Torque amplifier
More info
- Type
- Mechanical power amplifier
- Inventor
- H.W. Nieman
- Released
- ≈1925
- Principle
- Capstan / friction drum
A friction wheel gives the right rotation but almost no force — the torque amplifier let a nearly powerless turn command a strong one.
The mechanical integrator's friction wheel produces the correct angle but barely any force; it can scarcely move a pointer, let alone drive the next disk in a chain. That single limitation blocked Kelvin's dream of chaining integrators to solve differential equations for over fifty years. The torque amplifier fixed it. The principle is a sailor's capstan: a drum spun by a motor with a band lying loosely around it. The input — the weak rotation — tightens the band slightly, friction against the drum delivers a large torque, and the output faithfully follows the input's angle.
H.W. Nieman built it at Bethlehem Steel in the mid-1920s, and Vannevar Bush fitted a pair to every integrator in the 1931 differential analyzer — which is what finally let a chain of integrators drive one another. The same trick sat in fire-control gear and analog computers until digital machines took over.