Demonstrations

Trevelyan Rockers

Code Number :	4A30.46
Disclaimer:	Reprinted by permission of Dick Berg, University of Maryland, for use on this website. The demonstrations contained and referenced herein are listed for the purposes of cataloging and describing physics demonstrations which should be conducted only under the direction of a trained instructional support professional or physicist. These demonstrations are not presented for the purpose of being conducted by persons unconnected to this Facility and/or persons not consulting with or being supervised by the recognized instructional support professional or physicist and his/her staff. The University is responsible only for those demonstrations carried out using its own equipment using established safety and scheduling policies, and bears no responsibility for those choosing to use this source material for their own purposes. All demonstrations described and contained herein are public domain, and can also be found in reference materials in libraries, bookstores, and electronic sources. Further information regarding legal liability in use of demonstrations and labs will be found on the web site Injuries in School/College Laboratories in USA. The University of Iowa Disclaimers: University of Iowa Disclaimer All Rights Reserved..
Condition :	Good
Principle :	Expansion, Contraction, & Heat Transfer, Frequency of Sound Waves
Area of Study :	Acoustics
Equipment :	Trevelyan Rockers, Lead Blocks (Triangular), Bunsen Burner, Disposable Grill Lighter, Insulated Gloves.
Procedure :	Heat the large ends of the Trevelyan Rocker with the Bunsen burner for several minutes. Set it upon the lead brick with the small end of the rocker resting on a table. The rocker will start to vibrate due to the rapid expansion of the lead under the rocker. This rapid expansion causes the rocker to tip so that one edge and then the other is making close contact with the lead. One of these lead blocks is kept in the refrigerator as the greater the difference in temperature between the block and the rocker the better it works. Another interesting note is that the frequency of the rocker will not descend steadily, but will jump from one harmonic to another. NOTE: If the rocker does not start to vibrate spontaneously a gentle bump is enough to start the process.

References

Ira M. Freeman, "Department of Forgotten Lore", TPT, Vol. 12, # 6, Sept. 1974, p. 348.

H- 24: Richard Manliffe Sutton, Demonstration Experiments in Physics.

C.L. Stong, "On a Paradoxical Pump, Reversing Cubes, Vortex Rings, and Various Other Matters," The Amateur Scientist, (January, 1965).

Jearl Walker, "Thermal Oscillators: System That Seesaw, Buzz or Howl Under the Influence of Heat", The Amateur Scientist, Feb, 1983.

Mail Questions and Comments to: Dale Stille