AMAL was a British engineering company servicing the motorcycle and other light-engineering motor industries between 1927 and 1993 based in Birmingham, England .
107-474: AMAL is a British carburettor trademark. Amal was the supplier of carburettors to many marques within the British motorcycle industry including the largest of British manufacturers, such as Triumph , BSA and AMC , and to producers of small industrial engines . The main carburettor types commonly associated with Amal are slide carburettors for motorcycles. These were historically distinguishable as three types:
214-451: 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 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
321-407: A mold cavity . The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process. Most die castings are made from non-ferrous metals , specifically zinc , copper , aluminium , magnesium , lead , pewter , and tin -based alloys. Depending on the type of metal being cast, a hot- or cold-chamber machine
428-446: A bottom fill system that required a stable flow-front. Logical thought processes and trial and error were used because computerized analysis did not exist yet; however this modeling was the precursor to computerized flow and fill modeling. The Acurad system was the first die casting process that could successfully cast low-iron aluminium alloys, such as A356 and A357 . In a traditional die casting process these alloys would solder to
535-409: 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 the top of a vessel containing the fuel. The first float-fed carburetor design, which used an atomizer nozzle ,
642-409: A car, this throttle is connected to the vehicle's throttle pedal, which varies engine speed. At lesser throttle openings, 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
749-474: 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 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
856-454: 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 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
963-574: 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 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
1070-406: 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 the carburetor can be reduced by up to 40 °C (72 °F), due to a combination of
1177-440: A die is directly dependent on the temperature of the molten metal and the cycle time. The dies used in die casting are usually made out of hardened tool steels , because cast iron cannot withstand the high pressures involved, therefore the dies are very expensive, resulting in high start-up costs. Metals that are cast at higher temperatures require dies made from higher alloy steels . The main failure mode for die casting dies
SECTION 10
#17331065451511284-615: A highly refined process there will still be some porosity in the center of the casting. Most die casters perform other secondary operations to produce features not readily castable, such as tapping a hole, polishing, plating, buffing, or painting. After the shakeout of the casting it is inspected for defects. The most common defects are misruns and cold shuts . These defects can be caused by cold dies, low metal temperature, dirty metal, lack of venting, or too much lubricant. Other possible defects are gas porosity, shrinkage porosity , hot tears , and flow marks. Flow marks are marks left on
1391-406: A large composition of aluminium, magnesium and copper. The process for these machines start with melting the metal in a separate furnace. Then a precise amount of molten metal is transported to the cold-chamber machine where it is fed into an unheated shot chamber (or injection cylinder). This shot is then driven into the die by a hydraulic or mechanical piston. The biggest disadvantage of this system
1498-590: A large production volume is needed. Other disadvantages are: Acurad was a die casting process developed by General Motors in the late 1950s and 1960s. The name is an acronym for accurate, reliable, and dense. It was developed to combine a stable fill and directional solidification with the fast cycle times of the traditional die casting process. The process pioneered four breakthrough technologies for die casting: thermal analysis , flow and fill modeling, heat treatable and high integrity die castings, and indirect squeeze casting (explained below). The thermal analysis
1605-538: A new carburettor, the Concentric, was introduced for the 1968 model year. A hemispherical float chamber was introduced below and concentric with the main jet to eliminate differences in fuel height during cornering. There was no jet block, the jets being mounted directly into the body. The pilot jet reverted to a drilling instead of a removable jet. Right and left hand carburettors were available with flange mountings only. Three body sizes were initially produced: To satisfy
1712-407: A pipe which reduces to a narrows before widening again, forming 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
1819-403: A pool of molten metal to feed the die. At the beginning of the cycle the piston of the machine is retracted, which allows the molten metal to fill the "gooseneck". The pneumatic - or hydraulic -powered piston then forces this metal out of the gooseneck into the die. The advantages of this system include fast cycle times (approximately 15 cycles a minute) and the convenience of melting the metal in
