Retrotechtacular: Turn On the Magic of Colored Light

title cardChances are, you take color for granted. Whether or not you give it much thought, color is key to distinguishing your surroundings. It helps you identify fire, brown recluse spiders, and the right resistor for the job.

In the spotlight this week is a 1950s educational film called “This is Color“. It also happens to be a delightful time capsule of consumer packaging from the atomic age. This film was made by the Interchemical Corporation, an industrial research lab and manufacturer of printing inks. As the narrator explains, consistent replication of pigments is an essential part of mass production. In order to conjure a particular pigment in the first place, one must first understand the nature of color and the physical properties of visible light.

electromagnetic spectrumEach color that makes up the spectrum of visible rays has a particular wavelength. The five principal colors—red, yellow, green, blue, and violet—make possible thousands of shades and hues, but are only a small slice of the electromagnetic spectrum.

When light encounters a transparent material more dense than air, such as water or glass, it has to change direction and is bent by the surface. This is known as refraction. A straw placed in a glass of water will appear bent below the surface because the air and the water have different refractive indices. That is, the air and water will bend or refract different percentages of the light that permeates them. Continue reading “Retrotechtacular: Turn On the Magic of Colored Light”

Retrotechtacular: Forces Acting On An Airfoil

floating film title We’ve probably all experimented with a very clear demonstration of the basic principles of lift: if you’re riding in a car and you put your flattened hand out the window at different angles, your hand will rise and fall like an airplane’s wing, or airfoil. This week’s Retrotechtacular explains exactly how flight is possible through the principles of lift and drag. It’s an Army training documentary from 1941 titled “Aerodynamics: Forces Acting on an Air Foil“.

What is an airfoil? Contextually speaking, it’s the shape of an airplane’s wing. In the face of pressure differences acting upon their surfaces, airfoils produce a useful aerodynamic reaction, such as the lift that makes flight possible. As the film explains, the ideas of lift and drag are measured against the yardstick of relative wind. The force of this wind on the airfoil changes according to the acute angle formed between the airfoil and the direction of the air flow acting upon it. As you may already know, lift is measured at right angles to the relative wind, and drag occurs parallel to it. Lift is opposed by the weight of the foil, and drag by tension.

wind tunnel testing

Airfoils come in several types of thicknesses and curvatures, and the film shows how a chord is derived from each shape. These chords are used to measure and describe the angle of attack in relation to the relative wind.

The forces that act upon an airfoil are measured in wind tunnels which provide straight and predictable airflow. A model airplane is supported by wires that lead to scales. These scales measure drag as well as front and rear lift.

In experimenting with angles of attack, lift and drag increase toward what is known as the stalling angle. After this point, lift decreases abruptly, and drag takes over. Lift and drag are proportional to the area of the wing, the relative wind velocity squared, and the air density. When a plane is in the air, drag is a retarding force that equals the thrust of the craft, or the propelling force.

monometer tubesAirfoil models are also unit tested in wind tunnels. They are built with small tubes running along many points of the foil that sit just under the surface. The tubes leave the model at a single point and are connected to a bank of manometer tubes. These tubes compare the pressures acting on the airfoil model to the reference point of atmospheric pressure. The different liquid levels in the manometer tubes give clear proof of the pressure values along the airfoil. These levels are photographed and mapped to a pressure curve. Now, a diagram can be made to show the positive and negative pressures relative to the angle of attack.

In closing, we are shown the effects of a dive on lift as an aircraft approaches and reaches terminal velocity, and that lift is attained again by pulling slowly out of the dive. Remember that the next time you fly your hand-plane out the window.

Continue reading “Retrotechtacular: Forces Acting On An Airfoil”

Retrotechtacular: The Voder from Bell Labs


This is the under-the-hood view of the keyboard for the Voder (Voice Operating Demonstrator), the first electronic device capable of generating continuous human speech. It accomplishes this feat through a series of keys that generate the syllables, plosives, and affricatives normally produced by the human larynx and shaped by the throat and tongue. This week’s film is a picture montage paired with the audio from the demonstration of the Voder at the 1939 World’s Fair.

The Voder was created by one [Homer Dudley] at Bell Laboratories. He did so in conjunction with the Vocoder, which analyzes human-generated speech for encrypted transfer and re-synthesizes it on the other end. [Dudley] spent over 40 years researching speech at Bell Laboratories. His development of both the Voder and the Vocoder were instrumental in the SIGSALY project which aimed to deliver encrypted voice communication to the theatres of WWII.

Continue reading “Retrotechtacular: The Voder from Bell Labs”

Retrotechtacular: We Heard You Like Tubes, So Here’s a Film About Tube Tubes from the Webtubes


This lovely little number is the EF80 pentode thermionic valve, or vacuum tube, made by Mullard beginning in 1950. They were used in radio and radar applications, but most of them wound up in VHF television sets. This week’s Retrotechtacular takes a close look at the assembly of and on-site materials production for the EF80 in particular.

The film begins with slow and careful hand assembly of an EF80. The cathode is inserted into a mica disc, and a series of three grids are placed over the cathode. The semicircular anode sits around the outermost grid. Another mica disc is placed on top which does triple duty as a spacer, a base for the getter/plate assembly, and a firewall against the getter flash.The dark lining of the upper part of the tube is the residue of the vaporized getter, which is heated after the first stage of air removal.

Before the vacuuming begins, the inner assembly is mounted on a glass base with nine pins that have been pre-bent to meet the inner assembly wires. The heater, dissipating shield, and a meshy cylinder are added, and then the getter on its plate. A tube is slipped over the assembly and fused to the base in a jig, forming an airtight seal. Continue reading “Retrotechtacular: We Heard You Like Tubes, So Here’s a Film About Tube Tubes from the Webtubes”

Retrotechtacular: Designing and Building RCA Televisions

waveformWhile it’s almost cliché to say they don’t make things like they used to, this week’s Retrotechtacular offers fairly conclusive proof that, at the very least, they used to put more time and effort into manufacturing consumer electronics. Gather your homemade wisecrackin’ robots and settle in front of this 1959 film entitled “The Reasons Why”, a rah-rah film created for new employees of the RCA Victor television division.

It may open with a jingle, but things quickly turn serious. Quality is no laughing matter for the men and women devoted to bringing you the best television set for your money. This type of unmatched excellence begins with tireless R&D into improving sound and picture quality. Every transformer is tested at five times the rated voltage, and every capacitor at two times the rating. Every switch undergoes a series of mechanical tests, including a pressured steam bath to ensure they will hold up even if you drag your set out to the porch some unbearably hot deep South August night.

hot august nights

Cabinet design is just as important—what’s the use in housing a chassis and kinescope that’ll last for 60 years in some cheap box? Woods from all over the world are carefully considered for their beauty and durability. A television set is, after all, the centerpiece of the American family room furniture group. These carefully selected woods are baked in a series of ovens to prove they’ll stand up to hours of continuous use.

Continue reading “Retrotechtacular: Designing and Building RCA Televisions”

Retrotechtacular: We’re Gonna Have Manual Transmissions the Way My Old Man Told Me!

archimedesSimple machines are wonderful in their own right and serve as the cornerstones of many technological advances. This is certainly true for the humble lever and the role it plays in manual transmissions as evidenced in this week’s Retrotechtacular installment, the Chevrolet Motor Company’s 1936 film, “Spinning Levers”.

This educational gem happens to be a Jam Handy production. For you MST3K fans out there, he’s the guy behind shorts like Hired! from the episodes Bride of the Monster and the inimitable Manos: The Hands of Fate. Hilarity aside, “Spinning Levers” is a remarkably educational nine-ish minutes of slickly produced film that explains, well, how a manual transmission works. More specifically, it explains the 3-speed-plus-reverse transmissions of the early automobile era.

It begins with a nod to Archimedes’ assertion that a lever can move the world, explaining that the longer the lever, the better the magic. In a slightly different configuration, a lever can become a crank or even a double crank. Continuous motion of a lever or series of levers affords the most power for the least work, and this is illustrated with some top-drawer stop motion animation of two meshing paddle wheels.

gearsNext, we are shown how engine power is transferred to the rear wheels: it travels from a gear on the engine shaft to a gear on the drive shaft through gears on the countershaft. At low speeds, we let the smallest gear on the countershaft turn the largest gear on the drive shaft. When the engine is turning 90 RPM, the rear wheel turns at 30 RPM. At high speeds using high gears, the power goes directly from the engine shaft to the drive shaft and the RPM on both is equal. The film goes on to explain how the gearbox handles reverse, and the vast improvements to transmission life made possible through synchromesh gearing.

Continue reading “Retrotechtacular: We’re Gonna Have Manual Transmissions the Way My Old Man Told Me!”

Retrotechtacular: AT&T’s Hello Machine

1ESSHow many Ma Bell employees does it take to build an ESS mainframe? This week, Retrotechtacular takes you into the more poetic recesses of the AT&T Archive to answer that very question. This wordless 1974 gem is an 11-minute exploration of the construction and testing of a Western Electric 1ESS. It begins with circuit board population and ends with lots of testing.




The film is really quite groovy, especially the extreme closeups of wire wrapping and relay construction. The soundtrack is a string-heavy suite that moves you through the phases of bringing up the 1ESS while drawing parallels to the wires of communication. You may lose count of the punch down blocks and miles of cables, but there are surprisingly few mustaches.

Continue reading “Retrotechtacular: AT&T’s Hello Machine”