Curtiss C-46 Commando
The Curtiss C-46 Commando is a twin-engine transport aircraft derived from the Curtiss CW-20 pressurised high-altitude airliner design. Early press reports used the name'Condor III' but the Commando name was in use by early 1942 in company publicity, it was used as a military transport during World War II by the United States Army Air Forces and the U. S. Navy/Marine Corps, which used the designation R5C; the C-46 served in a similar role to its Douglas-built counterpart, the C-47 Skytrain, but it was not as extensively produced as the latter. After World War II, a few surplus C-46 aircraft were used in their designated role as passenger airliners, but the glut of surplus C-47s dominated the marketplace and the C-46 was soon relegated to cargo duty; the type continued in U. S. Air Force service in a secondary role until 1968; the C-46 continues in operation as a rugged cargo transport for Arctic and remote locations with its service life extended into the 21st century. The prototype for what would become the C-46, the Curtiss CW-20, was designed in 1937 by George A.
Page Jr. the chief aircraft designer at Curtiss-Wright. The CW-20 was a private venture intended to compete with the four-engined Douglas DC-4 and Boeing Stratoliner by the introduction of a new standard in pressurized airliners; the CW-20 had a patented fuselage conventionally referred to as a "figure-eight" which enabled it to better withstand the pressure differential at high altitudes. This was done by having the sides of the fuselage creased at the level of the floor that not only separated the two portions but shared in the stress of each, rather than just supporting itself; the main spar of the wing could pass through the bottom section, intended for cargo without intruding on the passenger upper compartment. A decision to utilize a twin-engine design instead of a four-engine configuration was considered viable if sufficiently powerful engines were available, allowing for lower operating costs and a less complex structure. Engineering work involved a three-year commitment from the company and incorporated an extensive amount of wind tunnel testing at the California Institute of Technology.
The resultant design was a large but aerodynamically "sleek" airliner, incorporating the cockpit in a streamlined glazed "dome". The engines featured a unique nacelle tunnel cowl where air was ducted in and expelled through the bottom of the cowl, reducing turbulent airflow and induced drag across the upper wing surface. After a mockup was constructed in 1938, Curtiss-Wright exhibited the innovative project as a display in the 1939 New York World's Fair; the company approached many airlines. No firm orders resulted, although 25 letters of intent were received, sufficient to begin production; the design of a 24–34 passenger airliner proceeded to prototype stage as the CW-20 at the St. Louis, Missouri facility with the initial configuration featuring twin vertical tail surfaces. Powered by two 1,700 hp R-2600-C14-BA2 Wright Twin Cyclones, the prototype, registered NX-19436 flew for the first time on 26 March 1940 with test pilot Edmund T. "Eddie" Allen at the controls. After testing, modifications were instituted, including the fitting of a large single tail to improve stability at low speeds.
The first prototype was purchased by the United States Army Air Forces to serve as a master for the series and was designated C-55. After military evaluation, the sole example was returned to Curtiss-Wright and subsequently re-sold to the British Overseas Airways Corporation. During testing, General Henry H. "Hap" Arnold became interested in the potential of the airliner as a military cargo transport and on 13 September 1940, ordered 46 modified CW-20As as the C-46-CU Commando. None of the C-46s purchased by the U. S. military were pressurized and the first 30 delivered to the AAF were sent back to the factory for 53 immediate modifications. The design was modified to the C-46A configuration, receiving enlarged cargo doors, a strengthened load floor and a convertible cabin that speeded changes in carrying freight and troops; the C-46 was introduced to the public at a ceremony in May 1942, attended by its designer, George A. Page Jr. A total of 200 C-46As in two initial batches were ordered in 1940, although only two were delivered by December 7, 1941.
At this time, one other important change was made. By November 1943, 721 modifications had been made to production models, although many were minor, such as fuel system changes and fewer cabin windows were adopted. Subsequent military contracts for the C-46A extended the production run to 1,454 examples, 40 of which were destined for the U. S. Marine Corps, to be designated R5C-1; the military model was fitted with double cargo doors, a strengthened floor and a hydraulically operated cargo handling winch. Tests indicated that the production C-46 was capable of carrying a substantial payload, it could fly well on one engine; when empty, the aircraft could climb on one engine at 200–300 ft per minute. The final large production-run C-46D arrived in 1944–45, featured single doors to facilitate paratroop drops. Although a one-off XC-46B experimented with a stepped windscreen and uprated powerplants, a small run of 17 C-46Es had many of the same features as the XC-46B along with three-bladed Hamilton-Standard propellers replacing the standard Curtiss-Electric four-bladed units.
