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Ernesto Figueroa6842290647Illumin Article5/2/14Engineering Isn’t All Fun and Games… Unless It’s Air HockeyIt is not every day that phenomena occur that seems to defy the laws of nature. Every so often there is some kind of human innovation of technology that appears to do just that. Hovercrafts are vehicles that seem to neglect the laws of physics and have become a prime example of how understanding simple physics concepts can be utilized to make it appear as if the laws of physics are a thing of the past. The mechanisms of how such an outstanding accomplishment and feat of engineering works may intimidate those who are interested in all the details and explanations, however in this case it is actually quite simple and can be a lot of fun to learn. As we explore the underpinnings of how a hovercraft operates, we need not to go to the nearest local library nor back to a well-respected professor to give oversight into the topic; all that is needed is a trip to the local arcade. Yes, understanding the context of this marvel can come in the form of a game. This game takes engineering and physics’ principles and utilizes them in a way to create an experience that has continued to be passed down from generation to generation. This game is Air Hockey.Air Hockey has been around since the early 1970’s and has been a staple for any arcade they were in. The game of Air Hockey is just what it sounds like. It is hockey played on air. Yes, on air. It involves 2 players who face off against each other trying to knock the puck into the other person’s goal [1]. It is virtually identical to its arcade counterpart PONG (Fig 1), but the catch is it is played on a special table designed to make the puck “float”. This table has tiny holes on the surface that continually pump a jet of air from underneath. The combination of these air jets and the specially designed puck, causes it to “lift” off of the surface and become practically frictionless as the opponents send it ricocheting back and forth [2]. How does this relate to hovercrafts you may ask; the name “hovercraft” was given thanks to its ability to “hover” off of the ground [3]. Air Hockey and hovercrafts use the exact same principles to defy physics. Understanding a simpler example, Air Hockey, will give all the insight and knowledge that is needed into understanding exactly how a hovercraft operates.50101491134110Pool Products Inc00Pool Products Inc10668001137285Wikipedia00WikipediaFigure SEQ Figure \* ARABIC 1: PONG VideogameFigure 2: Air Hockey TableGravity and Friction:4353560279527000An incredible feat of engineering has to be implemented in order to continuously neglect two of the most common forces of nature: gravity and friction. Gravity is responsible for the weight of all physical objects. It is defined as the force of attraction one object has to another; basically, how “hard” the Earth pulls down on an object. This force is constantly around us and acts on everything. There is no way around the pull of gravity; which is why there are no objects that float in air (balloons only float due to what is inside of them. The balloon itself cannot avoid gravity’s pull). Back to Air Hockey; the puck is constantly being pulled down and is forced to rest on top of the table’s surface (just as a book rests on top of a desk). This constant rubbing against the surface leads to our next engineering obstacle, Friction.43230801343660Figure 3: Holes on the surface of the table with the outline of a puck for size reference.Figure 3: Holes on the surface of the table with the outline of a puck for size reference.53905155926455Liberty Games00Liberty GamesFriction is the force that resists motion. It is responsible for objects’ abilities to remain in one spot and to start slowing down once in motion, eventually coming to a complete stop. Back to the book analogy; the book will not move once it is placed down on the desk. The reason for this is the friction that is caused by gravity. The book, even with gravity present, would still have the ability to move around if it weren’t for friction. The way friction works is the molecular bonds between the two surfaces in contact tend to cohere to one another when a force is applied. In other words, when gravity pushes one of the objects down it acts as Velcro and “attaches” to the surface. This attachment exerts a force that needs to be matched in order to move; while in motion it also needs to be matched otherwise the force from friction will slow the moving object down. Thus friction needs to be overcome in order to have the puck speed across the table. How can these two forces, gravity and friction, be overcome in Air Hockey? Well there has yet to be a discovery on how to turn off gravity so friction comes into question. To go about avoiding friction you need to go back to the definition. “A force that resists the relative motion or tendency to such motion of two bodies or substances in contact” [4]. Substances