B4-3.2 tubular slip ring B-Series

B4-3.2: four-circuit tubular slip ring, 3.2 in bore

The B4-3.2 is an open tubular slip ring with four circuits rated at 1 A. It mounts on the shaft, which passes through its 81.3 mm (3.2 in) bore, and carries strain gages, thermocouples, accelerometers and low voltages from rotor to stator. Its rings are solid silver alloy and its brushes silver-graphite. The rotor carries solder terminals and the stator a connector. It is 26.9 mm wide and runs up to 4 500 rpm, from −40 to 121 °C.

On installation, the rotor is secured to the shaft with set screws, square and concentric to the axis of rotation; a bushing adapts it to shafts smaller than 81.3 mm. Sensor wires run along the outside of the shaft and through slots in the rotor to the solder terminals, in stranded wire of 24 AWG at most, then are secured to the shaft and coated with RTV silicone. The stator is held by a flexible restraint, such as a small cable, a spring or a wire tie, rather than by its cable. The silver contacts are wear parts: they are inspected periodically and last about 100 million revolutions under ideal conditions.

It is used on large shafts on test rigs and dynamometers.