 6061 aluminum, preliminary analysis of the frame design suggests using 1¼ ” diameter tubing that has 1/8” thick walls, for a projected vehicle frame weight of 49.5 lbs. With an additional factor of safety, 1 ½” diameter tubing with 1/8” thick walls will be implemented in the final design. A half scale prototype based upon this design is shown below.
Conducting finite element analysis reveals the following displacement figure, with the maximum being 0.0518 inches deflection.
The shell of the vehicle is still under development; however, the shell will be modeled after current automobiles. The following CAD rendering was based upon the Lamborghini Murcielago.2
The sculpture of the shell will then be sectioned according to the frame dimensions to eliminate sharp corners and thereby eliminating drag-causing flow seperation, as shown below.
The design time, and build time will be plotted out for the upcoming semesters until the vehicle’s completion. Administrative decisions for the organization, manufacture, and testing of the final vehicle components for the future semesters will be constructed to meet the 2008 Shell Eco-marathon deadline. More information of the 2008 Shell Eco-marathon may be viewed in the following link.
References
1 About Shell Eco-marathon Americas http://www.shell.com/home/Framework?siteId=us-en&FC2=/us-en/html/iwgen/society_environment/ecomarathon_shared/about/zzz_lhn.html&FC3=/us-en/html/iwgen/society_environment/ecomarathon_shared/about/about_ecomarathon.html
2 Lamborghini Murcielago Photograph April 5, 2007 http://www.rccartips.com/