Your RF Cafe
April 1963 Popular Electronics[Table of Contents]
People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Popular Electronics was published from October 1954 through April 1985. All copyrights are hereby acknowledged. See all articles from Popular Electronics.
Our two intrepid techno-sleuths are in college by now, but that does not keep them from applying their well-honed mystery solving skills to hometown situations while on spring break. The boys invoke the scientific method of Mr. R.R. Dibble, a New Zealand scientist, to help prove to county commissioners that a certain part of their critical infrastructure was in need of repair. An nth-generation farmer's observation was not proof enough, so indisputable empirical data would be needed. Real-life inventors and company's unique instruments are often incorporated into the Carl & Jerry series that ran for many years in Popular Electronics.
Carl and Jerry, home from college on spring vacation, had spent the beautiful warm afternoon wandering along the banks of Wildcat Creek with their transistorized tape recorder gathering a collection of spring sounds. Already stored on the little reel of tape were the gay "churlik! churlik!" of a robin, the excited cawing of a surprised crow, the "barrrump! barrrump !" of a bullfrog, the scolding trill of a piney squirrel, and the sounds the flooding creek made as it poured over rocks and sucked at the swollen buds on the willow branches dipping into its muddy waters.
Now the youths were sitting cross-legged on the floor of a rustic wooden covered bridge that spanned the creek and staring curiously up at the great hewed timbers constituting the framework of the structure. They did not have to worry about traffic through the bridge. A bad washout in the winding road leading to it had taken care of that for several days to come.
"They had some darned good engineers away back when this bridge was built," Carl offered. "It's at least seventy-five years old; yet those timbers look perfectly sound."
"That was partly the reason for the roof," Jerry explained. "It protected the weight-bearing timbers from the weather. The covered bridge also provided the traveler with shelter from a sudden shower."
"Yeah, and what a dan-dan-dandy place to rest the horse and
pitch a little woo!" Carl added with a grin. "Hey!"
he exclaimed, "am I imagining it, or did this thing shake a little?"
"Most likely it did," a voice answered from the end of the bridge. Silhouetted against the light was the lanky frame of an elderly farmer.
"I'm Clyde Butcher," he introduced himself. "I own that farm over there in the bend of the creek that has the old grist mill on it. It was my daddy's before me and his daddy's before that.
"This old bridge needs care bad," he explained, "but we can't convince the county commissioners of it. Their smart-aleck young engineer knows nothing about wooden bridges, and he just laughs when we try to tell him the bridge doesn't sound right and it doesn't feel right."
"I'm not sure I understand," Jerry said politely.
"You know that a crack in a violin will show up in the sound long before you can see it through the varnish, and a tight-rope walker can tell by the feel of the rope when something is wrong with the rigging," the old man said earnestly. "Well, just remember that I and many like me have been passing over this bridge all our lives. We know the normal sound it has when a wagon rolls across this floor, and we know it used to have a little bounce to it even when a heavy dog trotted across it. Now it doesn't sound right, and the bounce has gone out of it. The floor is sagging, too, as you can see; but that snooty engineer says it has always sagged. That's a lie. He'd like to tear the whole thing down and put in a new concrete bridge."
"That would be barbaric!" Carl exclaimed. "Only a few of these fine old bridges are left in the whole state."
"I'm glad to meet young men with a little respect for something old," Mr. Butcher said as he shook hands with the boys. "This old bridge is settling a fraction of an inch or so every day, especially during this period when the frost is going out of the ground; and unless she's given some help, she won't be here much longer."
"If you just had some evidence of this settling you could present directly to the commissioners," Jerry said thoughtfully as he stared down at the tape recorder in his lap, "maybe they'd do something."
"Maybe," the old farmer said doubtfully; "but it would have to be something simple and convincing. They know as much about engineering as a hog knows about Sunday - even less than I do."
"Could you run an a.c. line from your barn over here to the bridge to power electronic equipment we would install to record the settling of the bridge?" Jerry asked.
"Sure, but the bridge only settles a freckle every few hours. Those commissioners aren't going to sit still listening to several hours of recording."
"They won't have to. I was reading the other day that RR Dibble, a scientist at the Department of Scientific and Industrial Research at Wellington, New Zealand, had modified a household tape recorder to operate 500 times slower than normal and used it to record 'ice quakes' at Antarctica. The tape only moves about a half-inch a minute; so an 1800-foot reel of tape will last a month of continuous operation. When the tape is played back at normal speed, the very slow vibrations of a quake become audible sounds. What's more, twenty-four hours of recording can be reviewed in slightly less than three minutes."
