Monthly Archives: May 2017

Science Fair Idea: How Lightning Rods Work

1937MayPS

For today’s science fair idea, we go back 80 years to find this idea from the May 1937 issue of Popular Science. Junior can demonstrate how lightning rods protect a building from fire caused by lightning. If the teacher insists that Junior answer a question, then he can use the experiment to answer the question, “do lightning rods protect buildings from fire?” Hopefully, Junior will discover that they do. But in the process, he gets to set fire to a paper model of a house using high voltage electricity.

The pictures should be self-explanatory.  At the left, the spark is being applied directly to the model house, which quickly bursts into flame after the simulated lightning bolt strikes.  At right, the structure is protected by a lightning rod, which safely carries the current to ground.

To generate the spark, the magazine recommends a “neon-sign transformer or a spark coil.”  If you don’t have a spark generating device around the house, the Internet is full of plans.  If you’re in a hurry, you can just purchase this Tesla coil at Amazon, and get the best of both worlds.  Junior doesn’t have to build the coil, but he did build the lightning rod, so he did the work to prove his hypothesis.  As a bonus, he gets sparks, flames, and smoke.  The teacher will certainly be impressed, and Junior will come home with a blue ribbon.

The decorations on the house are a nice touch, but are optional.



1927 Balloon Jumping

1927MayPMNinety years ago this month, the cover of Popular Mechanics, May 1927, shows a sport that inexplicably never caught on:   Balloon Jumping! As described in the magazine, a balloon of about 18 feet in diameter was attached to the jumper’s shoulders. In his pockets, he would carry lead weights. The balloon and ballast would be balanced so that the man’s net weight was about four pounds. Thus equipped, the jumper could leap to a height of about 40 feet and travel about a hundred yards. In favorable wind conditions, jumpers were known to travel over a quarter mile in one stride.

The balloon was filled with 3500 cubic feet of gas. In the event that the gas expanded in the hot sun, the balloon was fitted with a valve, allowing the jumper to vent excess gas, preventing uncontrollable lift.

After the jump was complete, the complete outfit could be packed into a large suitcase.

This video shows the sport in action, although it doesn’t look quite as graceful as depicted in the magazine:



Training Wireless Operators, 1917

1917MayPMA hundred years ago this month, the May 1917 issue of Popular Mechanics showed this image of woman students at Hunter College, New York.  The women were looking forward to the possibility of wartime labor shortages that would allow them to serve the government as wireless operators.



Fall of Corregidor, 1942

Japanese landing on Corregidor. Wikipedia image.

On this day 75 years ago, May 6, 1942, the island of Corregidor fell to the Japanese, not to be recaptured until 1945.

After the fall of Bataan on April 9, only the heavily defended island of Corregidor stood between the Japanese and control of Manila harbor.  In the first months of the war, the island was under aerial attack, and on May 5, Japanese landing craft began their assault. On May 6, General Johnathan M Wainwright sent a message to President Roosevelt, “There is a limit of human endurance, and that point has long been passed.”



Marine Direction Finding, 1957

1957MayPE

The mariner shown here 60 years ago on the cover of the May 1957 issue of Popular Electronics is demonstrating two methods of radio navigation described in the magazine, using a National NC-66 receiver and its optional external loop antenna.

Using the receiver alone, she is using the method that required no special direction finding antenna, and that provided accurate results even in a small bouncing boat.

That method used the “A-N” longwave radio ranges which were still operating between 200-400 kHz. While these aeronautical radio ranges were most often used by pilots, there was no reason why they couldn’t be used by boaters, as long as the craft had a longwave receiver aboard.

As we described in an earlier post, each of these beacons transmitted two signals in a four-leaf clover pattern. In two quadrants, the Morse letter A (dot-dash) could be heard. In the other two quadrants, the letter N (dash-dot) could be heard. At the intersections of the two signals (“on the beam” normally followed by pilots), the signals would merge and be continuous.