1926-472: A removable pilot jet introduced instead of the drilling on the Standard models. This allowed a common jet block to be used on different models. Three sizes were introduced: The 375 was also available with a cast in air filter in 25/32" and 13/16" bore diameters. These were designated type 363. All Monoblocs were initially manufactured with the float chamber projecting on the left side of the body when viewed from
2033-582: A single unit, using a die casting process . It nearly completely replaced setting type by hand in the publishing industry. The Soss die-casting machine, manufactured in Brooklyn, NY, was the first machine to be sold in the open market in North America. Other applications grew rapidly, with die casting facilitating the growth of consumer goods, and appliances, by greatly reducing the production cost of intricate parts in high volumes. In 1966, General Motors released
2140-401: A vacuum pump removes air and gases from die cavity and metal delivery system before and during injection. Vacuum die casting reduces porosity, allows heat treating and welding, improves surface finish, and can increase strength. Heated-manifold direct-injection die casting , also known as direct-injection die casting or runnerless die casting , is a zinc die casting process where molten zinc
2247-497: A very good surface finish (by casting standards) and dimensional consistency. Die casting equipment was invented in 1838 for the purpose of producing movable type for the printing industry . The first die casting-related patent was granted in 1849 for a small hand-operated machine for the purpose of mechanized printing type production. In 1885 Ottmar Mergenthaler invented the Linotype machine , which cast an entire line of type as
SECTION 20
#17331065451512354-408: Is wear or erosion . Other failure modes are heat checking and thermal fatigue . Heat checking is when surface cracks occur on the die due to a large temperature change on every cycle. Thermal fatigue is when surface cracks occur on the die due to a large number of cycles. The following are the four steps in traditional die casting , also known as high-pressure die casting , these are also
2461-424: 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 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
2568-515: Is cut into two cavity inserts , which are separate pieces that can be replaced relatively easily and bolt into the die halves. The dies are designed so that the finished casting will slide off the cover half of the die and stay in the ejector half as the dies are opened. This assures that the casting will be ejected every cycle because the ejector half contains the ejector pins to push the casting out of that die half. The ejector pins are driven by an ejector pin plate , which accurately drives all of
2675-475: Is forced through a heated manifold and then through heated mini-nozzles, which lead into the moulding cavity. This process has the advantages of lower cost per part, through the reduction of scrap (by the elimination of sprues, gates, and runners) and energy conservation, and better surface quality through slower cooling cycles. Semi-solid die casting uses metal that is heated between its liquidus and solidus (or liquidus and eutectic temperature), so that it
2782-540: Is in a "mushy" state. This allows for more complex parts and thinner walls. Low-pressure die casting (LPDC) is a process developed to improve the consistency and integrity of parts, at the cost of a much slower cycle time. In LPDC, material is held in a reservoir below the die, from which it flows into the cavity when air pressure in the reservoir is increased. Typical pressures range from 0.3 bar (4.4 psi) to 0.5 bar (7.3 psi). Somewhat higher pressures (up to 1 bar (15 psi)) may be applied after
2889-500: Is injected into the die before each shot to purge any air from the mould cavity. This causes small dispersed oxides to form when the molten metal fills the die, which virtually eliminates gas porosity. An added advantage to this is greater strength. Unlike standard die castings, these castings can be heat treated and welded . This process can be performed on aluminium, zinc, and lead alloys. In vacuum assisted high pressure die casting , a.k.a. vacuum high pressure die casting (VHPDC),
2996-401: 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 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
3103-401: 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 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
3210-401: Is often done using a special trim die in a power press or hydraulic press. Other methods of shaking out include sawing and grinding. A less labor-intensive method is to tumble shots if gates are thin and easily broken; separation of gates from finished parts must follow. This scrap is recycled by remelting it. The yield is approximately 67%. The high-pressure injection leads to a quick fill of
3317-434: 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 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
Amal (carburettor) - Misplaced Pages Continue
