MTS Series 215 Rotary Actuator - Manual (Page 57)

Rotational Inertial
Series 215 Rotary Actuator Product Manual Operation 57
Rotational Inertial
This subsection describes how to calculate the total rotational inertia of the Series
215 Rotary Actuator, specimen, and optional equipment. High rotational speeds
or large-diameter flexures and specimens can cause large torques even though the
masses involved are quite small. If the total rotational inertia exceeds
recommended levels and the actuator is allowed to rotate until the rotor vane
makes contact with the rotor vane stops at high rotational speeds, then the flange
adapter may rotate on the actuator shaft or the actuator may be damaged.
Do not depend on the internal actuator rotor vane stops to protect
equipment and personnel from damage and injury.
The internal actuator rotor vane stops can break if the rotor vane strikes
them with a rotational inertia greater than the maximum value. The internal
actuator rotor vane stops can also fail in fatigue if subjected to repeated
lesser impacts.
Ensure that the internal actuator rotor vane does not repeatedly impact with the
actuator rotor vane stops. Do not rely on the internal actuator rotor vane stops to
protect equipment and personnel from injury.
Determining Maximum Rotational Inertia (J
T
)
To determine if the internal actuator rotor vane stops are adequate, the total
rotational inertia (J
T ) must be determined for the rotating mass. J T equals the sum
of the calculated J, for the specimen, plus known J for the actuator, flange, and
flexures.
The following table provides the rotational inertia values for the actuator and
optional components.
CAUTION
Rotational Inertia for Actuator Components
M ODEL R OTARY A CTUATOR (J R ) F LANGE A DAPTER (J F ) D IAPHRAGM F LEXURE (J D )
LBM - IN . 2 KG · M2 LBM · IN . 2 KG · M2 LBM · IN . 2 KG · M2
215.32 11.67 0.00342 14.4 0.00421 85 0.0249
215.35 18.54 0.00544 21.8 0.00639 95 0.0278
215.41 20.23 0.00594 21.8 0.00639 210 0.0614
215.42 29.04 0.00852 208 0.0608 460 0.135