Making Cardboard Tubes for Electrical Coils
It is often difficult to obtain cardboard tubes as foundations for coils of special sizes, and the following is a practical method for making them as desired: Cut a strip of cardboard somewhat wider than the length of the tube desired and about 2 ft. long. Soak the cardboard in water until it is quite pliable. Wrap it tightly around a wooden rod of suitable size, gluing or shellacking each successive layer. When the desired thickness has been obtained, bind the tube with string, and place the whole in a moderately warm oven to dry. The tube may then be cut to length.—Alexander V. Bollerer, New Britain, Conn.