"You lost me," the old gentleman confessed; "but if you think it will work I'm game to try it. I'll string that wire first thing in the morning."
It didn't take the boys long to drive to their laboratory in the basement of Jerry's house. Once there, they immediately set to work revamping an old discarded tape recorder they had been hoarding against just such an emergency.
"You slow down the recorder, and I'll make up a special bridge-settling transducer and an ultra low-frequency amplifier," Jerry suggested. "I think you can substitute that powerful little 4-rpm synchronous motor for the one in the recorder to get pretty close to that 1/500 speed reduction, and then you can turn down the capstan to hit it right on the nose. Brother Dibble probably didn't do it that way, but it's the quick-and-dirty method we'll use."
"Aye, aye, sir!" Carl said mockingly, starting to remove the tape recorder motor; "but how are you going to make a bridge-settling transducer?"
"We could use a sensitive accelerometer if we had one - which we don't," Jerry mused, "and no ordinary mike will work because we're not trying to detect audible frequency vibrations. We need something that will translate a single slight vertical movement into an audible sound .. What do you think of this? We'll mount a crystal phono cartridge on its side. A length of springy piano wire will be inserted in the needle chuck, and a small weight will be put on the end of the wire. The length of the wire and the amount of the weight will be such that when it's disturbed it will vibrate back and forth at a slow rate, say a couple of cycles per second. The flexing of the crystal caused by this motion will produce a low-frequency alternating voltage that can be amplified and recorded on the slow-moving tape."
"Can't see anything wrong with it," Carl admitted, "but why don't we use the amplifier in the recorder?"
"Shame on you for asking instead of thinking!" Jerry chided. "That amplifier probably starts to fall off pretty rapidly at 100 cycles per second. We need one that will do a good job on 100 cycles per minute. I intend to throw together a little direct-coupled transistorized amplifier, using both pnp and npn transistors, that will amplify right down to d.c. If we use a cheap, high output crystal cartridge, we won't need too much amplification. We'll probably have to change that recording head to a low-impedance transistor type, but fortunately I've got a spare."
Before they went to bed that night, the whole project was completed, even to testing. The slightest movement set the weighted wire to bobbing, and this put a signal on the creeping tape that came out as a quickly damped "beep" when the tape was played back on their conventional recorder.
When the boys took their equipment housed in a sturdy weather-proof box to the bridge the next morning, .they found that Mr. Butcher was as good as his word. The a.c. line was ready and waiting for them at the end of the bridge. Under the curious gaze of the farmer, they fastened the box securely to the upper timbers of the bridge near the center of the span. The recorder was plugged into the a.c. line, and ropes carrying "Keep Off" signs were stretched across both ends of the structure.
"We'll let the recorder run for forty-eight hours and then see what we've got," the boys told the farmer. "That's about all the time we'll have before heading back to school."
It that on the morning the recorder was to be picked up Carl had to drive over to a neighboring town for his father. It was almost one o'clock when he came dashing into the basement laboratory and found Jerry anxiously awaiting him.
"Boy, I'm glad to see you!" Jerry exclaimed. "Mr. Butcher chickened out on presenting our recording to the commissioners. Says he would ball things up because he knows nothing about electronics. We have a one-thirty appointment with them at the court house."
The three commissioners and the county engineer received the youths with poorly concealed smiles of amusement when the boys explained that they wanted to present evidence that the old covered bridge was settling. However, the men showed mild interest as Jerry set up the transducer on a heavy table in front of them and connected it to the slow-speed recorder.
Next, Jerry slid a single postcard under one leg of the table. Then a short endless loop of tape was placed in the recorder, the wire was allowed to come to rest, and then the card was pulled from beneath the leg. The one-hundredth of an inch of vertical movement at one corner of the table set the wire to bobbing. When it finally came to rest again, Jerry transferred the loop of tape to the normal recorder and let the commissioners hear the beep of sound produced by the slight vertical movement of the table.
Finally, he put the tape that had been recorded in the bridge over a 48-hour period on the conventional recorder. During the six minutes it ran, beep after beep was heard, indicating that the bridge was settling a trifle every few hours. Just at the end of the recording, there was some Donald Duck quacking which sounded like nothing that had gone before.
"What's that?" one of the commissioners wanted to know.
"Oh, it's just some voice recording that got in on the end of the tape," Jerry explained hurriedly. "You wouldn't want to hear it."
"How do you know we wouldn't?" the commissioner said suspiciously. "Can you make it understandable?"
"I probably could by playing the tape at a slower speed," Jerry admitted with obvious, very obvious, reluctance.
"Well, do it then," the commissioner snapped.