3424-418: Is the slower cycle time due to the need to transfer the molten metal from the furnace to the cold-chamber machine. Two dies are used in die casting; one is called the "cover die half" and the other the "ejector die half". Where they meet is called the parting line . The cover die contains the sprue (for hot-chamber machines) or shot hole (for cold-chamber machines), which allows the molten metal to flow into
3531-480: Is used. The casting equipment and the metal dies represent large capital costs and this tends to limit the process to high-volume production. Manufacture of parts using die casting is relatively simple, involving only four main steps, which keeps the incremental cost per item low. It is especially suited for a large quantity of small- to medium-sized castings, which is why die casting produces more castings than any other casting process. Die castings are characterized by
3638-885: The Acurad process. The main die casting alloys are: zinc , aluminium, magnesium, copper, lead, and tin; although uncommon, ferrous die casting is also possible. Specific die casting alloys include: zinc aluminium ; aluminium to, e.g. The Aluminum Association (AA) standards: AA 380, AA 384, AA 386, AA 390; and AZ91D magnesium. The following is a summary of the advantages of each alloy: As of 2008 , maximum weight limits for aluminium, brass , magnesium, and zinc castings are estimated at approximately 70 pounds (32 kg), 10 lb (4.5 kg), 44 lb (20 kg), and 75 lb (34 kg), respectively. By late-2019, press machines capable of die casting single pieces over-100 kilograms (220 lb) were being used to produce aluminium chassis components for cars. The material used defines
3745-462: The Rochester Quadra jet and in the 1950s Carter carburetors. While the main metering circuit can adequately supply fuel to 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
3852-630: The Standard , with a separate float chamber, the Monobloc with an integral but offset float chamber and the Concentric , a later development with the float chamber directly below the body and air-slide. Less-common types, known as GP and TT, were mainly for road-racing and other competition use, and were used on high-performance road machines such as BSA Gold Star , BSA Spitfire and Velocette Thruxton . Amal also produced handlebars and control levers for
3959-445: The dashboard . Since then, automatic chokes became more commonplace. These either use a bimetallic thermostat to automatically regulate 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
4066-415: 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 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
4173-507: The 1960s, David Boshier Jones. Carburettor A carburetor (also spelled carburettor or carburetter ) 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
4280-415: 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 the compression-based combustion of diesel requires
4387-519: The 27, one mounted on either side of the carb. The TT (Series 27) was introduced in 1932 as a progression of the Type 27. A needle and needle jet were incorporated to provide additional tuning for road machines and when the carb was used with alcohol as a fuel. Pre-war models were suffixed with the year of manufacture but when production resumed after WW2 , all of the TTs had a 9 suffix regardless of year. As well as
Amal (carburettor) - Misplaced Pages Continue
4494-468: The 274, 275 and 289 types. The 'Monobloc' type was available from 1955 with designations 375, 376 and 389 The more modern Concentric , developed and introduced for the 1967 Model Year, was initially designated 600 and 900. The 600 series had bore sizes of 22mm, 24mm and 26mm, being known as 622, 624, and 626 respectively. Similarly, the 900 series with bore sizes of 28mm, 30mm and 32mm, were known as 928, 930, and 932 respectively. The largest bore at 32mm
4601-490: The British made version, they became known as Mark 1.5 or Mark 1 1/2 and a 1 prefix added to the product number, for example the modified 626 became the 1626. A derivative of the 400 series is still in production by Talleres Arreche in 16, 18 and 20 mm bores with Amal embossed on the body. Introduced in 1974, the Mark 2 used aluminium alloy for the main castings rather than the zinc alloy previously used. The cold starting system from
4708-565: The Mark 1, the Premier, was introduced in 2012. The castings for the body and float bowl were in aluminium alloy and the slide was made of hard anodised aluminium. A new float was introduced that was resistant to the ethanol in modern fuels. The pilot jet was removable. and the idle circuit improved. To supply demand for OEM carburettors for Spanish made motorcycles, Amal licensed Talleres Arreche to produce carburettors in Spain. Initially this production
4815-404: The Mark 1.5 was integrated into the new design. Whilst the float chamber was still concentric with the main jet, it was now a square section. The pilot jet reverted to being removable and could be inserted in an alternate position for higher downdraught applications. Flange mounting was discontinued and the Mark 2 was only available in spigot mounting. Three body sizes were available: The Type 27
4922-578: 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 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 :