A last contract
A valvetrain or valve train is a mechanical system that controls operation of the valves in an internal combustion engine, whereby a sequence of components transmits motion throughout the assembly. A conventional reciprocating internal combustion engine uses valves to control the flow of the air/fuel admix into and out of the combustion chamber. A typical ohv valvetrain consists of valves, rocker arms, pushrods and camshaft. Valvetrain opening/closing and duration, as well as the geometry of the valvetrain, controls the amount of air and fuel entering the combustion chamber at any given point in time. Timing for open/close/duration is controlled by the camshaft, synchronized to the crankshaft by a chain, belt, or gear. Valvetrains are built in several configurations, each of which varies in layout but still performs the task of opening and closing the valves at the time necessary for proper operation of the engine; these layouts are differentiated by the location of the camshaft within the engine: Cam-in-block The camshaft is located within the engine block, operates directly on the valves, or indirectly via pushrods and rocker arms.
Because they require pushrods they are called pushrod engines. Overhead camshaft The camshaft is located above the valves within the cylinder head, operates either indirectly or directly on the valves. Camless This layout uses no camshafts at all. Technologies such as solenoids are used to individually actuate the valves; the valvetrain is the mechanical system responsible for operation of the valves. Valves are of the poppet type, although many others have been developed such as sleeve and rotary valves. Poppet valves require small coil springs, appropriately named valve springs, to keep them closed when not actuated by the camshaft, they are attached to the valve stem ends, seating within spring retainers. Other mechanisms can be used in place of valve springs to keep the valves closed: Formula 1 engines employ pneumatic valve springs in which pneumatic pressure closes the valves, while motorcycle manufacturer Ducati uses desmodromic valve drive which mechanically close the valves. Depending on the design used, the valves are actuated directly by a rocker arm, finger, or bucket tappet.
Overhead camshaft engines use fingers or bucket tappets, upon which the cam lobes contact, while pushrod engines use rocker arms. Rocker arms are actuated by a pushrod, pivot on a shaft or individual ball studs in order to actuate the valves. Pushrods are slender metal rods seated within the engine block. At the bottom ends the pushrods are fitted with lifters, either solid or hydraulic, upon which the camshaft, located within the cylinder block, makes contact; the camshaft pushes on the lifter, which pushes on the pushrod, which pushes on the rocker arm, which rotates and pushes down on the valve. Camshafts must actuate the valves at the appropriate time in the combustion cycle. In order to accomplish this the camshaft is linked to and kept in synchronisation with the crankshaft through the use of a metal chain, rubber belt, or geartrain; because these mechanisms are essential to the proper timing of valve actuation they are named timing chains, timing belts, timing gears, respectively. Typical normal-service engine valve-train components may be too lightweight for operating at high revolutions per minute, leading to valve float.
This occurs when the action of the valve no longer opens or closes, such as when the valve spring force is insufficient to close the valve causing a loss of control of the valvetrain, as well as a drop in power output. Valve float will damage the valvetrain over time, could cause the valve to be damaged as it is still open while the piston comes to the top of its stroke. Upgrading to high pressure valve springs could allow higher valvetrain speeds, but this would overload the valvetrain components and cause excessive and costly wear. High-output and engines used in competition feature camshafts and valvetrain components that are designed to withstand higher RPM ranges; these changes include additional modifications such as larger-sized valves combined with freer breathing intake and exhaust ports to improve air flow. Automakers offer factory-approved performance parts to increase engine output, numerous aftermarket parts vendors specialize in valvetrain modifications for various engine applications.
