Chassis Design Consederations

Designing the chassis is one of the critical parts of our pod design as the chassis supports the entire structure of the pod and distributes the loads acting on the pod to the external forces and vibrations. For the designing process of the chassis, it is therefore important to select the optimum material, place the chassis supports in planned and strategic locations, maintain structural integrity and make it as light-weight as possible. We don’t want a very heavy chassis because that will increase the overall weight of our pod, resulting in a reduction of top speed and acceleration (Our eventual goal is to make the pod go as fast as possible). This post discusses the considerations our team has taken while designing the chassis, the evolution of our chassis system, the pros and cons of our system and future scope of work.

We have made the following considerations for our design:

1. Forces: The forces that act on the pod and how they are determined :

• Pressure Force: The flow of air in the tube exerts a pressure on a moving pod. This pressure depends on the outer profile of the pod and the velocity of the pod. CFD simulations give us the pressure distribution over a pod moving through the tube at specific speeds. The pressure distribution is then imported into the Static Structural Solver of ANSYS Workbench to give us the stresses and deformations of the chassis caused due to these forces.

• Forces due to acceleration and deceleration: The acceleration profile is taken into consideration to calculate forces due to acceleration and deceleration. The maximum values are extracted for each of them and are multiplied by the weight of the pod to determine the maximum force acting on the chassis.

• Weight of the systems: The weight of different systems of the pod (Propulsion, Levitation, Braking, etc.) is assumed to be uniformly distributed over the chassis base plate for simplicity while extra weight is added for the calculations to take into consideration any access weight.

• Frictional Resistance: The forces of friction generated due to the air drag and the wheels has been simulated and included in the chassis design. Forces caused due to friction while braking has also been taken into consideration.

2. Material Selection: It is critical to select a material that has the following properties:

• Lightweight

• Strong

• Economical

• Easy to manufacture

• Machinable

• Readily available

Al 6061-T6 Aluminum offers all these benefits and thus was selected as the material for the chassis.

3. Placement of supports and structural members: The simulations were started with analysis of a shell of the pod to assess the major areas of stress concentration. For the next design, supports and reinforcements were added at these locations to distribute stress and reduce material used. Analysis was again performed and this process was repeated till we got a highly-optimized design for the chassis.

4. Maximum deformation: Not only the maximum deformation should be within the elastic limit of the material but it should also ensure that the chassis does not come in contact with the I- beam or the track as this clearance is very low.

5. Maximum Von Mises Stress: The Maximum Von Mises Stress of the chassis should be much lesser than the yielding stress of the material and the design should a considerable factor of safety.

[endif]--

The primary components of the chassis and their functions are given below:

• Ribs: Ribs provide lateral structural strength, structural connection points for longerons, and a frame to which carbon fiber shell can be mounted. The thickness of the ribs is taken to be 5 mm.

• Longerons: Longerons provide longitudinal structural strength and distribute external loads. The cross section of the longerons is taken to be 12.7 mm x 12.7 mm square tubes.

• Base plate: The Base Plate provides longitudinal structural strength and a mounting surface for all internal components of the pod. Thickness of base plate is taken as 5 mm. ![endif]--![endif]--![endif]--