Decision Matrix

Overview

The chassis (aka roll cage or frame) is a space frame tubular steel structure that provides the primary structure of the vehicle. It is the glue that connects the sub components of the car together.

Additionally, the chassis must protects the driver, as defined by the SAE Baja rule book:

"The purpose of the roll cage is to maintain a minimum space surrounding the driver. The cage must be designed and fabricated to prevent any failure of the cage’s integrity during normal operation or during a collision or roll over."

The role cage consists of a series of "named points" by the rule book. These points define the general geometry of the structure. There are two different types of frames that can be constructed; a rear braced frame and a front braced frame.

Rear Braced Front Braced

Over view continued......

1. overview

2. constraints

   1. budget, rules, etc.

3. requirements

   1. inputs + outputs

   2. how do your parts affect neighbors parts

   3. weight

   4. timeline

   5. Assumptions

   6. ex. Assume the engine produces its rated max torque

   7. assume we will bottom out our suspension

   8. Design decision

   9. 2) Constraints

   10. The frame is largely defined by the rule book and is it currently assumed that it is overbuilt. This assumption has lead previous teams to decrease the quantity and size of frame members to save weight.

   11. The minimum size of the frame is constrained by the need to package the components inside it per the frame rules. The two main areas that need to be packaged are the driver and the engine / drivetrain.

   12. The frame also provides the mounting points for the suspension and the shocks.

   13. 3) Forces

   14. There are two main types of forces acting on the frame; inertial forces and suspension forces.

   15. In 2022 Tennessee competition the rear engine mounts of the frame were under designed to handle the inertial forces of the engine. As the car went off a drop in the suspension course its engine applied a downwards force on the frame and the frame flexed. The frame did not yield but it did elastically deformed enough to apply a torque on the drive shaft between the engine and the gearbox. This deflection increase drive shaft angle boke the flexible coupler, leaving the car without any power to the rear wheels.

   16. The suspension forces are applies to the frame from the suspension control arms and the shocks. Control arms can apply both forces and torques to the frame where as shocks should only apply forces to the frame.

   17. Steering system also transfers force to the frame.
       
       

Requirments:

• Decrease weight to under 65lbs (last year was 96lbs)

• Increase rear stiffness especially around the engine mounting

• Design for a 6'0" driver

• 
  

4) options

• Rear braced

  • Pros:

  • Cons:

• Front braced

  • Pros:

  • Cons:

Decision Matrix

Summary