Trailing Arm (Rear) Suspension Design

MSXII will implement a trailing arm suspension in the rear. There are several reasons for doing so, but the main advantages are a "shorter" (i.e. smaller chassis, as the suspension can extend further from the hardpoints) chassis and a more stable car while accelerating. 

Semi Trailing Arm vs Trailing Arm

First, some definitions. 

A semi-trailing arm suspension is a design in which the wheels and hubs are mounted on a fixed axle, with the arms attached to the wheels. This causes the line drawn through the centreline of the trailing arm hardpoints to intersect the centrepoint of the wheel. This is known as the "reaction point", and dictates camber change throughout wheel travel. Trailing arm, on the other hand, does not feature a common axle and allows both wheels to move independent of one another, with a reaction point at infinity. The image below explains this well. 

So why trailing arm over semi-trailing? Two main reasons: aerodynamics, and control. The aerobody of MSXII is a pontoon design, meaning each rear wheel assembly has to fit within a specific "pontoon" area to keep our aerodynamic profile as sleek as possible. An axle connecting both wheels would bridge the gap between the pontoons and add a significant amount of drag to our aerobody. Additionally, the lack of camber gain over a bump or through a turn achieved by allowing each wheel to rotate independently about it's respective hardpoint means we can achieve AND maintain the largest possible contact area at all times while driving (See Suspension - Camber, Caster and Toe for additional info on why contact area is good). Finally, a trailing arm suspension has no scrub throughout it's travel, as it only rotates through a single plane. 

Component Design

Our trailing arm suspension will be using a single-piece body, with an anti-twist gusset to mitigate the rotation of the body of the suspension throughout wheel travel, as well as braking/accelerating. By using a single piece body, both the design and manufacturing of the suspension becomes fairly straightfoward. Forces are easier to "track" through the component, and no additional fasteners/clevises/duct tape is required to put the body together. 

The main trailing arm, heavily inspired by MSX, is designed to emulate an I-Beam, which has a strong resistance to bending about the major axis. The use of a webbed arm provides a strong resistance to bending while reducing the weight of the component. The additional bracing arm will compensate for the low resistance to bending about the major axis present in the trailing arm.