Retrotechtacular: Fantastic Backyard Inventions of Yore

News corporation [British Pathé] created many newsreels and documentaries throughout their 60-year history. Recently, the company released scores of films from their archives and put them on the internet. Here is a delightful collection of short films they created that highlight strange and wonderful inventions in various fields, including transportation and communication.

One of the standout inventions is the Dynasphere, a mono-wheeled vehicle that probably deserves its own week in the Retrotechtacular spotlight. There are a couple of pedal-powered planes that may have inspired the Gossamer Condor, and a hover scooter that resembles an air hockey striker and doubles as a leaf blower. In another film, a man drives a Vespa to the banks of the Thames and parks it. He pulls a fin down from each side of the scooter, turning it into a seafaring craft. When he snaps his fingers, a cute girl appears from somewhere just outside the frame. She climbs on the back, and they take off across the water.

The average running time of these films is about two minutes. Some of them are much shorter, prompting many questions. Fortunately, most of the video descriptions have links with more information about these marvelous inventions. Almost all of the inventors in these films show a complete disregard for safety, but nearly everyone involved seems to be having the time of their lives.

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Shedding Light on the Mechanics of Film Projection

Do you know how a film projector works? We thought we did, but [Bill Hammack] made us think twice. We have covered the Engineer Guy’s  incredibly informative videos many times in the past, and for good reason. He not only has a knack for clear explanation, the dulcet tones of his delivery are hypnotically soothing. In [Bill]’s latest video, he tears down a 1979 Bell & Howell 16mm projector to probe its inner workings.

Movies operate on the persistence of vision (POV) principle, which basically states that the human brain creates the illusion of motion from still images. If you’ve ever drawn circles and figure eights in the nighttime air with a sparkler or perused a flip book, then you’ve experimented with POV.

A film projector is no different in theory. Still images on a strip of celluloid are passed between a lamp and a lens, which project the images on to a screen. A device called a shuttle advances the film by engaging its teeth into the holes on the edge of the film and moving downward, pulling the film with it. The shuttle then disengages its teeth and moves up and forward, starting the process again.

shuttersFilm is projected at a rate of 24 frames per second, which is sufficient to create the POV illusion. A projector’s shutter inserts itself between the lamp and the lens, blocking the light to prevent projection of the film’s physical movement. But these short periods of darkness, or flicker, present a problem. Originally, shutters were made in the shape of a semi-circle, so they block the light half of the time. Someone figured out that increasing the flicker rate to 60-70 times per second would have the effect of constant brightness. And so the modern shutter has three blades: one blocks projection of the film’s movement, and the other two simply increase flicker.

[Bill] explains how the projector reads the optical soundtrack. He also delves into the mechanisms that allow continuous sound playback alongside intermittent projection of the image frames. You’ll never look at a projector the same way again.

Want to know more about optical soundtracks? Check out this Retrotechtacular that explores the subject in detail.

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Retrotechtacular: Coopering Guinness Barrels by Hand

For almost exactly 200 years, the Guinness brewery in Dublin, Ireland employed extremely skilled craftsmen to shape and construct wooden casks by hand. These men were called coopers, and plying their trade required several years of apprenticeship. The cooperage was a kind of closed society as many of the positions were passed down through generations of families. With the rise of aluminium and then stainless steel barrels in the late 1950s, the master coopers of Guinness became a dying breed.

Almost every step of the coopering process shown in this film is done without any kind of precise measurement. A master cooper like [Dick Flanagan] here needs only his eyes and his practiced judgment. His barrels start out as oak planks called ‘staves’ that have been drying in racks for at least two years. A cooper selects the staves that strike his fancy and he saws off the ends. This seems to be the only part of the process where a power tool is used.

The cooper shapes each stave by hand with axe and adze so that its ends are tapered just so. Once he has shaped enough of them to make a barrel, he arranges them in a cylinder around the inside of a metal band known as a hoop. The bound staves are steamed for half an hour to make them pliable enough for shaping.

After steaming, the splayed end of the staves are bound with wire rope to pull them close enough together that a hoop can be fitted over them. The inside of the cask is then charred with burning oak shavings, a process that seals the wood and removes its acidity. After this, the ends are sanded and the bunghole is drilled.

For each barrel, the cooper crafts a custom set of hoops. These are installed after the outside of the barrel has been shaved smooth. Finally, the heads that cap each end of the cask are made from more oak staves held together with dowel rods. This is the only time the cooper uses a tool to measure anything, and he does so to achieve the proper circumference on the heads. He bevels the edges so the heads will fit into bored-out grooves in the cask walls. Once they’re seated, the keg is ready for dark, rich stout.

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Hackaday Prize Entry: Orchestral Invention Defies Convention

Like many of us, [Laurens] likes video game music and bending hardware to his will. Armed with a Printrbot, a couple of floppy drives, and some old HDDs, he built the Unconventional Instrument Orchestra. This 2015 Hackaday Prize contender takes any MIDI file and plays it on stepper and solenoid-based hardware through a Java program.

