Dec 4, 2010
A hubless wheel is a wheel lacking a central hub, first designed by an Italian mechanical engineer, Franco Sbarra especially for motor vehicles. but it is also been seen in the application of many bicycle prototypes over the years. The Orbital wheel, a type of hubless wheel was designed in 1990 by Dominique Mottas. Hubless wheels lack a central hub and an axle which form the major part of conventional wheels. The concept behind this is to reduce the number of rotating parts in the wheel to a bare minimum. Many scientists argue that the efficiency of the wheel is compromised by using hubless and spoke less wheels but others see its advantages as it claims to make the bike lighter and striking in appearance, not many prototypes have actually become commercially viable.
It consists of 3 parts, 1) a bearing with a thin section and a large diameter, 2) rotating part consisting of a tyre, a centre free rim and a brake ring all integrated with each other to form a rotating outer ring of the bearing and 3) fixed part consisting of the non rotating inner ring of the bearing on which the vehicle’s steering system is connected. With this arrangement we get an empty wheel that is free from midwheel structural constraints.
Due to the lack of a central hub this wheel is more advantageous than the conventional wheel. Steering becomes all the more easier due to the elimination of effects of deformation of stub axles and forks of the motorbikes and it is that kinda design that allows for more rational steering systems to be attached in the future. An automobiles stability is dependent on its roll angle, the greater the angle, the more stable the vehicle. But the manoeuvrability will be reduced on turns and tight bends. The hubless wheel comes with a roll angle variator. The greater the speed, the higher the roll angle and hence maximum stability is maintained at all times and when the speed is reduced, the roll angle is reduced thus increasing manoeuvrability. For any vehicle, be it an automobile or a railway car braking is a major source of concern. Conventionally braking occurs at the centre of the wheel which requires a complex braking system. As the hubless wheel has no central hub, braking power is applied close to the ground by using large diameter brake rings or discs and also the braking system has excellent ventilation.
In a traditional wheel, the dynamic forces acting on the wheel at the road-tyre interface passes through the midwheel causing damage to the forks of the wheel. But with the advent of hubless wheels, these forces are transmitted directly to the suspensions. As vibration and jarring are reduced by 50%, the driver is much more comfortable and can drive longer. Goods can be carried in better conditions as they undergo less vibration. There is less strain on the straps used for fastening the goods so road safety is also increased. As each tyre is subjected to the same load, the wear is evenly spread and is greatly reduced and hence its useful life is increased. Thus newer and cheaper tyres with an equal performance level can be used.
Although hubless wheels are striking in appearance and advantageous compared to the conventional wheel, their numerous practical disadvantages have impeded their widespread use as an alternative to conventional wheels. They are difficult and expensive to manufacture and require a great deal of precision while machining. And the design also leaves the bearings and other mechanical parts exposed, the drive system is also very difficult to design and is problematic hence conventional wheels are preferred to hubless ones though they are more efficient.
Oct 16, 2010
An Inertial Navigation System (INS) is a navigational aid that makes use of a clock, accelerometers (sensors for measuring acceleration), gyroscopes (sensors for measuring rotation) and a computer to continuously calculate the position, orientation and velocity of an object on the move without any external references. Inertial navigation is a self-contained navigation technique in which measurements provided by accelerometers and gyroscopes are used to track the position and orientation of an object relative to a known starting point, orientation and velocity. Inertial measuring units (IMUs) typically contain 3 orthogonal rate-gyroscopes and 3 orthogonal accelerometers, measuring angular velocity and linear acceleration respectively. These signals are processed with the help of the on board computer and the position and orientation of the object can be tracked.
All the IMUs fall into 1 of the 2 categories outlined below. The difference between the 2 categories is the frame of reference in which the gyroscopes and accelerometers operate. The 2 categories are stable platform systems or gimballed platform systems and the strap down systems.
