Conceptual Designs

Front Suspension Concepts

MacPherson Strut

This system is commonly used in production vehicles today. This performs well in road environments, has few components, and is cheap to manufacture.

Double Wishbone

This is the most common system used in SAE Baja vehicles, ATVs, and UTVs. It allows for high wheel travel and great control over camber of the wheel throughout the wheel travel if unequal control arms are used.

Twin I-Beam

This system, developed by Ford in the 1960s, uses two I-beams that run under the vehicle. It is very strong and durable. However, it has a low ground clearance and low control over the wheel's camber.

Chosen Concept: Double Wishbone due to its well-rounded nature in many environments, which is necessary in the SAE Baja competition. It has great control over camber gain, caster, and scrub radius, which is important for a fully custom design.

Rear Suspension Concepts

MacPherson Strut

This system is commonly used in production vehicles today. This performs well in road environments, has few components, and is cheap to manufacture.

Double Wishbone

This system allows for high wheel travel and great control over camber of the wheel throughout the wheel travel if unequal control arms are used. However, it is much more difficult to use this system in the rear due to the frame's geometry.

Semi-Trailing Arm

This system attaches the trailing arm to the upright at an angle between 50 and 70 degrees. This distributes the forces more, leading to higher durability. This design has a few, simple components.

Chosen Concept: Semi-Trailing Arm due to its ease of design and space for the addition of a braking system, which was not included on previous vehicles. Since we are novices, the choice of an easily manufactured system is beneficial in case any redesigns are necessary. This design has also proven to be quite successful for the Stevens vehicle built for the 2019-2020 season.

Individual Part Concepts

Much of the design was driven by the selected suspension designs for the front and rear with most components simply optimized for our weight and loading conditions. However, there were several components that required significant custom design work to reach the goals that the team was aiming for. The most involved components include the front upright (also known as the knuckle), the front wheel-side steering mount, and the rear brake caliper mount.

Front Upright

The front upright acts as the "backbone" of the double wishbone suspension design. It contains the ball joint mounting locations, the wheel bearing, and the wheel-side steering mount. It must be structurally sound and relatively simple/cheap to manufacture in case extras are necessary.

One-piece Design

This design is manufactured from one piece of aluminum. It promotes lightweight but presents a manufacturing and cost challenge.

Bolted Design

This design features an aluminum bearing carrier bolted to a steel sheet metal upright. This design focuses on weight reduction with aluminum but requires bolting to connect the pieces made of dissimilar materials.

Welded Design

This design focuses on manufacturability. It is made completely of steel to reduce packaging issues. The box-shaped upright is simple and cheap to manufacture, but it requires significant high-quality welding.

Chosen Concept: Welded design due to its low cost and high manufacturability. Most components can be plasma cut or cut on a band saw, which reduces lengthy machining times.

Wheel-side Steering Mount

The wheel-side steering mount is what connects the upright to the steering tie rod. This allows the tie rod to apply a torque around the steering axis to turn the wheels.

Square Tube Design

This design uses a piece cut out of square tubing to create the steering mount. Using square tubing removes the need for bending the steel to make the mount and creates a large welding area. However, it is difficult to locate this mount on the upright.

Sheet Metal Design

This design uses two piece of sheet metal extended off the upright. It uses less material, leaves more room for the steering heim joint, and can be plasma cut. However, it is even more difficult to locate the two plates on the upright because they must also align to each other.

Chosen Concept: The design selection is based solely on the structural analysis of both steering mounts. Since both mounts are relatively simple to produce, the selected concept will feature the lowest stresses. The results of this analysis can be seen on the Technical Analysis tab.

Rear Brake Caliper Mount

With the introduction of a 4WD powertrain, the location of the rear brakes was required to change. On previous vehicles, the brakes were mounted inboard, which means they were mounted on the drivetrain and contained inside the frame of the car. Due to the more complex drivetrain, the brakes needed to be relocated.

Inboard Brakes Design

This design maintains the inboard brakes design from previous designs but uses the outermost point of the drivetrain. A splined rotor is mounted to the output shaft on the rear differential. The splines are able to carry the braking torque while #6-32 screws hold the rotor against the output shaft on the differential. A caliper mount can be mounted to the bolts holding the rear differential together.

Outboard Brakes Design

This design moves the brakes out to the wheels by extending the bearing carrier inward towards the car to make room for a rotor. The extended bearing carrier must wrap around the CV axle to prevent interferences. The brake caliper is mounted to a plate that extends off the lateral link tab, and the rotor is mounted to the bolt holes in the wheel hub.

Chosen Concept: The outboard brakes design was chosen for manufacturing reasons. While the material will be more expensive to purchase, the manufacturing process of the outboard design is much more reliable. The inboard design requires tapping holes next to the splines in the output shaft. If the splines are damaged in the process, the entire differential would need to be replaced.

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