67-591: Or 5.9L (360ci) LA V8, optional 4-barrel carburetor The XR311 was a prototype military vehicle of US origin that was procured in limited numbers during the 1970s. It was originally developed as the High Mobility Combat Vehicle , or HMCV (not to be confused with the JGSDF MCV , which was also called the "HMCV" for a short time). Development of the XR311 commenced as a private venture in 1969, with
134-424: A TOW missile installation for use in the anti-tank/AFV role, three had an M2HB machine-gun for use in the reconnaissance role and three had 7.62mm M60 machine guns and the crew armor kit for use in the escort/security role. These trials were completed in 1972. They were then tested by the 2nd Armored Division. In 1974 they were also tested in the 2nd Armored Reconnaissance Scout Vehicle competition along with
201-420: A cold start . In order to ensure an adequate supply at all times, carburetors include a reservoir of fuel, called a "float chamber" or "float bowl". Fuel is delivered to the float chamber by a fuel pump . A floating inlet valve regulates the fuel entering the float chamber, assuring a constant level. Unlike in a fuel injected engine, the fuel system in a carbureted engine is not pressurized. For engines where
268-424: A torsion-bar spring and hydraulic telescopic shock absorber at each station. A stabilizer bar is provided for the rear suspension to limit body roll. Maximum speed is 80–90 mph for vehicles with the 318ci engine, dropping to 67 mph at full load. Acceleration was 12 seconds 0–60 mph time, falling to 10 seconds with the 360ci engine. The steering is power-assisted and the tubeless tires feature
335-467: A venturi (aka "barrel"). Fuel is introduced into the air stream through small tubes (the main jets ) at the narrowest part of the venturi, where the air is at its highest speed. Downstream of the venturi is a throttle (usually in the form of a butterfly valve ) which is used to control the amount of air entering the carburetor. In a car, this throttle is connected to the vehicle's throttle pedal, which varies engine speed. At lesser throttle openings,
402-460: A "mud tire"). Disc brakes are fitted on all four wheels. The electrical system is 24V DC , and two batteries with a capacity of 45 Amp/Hr are provided. The alternator is of the integral rectifier and regulator type. The XR311 is provided with a heavy duty towing pintle as well as a trailer wiring harness receptacle. It is air-transportable and can be air-dropped . Carburetor A carburetor (also spelled carburettor or carburetter )
469-412: A 5.89:1 drive ratio are used front and rear, and a lockable center differential ensures traction to all wheels. The fully independent suspension uses modified Dana 44 centersections, and used many off the shelf parts from the front wheel drive Oldsmobile Toronado / Cadillac Eldorado (e.g., CV joints and boots, spindle and bearings, and 11-inch disk brakes), and is of a double-wishbone design with
536-401: A common shaft. This forces both wheels to turn in unison, regardless of the traction (or lack thereof) available to either wheel individually. When this function is not required, the differential can be "unlocked" to function as a regular open differential. Locking differentials are mostly used on off-road vehicles, to overcome low-grip and variable grip surfaces. An undesirable side-effect of
603-429: A flexible diaphragm on one side of the fuel chamber, connected to a needle valve which regulates the fuel entering the chamber. As the flowrate of the air in the chamber (controlled by the throttling valve/butterfly valve) decreases, the diaphragm moves inward (downward), which closes the needle valve to admit less fuel. As the flowrate of the air in the chamber increases, the diaphragm moves outward (upward) which opens
670-426: A gearing reduction by having fewer teeth on the pinion than the ring gear . Milestones in the design or use of differentials include: During cornering, the outer wheels of a vehicle must travel further than the inner wheels (since they are on a larger radius). This is easily accommodated when the wheels are not connected , however it becomes more difficult for the drive wheels , since both wheels are connected to
737-400: A heat stove around the exhaust manifold. It was connected to the air filter intake via tubing and supplied warmed air to the air filter. A vacuum controlled butterfly valve pre heat tube on the intake horn of the air cleaner would open allowing cooler air when engine load increased. Differential (mechanical device) A differential is a gear train with three drive shafts that has
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#1732844807579804-440: A low-pressure area in the idle passage/port thus causing fuel to flow through the idle jet. The idle jet is set at some constant value by the carburetor manufacturer, thus flowing a specified amount of fuel. Many carburetors use an off-idle circuit, which includes an additional fuel jet which is briefly used as the throttle starts to open. This jet is located in a low-pressure area behind the throttle. The additional fuel it provides
871-414: A maximum load of 386 kg (851 lb). The minimum ground clearance is 11 inches, and a full length skid pan protects the hull and drivetrain, which allows the vehicle to slide over obstacles. The transmission is a Chrysler A-727 " TorqueFlite " torque converter automatic , with three forward and one reverse gears. The XR311 is a full-time 4WD vehicle . "Trak-lok" limited-slip differentials with
938-403: A mounting bracket on the hood until needed again. The passenger compartment is in the center of the vehicle with the driver on the left and the passenger seat to the right. There is space for 0.93 cubic metres (33 cu ft) of cargo behind the passenger seats. The engine and transmission are at the rear of the hull and there is an external load-carrying platform above this which can take
1005-468: A number of vehicles including the original FMC Technologies and Lockheed Martin designs. It has been stated that an XR311 with TOW missile installation cost around $ 50,000. The XR311 was designed to carry out a wide variety of roles including anti-tank, reconnaissance patrol , convoy escort, command and control , medivac , military police , mortar carrier, internal security and forward air defense communications vehicle. There were several models of
1072-464: A patent for a "gas or vapor engine", which ran on turpentine mixed with air. The design did not reach production. In 1875 German engineer Siegfried Marcus produced a car powered by the first petrol engine (which also debuted the first magneto ignition system). Karl Benz introduced his single-cylinder four-stroke powered Benz Patent-Motorwagen in 1885. All three of these engines used surface carburetors, which operated by moving air across
1139-412: A pointer which constantly pointed to the south, no matter how the chariot turned as it travelled. It could therefore be used as a type of compass . It is widely thought that a differential mechanism responded to any difference between the speeds of rotation of the two wheels of the chariot, and turned the pointer appropriately. However, the mechanism was not precise enough, and, after a few miles of travel,
1206-494: A regular ("open") differential is that it can send most of the power to the wheel with the lesser traction (grip). In situation when one wheel has reduced grip (e.g. due to cornering forces or a low-grip surface under one wheel), an open differential can cause wheelspin in the tyre with less grip, while the tyre with more grip receives very little power to propel the vehicle forward. In order to avoid this situation, various designs of limited-slip differentials are used to limit
1273-406: A single carburetor shared between all of the cylinders, though some high-performance engines historically had multiple carburetors. The carburetor works on Bernoulli's principle : the static pressure of the intake air reduces at higher speeds, drawing more fuel into the airstream. In most cases (except for the accelerator pump ), the driver pressing the throttle pedal does not directly increase
1340-418: A special high-pressure inner tire tube, which provides a built-in backup in case air pressure is lost from the main tire itself, as well as providing lateral support to eliminate leakage from the tire bead during high speed cornering. The tires are self-cleaning, meaning mud and other materials are flung free from the tread grooves by centrifugal force, rather than sticking to the tire (more commonly known as
1407-454: A type of mechanical analogue computer, were used from approximately 1900 to 1950. These devices used differential gear trains to perform addition and subtraction. The Mars rovers Spirit and Opportunity (both launched in 2004) used differential gears in their rocker-bogie suspensions to keep the rover body balanced as the wheels on the left and right move up and down over uneven terrain. The Curiosity and Perseverance rovers used
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#17328448075791474-748: Is a device used by a gasoline internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the Venturi tube in the main metering circuit, though various other components are also used to provide extra fuel or air in specific circumstances. Since the 1990s, carburetors have been largely replaced by fuel injection for cars and trucks, but carburetors are still used by some small engines (e.g. lawnmowers, generators, and concrete mixers) and motorcycles. In addition, they are still widely used on piston engine driven aircraft. Diesel engines have always used fuel injection instead of carburetors, as
1541-510: Is built around a tubular-steel frame safety roll-cage which protects the passenger compartment if the vehicle rolls over. This cage is covered by a heavy-gauge sheet metal forming the skin of the vehicle. An internally mounted electrical extraction winch with a capacity of 5,000 kg (11,023 lb) can be mounted at the front of the vehicle if required, and the 2-piece windshield can be removed to provide greater visibility and protect from flying glass fragments. The glass halves are stored in
1608-415: Is held shut by engine vacuum, is often used to do so. As the airflow through the carburetor increases the reduced manifold vacuum pulls the power valve open, allowing more fuel into the main metering circuit. In a two-stroke engine , the carburetor power valve operates in the opposite manner: in most circumstances the valve allows extra fuel into the engine, then at a certain engine RPM it closes to reduce
1675-400: Is limited mainly by the fuel's viscosity so that the fuel flow tends to be proportional to the pressure difference. So jets sized for full power tend to starve the engine at lower speed and part throttle. Most commonly this has been corrected by using multiple jets. In SU and other (e.g. Zenith-Stromberg ) variable jet carburetors, it was corrected by varying the jet size. The orientation of
1742-405: Is often used to prevent icing. This system consists of a secondary air intake which passes around the exhaust, in order to heat the air before it enters the carburetor. Typically, the system is operated by the pilot manually switching the intake air to travel via the heated intake path as required. The carburetor heat system reduces the power output (due to the lower density of heated air) and causes
1809-641: Is spelled "carburetor" in American English and "carburettor" in British English . Colloquial abbreviations include carb in the UK and North America or Carby in Australia. Air from the atmosphere enters the carburetor (usually via an air cleaner ), has fuel added within the carburetor, passes into the inlet manifold , then through the inlet valve(s) , and finally into the combustion chamber . Most engines use
1876-399: Is used to compensate for the reduced vacuum that occurs when the throttle is opened, thus smoothing the transition from the idle circuit to the main metering circuit. In a four-stroke engine it is often desirable to provide extra fuel to the engine at high loads (to increase the power output and reduce engine knocking ). A 'power valve', which is a spring-loaded valve in the carburetor that
1943-524: The Carter Carburetor WCFB and the identical Rochester 4GC, introduced in various General Motors models for 1952. Oldsmobile referred the new carburetor as the "Quadri-Jet" (original spelling) while Buick called it the "Airpower". In the United States, carburetors were the common method of fuel delivery for most US-made gasoline (petrol) engines until the late 1980s, when fuel injection became
2010-449: The "correct" time, so an ordinary clock would frequently have to be readjusted, even if it worked perfectly, because of seasonal variations in the equation of time. Williamson's and other equation clocks showed sundial time without needing readjustment. Nowadays, we consider clocks to be "correct" and sundials usually incorrect, so many sundials carry instructions about how to use their readings to obtain clock time. Differential analysers ,
2077-414: The 1970s. EEC legislation required all vehicles sold and produced in member countries to have a catalytic converter after December 1992. This legislation had been in the pipeline for some time, with many cars becoming available with catalytic converters or fuel injection from around 1990. A significant concern for aircraft engines is the formation of ice inside the carburetor. The temperature of air within
FMC XR311 - Misplaced Pages Continue
2144-614: The Sun and Moon position pointers. The ball was painted black and white in hemispheres, and graphically showed the phase of the Moon at a particular point in time. An equation clock that used a differential for addition was made in 1720. In the 20th century, large assemblies of many differentials were used as analogue computers , calculating, for example, the direction in which a gun should be aimed. Chinese south-pointing chariots may also have been very early applications of differentials. The chariot had
2211-764: The XR311: The following kits were available for the basic vehicle: crew compartment armor kit, consisting of a high-hardness steel doors, side body panels, toe panel, firewall, bulletproof windshield and bulletproof side windows, armored radiator, armored fuel tank, top and door kit (waterproof fabric with plastic windows and hinged doors) various communications installations, high output alternators (100 and 180 amp), litter-carrying kit, jump seat for two additional passengers, explosion-resistant reticulated foam fuel-tank filler, radial tires or foam-filled run-flat tires , extreme climate kits for winterization or desert temperatures, tool kit and portable fire extinguisher . The XR311
2278-413: The air speed through the venturi is insufficient to maintain the fuel flow, therefore the fuel is instead supplied by the carburetor's idle and off-idle circuits . At greater throttle openings, the speed of air passing through the venturi increases, which lowers the pressure of the air and draws more fuel into the airstream. At the same time, the reduced manifold vacuum results in less fuel flow through
2345-450: The barrels consist of "primary" barrel(s) used for lower load situations and secondary barrel(s) activating when required to provide additional air/fuel at higher loads. The primary and secondary venturi are often sized differently and incorporate different features to suit the situations in which they are used. Many four-barrel carburetors use two primary and two secondary barrels. A four-barrel design of two primary and two secondary barrels
2412-420: The carburetor can be reduced by up to 40 °C (72 °F), due to a combination of the reduced air pressure in the venturi and the latent heat of the evaporating fuel. The conditions during the descent to landing are particularly conducive to icing, since the engine is run at idle for a prolonged period with the throttle closed. Icing can also occur in cruise conditions at altitude. A carburetor heat system
2479-537: The carburetor is a key design consideration. Older engines used updraft carburetors, where the air enters from below the carburetor and exits through the top. From the late 1930s, downdraft carburetors become more commonly used (especially in the United States), along with side draft carburetors (especially in Europe). The main metering circuit consists of a pipe which reduces to a narrows before widening again, forming
2546-539: The carrier is rotated (by the input torque), the relationship between the speeds of the input (i.e. the carrier) and that of the output shafts is the same as other types of open differentials. Uses of spur-gear differentials include the Oldsmobile Toronado American front-wheel drive car. Locking differentials have the ability to overcome the chief limitation of a standard open differential by essentially "locking" both wheels on an axle together as if on
2613-466: The choke based on the temperature of the engine's coolant liquid, an electrical resistance heater to do so, or air drawn through a tube connected to an engine exhaust source. A choke left closed after the engine has warmed up increases the engine's fuel consumption and exhaust gas emissions, and causes the engine to run rough and lack power due to an over-rich fuel mixture. However, excessive fuel can flood an engine and prevent it from starting. To remove
2680-408: The compression-based combustion of diesel requires the greater precision and pressure of fuel-injection. The name "carburetor" is derived from the verb carburet , which means "to combine with carbon", or, in particular, "to enrich a gas by combining it with carbon or hydrocarbons ". Thus a carburetor mixes intake air with hydrocarbon-based fuel, such as petrol or AutoGas (LPG). The name
2747-408: The dial could be pointing in the wrong direction. The earliest verified use of a differential was in a clock made by Joseph Williamson in 1720. It employed a differential to add the equation of time to local mean time , as determined by the clock mechanism, to produce solar time , which would have been the same as the reading of a sundial . During the 18th century, sundials were considered to show
FMC XR311 - Misplaced Pages Continue
2814-480: The difference in power sent to each of the wheels. Torque vectoring is a technology employed in automobile differentials that has the ability to vary the torque to each half-shaft with an electronic system; or in rail vehicles which achieve the same using individually motored wheels. In the case of automobiles, it is used to augment the stability or cornering ability of the vehicle. Non-automotive uses of differentials include performing analogue arithmetic . Two of
2881-474: The differential's three shafts are made to rotate through angles that represent (are proportional to) two numbers, and the angle of the third shaft's rotation represents the sum or difference of the two input numbers. The earliest known use of a differential gear is in the Antikythera mechanism, c. 80 BCE, which used a differential gear to control a small sphere representing the Moon from the difference between
2948-405: The engine (usually via a transmission). Some vehicles (for example go-karts and trams ) use axles without a differential, thus relying on wheel slip when cornering. However, for improved cornering abilities, many vehicles use a differential, which allows the two wheels to rotate at different speeds. The purpose of a differential is to transfer the engine's power to the wheels while still allowing
3015-485: The engine in steady-state conditions, the inertia of fuel (being higher than that of air) causes a temporary shortfall as the throttle is opened. Therefore, an accelerator pump is often used to briefly provide extra fuel as the throttle is opened. When the driver presses the throttle pedal, a small piston or diaphragm pump injects extra fuel directly into the carburetor throat. The accelerator pump can also be used to "prime" an engine with extra fuel prior to attempting
3082-418: The excess fuel, many carburetors with automatic chokes allow it to be held open (by manually, depressing the accelerator pedal to the floor and briefly holding it there while cranking the starter) to allow extra air into the engine until the excess fuel is cleared out. Another method used by carburetors to improve the operation of a cold engine is a fast idle cam , which is connected to the choke and prevents
3149-614: The first of two prototypes being completed in 1970. The vehicle was developed as a possible replacement for the by that time over ten years old M151 jeep , years prior to the Lamborghini Cheetah and other competitors, including AM General 's design for the HMMWV , which was eventually selected. As a result of the trials of these two prototypes the US Army purchased ten improved or second generation models in 1971. Of these ten vehicles, four had
3216-433: The float chamber is located close to the engine, heat from the engine (including for several hours after the engine is shut off) can cause the fuel to heat up to the point of vaporization. This causes air bubbles in the fuel (similar to the air bubbles that necessitate brake bleeding ), which prevents the flow of fuel and is known as 'vapor lock'. To avoid pressurizing the float chamber, vent tubes allow air to enter and exit
3283-407: The float chamber. These tubes usually extend into the carburetor throat, placed to prevent fuel from sloshing out of them into the carburetor. If an engine must be operated when the carburetor is not in an upright orientation (for example in a chainsaw or airplane), a float chamber and gravity activated float valve would not be suitable. Instead, a diaphragm chamber is typically used. This consists of
3350-414: The flow of air at the entrance to the carburetor. This increases the vacuum in the main metering circuit, causing more fuel to be supplied to the engine via the main jets. Prior to the late 1950s the choke was manually operated by the driver, often using a lever or knob on the dashboard . Since then, automatic chokes became more commonplace. These either use a bimetallic thermostat to automatically regulate
3417-401: The front axle and the rear axle in an all-wheel drive vehicle. An advantage of the epicyclic design is that it is relatively compact width (when viewed along the axis of its input shaft). A spur-gear differential has an equal-sized spur gears at each end, each of which is connected to an output shaft. The input torque (i.e. from the engine or transmission) is applied to the differential via
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#17328448075793484-426: The fuel entering the engine. Instead, the airflow through the carburetor increases, which in turn increases the amount of fuel drawn into the intake mixture. The main disadvantage of basing a carburetor's operation on Bernoulli's Principle is that being a fluid dynamic device, the pressure reduction in a venturi tends to be proportional to the square of the intake airspeed. The fuel jets are much smaller and fuel flow
3551-465: The fuel entering the engine. This is done in order to extend the engine's maximum RPM, since many two-stroke engines can temporarily achieve higher RPM with a leaner air-fuel ratio. This is not to be confused with the unrelated exhaust power valve arrangements used on two-stroke engines. A metering rod or step-up rod system is sometimes used as an alternative to a power valve in a four-stroke engine in order to supply extra fuel at high loads. One end of
3618-424: The idle and off-idle circuits. During cold weather fuel vaporizes less readily and tends to condense on the walls of the intake manifold, starving the cylinders of fuel and making cold starts difficult. Additional fuel is required (for a given amount of air) to start and run the engine until it warms up, provided by a choke valve . While the engine is warming up the choke valve is partially closed, restricting
3685-409: The intake air filter to be bypassed, therefore the system is only used when there is a risk of icing. If the engine is operating at idle RPM, another method to prevent icing is to periodically open the throttle, which increases the air temperature within the carburetor. Carburetor icing also occurs on other applications and various methods have been employed to solve this problem. On inline engines
3752-411: The intake air travelling through the carburetor is pressurized (such as where the carburetor is downstream of a supercharger ) the entire carburetor must be contained in an airtight pressurized box to operate. However, this is not necessary where the carburetor is upstream of the supercharger. Problems of fuel boiling and vapor lock can occur in carbureted engines, especially in hotter climates. Since