5029-410: The air and draws more fuel into the airstream. At the same time, the reduced manifold vacuum results in less fuel flow through 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
5136-402: The air intake. This led to fitment problems on twin carb installation. Amal introduced a "chopped" version of the 376 and 389 without the float chamber so twin carburettors could be fitted. Both carbs were fed from the float chamber of the left hand carb. Triumph twins used two chopped monoblocs and a remote float chamber mounted centrally behind the carbs. In 1964 a right hand version of the 389
5243-434: The basis for any of the die casting variations: die preparation, filling, ejection, and shakeout. The dies are prepared by spraying the mould cavity with lubricant . The lubricant both helps control the temperature of the die and it also assists in the removal of the casting. The dies are then closed and molten metal is injected into the dies under high pressure; between 10 and 175 megapascals (1,500 and 25,400 psi). Once
5350-485: The body which led to blocked jets and tubes. To overcome this types 274, 275, 276 & 289 were introduced in 1939 which took the air feeds from the incoming filtered airflow. Introduced in 1954, the Monobloc was introduced to reduce production cost. Whilst the design relied heavily on the previous standard series, the float chamber had been combined into the carburettor casting. The jet block and slide had been simplified and
5457-411: The business was sold to Burlen Fuel Systems Limited, a company that also produces SU , Solex and Zenith , three other classic carburettor ranges. Amal carburettors were used on Cooper Formula 3 racing cars and racing motor cycles. Coopers fitted with the J.A.P. 1,100 cc engine with such a carburettor were popular in hill climbs and sprints competitions, and were used by the frequent champion in
SECTION 50
#17331065451515564-427: The casting machine. The disadvantages of this system are that it is limited to use with low- melting point metals and that aluminium cannot be used because it picks up some of the iron while in the molten pool. Therefore, hot-chamber machines are primarily used with zinc-, tin-, and lead-based alloys. These are used when the casting alloy cannot be used in hot-chamber machines; these include aluminium, zinc alloys with
5671-422: The casting's purpose. Other die components include cores and slides . Cores are components that usually produce holes or opening, but they can be used to create other details as well. There are three types of cores: fixed, movable, and loose. Fixed cores are ones that are oriented parallel to the pull direction of the dies (i.e. the direction the dies open), therefore they are fixed, or permanently attached to
5778-406: The demand for larger carburettors the 1000 series was introduced in 1970 with bore sizes of 34, 36 and 38mm. The British motorcycle industry was in decline and with the lack of orders for OEM carburettors, production was limited after 1975 for replacement and aftermarket sales. Following the introduction of other models of the Concentric, this model became known as the Mark 1. An updated version of
5885-423: The die by hand before each cycle and then ejected with the part at the end of the cycle. The core then must be removed by hand. Loose cores are the most expensive type of core, because of the extra labor and increased cycle time. Other features in the dies include water-cooling passages and vents along the parting lines . These vents are usually wide and thin (approximately 0.13 mm or 0.005 in) so that when
5992-416: The die, which is required so the entire cavity fills before any part of the casting solidifies. In this way, discontinuities are avoided, even if the shape requires difficult-to-fill thin sections. This creates the problem of air entrapment, because when the mould is filled quickly there is little time for the air to escape. This problem is minimized by including vents along the parting lines, however, even in
6099-533: The die. Movable cores are ones that are oriented in any other way than parallel to the pull direction. These cores must be removed from the die cavity after the shot solidifies, but before the dies open, using a separate mechanism. Slides are similar to movable cores, except they are used to form undercut surfaces. The use of movable cores and slides greatly increases the cost of the dies. Loose cores, also called pick-outs , are used to cast intricate features, such as threaded holes . These loose cores are inserted into
6206-448: The die. Similarly, Acurad castings could be heat treated and meet the U.S. military specification MIL-A-21180-D . Finally, the Acurad system employed a patented double shot piston design. The idea was to use a second piston (located within the primary piston) to apply pressure after the shot had partially solidified around the perimeter of the casting cavity and shot sleeve. While the system
6313-433: The dies; this feature matches up with the injector nozzle on the hot-chamber machines or the shot chamber in the cold-chamber machines. The ejector die contains the ejector pins and usually the runner , which is the path from the sprue or shot hole to the mould cavity. The cover die is secured to the stationary, or front, platen of the casting machine, while the ejector die is attached to the movable platen. The mould cavity