1957MayPE2For example, a boater shown at the position marked 1 near the bottom of this map would first tune to 227 kHz to beacon HEM at Mitchell Field, Long Island. She would hear the A. Then, she would tune to 248 to listen to the beacon IDL at Idlewild and hear the N. Finally, she could tune in EWR Newark on 341 kHz, where N would be heard.

By consulting the chart and using the process of elimination, this would narrow her location down to the relatively small quadrangle off the New Jersey coast.

The magazine also described the next logical step in navigation skill as use of the optional loop antenna and null meter shown at the top of the picture.  As we’ve described previously, such an antenna would allow an exact bearing to any station, using either a marine beacon or standard AM broadcast station.



1937 Electronic TV Receiver

1937MayRadioNews

Eighty years ago this month, the May 1937 issue of Radio News carried an ambitious construction project, this television receiver. TV receivers had been popular projects in earlier radio magazines, but the earlier ones were all mechanical televisions, employing a spinning Nipkow disk.

This set was all electronic, employing a cathode ray tube.  The construction article did not have an individual byline.  Instead, it was attributed only to “the Don Lee Television Staff,” referring to the Los Angeles broadcaster and licensee of W6XAO.

W6XAO image taken off the air.

W6XAO image taken off the air.

The plans for this set were also included in other magazines, and the broadcaster also made it available in kit form.

While the receiver was all electronic, it appears that the camera was still a mechanical device.  A spinning disk was used to produce a flying spot to convert previously filmed footage to a video signal.  Shortly thereafter, the station appears to have adopted an electronic camera.

The set, including both RF and video sections, contained a total of 14 tubes in addition to the CRT.  It did not contain an audio section.  Presumably, accompanying audio was received on a separate radio receiver.



WW2 Japanese-American Internment

Manzanar Internment Camp. WPA/NPS image.

Manzanar Internment Camp. NPS image.

The following order was issued 75 years ago today.

Western Defense Command and Fourth Army Wartime Civil Control Administration, Presidio of San Francisco, California

May 3, 1942

Instructions to All Persons of Japanese Ancestry Living in the Following Area:

All of that portion of the County of Alameda, State of California, within the boundary beginning at the point where the southerly limits of the City of Oakland meet San Francisco Bay; thence easterly and following the southerly limits of said city to U.S. Highway No. 50; thence southerly and easterly on said Highway No. 50 to its intersection with California State Highway No. 21; thence southerly on said Highway No. 21 to its intersection, at or near Warm Springs, with California State Highway No. 17; thence southerly on said Highway No. 17 to the Alameda-Santa Clara County line; thence westerly and following said county line to San Francisco Bay; thence northerly, and following the shoreline of San Francisco Bay to the point of Beginning.

Pursuant to the provisions of Civilian Exclusion Order No. 34, this Headquarters, dated May 3, 1942, all persons of Japanese ancestry, both alien and non-alien, will be evacuated from the above area by 12 o’clock noon, P. W. T., Sunday, May 9, 1942.

No Japanese person living in the above area will be permitted to change residence after 12 o’clock noon, P. W. T., Sunday, May 3, 1942, without obtaining special permission from the representative of the Commanding General, Northern California Sector, at the Civil Control Station located at:
920 “C” Street,
Hayward, California.

Such permits will only be granted for the purpose of uniting members of a family, or in cases of grave emergency.

The Civil Control Station is equipped to assist the Japanese population affected by this evacuation in the following ways:

  1.  Give advice and instructions on the evacuation.
  2.  Provide services with respect to the management, leasing, sale, storage or other disposition of most kinds of property, such as real estate, business and professional equipment, household goods, boats, automobiles and livestock.
  3.  Provide temporary residence elsewhere for all Japanese in family groups.
  4.  Transport persons and a limited amount of clothing and equipment to their new residence.