In stable platform type of systems, the inertial sensors are mounted on a platform which is isolated from any external rotational motion. This is achieved by using gimbals which allow the platform freedom to move in all the 3 axes. The gyroscopes on the platform detect rotations of the platform if any and the signals are fed back to the motors which rotate the gimbals in order to cancel out such rotations and hence keeping the platform aligned with the global frame. To track the position of the object, the angles between adjacent gimbals is calculated with the help of angle pick-offs and to calculate the position, the signals from the accelerometers mounted on the platform are double integrated. To get accurate results, we need to subtract acceleration due to gravity from the vertical channel before performing integration.
In strap down systems the sensors are mounted rigidly onto the device and hence the output is measured in the body frame and not global frame as in the case of stable platform systems. The orientation of the object can be determined by keeping track of the signals from the gyroscopes and integrating them while the position is determined from the accelerometer signals which are resolved into global co-ordinates and then integrated.
Both these types of systems are based on the same principles. Strap down systems are less complex and are physically smaller compared to stable platform systems. Due to this the strap down systems are the more dominant type of INS.
INS is autonomous and does not rely on external aids or visibility conditions and can operate in tunnels or underwater and anywhere. It is immune to jamming and inherently stealthy. It neither receives nor emits detectable radiation and requires no external antenna.
Errors increase with time as they are mean-squared. Cost of acquisition is high, the maintenance costs are also higher and so are the power requirements when compared to GPS receivers. With integration with GPS, these systems have become cheaper, maintenance costs have also gone down, the sensor errors have dropped to acceptable values and when there’s loss of GPS signals this integrated INS can be used.
Oct 7, 2010
The NAVSTAR-GPS (NAVigation System with Timing And Ranging Global Positioning System) commonly known as GPS, is a U.S. space based radio navigation system that provides reliable positioning, navigation and timing services to users on a continuous worldwide basis, freely available to all. GPS was originally intended for military applications, but in the 1980’s the government made the system available for civilian use. GPS works in all weather conditions, anywhere in the world, 24 hours a day. GPS was created by the U.S. Department of Defence (DOD) and was originally run with 24 satellites and there are currently 28 operational satellites orbiting the earth at a height of 20,180 km on 6 different orbital planes. Their orbits are inclined at an angle of 55° to the equator, ensuring that at least 4 satellites are in radio communication with any point on the planet. Each satellite orbits the earth in approximately 12 hrs and has 4 atomic clocks on board.
Before getting into the details of how the GPS works we should first know what signal transit time is and how it is measured. At some point or the other on a stormy night, you might have wondered how far away you are from a flash of lightning. This distance can be measured quite easily:
Distance = time the lightning flash was first perceived (start time) until the thunder is heard (stop time) multiplied by the speed of sound. The difference between the start and stop time is called transit time.
Hence distance = transit time * speed of sound
The GPS system exactly works under the same principle. In order to calculate one’s position, all that needs to be measured is the signal transit time between the point of observation and four different satellites whose positions are known.
Each satellite transmits its exact position and its precise on board time to earth at a frequency of 1575.42 Mhz. These signals are transmitted at the speed of light (3,00,000 km\s) and therefore require approx. 67.3 milli seconds to reach a position on the earth’s surface. The signals require a further 3.33 micro seconds for every extra km of travel.
Measuring the signal transit time and knowing the distance from a satellite isn’t enough to calculate one’s own position in 3-D space. To achieve this, 4 independent transit time measurements are required. It is for this reason that signal communication with 4 satellites is needed to calculate one’s exact position. All this time we have been assuming that the signal transit time that we measured was precise and highly accurate, but an error of 1 micro second can produce a positional error of 300m. As the clocks on all the satellites are synchronised, the transit time in all the measurements is inaccurate by the same amount. From the basic knowledge of mathematics we know that to solve a problem with n no. of unknowns, we need n no. of equations. To precisely determine the position of a person we need 4 equations i.e. one each for longitude, latitude, height and time error hence 4 satellites are required.
The most important applications of GPS are to determine one’s exact location and the precise time anywhere on the earth. The traditional fields of application for GPS are surveying, shipping and aviation. However with the increasing demand and popularity of the GPS, now it is being used in archaeology, geology, cartography, forestry and agricultural sciences, planning and managing of plantations, fleet management, navigation systems, trekking and sports activities and most importantly military services for which it was mainly developed for.
Oct 2, 2010
Ekranoplan is a Russian word which means 'screen craft' or 'skimmer'. It is not a plane nor is it a ship, moreover its a mixture of both. It is a transition between a hovercraft and an aircraft. It is a vehicle that attains level flight close to the surface of the earth which is possible by the cushion of high pressure air created by the aerodynamic interaction between the wings and the surface of the earth generated by its forward movement called as ground effect. It is also known as a flarecraft, sea skimmer, wing in surface effect ship etc.
In the 1970's when this vehicle was first photographed by the American satellite, it was believed to be a normal Jumbo jet sized aircraft under construction but when the vessel was later photographed sitting in water the American’s were puzzled! These crafts are big, fast and were kept secret from the west until the fall of communism in the early 1990's, when information about them was slowly revealed.
It can quite easily be envisaged that a hundred of such crafts zooming across the ocean, flying undetected by the radar as they fly underneath it and invading a country! By the time that country realized what was going on, it would have been too late. The front of the fuselage would have opened to allow soldiers, tanks, trucks, jeeps, and armoured cars to deploy and invade. You have to imagine several hundred of these craft, all flying at over 290 knots, all under radar in a mass invasion. We could then fully realise the element of surprise that they would have had.
It’s one hell of a ship, fast, manoeuvrable, and heavily armed but maybe not so well protected. Unlike a warship that has armor plating, the Ekranoplan would be susceptible to enemy firepower, a couple of rocket or bazooka hits could seriously damage or render the Ekranoplan inoperable. As the Ekranoplan picks up speed, the air is compressed under its short stabilizing wings until enough pressure produces lift and this supports the craft. Ekranoplan's as they are bigger, have more power and travel just a few feet over the water surface. Infinitely faster than any sea vessel ever designed the Ekranoplan is a marvel to behold. The terrific speed that these crafts can reach is mainly due to the fact that there is no friction between the hull of the craft and the water. This of course is a factor that keeps normal ships at such a comparatively slow speed, as they must push themselves through the water and not over it. They have better fuel efficiency than an equivalent aircraft flying at low level due to the close proximity of the ground, reducinglift-induced drag. There are also safety benefits for the people travelling in the craft in flying close to the water as an engine failure will not result in severe ditching. However, this particular configuration is difficult to fly even with computer assistance. Flying at very low altitudes, just above the sea, is dangerous if the craft banks too far to one side while making a small radius turn.
All Ekranoplan's are amphibious and will easily fly over land just as well as the sea, and at high speed, just as long as the surface is relatively flat. The last Ekranoplan from the former Soviet Union was the 400 ton LUN. It was built in 1987 with 100% military application in mind as a missile launcher and troop carrying ship. It was equipped with six large missiles on top of the fuselage, and could carry tanks and trucks in its large cargo hold. Also it must be reiterated here that it would not have been detected by radar as it would have travelled under the radar waves but the modern radar now has the ability to scan vessels on the surface of the sea so the surprise element of the Ekranoplan can be negated.
At the time when the Soviet Union fell apart, there was a second LUN under construction, it was about 90 percent finished when the military funding stopped. This was because of Russia's poor financial situation and also the end of the cold war. Later the eventual collapse of communism was enough to create further financial upheavals in much of Russia's economy. Most countries have now built prototypes of the Ekranoplan design as it has very useful application both in the military and commercial fields. As yet no commercial flights have been instigated but there are reports that a lot of private ventures are being developed, mostly in the USA.
Jan 19, 2010
Now let us know the basic parts that make up the Segway. The Segway is a combination of a series of sensors, a control system and a motor system. The primary sensor system consists of an assemblage of gyroscopes. Gyroscopic sensors are used to detect tilting of the device which indicates a departure from perfect balance. Motors driving the wheels are commanded as needed to bring the PT back into balance. The Segway PT has five gyroscopic sensors, though it only needs three to detect forward and backward pitch as well as leaning to the left or right. The extra sensors add redundancy, to make the vehicle more reliable. Additionally, the Segway has two tilt sensors filled with electrolyte fluid. Like your inner ear, this system figures out its own position relative to the ground based on the tilt of the fluid surface.
All of the tilt information is passed on to the "brain" of the vehicle, two electronic controller circuit boards comprising a cluster of microprocessors. The Segway has a total of 10 onboard microprocessors, which boast, in total, about three times the power of a typical PC. Normally, both boards work together, but if one board breaks down, the other will take over all functions so that the system can notify the rider of a failure and shut down gracefully. When the vehicle leans forward, the motors spin both wheels forward to keep from tilting over. When the vehicle leans backward, the motors spin both wheels backward. When the rider operates the handlebar control to turn left or right, the motors spin one wheel faster than the other, or spin the wheels in opposite directions, so that the vehicle rotates.
The Segway is only slightly larger than a person, so it does not cause as much congestion as a car or a bike. Once they get to their destination, riders can carry their Segways inside with them without worrying about parking. And there's no need to stop by the gas station, as the vehicle runs on ordinary household electricity. There is really no limit to how people might use the vehicle. The Segway can fit in most places you might walk, but it will get you there faster, and you won't exert much energy. So what are you waiting for? Go get yourself the worlds first self balancing electric vehicle.
Jan 18, 2010
NORTHROP SWITCHBLADE
BELL X-5
A variable-sweep wing is an aircraft wing that can be swept back or front and then returned to its original position during flight. It allows the aircraft's geometry to be modified in flight, and is an example of variable geometry. With different wing positions allowing for greater efficiency and performance in various flight modes, these aircraft are more versatile than aircraft with fixed wings. During the World War I and II, one would notice that most of the aircrafts had wings perpendicular to the fuselage and in very rare cases a couple of degrees swept back. But with the advent of jet engines after the World War II which gave a boost to the speed of the aircrafts, the traditional wing shapes weren't that efficient at such high speeds. So jet planes started using tapered wings, but this came at a cost of low efficiency at lower speeds.
And hence came the need for an aircraft which can alter its wing geometry in mid flight. This feature gives the airplane the best possible performance characteristics for any given speed. The German Messerschmitt company first tested planes with variable wing geometry during World War II. The Messerschmitt P-1101's wings could be moved to different sweep angles, only while the plane was on the ground. Based on the Messerschmitt design, the U.S. developed a working test craft, the Bell X-5, which was slightly larger than the P-1101 and could change its wing-sweep angle while in flight.
Designers had to take into consideration many factors regarding sweep while designing a swing wing. Swept back wings make the aircraft more stable at high speeds while forward swept wings allows the aircraft to be agile. In the 1990s, Northrop Grumman tested variable-geometry wings on another plane with the "Switchblade" nickname. The Northrop Bird of Prey had three wing configurations:
- full-back position - The wings were perpendicular to the fuselage for low-speed flight.
- intermediate position - The wings were swept forward for exceptional maneuverability.
- full-forward position - The leading edge of the wings folded in against the fuselage, allowing the trailing edge to become the front of the wing for high speeds. This resulted in a triangular, or delta wing shape.
Aug 5, 2009
The drive starts out like any other, just a quick trip across town to pick up some groceries. You drive effortlessly through the first green light and somehow drive past the next intersection as well. To your growing amazement, you easily make the third traffic light, too. Will this streak of traffic luck hold out? Will you arrive at your destination without stopping for a single light? You may have a great feel for the road, but you can't talk to the traffic lights. Or can you? In the German city of Ingolstadt, something peculiar is happening. Certain luxury vehicles have been observed gliding effortlessly through intersections. Even when they're forced to stop, they never seem to have to wait long. Who are these mysterious drivers and what allows their cars to cut though the municipal traffic system? It's no coincidence that the vehicles are all Audis, and that the automotive manufacturer is headquartered in Ingolstadt. The Bavarian city is currently playing host to an experiment in the future of driving called Travolution. With Audi's Travolution system, intelligent traffic lights talk to each other and cars talk to traffic lights, all to the benefit of human drivers.
As more and more vehicles take to the streets, cities face greater traffic congestion -- to the point where simply building larger roads is no longer a valid fix. Instead of adding more lanes, traffic engineers and scientists have worked to create intelligent transportation systems. Instead of simply managing vehicles at a specific intersection or on a particular road, the system would regulate a city's collective traffic flow in all its stops and surges. On the infrastructure side, intelligent traffic lights play a major role in keeping vehicles moving along, and feature prominently in Audi's Travolution system. The Travolution system also features an intelligent vehicle component, and this is where the system really appeals to people. Green means go, red means stop – this is simple. But what exactly does a yellow traffic light mean to the average driver? Most driving instructors will tell you it means to come to a complete stop if you can safely, otherwise, proceed into the intersection cautiously. Traffic engineers call this scenario the dilemma zone. A Travolution-equipped vehicle receives signals from intelligent traffic lights in the area, informing it exactly when the light will change. The vehicle's onboard computer then calculates exactly what speed the driver needs to maintain to continue through the light without stopping the vehicle. The computer then relates this information to the driver, via the Audi multimedia interface (MMI) infotainment system. The driver might need to maintain a slightly higher or lower speed to make the light, but he or she won't have to come to a complete stop. This doesn't just cut down on driver irritation, it cuts down on fuel consumption and exhaust associated with accelerating back up from zero.
Most intersections don't have intelligent traffic lights, and it will require a great deal of time and money to install them. On top of this, there's vehicle compatibility to consider. Plus, even if you fully update every street with the latest technology and sync it up to a network, you still have to worry about human error and good-old fashioned driver stupidity. Obeying Travolution might not be the best idea if the vehicle in front of you just came to an abrupt stop to avoid running over a squirrel. Many futurists think that driving technology such as Travolution will eventually lead to the existence of automated highways, where the opportunity for human error is negated entirely. So let’s hope that this experimental technology gets a nod from the German government and it soon spreads all over the world to reduce the wastage of time and fuel when caught in an unsympathetic traffic snarl.
Aug 2, 2009
Airspeed is a measurement of the plane's speed relative to the air around it. The airspeed indicator is used by the pilot during all phases of flight, from take-off, climb, cruise, descent and landing in order to maintain airspeeds specific to the aircraft type and operating conditions as specified in the Operating Manual. The pitot (pronounced pee-toe) static tube system is an ingenious device used by airplanes and boats for measuring forward speed. The device is a differential pressure gauge which was invented by Henri Pitot in 1732.
Airspeed indicators work by measuring the difference between static pressure, captured through one or more static ports; and stagnation pressure due to "ram air", captured through a pitot tube. This difference in pressure due to ram air is called impact pressure.
Internal mechanism of an airspeed indicator
The static ports are located on the exterior of the aircraft, at a location chosen to detect the prevailing atmospheric pressure as accurately as possible, that is, with minimum disturbance from the presence of the aircraft. The open end of the pitot tube, usually mounted on a wing, faces toward the flow of air or water. The air speed indicator actually measures the difference between a static sensor not in the air stream and a sensor (Pitot tube) in the air stream. When the airplane is standing still, the pressure in each tube is equal and the air speed indicator shows zero. The rush of air in flight causes a pressure differential between the static tube and the pitot tube. The pressure differential makes the pointer on the air speed indicator move. An increase in forward speed raises the pressure at the end of the pitot tube. In turn, the air pressure pushes against a flexible diaphragm that moves a connected mechanical pointer on the face of the indicator. The indicator is calibrated to compensate for winds in the air current.
Airspeed indicators are calibrated for a sea level standard atmosphere. When the pressure/temperature combination yields a density altitude higher than sea level, the airspeed indicator displays a lower airspeed. Conversely, if the density altitude is below sea level (which is not uncommon in the Winter months at lower elevations), the airspeed indicator reads a faster airspeed.This brings you to ICE T.
The speed that you read right off the face of the airspeed indicator is indicated airspeed. That's the I in ICE T.
The C in ICE T stands for calibrated airspeed, which is indicated airspeed corrected for position error, which typically means that the static port is located in a place where its measurements are not accurate in certain flight configurations.
The E in ICE T stands for equivalent airspeed, but it might as well stand for expensive, because it reconciles an error that only becomes significant in airplanes flying faster than 300 knots and/or higher than 25,000 feet. The error is called compressibility error.
Finally, you come to the T, which is true airspeed. True airspeed is equivalent airspeed corrected for non-standard pressures and temperatures (density altitude). It is the actual speed at which the airplane moves through the air, and the only thing standing between it and ground speed is a correction for the effect of the wind.
The C in ICE T stands for calibrated airspeed, which is indicated airspeed corrected for position error, which typically means that the static port is located in a place where its measurements are not accurate in certain flight configurations.
The E in ICE T stands for equivalent airspeed, but it might as well stand for expensive, because it reconciles an error that only becomes significant in airplanes flying faster than 300 knots and/or higher than 25,000 feet. The error is called compressibility error.
Finally, you come to the T, which is true airspeed. True airspeed is equivalent airspeed corrected for non-standard pressures and temperatures (density altitude). It is the actual speed at which the airplane moves through the air, and the only thing standing between it and ground speed is a correction for the effect of the wind.
Thus the AIRSPEED INDICATOR is similar to a speedometer in a car. It shows the speed (in knots) of the airplane traveling through air.
Aug 1, 2009
Turbochargers allow an engine to burn more fuel and air by packing more into the existing cylinders. The typical boost provided by a turbocharger is 6 to 8 pounds per square inch (psi). Since normal atmospheric pressure is 14.7 psi at sea level, you can see that you are getting about 50 percent more air into the engine. Therefore, you would expect to get 50 percent more power. It's not perfectly efficient, so you might get a 30- to 40-percent improvement instead.
One of the main problems with turbochargers is that they do not provide an immediate power boost when you step on the gas. It takes a second for the turbine to get up to speed before boost is produced. This results in a feeling of lag when you step on the gas, and then the car lunges ahead when the turbo gets moving.One way to decrease turbo lag is to reduce the inertia of the rotating parts, mainly by reducing their weight. This allows the turbine and compressor to accelerate quickly, and start providing boost earlier.
Thus turbochargers are used to significantly boost the engine horsepower of high performance sports cars etc.
Jul 31, 2009
A muffler is a device for reducing the amount of noise emitted by a machine. If you've ever heard a car engine running without a muffler, you know what a huge difference a muffler can make to the noise level. Mufflers are typically installed along the exhaust pipe as part of the exhaust system of an internal combustion engine (of a vehicle, or stationary) to reduce its exhaust noise. The muffler accomplishes this with a resonating chamber, which is specifically tuned to cause destructive interference, where opposite sound waves cancel each other out. Inside a muffler, you'll find a deceptively simple set of tubes with some holes in them. These tubes and chambers are actually as finely tuned as a musical instrument. They are designed to reflect the sound waves produced by the engine in such a way that they partially cancel themselves out.Take a look at the inside of the above muffler:
The exhaust gases and the sound waves enter through the center tube. They bounce off the back wall of the muffler and are reflected through a hole into the main body of the muffler. They pass through a set of holes into another chamber, where they turn and go out the last pipe and leave the muffler.
A chamber called a resonator is connected to the first chamber by a hole. The resonator contains a specific volume of air and has a specific length that is calculated to produce a wave that cancels out a certain frequency of sound. When a wave hits the hole, part of it continues into the chamber and part of it is reflected. The wave travels through the chamber, hits the back wall of the muffler and bounces back out of the hole. The length of this chamber is calculated so that this wave leaves the resonator chamber just after the next wave reflects off the outside of the chamber.
Mufflers that reduced backpressure relative to earlier models became increasingly available in the late 20th century, and resulted in increased engine efficiency, performance, power output, and simultaneously decreased overall wear and tear on the engines' components, as well as sound to levels in compliance with the law. Thus the usage of mufflers in the exhaust system of engines is advisable which has so many merits.
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