If Junior is looking for a spectacular science fair project that can be built at little expense, but still uses a slightly dangerous chemical, he can’t go wrong building this real submarine, according to plans contained in the August 1940 issue of Popular Science.

When released in the local pond, the submarine repeatedly submerges and surfaces, all the time moving forward in the water. The secret of all of this is a small amount of calcium carbide, the same chemical used in old-fashioned miner’s lamps. When the chemical is exposed to water, it generates a high pressure gas, which is used to propel the vessel and provide buoyancy. The chemical is readily available at Amazon, and probably at your friendly local hardware store.

School will eventually reopen, so your young submariners can take advantage of their summer vacation to build and test the craft, which can be made out of scraps of sheet metal and tin cans. Soldering is required, but kids naturally enjoy working with molten lead. When school reopens and the science fair is on, the submarine can be used for a variety of scientific experiments involving buoyancy, propulsion, or chemical reactions. The teacher has probably seen old movies with miners wearing headlamps, but this will probably be their first exposure to the actual chemical used. A blue ribbon is almost guaranteed.

The young man shown here is probably getting ready to collect his first Social Security check, but fifty years ago, he undoubtedly took home the blue ribbon at the 1970 Science Fair. His project was shown in the August-September 1970 issue of Science and Electronics. According to the magazine, the project would show off knowledge and understanding, but would also require dexterity with tools.

The project was a moving-coil ammeter, not unlike a commercially made meter movement. While the magazine didn’t use the moniker, this type of meter is also commonly known as a d’Arsonval meter movement, after Jacques-Arsène d’Arsonval. For less advanced students, the article referred back to construction articles for some more primitive meters, such as the hot-wire ammeter we previously profiled. Most of the meter’s mechanical parts were made of wood, so the project required some expertise in the wood shop. The form for the moving coil was made with balsa wood, whose light weight ensured a sensitive movement.

The finished product could be accurately calibrated by using a commercial VOM, a battery, and a potentiometer. Current readings were noted on the commercial meter, and then marked on the face of the homemade meter.

According to the article, if the builder used reasonable care and followed instructions, they would be assured of a good grade and congratulations from friends and teachers.  And fifty years later, there’s no reason to think the result would be any different.