Which type of dyno is most able to add and subtract load quickly?

• A. Waterbrake
• B. Eddy current
• C. Inertia
• D. Hydraulic

Answer: (B)

Fast load changes come from braking methods that respond electronically with minimal mechanical delay. An eddy current dynamometer controls braking torque by adjusting the magnetic field on a conductive disk, which creates eddy currents that produce drag. Because this actuation is largely electrical and there’s no physical contact or fluid flow to move, the load can be added or removed almost instantly in response to control signals.

In contrast, waterbrake and hydraulic brakes rely on moving fluids through valves and passages, which introduces delays from pump response, valve actuation, and fluid dynamics. Inertia dynos depend on the flywheel’s energy and mechanical braking, so changing load is limited by inertia and thermal effects, making their response slower.

So, the eddy current type is the best choice for rapid load changes.