Free Vibration Unit

The Free Vibration Unit, to perform demonstrations and experiments which provide an understanding of the free vibrations of a simple spring-mass-damper system.

ATENG 12118 — Free Vibration Unit

The main structure of the unit is a rigid frame, made of steel and aluminum, with two vertical guides, an upper mounting plate for the spring

and a lower mounting plate for the damper. This rigid frame supports the different elements of the unit.

The mass carriage, to which various slotted weights may be attached, is constrained by

rollers which run along the vertical guides to provide a single degree of freedom with

minimum uncontrolled damping. The lower end of the spring is attached to the mass

carriage and the upper end is attached to the frame. This section of the frame is adjustable

so that the free position of the carriage may be varied.

The system produces amplitude versus time recordings using a mechanical strip chart

recorder that consists of a drum recorder and a pen holder. The drum recorder is attached

to the rigid frame and consists of a drum, driven by a synchronous motor, and a roll of

paper. Before being rolled around the drum, the paper passes through a tensioning device

ATENG 12118 detail

that provides enough tension to ensure that the paper speed is constant (0.02 m/s). The

pen holder is attached to the mass carriage and uses a spring to maintain continuous contact between the pen tip and the paper on the

drum.

An electronic console is used to switch the synchronous motor on and off during experiments.

• Three springs, with varying stiffness, can be interchanged as the connection between the rigid frame and the mass carriage:
• Spring 1: k = 3.30 kN/m.
• Spring 2: k = 1.22 kN/m.
• Spring 3: k = 0.47 kN/m.
  Five weights of 1 Kg each can be added and secured to the mass carriage.
  An adjustable oil damper provides controlled damping and can be attached to the carriage by means of a screw.
  Oil is provided to fill the damper.
  Cables and accessories, for normal operation.