10217

# Gridiron Pendulum

The gridiron pendulum was designed by John Harrison in 1726 to make the swing period insensitive to changes in temperature. It consists of alternating brass and iron rods with lengths selected so that the effects of thermal expansion counteract. In this Demonstration, you can explore the effects of the temperature and the length of the gridiron pendulum on the clock error.

### DETAILS

The period of a pendulum is , where is the pendulum length and is the acceleration due to gravity. The thermal expansion of a pendulum made of all iron or brass can lead to minutes of inaccuracy per day. The gridiron pendulum consists of a framework of nine alternating iron and brass rods. These metals have different coefficients of thermal expansion, where and .
The total expansion of the gridiron pendulum is , where is the length of the gridiron portion. The variable can be selected so that the total expansion is always zero.
Reference
[1] The Engineering ToolBox. "Coefficients of Linear Thermal Expansion." www.engineeringtoolbox.com/linear-expansion-coefficients-d_ 95.html.

### PERMANENT CITATION

 Share: Embed Interactive Demonstration New! Just copy and paste this snippet of JavaScript code into your website or blog to put the live Demonstration on your site. More details » Download Demonstration as CDF » Download Author Code »(preview ») Files require Wolfram CDF Player or Mathematica.

#### Related Topics

 RELATED RESOURCES
 The #1 tool for creating Demonstrations and anything technical. Explore anything with the first computational knowledge engine. The web's most extensive mathematics resource. An app for every course—right in the palm of your hand. Read our views on math,science, and technology. The format that makes Demonstrations (and any information) easy to share and interact with. Programs & resources for educators, schools & students. Join the initiative for modernizing math education. Walk through homework problems one step at a time, with hints to help along the way. Unlimited random practice problems and answers with built-in Step-by-step solutions. Practice online or make a printable study sheet. Knowledge-based programming for everyone.