The story
I built Bumblebee on a 2010 Camaro SS shell because the fifth-gen unibody has a fully boxed rear subframe I could bolt the pelvis casting to without touching the crumple structure. The transformation is driven by six SEW-Eurodrive 7.5 kW servo gearmotors on 80:1 planetary reducers, one per hip and shoulder, plus two more for the torso split, all fed by a 350 V bus off a 42 kWh pack of Nissan Leaf modules I rebalanced by hand. Every rotational joint runs on a cross-roller slewing bearing rated to 40 kN moment, and the knee uses a four-bar linkage rather than a pin so the center of rotation migrates forward as it flexes, which is the only reason the thing can crouch without its own shins fouling the front quarter panels. Kinematics run on a Beckhoff PLC over EtherCAT at 1 kHz, with a 9-axis IMU in the chest and load cells in each foot feeding a zero-moment-point controller that pulls the bipedal target off the moment the CoP leaves the support polygon, at which point it just drops into a kneel, which it has done in public more than once. The hood halves fold into pectoral armor on a pair of Bimba pneumatic cylinders because the servo budget ran out somewhere around the elbows. Walking speed is 0.4 m/s on flat concrete, standing height is 4.9 m, all-up mass is 4,180 kg, and the radio-clip voice is a Jetson Orin running a fine-tuned Whisper embedding search against a 2 TB library of FM airchecks, indexed by sentiment, which is how he ended up telling a nine-year-old at Open Sauce that the freeway was backed up to the 605.
