19XT 4WD Drivetrain
As drivetrain lead for the Hopkins Baja team, I oversaw the design of all power transmission components in the 2023 4WD system. My primary goal as subsystem lead was to facilitate the design of more lightweight and aggressive components to maximize peak performance while still reducing risk. This was done primarily through the implementation of a rigorous review and formal design freeze process to ensure all analysis was set up and conducted properly and all components were checked for manufacturability. I placed additional emphasis on allowing each component to be removed and serviced with minimal dependencies to reduce the impact of potential failures. See below for some design highlights!
Front Differential
The second iteration of our overrunning differential saw the sprag clutches moved externally and pressed into titanium cups to eliminate the cage and allow for the bevel gears to be reduced in size. In addition, the titanium cups were used to mount inboard brake rotors to reduce unspring weight and improve suspension packaging.
Friction-clutch Torque Limiter
Replacing the bulky off the shelf torque limiter used on the 18XT, a smaller and lighter custom solution was designed to reduce the peak loads seen by the prop shaft and front drivetrain, allowing components to be designed to the necessary driving load rather than inertial spikes seen during jump landings and similar events. The pressure on the sintered copper friction material is adjusted using a large locknut and a pair of Belleville spring washers to tune the slip torque.
2WD/4WD Shifter
An iteration of the 18XT design, the 2WD/4WD shifter allows the driver to use rear wheel drive for the handling and acceleration performance and 4WD to clear obstacles. The shifter consists of a pair of dog clutches which are engaged and disengaged through a motorized linear actuator.
19XT Drawing Tree
The following spreadsheet was created to track every component of the car, from the modelling stage through to final manufacturing and assembly. At a glance, sub-team leads can tell the status of each component and mark-off models as they are completed, frozen, and released for manufacturing.
Design Freeze Checklist
Prior to making drawings and beginning manufacturing, each component designer was required to go through a formal design freeze process with team leadership using the following checklist. This ensured that the final on-car version of each system would be manufacturable, capable of easy assembly and installation, and serviceable. In addition, all components and stock were checked for availability at the quantities needed, including provisions for backups in case of failure.
Master Design Sheet
The master design sheet was used to set design factors for various components based on their testing, failure risk, and impact of failure. In addition, material properties and expected system loads were compiled to ensure every component designer was operating with the same allowables and appropriate loads for their analysis.