3819-490: The intake and exhaust manifolds are on the same side of the head. Heat from the exhaust is used to warm the intake manifold and in turn the carburetor. On V configurations, exhaust gases were directed from one head through the intake cross over to the other head. One method for regulating the exhaust flow on the cross over for intake warming was a weighted eccentric butterfly valve called a heat riser that remained closed at idle and opened at higher exhaust flow. Some vehicles used
3886-480: The needle valve to admit more fuel, allowing the engine to generate more power. A balanced state is reached which creates a steady fuel reservoir level, that remains constant in any orientation. Other components that have been used on carburetors include: The basic design for a carburetor consists of a single venturi (main metering circuit), though designs with two or four venturi (two-barrel and four-barrel carburetors respectively) are also quite commonplace. Typically
3953-475: The preferred method. One of the last motorsport users of carburetors was NASCAR, which switched to electronic fuel injection after the 2011 Sprint Cup series . NASCAR still uses the four-barrel carburetor in the NASCAR Xfinity Series . In Europe, carburetors were largely replaced by fuel injection in the late 1980s, although fuel injection had been increasingly used in luxury cars and sports cars since
4020-481: The property that the rotational speed of one shaft is the average of the speeds of the others. A common use of differentials is in motor vehicles , to allow the wheels at each end of a drive axle to rotate at different speeds while cornering. Other uses include clocks and analogue computers . Differentials can also provide a gear ratio between the input and output shafts (called the "axle ratio" or "diff ratio"). For example, many differentials in motor vehicles provide
4087-410: The propshaft to the half-shafts) and provide a reduction in the gear ratio . The components of the ring-and-pinion differential shown in the schematic diagram on the right are: 1. Output shafts ( axles ) 2. Drive gear 3. Output gears 4. Planetary gears 5. Carrier 6. Input gear 7. Input shaft ( driveshaft ) An epicyclic differential uses epicyclic gearing to send certain proportions of torque to
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#17328448075794154-489: The rods is tapered, which sits in the main metering jets and acts as a valve for fuel flow in the jets. At high engine loads, the rods are lifted away from the jets (either mechanically or using manifold vacuum), increasing the volume of fuel can flow through the jet. These systems have been used by the Rochester Quadra jet and in the 1950s Carter carburetors. While the main metering circuit can adequately supply fuel to
4221-418: The rotating carrier. Pinion pairs are located within the carrier and rotate freely on pins supported by the carrier. The pinion pairs only mesh for the part of their length between the two spur gears, and rotate in opposite directions. The remaining length of a given pinion meshes with the nearer spur gear on its axle. Each pinion connects the associated spur gear to the other spur gear (via the other pinion). As
4288-399: The throttle from closing fully while the choke is in operation. The resulting increase in idle speed provides a more stable idle for a cold engine (by better atomizing the cold fuel) and helps the engine warm up quicker. The system within a carburetor that meters fuel when the engine is running at low RPM. The idle circuit is generally activated by vacuum under the throttle plate, which causes
4355-544: The top of a vessel containing the fuel. The first float-fed carburetor design, which used an atomizer nozzle , was introduced by German engineers Wilhelm Maybach and Gottlieb Daimler in their 1885 Grandfather Clock engine . The Butler Petrol Cycle car—built in England in 1888—also used a float-fed carburetor. The first carburetor for a stationary engine was patented in 1893 by Hungarian engineers János Csonka and Donát Bánki . The first four-barrel carburetors were
4422-400: The wheels to rotate at different speeds when required. An illustration of the operating principle for a ring-and-pinion differential is shown below. A relatively simple design of differential is used in rear-wheel drive vehicles, whereby a ring gear is driven by a pinion gear connected to the transmission. The functions of this design are to change the axis of rotation by 90 degrees (from
4489-527: Was commonly used in V8 engines to conserve fuel at low engine speeds while still affording an adequate supply at high. The use of multiple carburetors (e.g., a carburetor for each cylinder or pair of cylinders) also results in the intake air being drawn through multiple venturi. Some high-performance engines have used multiple two-barrel or four-barrel carburetors, for example six two-barrel carburetors on Ferrari V12s. In 1826, American engineer Samuel Morey received
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