Blog #1 - Starting the Journey

The current problems we are presented with, when designing the suspension system for a quarter formula race car, involve the problems that occurred from the UH FSAE suspension team from the 2018-2019 year. One of the problems involved having a high driver steering torque input to turn the wheels. The required amount of torque, on the steering wheel, to turn the wheels through their full range of motion was 22 ft-lb. We obtained this value by applying a minimum torque on a torque wrench that was mounted onto the steering column to turn the front wheels through their full range of motion (Figure 1). This high steering torque input made it tough for the driver to turn the 2018-2019 race car. We will be reducing this number down to 4 - 10 ft-lbs. Also, the suspension components from last year were heavy, including the uprights. We will  reduce the weight of the suspension components, including the uprights, while ensuring the suspension system can still handle max cornering, braking, and accelerating forces. Finally, the power team for the 2019-2020 UH FSAE team decided to use a heavier and larger engine when building the power system for the race car. Our suspension system will need to account for this. 

Figure 1. The torque wrench is attached to the socket; the plate is mounted to the steering column; the wrench is turned to measure the torque required to turn wheels the full range of motion.

From October 18 - November 1, we conducted and completed several things. We finalized the kinematic and dynamic parameters of the suspension. This includes suspension point attachments, steering geometry, and the optimization of several other parameters like scrub radius and king pin angle. We modeled the uprights on Onshape and performed FEA on them using Abaqus (Figures 2 and 3), and we are currently modifying the uprights, as needed, to ensure they can handle maximum cornering, braking, and accelerating forces. The front wheel package are currently being modeled on Onshape, and the steering rack was modeled on Onshape (Figure 4).

The biggest challenge we faced was making sure suspension parts were not interfering with each other or with other objects (e.g. chassis). In order to make sure the suspension links and steering weren’t interfering with each other, we took advantage of Optimum Kinematics where we designed the suspension geometry. In order to ensure suspension components (e.g. anti-roll bar) weren’t interfering with other objects (e.g. chassis), we took advantage of Onshape to ensure parts fit in properly.

Figure 2. The displacement of the upright was generated on Abaqus subjected to 1533 Newtons on the upper segment (between the two upper holes) and 1557 Newtons on the lower segment (between the two lower holes) force based on boundary conditions. The displacement will be used to assess whether or not the upright design will be changed. In this case, the red and yellow sections of the upright are likely to be redesigned for a lower displacement. The uprights will be used to allow for suspension link attachment from the wheels towards the vehicle.

Figure 3. This picture shows the von Mises stress on the upright. This indicates the stronger and weaker areas of the upright when loads are applied under boundary conditions. It is important to have uprights that can handle the forces they will be subjected to.

Figure 4. The front wheel assembly of the suspension system and steering rack were modeled on Onshape. These suspension components are crucial for the vehicle.

From November 1-November 15, we hope to finalize the selection of bearings for the front and rear uprights and ball joints for rod ends. We also hope to finish modelling the rear wheel assembly package on Onshape and integrate it with the chassis. We also hope to start and finish the creation of jigs for multiple suspension components and finalize the design of the uprights by November 15. Also, the steering rack plate and anti-roll bar plate should be completed in this time frame. These plates will be used to properly constrain the steering rack and anti-roll bar onto the vehicle.

Time management will be the biggest challenge to complete the goals listed above due to every person on the team having to devote time to other classes at the University of Houston. While that is the case, everyone will continue to meet together to address the tasks and milestones.

The other challenge that we are currently facing includes having the correct force calculations on the suspension system. We will be running lots of simulations to help ensure that our calculated force values are very accurate. The simulations can help with knowing whether or not the numbers we are receiving are ideal based on your selected design value criteria for the suspension components (e.g. negative numbers vs. positive numbers to indicate direction of suspension components at a given instant).