Cam-in-block Overhead camshaft Camless Animation
Cincinnati is a major city in the U. S. state of Ohio, is the government seat of Hamilton County. Settled in 1788, the city is located at the northern side of the confluence of the Licking and Ohio rivers, the latter of which marks the state line with Kentucky; the city drives the Cincinnati–Middletown–Wilmington combined statistical area, which had a population of 2,172,191 in the 2010 census making it Ohio's largest metropolitan area. With a population of 296,943, Cincinnati is the third-largest city in Ohio and 65th in the United States, its metropolitan area is the fastest growing economic power in the Midwestern United States based on increase of economic output and it is the 28th-largest metropolitan statistical area in the U. S. Cincinnati is within a day's drive of 49.70% of the United States populace. In the nineteenth century, Cincinnati was an American boomtown in the middle of the country. Throughout much of the 19th century, it was listed among the top 10 U. S. cities by population, surpassed only by New Orleans and the older, established settlements of the United States eastern seaboard, as well as being the sixth-biggest city for a period spanning 1840 until 1860.
As Cincinnati was the first city founded after the American Revolution, as well as the first major inland city in the country, it is regarded as the first purely "American" city. Cincinnati developed with fewer immigrants and less influence from Europe than East Coast cities in the same period. However, it received a significant number of German immigrants, who founded many of the city's cultural institutions. By the end of the 19th century, with the shift from steamboats to railroads drawing off freight shipping, trade patterns had altered and Cincinnati's growth slowed considerably; the city was surpassed in population by other inland cities Chicago, which developed based on strong commodity exploitation and the railroads, St. Louis, which for decades after the Civil War served as the gateway to westward migration. Cincinnati is home to three major sports teams: the Cincinnati Reds of Major League Baseball; the city's largest institution of higher education, the University of Cincinnati, was founded in 1819 as a municipal college and is now ranked as one of the 50 largest in the United States.
Cincinnati is home to historic architecture with many structures in the urban core having remained intact for 200 years. In the late 1800s, Cincinnati was referred to as the "Paris of America", due to such ambitious architectural projects as the Music Hall, Cincinnatian Hotel, Shillito Department Store. Cincinnati is the birthplace of the 27th President of the United States. Cincinnati began in 1788 when Mathias Denman, Colonel Robert Patterson, Israel Ludlow landed at a spot at the northern bank of the Ohio opposite the mouth of the Licking and decided to settle there; the original surveyor, John Filson, named it "Losantiville". In 1790, Arthur St. Clair, the governor of the Northwest Territory, changed the name of the settlement to "Cincinnati" in honor of the Society of the Cincinnati, made up of Revolutionary War veterans, of which he was a member; the introduction of steamboats on the Ohio River in 1811 opened up the city's trade to more rapid shipping, the city established commercial ties with St. Louis and New Orleans downriver.
Cincinnati was incorporated as a city on March 1, 1819. Exporting pork products and hay, it became a center of pork processing in the region. From 1810 to 1830 its population nearly tripled, from 9,642 to 24,831. Completion of the Miami and Erie Canal in 1827 to Middletown, Ohio further stimulated businesses, employers struggled to hire enough people to fill positions; the city had a labor shortage until large waves of immigration by Irish and Germans in the late 1840s. The city grew over the next two decades, reaching 115,000 people by the year 1850. Construction on the Miami and Erie Canal began on July 21, 1825, when it was called the Miami Canal, related to its origin at the Great Miami River; the first section of the canal was opened for business in 1827. In 1827, the canal connected Cincinnati to nearby Middletown. During this period of rapid expansion and prominence, residents of Cincinnati began referring to the city as the Queen City. After the steamboats, railroads were the next major form of commercial transportation to come to Cincinnati.
In 1836, the Little Miami Railroad was chartered. Construction began soon after, to connect Cincinnati with the Mad River and Lake Erie Railroad, provide access to the ports of the Sandusky Bay on Lake Erie. Cincinnati acted as a "border town" during the slave-owning period between 1810 and 1863, its location, on the border between the free state of Ohio and the slave state of Kentucky, made it a prominent location for slaves to escape the slave-owning south. Many prominent abolitionists called Cincinnati their home during this period, made it a popular stop on the Underground Railroad. In 2004, the National Underground Railroad Freedom Center was completed along Freedom Way in Downtown, honoring the city's past involvement in the Underground Railroad. In 1859, Cincinnati laid out six streetcar lines. By 1872, Cincinnatians could travel on the streetcars within the city and transfer to rail cars for travel to the hill communities; the Cincinnati Inclined Plane Company began transporting people t
The Martin 187 Baltimore was a twin-engined light attack bomber built by the Glenn L. Martin Company in the United States ordered by the French in May 1940 as a follow-up to the earlier Martin Maryland in service in France. With the fall of France, the production series was diverted to Great Britain and it was subsequently used exclusively in the Mediterranean and Middle East theatre of World War II. Development of the Baltimore was hindered by a series of problems, although the type became a versatile combat aircraft. Produced in large numbers, the Baltimore was not used operationally by United States armed forces, but served with the British, Australian, South African and the Italian air forces. Designated the A-23, the Model 187 had a deeper fuselage and more powerful engines; the Model 187 met the needs for a light-to-medium bomber ordered by the Anglo-French Purchasing Commission as a joint project in May 1940. The French Air Force sought to replace the earlier Maryland. With the Fall of France, the Royal Air Force took over the order and gave it the service name Baltimore.
