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Free and forced torsional vibrations (TM 140)

Free and forced torsional vibrations (TM 140)

investigation of torsional stiffness and torsional vibrations

Code TM140


  • Torsional vibrations are often observed in belt-driven systems.
  • With appropriate excitation of resonances, large vibration amplitudes can occur, which can lead to strong loads on shafts and gears, potentially resulting in damage.
  • The TM 140unit can be used to produce free and forced torsional vibrations and to study the effects of torsional stiffness, mass and damping on frequency and amplitude.
  • The core of the experimental unit is a metal torsion bar.
  • Mass disks with different rotational inertias can be attached to the bar using clamping chucks.
  • This allows a torsional vibration system to be created with up to three masses.
  • The torsional stiffness can be adjusted by varying the effective bar length.
  • An exciter unit driven by an electric motor is used to represent forced vibrations.
  • The frequency can be adjusted and read on the control unit.
  • A damper makes it possible to set different degrees of damping.
  • The torsional vibrations are picked up via rotary encoders on the bearings of the torsion bar and are available on the control unit as an electrical signal.
  • All signals are also available via a USBport and can be transferred to a PC.
  • The GUNTsoftware allows the signals to be recorded and analysed, for example recording a resonance curve or displaying the natural mode.

Technical Details:


  • experimental unit for investigating torsional vibrations and torsional stiffness
  • 3 mass disks
  • 4 freely position able ball-bearing-mounted bearing units with clamping chucks
  • sealed oil damper
  • exciter unit with drive crank; exciter amplitudes 1,4°, 1,8°, 2,4°
  • 4 rotary angle sensors, 0,03V/°
  • electrical exciter control unit for setting and displaying the exciter frequency and for powering the rotary encoder
  • GUNT software for data acquisition via USB under Windows 8.1, 10

Technical Data:

  • Torsion bar:
    • 1300mm
    • Ø 6mm
    • stainless steel
  • Rigidity: approx. 1,0Nm/rad/m
  • Mass disks
    • Ø 150mm, approx. 2,7kg
    • Ø 228mm, approx. 4,8kg
  • Exciter frequency: 1…20Hz
  • Damper coefficient: 0,25…3,5Nm/rad/s
  • 230V, 50Hz, 1 phase
  • 230V, 60Hz, 1 phase; 120V, 60Hz, 1 phase
  • UL/CSA optional

Dimensions & Weight:

  • L x W x H: 1400x410x400mm
  • Weight: approx. 50kg

Required for Operation:

  • PC with Windows recommended.

Learning Objections/Experiments:

  • determine the torsional stiffness of a torsion bar
  • determine the mass moments of inertia
  • decay behaviour of torsional vibrations
  • determine the damping in torsional vibrations
  • forced torsional vibrations, resonance
  • torsional vibration systems with multiple masses:
  • two-mass torsional oscillator
  • three-mass torsional oscillator

Scope of Delivery:

  • 1 frame
  • 4 bearing units
  • 1 torsion bar
  • 3 mass disks
  • 1 exciter
  • 1 rotational damper
  • 1 display and control unit
  • 1 set of cables
  • 1 hexagon screwdriver size 4
  • 1 GUNTsoftware + USB cable
  • 1 set of instructional material


  • behaviour of two-mass and three-mass torsional oscillators


  • WP 300.09: Laboratory Trolley

Due to the continuous development of our products, the goods supplied may vary in detail to that illustrated on this Website.