The first phase of any effort to boost the efficiency of a piece of machinery in order to lower its operating costs and reduce power consumption is gathering accurate data on the machine’s initial performance, particularly torque data. The ability to measure torque reliably is crucial for applications ranging from determining the level of force required to lower an automobile’s window to testing a tugboat’s high-horsepower engines.
The nature of turbo machinery can make it especially challenging to measure torque accurately. Electric motors, pumps, compressors and turbine engines can all generate high torques at high RPMs. In addition, torsional vibration can sometimes lead to premature failures in the driveline. Historically, this has created limitations on how torque can be measured both accurately and safely. This article addresses some of the basics associated with minimizing torque measurement uncertainty to allow making more informed modifications to a machine’s design or operating parameters.
As every former first-year engineering student should recall, “torque” is defined as the amount of force needed to rotate an object about an axis, fulcrum, or pivot. The mathematical equation for torque is “force multiplied by distance.” To illustrate, imagine a foot-long lever arm attached to the center of a wheel; if hanging a one-pound weight on the end of the lever arm makes the wheel turn, the force needed to turn the wheel can be described as 1 lb-ft of torque.