Blog #2 - The Design Process

   On monday, November 4th, during the usual integration meeting held by Formula Society of Automotive Engineers (FSAE) at the University of Houston, the team presented the improvements done to the suspension system to the FSAE organization, while also receiving feedback for the changes done during the previous week. One of the topics discussed include the modification of the chassis tubes and possible interference between the bellcrank-damper system and the tubes. To solve this problem, new positions for the dampers and the anti roll bar needed to be developed. The team also noticed a problem in the dimensions of the rear hub, the available CAD model did not reflect the engineering drawings that were used during its fabrication, for this reason new CAD models needed to be produced. The inaccuracy of the hub model also presented problems when integrating with the “Man-Machine Interface” team (MMI), resulting in problems with the rotor and it’s mounts. To solve this problem, the suspension team decided to visit the FSAE machine shop and measure the hubs dimensions again. Finally, to continue with the fabrication process the jeggings load and attachment needed to be designed, alongside its placement to the chassis plate.

       The team repositioned of the rear damper along the chassis (Interference with chassis tubes) Which changed the position of the bellcrank and the anti roll bar (Figures 1-a & 1-b). A-arms and steering rack were updated to be thicker for strength. Problems with the hub dimensions because the cad models for last year was not matching the actual hubs therefore, the cad models were redone and all the integrated components were resized. This included fixing problems that occured within the placement of the rotor and it’s mounts.Moreover, jeggings loading and attaching needed to be figured out. Placement of the jegging supports on the chassis plate.

Figure 1-a. Rear Suspension Bellcrank-Damper system placement as of October 31th

Figure 1-b. Rear Suspension Bellcrank-Damper system placement as of November 12th

  During the first two weeks of November, Team #9 focused on attaching the suspension components to the master assembly for the UH FSAE car CAD model( Figure 3-a), and started the process of modeling the jeggings to get an idea of the actual assembly process. After that, the team decided to change the orientation of the rear bellcrank and dampers to accommodate the chassis changes and the power components placement. Also, team #9 ran iterative simulations on the uprights and calculated the tension/compression forces on the the A-arms. Based on the FEA and the forces calculations, thicker dimensions were used to get a higher safety factor. A-arms outer diameters changed from 0.5 inches to 0.75 inches and uprights thickness at critical points were increased by 0.25 inches. The overall suspension system is larger that the previous year’s suspension systems, but the ratio of the weight of the suspension components to the actual power and total weight of the car is lower than the previous year’s suspension system. Finally, some dynamic simulations were analyzed using optimumD for measuring the parameters that are responsible for the motion of the car. 

Figure 2-a. Suspension Components assembled to the master assembly

Figure 2-b. Rear Suspension Bell Crank-Damper assembled to the 3D model

    Integrating with sub-FSAE teams has been a major challenge since each team is working on optimizing different parameters. This can cause our team to change the direction of motion, orientation or the whole location of our parts to accommodate other teams’ requirements. When integrating with other teams, each team needs to sacrifice up to a certain point in order to make the whole system works and the suspension team made changes to the location of certain components after running simulations using the OptimumG suite softwares and managed to keep most of the parameters in the range required. The second challenge is that the FSAE team lead advised the team to change the material of the uprights from Aluminum 7075 to Steel 4043 due to the high price of Aluminum and the cost of machining it. The team is currently looking for sponsors who are willing to offer Aluminum 7075.

For the following next two weeks the team expects to complete the design of the jeggings for the fabrication process, also minor redesign for the uprights is expected due to a possible change in the material and its fabrication, the tubes required for the manufacturing of the A-arms will also be ordered, resulting in a possible challenge for the project due to the time expected for the delivery of the material.