in contact. What if the puck and table weren’t in contact? There would be no friction between the objects because they aren’t touching. This is precisely what engineers did. They created a pocket of air that the puck sits on to avoid exhibiting friction to the table.Does this correlate back to the ability of a hovercraft to hover? Absolutely. Gravity pulls the hovercraft down just as it does to the puck. Friction also plays a role and is even more of an effect when it comes to hovercrafts since they are typically not on top of a smooth surface, unlike that of the Air Hockey puck. Both of these forces will need to be overcome before any kind of motion would be present. If you haven’t made the connection already, the way to overcome this dilemma is indeed a similar pocket of air in order to reduce the amount of friction between the hovercraft and the earth that it will be voyaging over.Lift:53143153442335Amazon00AmazonThe key engineering marvel of this game is the ability to create a puck that is virtually frictionless. Every Air Hockey table consists of hundreds of tiny holes aligned uniformly all throughout the area of the table. On the underside of these holes is an air compressor that will blow a continuous stream of air through each and every hole. The combination of the holes and the air compressor create the necessary lift that is needed to negate the force of gravity and thus reducing friction. Lift is the force that opposes gravity. Gravity pulls objects down, while an object that has a lift force would go up (or counteract only a portion of the gravity thus making the force of gravity less than what would be felt without the added lift). Because the holes are uniformly placed on the surface of the table, no matter where the puck happens to be there will always be a continuous and evenly distributed 44767503657600Figure 4: Generic Air Hockey PuckFigure 4: Generic Air Hockey Puck4476750194310000lift force that pushes up against the puck in order to maintain its state of reduced friction. -3429003232150Figure 5: Air Hockey puck diagram showing how the pocket of air creates an artificial cushion beneath the puck.Figure 5: Air Hockey puck diagram showing how the pocket of air creates an artificial cushion beneath the puck.12376153046095Physics Forum00Physics Forum-342900215392000The puck itself also plays a key role in aiding in lift. Air Hockey pucks are not only made out of light plastic to reduce their weight but are specially designed to create a pocket of air that is used to separate the puck from the table, thus reducing even more friction. The ridges found near the perimeter of the puck act as a skirt that traps some of the air coming from underneath the table. This trapped air acts as an air pocket that the rest of the puck can “sit” on [5]. Once this recess is filled with air, the air is forced to escape from underneath the perimeter of the puck. This air that escapes goes underneath the portion of the puck that is in contact with the surface. Less of the surface in contact with the table then results in less friction; less friction results in greater speed that the puck can obtain and ultimately faster paced play.Real World Applications:49714151834515Wikipedia00WikipediaAir Hockey is cool and all but it’s only a game right? Wrong. Air Hockey is itself only a game that is played as a form of entertainment but the same principles engineers used to create this game are also used to create hovercrafts. Hovercrafts are considered to be a hybrid vehicle that is capable of traveling at high speeds over terrain most normal vehicles would not be able to. They can travel over water to sand to mud to ice all in a single run. These have already been utilized historically for commercial 38957252063115Figure 6: Hovercraft and skirt componentFigure 6: Hovercraft and skirt component389572517145000transportation uses, novelty items, and even in the military. All from principles that are found in an arcade game. There are no true hovercrafts in the truest sense of the word but rather ACVs (Air-Cushioned Vehicles). These vehicles are identical to the Air Hockey puck; a pocket of air is utilized in order to separate as much of the surface of the vehicle from the ground, thus reducing friction. ACVs have a flexible skirt underneath the vehicle in which the pocket of air is held [7]. These skirts are typically made from some sort of composite material that is flexible and lightweight in order to reduce the amounts of weight and the properly function, but are also sturdy and durable enough to not breakdown and rip midway through a ride. Currently, there is no perfect median between lightweight and strength for this skirt so any material that is utilized tends to eventually fail do to the other constraint (i.e. One material is light enough but too weak, while another is durable enough to last but ultimately weighs down the vehicle to negate any lift produced). Instead of needing to rely on a table to blow air up into the skirt, ACVs