To enable the aircraft to be supplied to the British under the Lend-Lease Act the United States Army Air Forces designation A-30 was allocated. With the passing of the Lend Lease Act two further batches of 575 and 600 were provided to the RAF; the first British aircraft were delivered in late 1941 to equip Operational Training Units. The RAF only used the Baltimores operationally in North Africa. Many users were impressed by the step up that the Baltimore represented from older aircraft like the Bristol Blenheim. Users of the Baltimore, Martin pilot Benjamin R. Wallace, praised the aircraft for its heavy armament, structural strength, bombing accuracy, high performance, but crews complained of cramped conditions similar to those in the earlier Maryland bomber; the narrow fuselage design made it nearly impossible for crew members to change positions during flight if wounded. Crews complained about the difficulties in handling the aircraft on the ground. On takeoff, the pilot had to co-ordinate the throttles to avoid a nose-over, or worse.
Thrown into action to stop Rommel's advance, the Baltimore suffered massive losses when it was utilized as a low-level attack aircraft in the chaos of the desert war where most missions went unescorted. However, operating at medium altitude with fighter escorts, the Baltimore had a low loss rate, with the majority of losses coming from operational accidents. Undertaking a variety of missions in the Middle East and European theaters, the Baltimore's roles included reconnaissance, target-towing, maritime patrol, night intruder and served as uncomfortable fast transports; the Baltimore saw limited Fleet Air Arm service with aircraft transferred from the RAF in the Mediterranean to equip a squadron in 1944. Used in the anti-submarine role during the war, the Baltimore achieved moderate success, sinking up to eight U-boats; the RAF transferred aircraft to other Allies in the Mediterranean area. The Baltimore was used intensively in the Italian campaign to clear the road to Rome for advancing Allied forces after the capitulation of Italy in 1943.
After the armistice an Italian-manned squadron, the 28th Bomber Wing, was equipped with ex-RAF Baltimores, becoming the co-belligerent Stormo Baltimore. The Italians suffered considerable attrition during their training phase on the Baltimore; the majority of accidents were during takeoffs and landings due to the aircraft's high wing loading, high approach speed and a directional stability problems during takeoffs. The Italians operated the Baltimore for only six months. Many of those operations were in Yugoslavia and Greece, providing air support for partisan forces or dropping supplies. Most Baltimores were scrapped soon after the war, although one RAF squadron continued to use the type in Kenya where the aircraft were used in aerial mapping and locust control until 1948. In post-war service, the Baltimore took part in United States Navy instrument and control surface tests in the effort to break the sound barrier. With its powerful engines and light, yet robust construction, the aircraft was able to be dived at high speed, reaching Mach.74 in tests.
All Baltimores were withdrawn from service by the end of 1949, the last one being retired on 23 December 1949. Baltimore B. I Fitted with 1,600 hp Wright GR-2600-A5B radial piston engines, armed with ten 0.303 in machine guns, eight fixed Brownings and two flexible Vickers K machine guns. 50 aircraft built. Baltimore B. II As with the Mk I. 100 aircraft built. Baltimore B. III Modified Mk II design defensive armament was increased to 14 0.303 in guns and improved with a hydraulically powered dorsal turret supplied by Boulton Paul in the UK with 4 Browning machine guns. 250 aircraft built. Baltimore B. IIIa Ordered by USAAF and supplied under Lend-lease to the RAF, two 0.50 in
An impeller is a rotor used to increase the pressure and flow of a fluid. An impeller is a rotating component of a centrifugal pump which transfers energy from the motor that drives the pump to the fluid being pumped by accelerating the fluid outwards from the center of rotation; the velocity achieved by the impeller transfers into pressure when the outward movement of the fluid is confined by the pump casing. An impeller is a short cylinder with an open inlet to accept incoming fluid, vanes to push the fluid radially, a splined, keyed, or threaded bore to accept a drive shaft; the impeller made out of cast material in many cases may be called rotor, also. It is cheaper to cast the radial impeller right in the support it is fitted on, put in motion by the gearbox from an electric motor, combustion engine or by steam driven turbine; the rotor names both the spindle and the impeller when they are mounted by bolts. In a failing heart, mechanical circulatory devices utilize a continuous axial-flow impeller pump design.
