Click. Click. The two clicks that you hear when pressing the top button on a retractable ballpoint ‘click pen’ are a key to understanding the mechanics happening inside of it: A rotation, extension, and lock of the spring-loaded ink cartridge, pushing the ballpoint tip into place outside of the casing. The two clicks that follow, the sound of pressing the button a second time, rotates and retracts the tip. How exactly does this ubiquitous writing tool work?
Bill [Hammack] details the key engineering principles underlying plastic injection molding. He describes its history and then reveals the intricate details of the process. He shows viewers where to found, on any injection-molding product, the markings created by injection molding. He closes with a description of the one of the finest examples of the injection molding: the Lego brick.
What do astronauts dream of? How do they feel while they float above the clouds? In 1991 Helen Sharman became the first Briton in space; in this animation, hand-drawn by Ri animator-in-residence Andrew Khosravani, Sharman shares a dream she often has about returning to space, and talks about what it’s like to gaze down on the earth from above.
The first generation of American children to have grown up on Miyazki films - My Neighbor Totorowas released in the States in 1993 - has entered their college years. A portion of them will have eagerly sought out his latest offering, a semi-autobiographical tale directed by his son, Goro. Some will have felt themselves too mature for such fare. Being college students, both groups are likely to be horking down a fair amount of cheap packaged ramen noodles.
As evidenced above, Miyazaki has some pretty specific ideas on what to do with those. Preparing a late night workplace dinner for his Spirited Away team, the great director rivals Good Fellas' sliced garlic maven Paul Sorvino for culinary sang-froid. Stuffing ten blocks of the stuff into a single pot might get an ordinary mortal voted off of Top Chef, but aside from that Miyazaki's staff meal is an excellent, instant tutorial for those interested in souping up low budget, collegiate cuisine.
Why do ‘leaves on the line’ cause train delays, especially in autumn? The serious danger comes from a series of physics challenges: Leaves are sucked onto the tracks by the fast moving trains. The train wheels crush them into a slimy black pulp, releasing leaf oils that lessen friction. Mixed with rain, this super thin lubricant becomes more slippery than soapy water on the tracks.
From the BBC’s Bang Goes The Theory, Liz Bonnin demonstrates just how slippery it can get for a fast moving train (or even a not-so-fast moving train) on leaf-slimed tracks.
Here's the scenario. Leaves fall to the ground and some inevitably land on the train tracks. A train runs over the leaves and compresses them to the tracks where they stick fast due to leaf oils. More leaves fall, or get blown onto the track in the wake of the train, and the process of leaf compression and build up continues. The residue black slime that results is remarkably resilient and rainy weather only adds to the problem.
The surface becomes so slick that trains have to accelerate and decelerate much more slowly than normal in order to avoid slipping, which could cause catastrophic accidents. Many trains, if they detect some acceleration due to 'spinning' wheels, can automatically apply breaks which lock the wheels, only making the problem worse. A locked wheel sliding along a track will wear and deform along a particular side, creating a 'flat'. Damage repair can run into the tens of millions for a single season, along with the frustration of delays.
Commuter trains, with their frequent stops, are affected by this problem much more than freight trains. Often slower travel times are built into autumn timetables, much to the consternation of commuters.
So what's happening here? Time for a bit of mid-week physics!
Trains rely on maintaining a rolling, not sliding, movement along the tracks, in order to avoid uneven wear on the wheels. To prevent the wheels from sliding, static friction between the steel train wheel and the steel track is needed. Normally as the train moves forward, the point at which the wheel touches the track at any given moment is stationary and not slipping, balanced exactly by the static friction force and the force applied to the wheel.
A wheel rolling forwards experiences a static friction force in the same direction of motion, which counters the force driving the base of the wheel backwards, such that static contact is maintained. A slippery surface means that the applied force might exceed the maximum static friction force and the wheel will start to 'spin'.
The strength of friction between any two surfaces is characterized by the coefficient of friction, μ, and this is different depending on whether that friction is static or kinetic (sliding). Some surfaces are 'stickier' than others and have higher coefficients of friction. If a train driver wants to avoid 'spinning' the wheels, then she or he must not accelerate or decelerate too quickly. The maximum force a rolling wheel can withstand before sliding at the base is given by this equation:
This says that the maximum static friction force depends on how sticky the interface is between the wheel and the track and, on flat terrain, the weight of the train (mass times acceleration due to gravity).
What happens when slippery leaves are added to the surface of tracks? The coefficient of friction between the wheels and the track surface decreases dramatically. Determining the value of the coefficient of friction is something that has to be done experimentally, and depends on the exact material composition, amount of leaves, level of moisture, temperature, and so on.
But we can do a rough estimate:
The British train company, South West Rail, likens the slick compressed leaves on the track to a layer of teflon, creating a 'non-stick' surface.
Following this analogy, we can turn to a look-up table of friction coefficients. For dry steel on steel, as would be the case on an ideal train track, μ is between 0.5 and 0.8. But for steel on teflon, this value falls to between 0.05 and 0.2.
Let's say we have a railcar with a mass of 80,000 kg (this is roughly the mass of a fully loaded Pennsylvania regional Silverliner V). How quickly can it stop from an initial velocity of, say, 80 miles an hour without sliding?
The work required to stop the railcar is equal to its initial kinetic energy:
The kinetic energy is related to the mass of the train and its velocity, while the work done on the train is force times distance traveled:
In our case, we want to apply has much braking force as possible without actually causing the wheels to slip, so we plug in the force from the first equation:
Now we simply cancel out the mass of the train on both sides, and solve for 'd', the distance required to stop a train without sliding.