6420-429: The early 1930s, replacing the earlier 6 series, which were of bronze construction, although basically the same design. The 276 type was introduced in 1940 in an attempt to improve the carburettor's durability in dusty and dirty operating environments. In the same design range were the 4 and 5 types with smaller bore sizes and the 29 type with larger bore sizes. These were replaced with the 74, 75 and 89 and then, later, by
6527-405: 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 the intake and exhaust manifolds are on the same side of the head. Heat from the exhaust is used to warm
SECTION 60
#17331065451516634-399: 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 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
6741-417: The engine until it warms up, provided by a choke valve . While the engine is warming up the choke valve is partially closed, restricting 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
6848-421: 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 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
6955-407: 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. Die cast Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into
7062-414: 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 the intake air filter to be bypassed, therefore the system is only used when there is a risk of icing. If
7169-412: 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 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
7276-603: 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 is spelled "carburetor" in American English and "carburettor" in British English . Colloquial abbreviations include carb in
7383-534: The high temperatures found in die casting, they form a thin film. Other substances are added to control the viscosity and thermal properties of these emulsions, e.g. graphite , aluminium , mica . Other chemical additives are used to inhibit rusting and oxidation . In addition emulsifiers are added to improve the emulsion manufacturing process, e.g. soap , alcohol esters , ethylene oxides . Historically, solvent-based lubricants, such as diesel fuel and kerosene , were commonly used. These were good at releasing
7490-457: 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 the preferred method. One of
7597-436: 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 a patent for a "gas or vapor engine", which had a carburetor that mixed turpentine and air. The design did not reach production. In 1875 German engineer Siegfried Marcus produced
7704-405: 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 a heat stove around
7811-542: 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 the 1970s. EEC legislation required all vehicles sold and produced in member countries to have
7918-400: The left or right hand sides of the carburetter body. The available bore sizes are 15/16", 1" and 1 1/16" diameters. The 276 type carburettor is, in virtually all aspects, identical to the 76 version, except that the main emulsion air is drawn from inside the air intake (air filter) whilst the 76 carburettor uses unfiltered air. The 76 types are of die-cast zinc construction and were introduced in
8025-461: The lubricant is applied, the water cools the die surface by evaporating, hence depositing the oil that helps release the shot. A common mixture for this type of emulsion is thirty parts water to one part oil, however in extreme cases a ratio of one-hundred to one is used. Oils that are used include heavy residual oil (HRO), animal fat , vegetable fat , synthetic oil , and all sorts of mixtures of these. HROs are gelatinous at room temperature, but at
8132-454: The material is in the die, to work it into fine details of the cavity and eliminate porosity. Typical cycle times for a low-pressure die casting process are longer than for other die-casting processes; an engine block can take up to fifteen minutes. It is primarily used for aluminum, but has been used for carbon steel as well. Integrated die casting refers to the high-level integration of multiple separate and dispersed alloy parts through
8239-487: The merger of Amac, Brown and Barlow, and Binks to form Amal, a new range of carburettors were introduced in 1929, the 'Standard' range. The body of these carburettors was cast in bronze and the other components made of brass. The float chamber was manufactured as a separate unit and attached to the carburettor by an arm. To mount the carburettor to the engine, the carburettors were available in both flange and spigot options. Four body sizes were available: The sand cast body
8346-620: The minimum section thickness and minimum draft required for a casting as outlined in the table below. The thickest section should be less than 13 mm (0.5 in), but can be greater. There are a number of geometric features to be considered when creating a parametric model of a die casting: There are two basic types of die casting machines: hot-chamber machines and cold-chamber machines . These are rated by how much clamping force they can apply. Typical ratings are between 400 and 4,000 st (2,500 and 25,400 kg). Hot-chamber die casting, also known as gooseneck machines , rely upon
