This project by Conrad Shawcross involved a car that slowly spun as it hung from a gantry frame. The project was completed with an extremely fast turn around and I was employed to calculate the relevant loads to rate the necessary out-sourced components, as well as help design and fabricate the drive system (built in-studio).
The torque required to accelerate the car to 8 rpm in 1.5 s was calculated, and used to rate subsequent components. This torque was calculated by estimating the moment of inertia of the car from a parts list and a 3D model.
A motor with sufficient torque was sourced, as well as a slew ring that could withstand the calculated axial load.
I worked closely with the studio to develop a drive system for the assembly. This comprised a DC motor driving a slew ring via a gear train.
The motor connected to the gear via a sprag clutch to allow the car to continue spinning when the motor was turned off (this acted as a safety feature to prevent the inertia of the car from damaging the gantry frame). The sprag clutch was rated for the given torques and accelerations.
A static analysis was completed for the retaining unit, using hand calculations to verify the FEA (conducted in Fusion 360). A sufficient safety factor was confirmed. Owing to the load and the possibility for damage (people would be able to walk beneath the spinning car in the gallery), this was a critical process.
The final piece, in gallery.