Four-square test stands
A “four-square” or “power-multiplier” test stand is a closed-loop torque circle. The test object is installed in one shaft line, the output torque is recycled through transmission components and a second drive line. The driving test torque load is routed around in a reversed direction. This means the load torque is generated and maintained in the loop without outside driving power. Only the power losses in the rotating loop are to be supplied by a drive motor. This motor is typically a low percentage of the testing load mechanical-loop power. Note this is real mechanical power loading the test object.
A four-square installation is suited for mechanical transmission components: gearboxes, drive shafts, couplings, belts, chains. Low installed driving power makes this layout suitable for long-term tests and/or may hours per year.
Four-square installation features:
- Torque range 1 Nm up to 10 MNm 10 lb-in up to 100,000,000 in-lb
- Speed range 1 rpm to 6,000 rpm
- Power range any, typically 10 kW to 100 kW, up to 500 kW and over 500 kW
- Extremely simple and low cost layouts possible for low power installations
- Low investment cost for low to medium power installation
- Low supply power demand relative to real mechanical test load power
- Low energy cost for high running hours
- Larger footprint than brake stand