rely on their own fans and compressors to blow air downwards into the skirt [6]. Once these air pockets get filled, the air then escapes down and underneath the vehicle causing it to ever so slightly lift off the ground. As aforementioned, lift is the key to allowing an Air Hockey puck, and its hovercraft counterpart, to reduce the forces of friction. This reduction of friction is what truly sets this vehicle apart from the rest. No other vehicle has utilized this sort of technology and it still amazes audiences to this day. With reduced friction, less fuel is needed in order to propel the vehicle and faster speeds are more easily attainable. Due to the lift, there is another easily overlooked significance; there is less force that pushes on the ground by the vehicle. One professional golfer took this knowledge and decided to convert his golf cart into a hovercraft [8]. This allowed him to take his new golf cart places traditional golf carts could not. Not only could he traverse from grass to sand trap to water with ease, he could also drive over the green because the amount of force delivered from the vehicle was so incredibly small. Typically, even a person who walks across the green will leave footprints but astonishingly this vehicle could traverse over it time and time again without leaving a mark.With the technology to “hover” above the ground already been implemented in the past, one would certainly think hovercrafts would be more common than they are. Unfortunately, there are too many downfalls currently present. One of the most disastrous is the fact that these vehicles lack maneuverability. Hovercrafts lack contact with the ground so the only way in which they can move is by air. In order for the vehicle to be put into motion, air would have to be blown in the opposite direction of travel to push it along [9]. This feat is far easier said than done. One small deviation from the intended angle the fans need to be placed in can be catastrophic. While maneuvering, if the fans aim too high the vehicle would be pushed into the ground, if they are aimed too low no forward movements would occur. Even the most successful hovercrafts have trouble maneuvering exactly the way the driver intends to. Progress has been made but it is still unreliable at this time.Other problems deal with the weight and amount of lift that is required. In order to produce more lift, either more air is needed or less weight is required. Hovercrafts can only be so light; they still need to be structurally sound in order to function. However, the production of more air also increases the amount of noise produced by the hovercraft. There are no silent Air Hockey tables, as an easy reference to understand the dilemma, due to the fact that an air compressor is required in order to function. Similarly, noise reduction in hovercrafts has not progressed far enough to the point that comfortable decibel levels have been attained [10]. Conclusion:Air Hockey is much more than a game that you might find in the corner of some arcade. It is a true engineering masterpiece. Every aspect has been meticulously fabricated in a way that would help to overcome the natural forces of nature. Although creating a truly frictionless game, and vehicle, is impossible, Air Hockey and hovercrafts comes close. From the way the holes in the table are placed, to the design of the puck itself, the engineers constructed their game in such a way to reduce all the friction between the puck and the table as possible allowing for faster puck speeds and ultimately more fun. The engineering goes beyond just a game though. It can be a learning tool utilized to understand how hovercrafts work. These same principles may someday become what the future is reliant on. Slowly engineers will be defying the laws of nature one step at a time.References[1] Dexheimer, Eric. “Married to the Mallet.” Denver Westwood 21 November 2002[2] Jacobson, Mark. “Gone with the Wind.” Village Voice 17 November 1974[3] Herring, Sharolyn, and Christopher Fitzgerald. "History of the Hovercraft." NeotericHovercraft, Inc 17 (2006).[4] friction.(n.d.)?The American Heritage? Science Dictionary.(2005).Retrieved February 212014[5] Grant. Dimpled air hockey puck. US 7207909 B2. 2005[6] ?Bill Gunston, "Hydrofoils and Hovercraft: new vehicles for sea and land", Doubleday, 1969,p.93[7] Pendzich, Jerome S. "Vertical lift vehicle." U.S. Patent No. 7,481,290. 27 Jan. 2009.[8] Kay, Emily. "Bubba Watson's hovercraft golf cart to debut at Ohio course." SBNATION.Vox Media, 8 July 2013. Web. 29 Apr. 2014.[9] Wang Cheng-long; Zhang Hong-yu; Fu Ming-yu, "Motion control of an amphibioushovercraft based on fuzzy weighting,"?Communication Technology (ICCT), 2012 IEEE14th International Conference on?, vol., no., pp.1006,1011, 9-11 Nov. 2012[10] Burke, Richard E. "Noise levels of Hong Kong marine craft." The Journal of the AcousticalSociety of America 72.S1 (2005): S46-S46. ................
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