And that's it! We can already see that if a train is traveling twice as fast, then it would take four times as long to safely bring it to a halt.
(Side note: this assumes that all of the wheels of the railcar are equally capable of braking and that the weight of the train is evenly distributed over the wheels. If only some cars or engines can brake, then we cannot simply cancel our masses on either side of the equation.)
Now let's consider our leaf scenario:
On a dry, summer day with clean tracks, the coefficient of static friction might be 0.5 while on an autumnal day with lots of wet, compressed leaves on the track, the coefficient of friction might be as low as 0.05.
If the mass and initial velocity of the train are the same in both scenarios, then the stopping distance for a slippery, leafy track would be 10 times greater than on a dry, clean track. So if the train on a dry track only takes 130 meters to stop, then a train on a leafy track will take 1.3 kilometers! That's a huge difference and means train drivers tend to travel much more slowly rather than risk missing their next platform altogether.
This seasonal problem is not going away anytime soon and rail companies have tried a number of different techniques to combat the foliage problem. Of course, trimming back the actual source of the leaves along the track is an obvious solution. In the days of steam-powered trains, this was done routinely by large teams of men since grass and leaves could easily catch fire from stray sparks and coals. Today the fire risk from diesel and electric engines is minimal and the large amount of manual labor required would be hugely expensive.
Alternative methods of clearing the track tend to be more temporary. Some companies employ 'leaf buster' trains which blast the tracks with high-power jets of water, sometimes in addition to 'sandite' trains which apply a sandy paste to the tracks to increase friction. There are also passenger trains that automatically release sand when they detect wheel slippage. Even intense laser beams have been shown to effectively disintegrate and blow away the leaves, but at a high cost.
All this from a simple autumnal leaf. Next time your train is delayed by 'leaves on the line' you'll have much to ponder.
The Utt Juice Co. plant, which ran along the west side of Prospect between Main and Third streets, produced 7 million gallons of juice during the 50 years it was in operation.
C. E. Utt, who developed the San Joaquin Fruit Co. along with Sherman Stevens and James Irvine, experimented with a number of agricultural crops, citrus, peanuts, chili peppers and grapes during his lifetime, but his involvement with grapes continued for many years.
It all began when he leased property on Lemon Heights from the Irvine Co. in 1915 and planted two acres of Concord grapes. By 1918 when the vines came into production, he had more grapes than he could find a market for. His solution was to start making grape juice at home, using the back porch for his kitchen. When he had more juice than his family could consume, he bottled the excess and started giving it to his friends.
People raved about the drink and told him he should bottle it commercially. Soon he was marketing a drink labeled Home Made Grape Juice. On Sept. 9, 1918, he founded a new enterprise, which he called the Utt Juice Co. When it outgrew his back porch, he moved to a Victorian-Italianate building on the northwest corner of Main and Prospect. The building, which he had owned since 1907, had been the home of Sauers and Berkquist grocery. Set up with boilers, vats, presses and bottling equipment , it became the Utt Juice Co. Sheds and additional buildings were added as the company grew.
Arcy Schellhous, a young man of 27, bought a quarter interest in the business in 1922 and took over the management, giving Utt more time for his duties as president of the San Joaquin Fruit Co., president of the First National Bank of Tustin and owner of Tustin Water Works. They adopted the brand name of Queen Isabella and added pomegranate, rhubarb and guava juice to their inventory. Schellhous bought out Utt in 1931 although the company continued to use the Utt name.
Production reached a peak of 200,000 gallons of juice in 1965. The company was ahead of its time in producing juices that could be labeled �100% Pure, No Sugar Added.� Queen Isabella jams and jellies were added to the product mix as well as boysenberry products that carried the Knott label. However, grapes and other fruits produced locally became increasingly hard to find and Schellhous was forced to buy fruit from other parts of California.
Utt died in 1951, but Schellhous continued to run the company until he died in an automobile accident in 1970. Jack Hall who had joined the company in 1946 as office manager became president and served until 1973 when a scarcity of fruit and increasing competition forced the company to close. It was calculated that Utt Juice Co. had produced 7 million gallons of juice in 50 years.
Cleared of equipment, the building stood empty until a few years ago when building began on the recently completed Prospect Village complex.
“People know that the system is old, but I don’t think they realize just how old it is… in our system, it’s not just the architecture that’s 100 years old. It’s a lot of the basic technology, as well. The infrastructure is old.”
From the MTA in New York City, this is CBTC: Communications-Based Train Control, an astounding behind-the-scenes video about the technologies running the NYC subway system. Get a gander at West 4th Street station’s electromechanical relays, a pre-1930s technology that’s no longer supported by anyone but the MTA themselves. Plus, learn about their multi-decade plan to modernize the traffic control system, and see the Corona Subway Maintenance Shop, temporary home of the new CBTC-equipped subway cars.
As Service Delivery Division VP & Chief Officer Wynton Habersham explains, Communications-Based Train Control provides constant, centralized data about a train’s location, direction of travel, and speed, a leap forward from the safe but less precise fixed block signaling of the current system. The MTA invested seven years into converting the L train (14th Street – Canarsie Local) to CBTC, and is currently working on the 7 line (the Flushing local and express).
Geographer turned Software Engineer, looking to shape the invisible systems that guide our world. Professionally interested in mapping, data visualization, values-based programming, and STEAM evangelism. Personally interested in crochet, knitting, textiles, and archery.