Open shrouded impeller. The main part of a centrifugal compressor is the impeller. An open impeller has no cover, therefore it can work at higher speeds. A compressor with a covered impeller can have more stages than one; some impellers are similar without the large blades. Among other uses, they are used in water jets to power high speed boats. Since impellers have no large blades to turn, they can spin at much higher speeds than propellers; the water forced through the impeller is channelled by the housing, creating a water jet that propels the vessel forward. The housing is tapered into a nozzle to increase the speed of the water, which creates a Venturi effect in which low pressure behind the impeller pulls more water towards the blades, tending to increase the speed. To work efficiently, there must be a close fit between the housing; the housing is fitted with a replaceable wear ring which tends to wear as sand or other particles are thrown against the housing side by the impeller. Vessels using impellers are steered by changing the direction of the water jet.
Compare to propeller and jet aircraft engines. Impellers in agitated tanks are used to mix fluids or slurry in the tank; this can be used to combine materials in the form of solids and gas. Mixing the fluids in a tank is important if there are gradients in conditions such as temperature or concentration. There are two types of impellers, depending on the flow regime created: Axial flow impeller Radial flow impellerRadial flow impellers impose shear stress to the fluid, are used, for example, to mix immiscible liquids or in general when there is a deformable interface to break. Another application of radial flow impellers are the mixing of viscous fluids. Axial flow impellers impose bulk motion, are used on homogenization processes, in which increased fluid volumetric flow rate is important. Impellers can be further classified principally into three sub-types Propellers Paddles TurbinesAll these can be discussed after example. If one heats a pot of soup on the stove the pot will develop a temperature gradient.
Mild agitation will increase the rate of heating by dissipating the heat through the entire pot. See: Law of cooling. More significant, agitation disturbs the soup directly in contact with the hotter pot surface. Turbulent flow at the warming surface is important to good heat transfer; this is the same effect as the "wind chill" factor where moving air and turbulent action on surfaces resulting in enhanced heat transfer. In unusual circumstances, overly-severe agitation may decrease the rate of heating which defeats the purpose. Propellers are axial thrust-giving elements; these elements give a high degree of swirling in the vessel. The flow pattern generated in the fluid resembles a helix; some constructions of top loading washing machines use impellers to agitate the laundry during washing. Fire services in the United Kingdom and many countries of the Commonwealth use a stylized depiction of an impeller as a rank badge. Officers wear one or more on their epaulettes or the collar of their firefighting uniform as an equivalent to the "pips" worn by the army and police.
Impellers are an integral part of axial-flow pump, used in ventricular assist devices to augment or replace cardiac function. Air pumps, such as the roots blower, use meshing impellers to move air through a system. Applications include blast furnaces, ventilation systems, superchargers for internal combustion engines. Axial fan design Centrifugal fan
Overhead valve engine
An overhead valve engine, or "pushrod engine", is a reciprocating piston engine whose poppet valves are sited in the cylinder head. An OHV engine's valvetrain operates its valves via a camshaft within the cylinder block, cam followers and rocker arms; the OHV engine was an advance over the older flathead engine, whose valves were sited within the cylinder block. Some early "OHV" engines known as "F-heads" used both side-valves and overhead valves. A variation over the OHV design is the overhead camshaft, or "OHC", whose camshaft lies in the cylinder head itself, above the valves. To avoid confusion, OHC engines are not referred to as OHV despite having their valves in the head. In early 1894, Rudolf Diesel's second Diesel engine prototype was built with a cylinder head featuring push rods, rocker arms, poppet valves. Diesel had published this design in 1893. In 1896, U. S. patent 563,140, awarded to William F. Davis, illustrated a gasoline engine with the same head configuration, patenting his solution to the problem of how to cool the head, which problem had made the overhead valve engine difficult before then.
