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  • A variety of balance weights are provided with weights as low as 0.1 gram
  • ±5 volt analog control input for remote control of the DC motor
  • Digital tachometer with large LCD readout
  • Reversible motor direction
  • Adjustable slow roll speed capability
  • Compact Proximitor assembly with easy-to-use connectors
  • V-frame design for better control of housing dynamic stiffness properties
  • Better alignment through improved machining


The Bently Nevada RK4 rotor kit is a miniature, bench top rotating machine that simulates a number of machinery malfunctions including unbalance, rubs, fluid-induced instabilities, loose rotating parts, preloads, and others. Its unique geometry and its ability for users to isolate and control individual machine characteristics make it useful as both a teaching tool and as a laboratory tool for theoretical research.

In addition to machinery behavior, the rotor kit can be used to teach the fundamentals of proximity probe placement, gapping, and troubleshooting. It can also help technicians learn how to read and interpret proximity probe signals using an oscilloscope.

The Bently Nevada RK4 rotor kit has a V-frame design that has been developed to provide better control of the housing dynamic stiffness properties. The mechanical tolerances have also been tightened, resulting in more accurate machine behavior modeling. The RK4 rotor kit motor can closely hold the desired speed with changes in loading conditions. This has been accomplished by incorporating a direct current motor and high performance control circuitry. The motor can run in either a clockwise or counter-clockwise direction and has adjustable slow roll speed capability. It can be controlled remotely by using a ±5 volt control input, such as a signal generator or dc power supply, to drive the motor speed control device. Rotor speed is displayed on a digital tachometer with a large LCD readout.

The Bently Nevada RK4 rotor kit includes:

  • A mechanical base (including motor, coupling, rotor shaft, two balance wheels, two journal bearings and bearing blocks, six proximity probes, three probe mounts, a rub screw, and three safety covers)
  • A Proximitor assembly that contains five Proximitor units
  • A direct current motor speed control device

The motor speed control device provides power for both the rotor kit and the Proximitor assembly. A measurement and diagnostic tool, such as an oscilloscope or other diagnostic instrument, should be ordered separately in order to observe the RK4 machine behavior.

An optional Oil Whirl/Whip kit is also available to help users observe and demonstrate fluid-induced instabilities.

The Oil Whirl/Whip kit includes:

  • A high pressure oil pump assembly
  • An oil whirl bearing assembly
  • A rotor kit shaft with oil bearing journal
  • A load frame


This product can be used in the following applications: