Retrotechtacular: The Diesel Story

title cardThe diesel engine was, like many things, born of necessity. The main engine types of the day—hot bulb oil, steam, coal gas, and gasoline—were not so thermally efficient or ideal for doing heavy-duty work like driving large-scale electrical generators.  But how did the diesel engine come about? Settle in and watch the 1952 documentary “The Diesel Story“, produced by Shell Oil.

The diesel engine is founded on the principle of internal combustion. Throughout the Industrial Age, technology was developing at breakneck pace. While steam power was a great boon to many burgeoning industries, engineers wanted to get away from using boilers. The atmospheric gas engine fit the bill, but it simply wasn’t powerful enough to replace the steam engine.

hot bulb oil engineBy 1877, [Nikolaus Otto] had completed work on his coal gas engine built on four-stroke theory. This was the first really useful internal combustion engine and the precursor of modern four-stroke engines. It was eventually adapted for transportation with gasoline fuel. In 1890, the hot bulb oil engine was developed under the name Hornsby-Akroyd and primarily used in stationary power plants. Their flywheels had to be started manually, but once the engine was going, the bulb that drove combustion required no further heating.

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Retrotechtacular: The CURTA Mechanical Calculator

CURTA mechanical calculatorThe CURTA mechanical calculator literally saved its inventor’s life. [Curt Herzstark] had been working on the calculator in the 1930s until the Nazis forced him to focus on building other tools for the German army. He was taken by the Nazis in 1943 and ended up in Buchenwald concentration camp. There, he told the officers about his plans for the CURTA. They were impressed and interested enough to let him continue work on it so they could present it as a gift to the Führer.

This four-banger pepper mill can also perform square root calculation with some finessing. To add two numbers together, each must be entered on the digit setting sliders and sent to the result counter around the top by moving the crank clockwise for one full rotation. Subtraction is as easy as pulling out the crank until the red indicator appears. The CURTA performs subtraction using nine’s complement arithmetic. Multiplication and division are possible through successive additions and subtractions and use of the powers of ten carriage, which is the top knurled portion.

Operation of the CURTA is based on [Gottfried Leibniz]‘s stepped cylinder design. A cylinder with cogs of increasing lengths drives a toothed gear up and down a shaft. [Herzstark]‘s design interleaves a normal set of cogs for addition with a nine’s complement set. When the crank is pulled out to reveal the red subtraction indicator, the drum is switching between the two sets.

Several helper mechanisms are in place to enhance the interface. The user is prevented from ever turning the crank counter-clockwise. The crank mechanism provides tactile feedback at the end of each full rotation. There is also a lock that disallows switching between addition and subtraction while turning the crank—switching is only possible with the crank in the home position. There is a turns counter on the top which can be set to increment or decrement.

You may recall seeing Hackaday alum [Jeremy Cook]‘s 2012 post about the CURTA which we linked to. A great deal of information about the CURTA and a couple of different simulators are available at Make the jump to see an in-depth demonstration of the inner workings of a CURTA Type I using the YACS CURTA simulator.

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Retrotechtacular: There’s More Than One Way to Escape a Submarine

submarine escape title cardAnd this 1953 United States Navy training film describes two ways to do so: collective escape via rescue chamber, and individual escape using SEAs.

The film first follows a fellow named [Baxter] and his men in the aft torpedo room.  His sub has failed to surface as scheduled. There are no officers present at the time of distress, so [Baxter, Torpedoman First] is in charge. His first directive is that [Johnson] extinguish his Chesterfield. There’ll be time enough for smoking on the rescue ship, [Johnson].

[Baxter] releases a marker buoy because it is daytime and the weather is fair. Had other conditions prevailed, [Baxter] would send up flares and bang on the hull to provide a sonic beacon for rescuers. Next, he checks the forward compartments. If they are clear, he leaves the hatches open to give his men more air. He checks the air purity and engages [Brooklyn] to pull down some COabsorbent.

[Baxter] and his men will be okay for a while. They have plenty of drinking water, food, juice, supplemental oxygen, and COabsorbent. Their best move is to take it easy and wait for the rescue chamber. That way, they’ll avoid drowning, exposure, and COpoisoning.

Elsewhere in the forward torpedo chamber, there’s a chlorine leak and it can’t be stopped. These nameless sailors have to work quickly to escape the noxious gas. First, they pass around the SEAs and turn them into respirators. Soda lime will filter out the chlorine gas from their lungs and eyes. They too will release a marker buoy, but the first order of business is to move to the escape trunk.

Communicating through gestures, the lead man assigns three men to break out the life raft. The men move to the trunk with the buoy, raft, ascending line, and a divers’ knife. They also take a battle lantern, hand tools, and spare SEAs, but leave their shoes behind. After equalizing the pressure in the trunk, they can get going on their escape. They open the hatch, float the buoy, and tie it off. Now the raft can be floated up the buoy line. Since they are 100 feet down, they send a man every ten seconds up the buoy line and he is to move approximately one foot per second. First man to surface inflates the raft, and Bob’s your uncle. Now, they just have to prevent sunburn and tell stories until the rescue ship finds them.

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Retrotechtacular: Time For Coffee

coffee fruitIf you ask us, it’s almost always a good time for coffee. In the spotlight this week is an educational/promotional film made by A&P, who started in the 1800s as with a chain of shops offering coffee and tea. By the 1950s, they were operating full self-serve grocery stores with a trail of shuttered mom and pop operations in their wake.

This is the story of coffee as it goes from the nursery to the field to the shelves of your local A&P. It covers the growing, cultivation, and distribution of coffee from South American crops that at the time covered more than one million square miles of Brazil alone.

Coffee trees leave the nursery at two years old and are planted in nutrient-rich red soil. Two to three years later, they bear their first crop. Coffee blossoms appear first, and the fruit ripens over the next 8-9 months. Skilled workers pick the berries by hand. We are told that the average tree produces one pound of roasted coffee per year.

sun dried beansThe day’s harvest is collected, weighed, and bagged for further production. The fruits are crushed to remove each bean from its red jacket. Then, the beans are washed and spread out in the sun for 8-10 days. They are frequently rotated so they dry evenly. The dried coffee is packed in bags and sent into the city.

bag stabbingAt a warehouse, the coffee is inspected, sorted, and graded. Bags are stamped with the coffee’s country of origin and intended destination before going to the seaport. A very important step happens here. As each bag walks by on the shoulders of a worker, another guy stabs it to get a sample of the beans. The on-site A&P officials take over at this point and do their own inspections, sending samples to the US. Here, the coffees are roasted and taste tested for both strength and flavor from a giant lazy Susan full of porcelain cups. taste testing

The film takes a brief detour to tell us that the great cities of Latin America were built upon the labors of coffee exportation. We see a montage of vistas, skylines, and shorelines, which bring it back to the subject of shipping the coffee to various ports of call. At the dock, bags are tumbled onto large nets to be loaded on the ship. As coffee is susceptible to moisture, special care is taken to avoid the ill effects of traveling out of the tropics.

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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. [Read more...]

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.

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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.

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