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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A Peach of a Homemade Parts Tumbler

tumbler[Chris] finds the average price of rock tumblers insulting. Almost as insulting, in fact, as prepackaged fruit salad made with Chinese peaches. While there may be little he can do about the peaches, he has given the finger to lapidary pricing by making his own tumbler on the very cheap.

Simply put, he drilled a hole in bottom of the peach vessel and then stuck a threaded rod through it. He held the rod in place with a nut and a washer. After securing the proper permits to source sand and water from his property, he put both in the jar along with some old nails that had paint and crud on them. [Chris] put the rod in the chuck of his drill and clamped the drill in his bench vise. Half an hour later, he had some nice, shiny nails. Make the jump to be amazed and entertained. If you prefer using balls, check out this homemade mill.

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Voices From the Past: Recovering Audio From Wire Recordings

wire recorder setup[Nick]‘s grandfather was quite the old school hacker. In the 1940s, he built his own wire recorder and microphone to capture everything from his children’s Chirstmas wishes to his favorite songs and programs from the radio. Only 20 or so spools have survived and were doomed to silence until [Nick] was able to find a vintage wire recorder, restore it, and feed digitized audio into Audacity.

Once he restored one of the two machines that he was able to get his hands on, [Nick] was in business. Since his grandfather also rolled his own spools, [Nick] had to build a playback spindle that would hold them. His uncle found an old mechanical counter to do the job, which [Nick] secured to the workbench. He fed the output from the wire recorder’s playback head into a guitar pre-amp, effectively digitizing the audio for recording in Audacity.

After playing all the spools, he adjusted the levels where necessary and cleaned up the recordings. His biggest challenge was feeding the wires back on to their original spools, which he managed with an electric drill and a rubber grommet. Be sure to check out the mp3 clips on [Nick]‘s page. If you’re in the mood for old audio hacking stories, here’s one about building a tape recorder in 1949.

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...]

RFID Audio Book Reader For the Visually Impaired

RFID audio book reader

When [Willem] visited home last year, he stopped in at his grandparents’ house and found that his very active 93-year-old grandfather had recently gone almost completely blind and was passing the days just sitting in a chair. [Willem] suggested that he listen to audio books, but his grandfather wasn’t receptive to the idea until [Willem] convinced him that the well-narrated ones can be very gripping and entertaining. Once his grandfather was on board, [Willem] knew that he needed a much more accessible solution than a tiny device with tiny controls, so he built an RFID audio reader using a Raspberry Pi.

[Willem] has posted the build details at his personal site. Essentially, the box you see above contains a Raspi and an RFID reader. He created different ‘books’ by placing RFID cards inside of DVD boxes, which makes them more tangible and accessible. When a book is placed on the box, the RFID reader tells the Pi which mp3 files to load. The large colored buttons let the user pause, rewind 20 seconds, and control the volume.

We love to see this kind of build. It’s simple, effective, and greatly enhances the user’s quality of life. [Willem]‘s grandfather loves it and uses it every day.

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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Dampen Workshop Noise with Paper Pulp and Kool-Aid — OH YEAH!

noise dampener

If you’re fortunate enough to have a garage and a workshop, you probably also have neighbors. The truly blessed must work within the confines of an HOA that restricts noise, porch couches, and most types of fun. [Mike] is among the truly blessed, and when he decided to design a cabinet for his CNC equipment, he took noise dampening into consideration.

[Mike]‘s design isn’t a blanket noise dampener; it’s specifically designed for the high-pitch symphony of his router, compressor, and vacuum. He also sought to avoid vibrating the cabinet. To achieve this, the sound-dampening panels are hung on eye hooks with a 1/2″ gap between them and the frame. The backer boards are cut from 3/4″ plywood. [Mike] considered using cement board, but thought it might be overkill since he plants to shell the cabinet in a layer of 3/4″ plywood.

The deadening material is paper pulp made from various shredded papers. After soaking the shreds in water and blending the mixture to an oatmeal consistency, he drained most of the water through a cloth bag. Then he added just enough wood glue to hold the pulpy goo together. The tropical punch Kool-Aid powder isn’t just for looks; it provides visual confirmation of even glue distribution.

[Mike] made some tape walls around the edge of his backer boards to hold the mixture in place and painted on some wood glue to hold the pulp. He spread the tropical concoction to 1/2″ thickness with a tiling trowel to avoid compressing it. The peaks and valleys help scatter any sound that isn’t absorbed. Pudding awaits you after the jump.

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