The Following Instructions Must Be Observed:

  1. A responsible member of each family, preferably the head of the family, or the person in whose name most of the property is held, and each individual living alone, will report to the Civil Control Station to receive further instructions. This must be done between 8:00 A. M. and 5:00 P. M. on Monday, May 4, 1942, or between 9:00 A. M. and 5:00 P. M. on Tuesday, May 5, 1942.
  2. Evacuees must carry with them on departure for the Assembly Center, the following property:
    (a) Bedding and linens (no mattress) for each member of the family;
    (b) Toilet articles for each member of the family;
    (c) Extra clothing for each member of the family;
    (d) Sufficient knives, forks, spoons, plates, bowls and cups for each member of the family;
    (e) Essential personal effects for each member of the family.
    All items carried will be securely packaged, tied and plainly marked with the name of the owner and numbered in accordance with instructions obtained at the Civil Control Station. The size and number of packages is limited to that which can be carried by the individual or family group.
  3. No pets of any kind will be permitted.
  4. No personal items and no household goods will be shipped to the Assembly Center.
  5. The United States Government through its agencies will provide for the storage, at the sole risk of the owner, of the more substantial household items, such as iceboxes, washing machines, pianos and other heavy furniture. Cooking utensils and other small items will be accepted for storage if crated, packed and plainly marked with the name and address of the owner. Only one name and address will be used by a given family.
  6. Each family, and individual living alone, will be furnished transportation to the Assembly Center or will be authorized to travel by private automobile in a supervised group. All instructions pertaining to the movement will be obtained at the Civil Control Station.

Go to the Civil Control Station between the hours of 8:00 A. M. and 5:00 P. M., Monday, May 4, 1942, or between the hours of 8:00 A.M. and 5:00 P. M., Tuesday, May 5, 1942, to receive further instructions.
J. L. DeWITT
Lieutenant General, U.S. Army
Commanding



Ice Cream Goes to War: 20 Flavors

1942May2ChiTrib

During World War II, the War Production Board (WPB) had sweeping powers to control the U.S. economy. The idea was to make sure that U.S. industry was geared up as completely as possible for war production, and no industry was exempt.

In many cases, such as in the radio industry, the restrictions, while draconian, at least made a certain amount of sense. For example, the production of civilian radio receivers was banned during the war, so that the entire output of U.S. electronics factories could be devoted to the war effort.

But it also appears clear that there was a desire to regulate simply for the sake of regulating. As we previously reported, the sale of sliced bread was banned for a time, until consumer objections caused the WPB to relent.

And just like bread, ice cream went to war.  75 years ago today, the May 2, 1942, issue of the Chicago Tribune shown here shows how the dairy industry was affected. Cardboard packaging was not allowed for butter packages of less than a pound. But as the headline notes, the most noticeable regulation related to ice cream.

For the duration of the war, ice cream manufacturers were limited to twenty (20) flavors. Similar restrictions were imposed on ice cream novelty items.

Probably more significant for the manufacturers was the requirement that distribution could be made only by common carriers. In other words, the manufacturer was prohibited from running its own fleet of trucks.



1942 One Tube Emergency Broadcast Receiver

1942MayPMSeventy-five years ago this month, the May 1942 issue of Popular Mechanics carried the plans for the “Veep” one-tube AC-DC broadcast receiver. The set was built on a simple galvanized chassis, and mounted in a cigar box, the “Veep” name coming from the brand of cigars.

The sew was designed to be rugged and compact, and the part count was kept to an absolute minimum to keep costs down. The set ran off standard household current, eliminating the worry of batteries running down. It was designed for instant emergency use. The set could be kept in a pocket, and in case of need for the latest news, air-raid warnings, or other programs, it ccould be put into action at the plant, office, or home at odd times.

The set used a single 117L7-GT serving as rectifier and detector. Since the set ran right off the line cord, the article warned not to use an external ground connection.

1942MayPM2The set would pull in local stations with a 3-4 foot antenna. For greater range, the antenna could be connected to an ungrounded metal object such as a hand rail or bed springs. While the set was designed for headphone operation, it could drive a speaker for strong local stations.1942MayPMSchematic