Shell Eco-Marathon — Chassis Development

Junior Frame Lead · Structural Design · SolidWorks Weldments · FEA Preparation

SolidWorks ANSYS Altair Weldments FEA Aluminum In Progress

Current Status CAD is complete. The weldment model has been cleaned up, the bulkhead is in, aluminum material is applied, and the dimensions have been redrawn from the senior team cutlist. FEA is waiting on Altair suite onboarding (SEM provides both Altair and Siemens). A scale 3D print is done. CFD geometry came from the senior team's temporary shell.

Leadership Role

I was appointed Frame Lead for the JMU Junior Team based on prior structural analysis and FEA work. The role covers chassis layout decisions, structural validation, and making sure the frame plays nicely with suspension, powertrain, and the body shell. On the technical side that means material selection, section sizing, and setting up analysis procedures that future teams can actually follow.

Tools & Methods

CAD: SolidWorks (Weldments, Drawings) · Simulation: Altair (SEM-provided), ANSYS Mechanical · CFD: Siemens suite (SEM-provided) · Fabrication reference: 3D printing (PLA, scale model)

Frame Specification

All tubing is aluminum across three member types. Sections were chosen around structural need, weldability, and keeping weight down.

Member Type	Section	Material	Application
Main body / primary structure	2 in square tube	Aluminum	Floor rails, longitudinal members, primary load paths
Main rollbar	2 in diameter pipe	Aluminum	Primary overhead protection structure
Side supports & frontal sub-rollbar	1 in diameter pipe	Aluminum	Secondary bracing, bent support members

Early Concept Development

Before touching CAD, I sketched out packaging and structural layout ideas by hand. The goal was to work through load path intent, driver positioning, and rough proportions before locking anything into SolidWorks.

Early chassis sketch, initial frame layout

Concept Sketch — Rules & Popular Frame Renditions

Early chassis sketch, packaging and load paths

Concept Sketch — Dimensional Limits ∧ Prefrred Layouts

Reference — Model 5 (Previous Competition Year)

The Model 5 chassis from a prior year is the main structural and packaging reference. It's noticeably shorter and stubbier with a rounder, kayak-like cross section. This year's frame is a pretty significant departure: longer wheelbase, more angular primary structure, and updated rollbar geometry to match current SEM regulations.

Model 5 reference chassis from a prior competition year

Model 5 reference frame. Shorter, stubbier, and rounder than the current design. Kept as a packaging and geometry benchmark.

Shell Integration — Senior Team CFD/FEA Reference Geometry

The senior team provided a temporary aluminum shell mated to the chassis for CFD and FEA groundwork. It represents the vehicle's aerodynamic outer envelope and is useful for early drag estimation and getting structural load inputs defined.

After team review, we decided to move FEA and CFD work into the SEM-provided Altair and Siemens suite rather than ANSYS. It lines up better with official competition toolchain support and is what other teams are using, so comparisons are cleaner. The shell geometry is still a good reference asset for both.

Chassis with temporary aluminum shell for CFD and FEA

Chassis with the senior team's temporary aluminum shell. Used for initial CFD and FEA geometry. Team has since moved to the SEM-provided Altair and Siemens toolchain.

FEA-Ready Weldment Model

The main deliverable so far is a fully cleaned SolidWorks weldment with aluminum material applied, a bulkhead added, and geometry ready for structured load case analysis per SEM structural codes. This is the input model for Altair FEA once we get the toolchain set up.

Getting here meant fixing a lot of inherited problems from the senior team's file: corrupted and disconnected weldment features, structural member profiles that needed redefining, and joint continuity issues throughout the assembly.

Cleaned aluminum weldment chassis prepared for FEA

Cleaned SolidWorks weldment with aluminum material applied and bulkhead integrated. Geometry is validated and ready for Altair FEA load case analysis per SEM structural standards.

Dimensioned Frame Drawing

I pulled a contour outline view from SolidWorks and manually added dimensions from the senior team's cutlist and weldment data. Their original drawing had cluttered, corrupted, and disconnected dimensions throughout, so this is a clean redraw that's actually usable for fabrication and structural review.

Dimensioned outline drawing from SolidWorks weldment

Outline drawing with dimensions pulled from the senior team cutlist and weldment data. Redrawn from scratch after the original file had corrupted dimensions throughout.

Scale 3D Print — Physical Reference Model

I printed a small scale PLA version of the polished frame for team demos and advisor communication. Obviously you can't draw real conclusions about the aluminum weldment from a plastic print, but it's useful for getting a feel for the geometry, checking proportions, and doing a quick manual twist to see how the structure behaves under torsion. It's also just a lot easier to hand someone a physical model than pull up SolidWorks every time someone wants to see the frame.

Scale PLA print of the SolidWorks frame. Useful for geometry demos and a quick manual twist test. Not a structural stand-in for the aluminum weldment, but good enough to get the point across.

Planned Analysis Scope

Once Altair is set up, these are the load cases I'm planning to run first:

Torsional stiffness: opposing vertical loads at suspension pickups
Bending stiffness: distributed driver and powertrain mass loading
Braking and cornering: longitudinal and lateral acceleration inputs
Joint and mounting stress: rollbar base and bulkhead attachments
SEM structural compliance checks per competition rules

Toolchain Note FEA will run in the SEM-provided Altair suite and CFD in the Siemens suite, replacing ANSYS Mechanical. SEM supports these tools directly, which also makes it easier to compare results with other competing teams. Boundary conditions, mesh strategies, and assumptions will all be documented.

Engineering Objectives

Build a lightweight, structurally efficient frame within the SEM competition rules
Validate the design in Altair FEA against load inputs from the MATLAB/Simulink road load model
Beat the Model 5 stiffness-to-mass ratio
Keep the geometry compatible with the body shell, drivetrain, and suspension
Leave behind documented analysis workflows that future JMU teams can pick up

Next Steps

PENDING Altair FEA onboarding — Get the SEM-provided Altair suite set up and start running structured load cases against the cleaned weldment geometry.

PENDING Torsional stiffness baseline — First FEA run: opposing vertical loads at suspension pickups. Get a stiffness number to design against.

PENDING CFD geometry prep — Move the shell and chassis geometry into the Siemens suite and run a drag baseline.

PENDING Road load model integration — Pull load inputs from the MATLAB/Simulink vehicle dynamics model and feed them into FEA.

PENDING Fabrication prep — Finalize the cutlist from the dimensioned drawing, confirm tube sourcing, and nail down weld joint details.