Engineering education relies heavily on hands-on experimentation, yet the high cost of commercial dynamometers—often exceeding USD 15,000—places them out of reach for many teaching laboratories. This paper presents an open-source test bed that systematically tackles the four main cost drivers of conventional systems: precision torque transducers (USD 500–USD 4,000), external electrical sensors (USD 200–USD 500), proprietary data acquisition hardware (USD 500–USD 3,000), and specialized mechanical fabrication (USD 300–USD 800). Our approach repurposes the built-in telemetry of a commercial electronic speed controller (ESC) to obtain real-time voltage, current, speed, and temperature measurements, thereby eliminating external instrumentation. A hydraulic disc brake provides mechanical loading, while torque is measured through a floating-caliper reaction method using a low-cost load cell and a precision lever arm. An ESP32 microcontroller handles throttle control, data acquisition, and telemetry decoding, with all firmware released open-source. The entire platform, built from off-the-shelf e-bike components and basic welding, costs under USD 400. Validation tests show measurement errors below 3% for electrical parameters and 5% for torque—well within the needs of undergraduate laboratories. A detailed uncertainty budget following ISO GUM guidelines confirms expanded torque uncertainty below 0.5%, meaning observed discrepancies stem from transmission losses, not measurement flaws. All design files, source code, and documentation are permanently archived under an open-source license, inviting global adaptation and reuse.
Kurniawan et al. (Thu,) studied this question.