A while back, [Laurens] won a Fubarino in our contest by using a MIDI keyboard and an Arduino to control the Minecraft environment with Legend of Zelda: Ocarina of Time songs. The Unconventional Instrument Orchestra uses that Fubarino of victory to control the steppers of two floppy drives. He only needed three pins to control the drives—one to enable, one to set the head’s direction, and one to make it step once per pulse.

If ever you’ve been around a 3D printer, you know they make music as a natural side effect. The problem is getting the printer to obey the rests in a piece of music. In order to do this, [Laurens] used his software to control the printer, essentially withholding the next command until the appropriate time in the song.

The percussive elements of this orchestra are provided by a hard drive beating its head against the wall. Since it’s basically impossible to get an HDD to do this as designed (thankfully), [Laurens] replaced the control board with a single transistor to drive the coil that moves the head.

[Laurens] has made several videos of the orchestra in concert, which are a joy all their own. Most of the visual real estate of each video is taken up with a real-time visualization of the music produced by the software. There’s still plenty of room to show the orchestra itself, song-specific gameplay, and a textual commentary crawl in 16-segment displays. Check out the playlist we’ve embedded after the break.

The 2015 Hackaday Prize is sponsored by:

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Retrotechtacular: The J-57 Afterburner Engine

The J-57 afterburner engine appeared in many airplanes of notable make, including the F-101, -102, and -103. This USAF training film shows the parts of the J-57, explains the complex process by which the engine produces thrust, and describes some maintenance and troubleshooting procedures.

The name of this game is high performance. Precision thrust requires careful rigging of the engine’s fuel control linkage through a process called trimming. Here, the engine fuel control is adjusted with regard to several different RPM readings as prescribed in the manual.

One of the worst things that can happen to a J-57 is known as overtemping. This refers to high EGT, or exhaust gas temperature. If EGT is too high, the air-fuel ratio is not ideal. Troubleshooting a case of high EGT should begin with a check of the lines and the anti-icing valve. If the lines are good and the valve is closed, the instruments should be checked for accuracy. If they’re okay, then it’s time for a pre-trimming inspection.

In addition to EGT, engine performance is judged by RPM and PP7, the turbine discharge pressure. If RPM and PP7 are within spec and the EGT is still high, the engine must be pulled. It should be inspected for leaks and hot spots, and the seals should be examined thoroughly for cracks and burns. The cause for high EGT may be just one thing, or it could be several small problems. This film encourages the user to RTFM, which we think is great advice in general.

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Retrotechtacular: The Omega Navigational System

In 1971, the United States Navy launched the Omega navigational system for submarines and surface ships. The system used radio frequencies and phase difference calculations to determine global position. A network of eight (VLF) transmitter sites spread around the globe made up the system, which required the cooperation of six other nations.

Omega’s fix accuracy was somewhere between one and two nautical miles. Her eight transmitter stations were positioned around the Earth such that any single point on the planet could receive a usable signal from at least five stations. All of the transmitters were synchronized to a Cesium clock and emitted signals on a time-shared schedule.

LOP-thumbA ship’s receiving equipment performed navigation by comparing the phase difference between detected signals. This calculation was based around “lanes” that served to divvy up the distance between stations into equal divisions. A grid of these lanes formed by eight stations’ worth of overlapping signals provides intersecting lines of position (LOP) that give the sailor his fix.

In order for the lane numbers to have meaning, the sailor has to dial in his starting lane number in port based on the maps. He would then select the pair of stations nearest him, which were designated with the letters A to H. He would consult the skywave correction tables and make small adjustments for atmospheric conditions and other variances. Finally, he would set his lane number manually and set sail.

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Legit Hack Creates TEA Laser Power by Mr. Wimshurst

It’s a bit scary what you can make with stuff found in the average household, provided you know what you’re doing. How about a TEA laser? Don’t have a high-voltage power supply to run it? Do what [Steven] of rimstar.org did, and power it with a homemade Wimshurst machine.

TEA lasers give off ultraviolet light. In order to see the beam, [Steven] aims it through a glass of water tinted with highlighting-marker juice and onto a sheet of white paper. [Steven] originally used his homemade 30kV DC power supply to light up his TEA laser. He made the laser itself from aluminium foil, angled aluminium, transparency sheets, some basic hardware components, and a 100kΩ resistor.

Although the components are simple, adjusting them so that the laser actually works is quite a feat. [Steven] says he burned holes through several transparencies and pieces of foil before getting it right. Using a Wimshurst machine to power the TEA laser takes another level of patience. It takes about 25 cranks of the static electricity-producing machine to build up enough energy to attempt lasing.

Want to make your own TEA laser, perhaps in a different configuration? [Steven]’s design was based on one of [sparkbangbuzz]’s lasers, which we covered several years ago.

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