Concept Design of a Double Wishbone Suspension in Fusion 360

Convert vehicle specifications into a CAD reference for a double wishbone suspension, detailing front and rear axle weights, sprung and unsprung mass, and bump to rebound travel.

Derive wheel design specifications from vehicle data and input a wheel reference into the Fusion 360 CAD workspace to guide the front and rear wheel coordinates for the suspension layout.

Identify and locate critical pivot points, upper and lower ball joints, and steering knuckle 3D coordinates to guide the double wishbone suspension design.

Model the wheel end from detailed specs, set wheel offset and center plane, and align brake disk mounting. Size the hub and bearing, then position the knuckle and caliper mounts.

Explore ball pins and steering knuckle design in a double wishbone suspension, covering ball joint housing, mounting points for hub, caliper, and steering link, plus packaging, clearance, and fastener considerations.

Locate suspension pivots on the chassis in 3D by connecting key points and placing bushes to define upper and lower controllers, while minimizing overhang to preserve bracket durability.

Locate steering points by defining steering axis formed by upper and lower ball joints, connect rack and pinion with steering link, and consider packaging, clearance, and acromion geometry.

Locate the shock absorber axis on the lower control arm and mount the top to the chassis, ensuring a durable bracket and proper overhang to handle bump loads.

Design the upper control arm by creating a plane through three points from the ball joint and bush locations, then profile and extrude, ensuring shock absorber and steering clearance.

Model the upper control arm housing and ball joint in Fusion 360 using a CAD workflow. Create reference planes, extrude profiles, and ensure shock absorber clearance.

Design the lower control arm by creating a reference plane from three points, sketching and extruding a simple profile, then adding depressions and ensuring shock absorber and knuckle clearances.

Develop a concept-level cad workflow for a double wishbone suspension, detailing ball joint housing creation, symmetric extrusion, sectioning, projected reference geometry, bracket design, and planning for packaging and detailed design.

Design the shock absorber assembly in tandem with the control arms, detailing the top plate, spring seats, damper, and helix spring, and check packaging and articulation with the LCA.

Explore calculations linking suspension design to vehicle dynamics, including right rate, rate frequency, spring rate, motion ratio, damper travel, bump steer, and load transfer.

Discover how ride frequency, the natural vibration of a sprung mass-spring-damper system, governs suspension isolation. Learn to estimate it using the spring rate and vehicle mass with a quarter-car model.

Define ride rate and wheel center rate as vertical force per unit displacement of the wheel center; center and contact-point movements differ due to tire and tower springs.

Calculate the wheel center rate and ride rate for a double wishbone suspension by comparing laden and unladen wheel travel, avoiding bottoming out and keeping the frequency within limits.

Calculate the sprung and unsprung ride frequencies, confirming the sprung mass lies in the 1–2 Hz range. Reduce the unsprung mass to raise its frequency and improve ride and handling.

Compute motion ratio to convert wheel rate to spring rate in a double wishbone suspension. Apply wheel rate equals spring rate times motion ratio squared in Fusion 360 concept design.

Create a front-view projection of suspension points, define fixed and moving pivots, and constrain lengths to simulate the kinematic articulation of a double wishbone suspension in Fusion 360.

Create the shock absorber point and axis from the predicted sketch, constrain the parametric sketch by fixing the steering axis angle relative to the horizontal for the suspension kinematics.

Derive the motion ratio from a parametric sketch of a double wishbone suspension. Dimension key points and articulation angle to compare wheel and shock travel along the angled shock line.

Calculate the coil spring stiffness using a motion ratio of 0.5 and a reference design to finalize height, turns, and diameters while ensuring shear stress remains within limits.

Calculate spring heights for layering, rebound, and bump states from a 170 mm reference and motion ratio; increase the capital diameter to reduce stress to about 883 MPa.

Explore how to specify damping coefficient and damping ratio for a suspension system, comparing critical damping, underdamped, overdamped responses, and why underdamped motion improves road grip and ride comfort.

Explore specifying a double wishbone suspension damper using a 0.3 damping ratio, derive a damping coefficient of about 4.647 N·s/mm, and plot the damping curve to determine damper length.

Lowering the unsprung mass shifts the natural frequency peaks at 1.5 Hz and 15 Hz apart. It reduces peak amplitude; increasing mass brings peaks closer and may degrade ride quality.

Calculate roll stiffness from springs to control body roll caused by lateral forces at the vehicle’s center of gravity, using the spring stiffness, span, and absorber position.

Project the wheel's ball joints from the three-dimensional double wishbone to the ground plane and measure the caster angle, scrub radius, and resulting steering behavior.

Compute the instantaneous center of the double wishbone suspension from front and rear pivot projections, then determine the roll center relative to the vehicle center plane.

Analyze how the anti dive feature of the suspension uses inclined control arms to increase antidote percentage, accounting for CG, instantaneous center, and front and rear braking distribution.

Explore bump steer in a double wishbone suspension by projecting ball joints to the ICC, comparing ideal and actual steering link trajectories to quantify steering deviation during travel.

This lecture analyzes bump steer dynamics, showing how movement in bump and rebound causes tow in or out, and demonstrates calculating steering angle change from suspension travel using steering geometry.

Analyze load transfer at the tower contact point by combining vertical and lateral loads into a resultant, then resolve components with a force triangle for a rigid-body suspension.

Use CAD for a parametric force-triangle analysis of the wheel end in a double wishbone suspension. Find the resultant direction at 33.69 degrees and obtain the three force magnitudes.

Analyze the lower control arm as a three-force member, identifying the LBJ force, pivot reaction, and shock absorber axis to determine the concurrent point and full force system.