Some Basic of Electronic Torque Control (ETC)
Electronic Torque Control utilizes advanced sensing and control capabilities of a Brushless DC (BLDC) Motor to precisely regulate current going into the motor. Specific torque at each Stage was tuned according to the brushless motor specification, gears/impact mechanism, current and timing. It is similar to a car gear shit table.
Torque vs Tension
While there is good reason we use “Torque” (force x length) to relate to pivoting force with tool of different lengths, However, it is an indirect measurement of force on a bolt. The direct measurement of force on a bolt is “Tension“, the force applied along the bolt.
On the Electronic Torque Control (ETC) tool, the device measures and controls the current to a preset level and the motor would deliver a specific rotational force (not “Torque” by definition). The higher the Stage#, the higher the current allowed to motor, and thus, the higher twisting force to the bolt. and the higher “Tension” applied to the bolt (or pressure on plane as a reactional force). But this is NOT exactly “Torque” (force x length) by definition
Measuring Torque Using Torque Tester
On the torque tester, it translates the “Tension” on the bolts to “Torque” with below relation. While the ETC tool created a specific tension regardless the bolt size, the measured Torque will nevertheless varies depends on the bolt size, “D”, in below relation.
T = ( K * D * P ) / 12
- T = Torque (ft-lbs)
- D = Nominal Diameter (inches)
- P = Desired Clamp Load Tension (lbs)
- K = Torque Coefficient (dimensionless, includes friction, heat dissipated … and the like)
Due to above Torque and Tension relation, the torque delivered at each ETC Stage and bolt size will look like blow chart