History of the Construction of the NIMA Sand Museum
The idea for big size hour glass, which is biggest in the world ,was a idea of a mayor of NIMA-town, Michio Izumi. He has a random remark at my lecture meeting, May,1986. He said that "I want to construct a big hour glass, which is biggest in the world. Help me."
This is a start point. I have no experience to make even a small hour glass. I start from one minute, then gradually more and more bigger one. A glasswork for make scientific instrument was in cooperation with me. By my technical advise, many cooperator made an effort to realize the idea under very hard schedule. A person of distinguished service was YASUMARO SIWA , who engaging now the controller of the Sand Museum.
Most difficult engineering problem of the device is preparation of the sand.
We must use just 1 ton of sand, which was defined by glass used. Biggest diameter of the glass tube 1 meter, which was imported from Germany.
From the shape of a hour glass of the traditional shape, we can define the dimension the glass. The flow rate of the sand was 114 gram per hour. The diameter of nozzle of glass must be 0.15 millimeter. From a previous theory of powder technology, it was impossible size.
We must break the theory. We challenge the limit. After many experiment , we could break the limit.
Following are the gateways to realize one year hour glass.
1. First gateway was selection of sand We tested volcanic ashes of SAKURAJIMA, beach sand, Zircon sand, and so on. The final selection was silica sand.
2. Second gateway is small dust in the atmosphere. To prepare the sand, we use special screening machine, Gyro-sifter, which is industrial use. But, to remove the fine dust from cloth of the worker, we must developed new special screening machine.
3. The next gateway is one day hour glass. The first one day hour glass was displayed at the Science Museum, Tokyo. But the device stopped frequently when gathered many children around the device. The reason for the stop was room temperature rise of under bulb by tach of the children. I can find that this is due to the gas low (Boyle-Charles low). A small hour glass, for instance 1 minute, the effect is negligible small. As the great volume of upper and under bulb, at very small temperature change , for example 0.1 degree Centigrade, induce gas flow through the orifice, upward or downward, which induced change of the flow rate. For prevent the change, we must introduce precise automatic air pressure control system using computer.
4. Last more difficult problem was scale up from one day to 365 days.
There was a rumor that the big supplemental budget was covered by the effort of the mayor, who supported by prime minister at that time, NOBORU TAKESITA.