Henry Ford's Quadricycle of 1896 had valves in the head, with push rods for exhaust valves only, the intake using suction valves. In 1898, Detroit bicycle manufacturer Walter Lorenzo Marr built a motor-trike with a one-cylinder OHV engine with push rods for both exhaust and intake. In 1900, David Buick hired Marr as chief engineer at the Buick Auto-Vim and Power Company in Detroit, where he worked until 1902. Marr's engine employed pushrod-actuated rocker arms, which in turn pushed valves parallel to the pistons. Marr left Buick to start his own automobile company in 1902, the Marr Auto-Car, made a handful of cars with overhead valve engines, before coming back to Buick in 1904; the OHV engine was patented in 1902 by Buick's second chief engineer Eugene Richard, at the Buick Manufacturing Company, precursor to the Buick Motor Company. The world's first production overhead valve internal combustion engine was put into the first production Buick automobile, the 1904 Model B, which used a 2-cylinder Flat twin engine, with 2 valves in each head.
The engine was designed by David Buick. Eugene Richard of the Buick Manufacturing Company was awarded US Patent #771,095 in 1904 for the valve in head engine, it included rocker arms and push rods, a water jacket for the head which communicated with the one in the cylinder block, lifters pushed by a camshaft with a 2-to-1 gearing ratio to the crankshaft. Arthur Chevrolet was awarded US Patent #1,744,526 for an adapter that could be applied to an existing engine, thus transforming it into an Overhead Valve Engine; the Wright Brothers built their own airplane engines, starting in 1906, they used overhead valves for both exhaust and intake, with push rods and rocker arms for the exhaust valves only, the intake valves being "automatic suction" valves. They built a V-8 engine with this valve configuration in 1910. In 1949, Oldsmobile introduced the Rocket V8, the first V-8 engine with OHV's to be produced on a wide scale. General Motors is the world's largest pushrod engine producer, producing I4, V6 and V8 pushrod engines.
Most other companies use overhead cams. Nowadays, automotive use of side-valves has disappeared, valves are all "overhead". However, most are now driven more directly by the overhead camshaft system. Few pushrod-type engines remain in production outside of the United States market; this is in part a result of some countries passing laws to tax engines based on displacement, because displacement is somewhat related to the emissions and fuel efficiency of an automobile. This has given OHC engines a regulatory advantage in those countries, which resulted in few manufacturers wanting to design both OHV and OHC engines. However, in 2002, Chrysler introduced a new pushrod engine: a 5.7-litre Hemi engine. The new Chrysler Hemi engine presents advanced features such as variable displacement technology and has been a popular option with buyers; the Hemi was on the Ward's 10 Best Engines list for 2003 through 2007. Chrysler produced the world's first production variable-valve OHV engine with independent intake and exhaust phasing.
The system is called CamInCam, was first used in the 600 horsepower SRT-10 engine for the 2008 Dodge Viper. Early air-cooled ohv BMW boxer motorcycle engines had long pushrods and a single centrally-mounted camshaft; the pushrods were short, allowing higher rpm and more power. For instance, the BMW R1100S could achieve an output of 98 hp at 8,400 rpm, with no risk of valve bounce. Since 2013, BMW flat-twin motorcycle engines have had OHC valve actuation. OHV engines have some advantages over OHC engines: Smaller overall packaging: because of the camshaft's location inside the engine block, OHV engines are more compact than an overhead cam engine of comparable displacement. For example, Ford's 4.6 L OHC modular V8 is larger than the 5.0 L I-head Windsor V8. GM's 4.6 L OHC Northstar V8 is taller and wider than GM's larger displacement 5.7 to 7.0 L I-head LS V8. The Ford Ka uses the Kent Crossflow/Endura-E OHV engine to fit under its low bonnet line; because of the more compact size of an engine of a given displacement, a pushrod engine of given external dimensions can have greater displacement than an OHC engine of the same external size.
As a result, the pushrod engine can sometimes produce just as much power as the OHC engine, but with greater torque (contrary to popular belief, this is due to the greater displacement of