Jerry switched the recorder from 7 1/2 ips to 1 7/8 ips, and the voices on the tape came out clearly and distinctly. Carl recognized one voice as Mr. Butcher's, and the other apparently belonged to a neighbor he had encountered in the bridge.
"Well, guess the commissioners are going to let the old bridge fall down," the first voice said.
"Seems like it," the other agreed. "Too bad some people care nothing about tradition and history. People drive hundreds of miles to take pictures of this bridge. And it means still more to folks around here. Why, half the men in the county learned to swim beneath it."
"I'm one, and you're another. What's more, I proposed to my wife inside that bridge. Seems a pity three short-sighted, bull-headed men can destroy something that means so much to folks who elected them."
"Maybe that's an idea. The election will be rolling around before we know it. Let's forget party lines, as far as commissioners go, and turn these jokers out and put in men who promise to do something about the bridge. Suppose we start right now talking it up among our neighbors and friends."
"That's a fine idea! I'll start the ball rolling at our grange meeting next Friday. Well, got to be going now. Be seeing you."
Jerry switched off the tape recorder and began collecting his equipment. Out of the corner of his eye he could see the three commissioners in a whispered colloquy.
"Hm-m-m-m !" the one who had been so insistent on hearing the voices said eventually; "boys, your scientific demonstration has been most convincing. It has convinced us that the bridge needs attention immediately. We are hereby instructing our engineer to go to the bridge at once and make a careful study to see what is needed to restore it to its original strength and condition, being careful not to impair its historical significance. As soon as we have his report, work will begin."
While the boys were loading their equipment back into the car, Jerry could feel Carl's eyes looking at him suspiciously. Finally Carl exclaimed:
"There's some hanky-panky going on here. You know audio frequencies would never record on that tape at that slow speed. Furthermore, that transducer is no mike. Finally, even if the voices did record at one-half inch per minute, you couldn't play them back at 1 7/8 inches per second and make sense. Come on; give!"
"I didn't say the voice recording was picked up by the transducer; the commish just jumped to that conclusion," Jerry said with a grin. "Actually I had Mr. Butcher and a crony record that conversation on our regular recorder when I picked up the other equipment. They did darned well without a script. I just had a hunch the commissioners might not be thoroughly convinced by scientific proof; so I decided to include a little something they would be sure to understand. "
"And you sure did! Come on; let's go tell the good news to Mr. Butcher!"
Carl & Jerry: Their Complete Adventures is now available. "From 1954 through 1964, Popular Electronics published 119 adventures of Carl and Jerry, two teen boys with a passion for electronics and a knack for getting into and out of trouble with haywire lashups built in Jerry's basement. Better still, the boys explained how it all worked, and in doing so, launched countless young people into careers in science and technology. Now, for the first time ever, the full run of Carl and Jerry yarns by John T. Frye are available again, in five authorized anthologies that include the full text and all illustrations."
Carl & Jerry Episodes on RF Cafe
- Geniuses at Work, June 1956
- Eeeeelectricity!, November 1956
- Anchors Aweigh, July 1956
- Bosco Has His Day, August 1956
- The Hand of Selene, November 1960
- Feedback, May 1956
- Abetting or Not?, October 1956
- Electronic Beach Buggy, September 1956
- Extra Sensory Perception, December 1956
- Trapped in a Chimney, January 1956
- Command Performance, November 1958
- Extracurricular Education, July 1963
- Treachery of Judas, July 1961
- The Sucker, May 1963
- Stereotaped New Year, January 1963
- The Snow Machine, December 1960
- Extracurricular Education, July 1963
- Slow Motion for Quick Action, April 1963
- Sonar Sleuthing, August 1963
- TV Antennas, August 1955
- Succoring a Soroban, March 1963
- "All's Fair --", September 1963
- Operation Worm Warming, May 1961
- The Sparkling Light, May 1962
- Pure Research Rewarded, June 1962
- The Hot Dog Case, December 1954
- A New Company is Launched, October 1956
- Under the Mistletoe, December 1958
- Electronic Eraser, August 1962
- Blubber Banisher, July 1959
- "BBI", May 1959
- Ultrasonic Sound Waves, July 1955
- The River Sniffer, July 1962
- Ham Radio, April 1955
- El Torero Electronico, April 1960
- Wired Wireless, January 1962
- Electronic Shadow, September 1957
- Elementary Induction, June 1963
- He Went That-a-Way, March1959
- Electronic Detective, February 1958
- Aiding an Instinct, December 1962
- Two Detectors, February 1955
- Tussle with a Tachometer, July 1960
- Therry and the Pirates, April 1961
- The Crazy Clock Caper, October 1960
Posted April 2, 2014