Low Cost Category

2002 AAPT Apparatus Competition, Boise State University

Name: Clarence Bennett

Address: Staff Emeritus

Oakland University

111Hannah Hall

Rochester, MI 48309

Phone: 248-370-3418

Fax: 248-370-3408

E-mail: bennett@oakland.edu

Apparatus Title: The Lead Bell Project

The lead bell is an old demonstration to show some of the effects of extreme temperatures on materials;

When the bell is struck at ambient temperature, it produces a dull, un-bell-like sound, but after it is cooled in liquid Nitrogen, it sounds somewhat more like a bell.

The only lead bells that were available, as far as I could determine, were simply made by folding lead sheet into a Cow Bell shape.

I considered this to be inelegant, and suitable perhaps only for Physics Departments at Agricultural Colleges. :)

Many years ago I decided to try to make a mold in the form of the bronze dinner bell that has always been in my family.

The first try was to make negative and then positive forms of RTV Silicone rubber in order to cast a negative mold of plaster of paris or various other materials.

I had only limited success because the plaster was always destroyed, and I wanted a reusable system, in case I could supply bells to my colleagues.

Then last year, a friend I was telling about the project suggested using the RTV for the mold, which I had never thought of, thinking it would be destroyed by the high temperature of the molten Lead.

But I tried it, and it worked.

Displayed below are the original Bronze bell. A bell of (relatively) pure lead, and one made of Lead from the shielding of some donated hospital equipment, which is evidently an alloy that is much more rigid , and sounds similar to the frozen Lead bell.

I brought the Pewter bell so that you can compare the sounds even if there is no LN available.

If you wish to have a Lead Dinner Bell of your own, please come to the PIRA Resource Room.

Equipment List

Item Supplier Cost

RTV Silicone Rubber McM. Carr $55 (enough for several molds)

Lead surplus

PVC pipe fittings Home Depot ~$5

Total Cost: $60 (for several molds and bells)