8453-486: The molten metal starts filling them the metal quickly solidifies and minimizes scrap. No risers are used because the high pressure ensures a continuous feed of metal from the gate. The most important material properties for the dies are thermal shock resistance and softening at elevated temperature; other important properties include hardenability , machinability , heat checking resistance, weldability, availability (especially for larger dies), and cost. The longevity of
8560-469: The motorcycle industry, via a subsidiary business, Lozells Engineering, twist grips, cables and wire, plus ICI silicone grease . All AMAL chromium plated components were stated to be finished in "Nickel Chromium Plating, British Standard Approved." Amal's light-alloy levers with click-stop adjusters 509/001 brake and 509/002 clutch were taken-over by BSA and marketed under their 'Motoplas' accessories branding from 1967, with Doherty taking-over production of
8667-408: The mould cavity is filled, the pressure is maintained until the casting solidifies. The dies are then opened and the shot (shots are different from castings because there can be multiple cavities in a die, yielding multiple castings per shot) is ejected by the ejector pins. Finally, the shakeout involves separating the scrap, which includes the gate , runners , sprues and flash , from the shot. This
8774-445: The name Amalgamated Carburetters Ltd . The name changed to Amal Ltd in 1931. Amal subsequently became partly owned by IMI Group , and the product range was expanded to include handlebars and controls with full IMI ownership by the middle 1960s. It was sold after June 1973 to Grosvenor Works Ltd of North London - a supplier of fuel system components. Under Grosvenor some of the most popular obsolete ranges were remanufactured. In 2003,
8881-492: The part from the die, but a small explosion occurred during each shot, which led to a build-up of carbon on the mould cavity walls. However, they were easier to apply evenly than water-based lubricants. Advantages of die casting: The main disadvantage to die casting is the very high capital cost . Both the casting equipment required and the dies and related components are very costly, as compared to most other casting processes. Therefore, to make die casting an economic process,
8988-451: The pilot circuit occurred. The GP2 series was introduced in 1962 to try to overcome the shortcomings of the GP. The pilot circuit was moved to the inlet side if the slide. The air bleed was taken from the incoming air rather than the outside, reducing the possibility of dirt ingress to the circuit. The moving of the pilot jet allowed far greater downdraught angles without the jet flooding. The GP2
9095-434: The pins at the same time and with the same force, so that the casting is not damaged. The ejector pin plate also retracts the pins after ejecting the casting to prepare for the next shot. There must be enough ejector pins to keep the overall force on each pin low, because the casting is still hot and can be damaged by excessive force. The pins still leave a mark, so they must be located in places where these marks will not hamper
9202-438: The power output and reduce engine knocking ). A 'power valve', which is a spring-loaded valve in the carburetor that 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
9309-431: 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 is often used to prevent icing. This system consists of a secondary air intake which passes around
9416-503: The same sizes as the 10TT and 15TT. This type was less popular than its parent TT. Production ended with the introduction of the GP in 1954. The GP (Series 316) was introduced in 1954 replacing both the TT and RN, and was a further development of the RN. Although the needle and jets were still offset, they were moved away from the side of the bore which simplified the needle mounting. Air for the pilot feed
9523-404: The side of the carburettor bore to give a less obstructed flow through the carburettor, although this caused a complicated attachment of the needle to the slide. Although at the time the less restricted flow was seen as an advantage, later opinion was less positive. Initial the RN was designated as a type of TT, eg 10TT37KN, but soon it was given its own type reference, eg 10RN. It was available in
9630-450: 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 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
9737-436: The spigot mounting as used by the Type 27, flange fixing was introduced. As the spigot mountings were susceptible to air leaks, flange mounting was seen as an improvement. Three body sizes were made: Sales of the 25TT were small and the model was discontinued in 1934. Production of the other two versions continued to 1954. The RN (Series 185) was introduced in 1937 as a development of the TT. The needle and jets were moved to
9844-523: The surface of the casting due to poor gating, sharp corners, or excessive lubricant. Water-based lubricants are the most used type of lubricant, because of health, environmental, and safety reasons. Unlike solvent-based lubricants, if water is properly treated to remove all minerals from it, it will not leave any by-product in the dies. If the water is not properly treated, then the minerals can cause surface defects and discontinuities. Today "water-in-oil" and "oil-in-water" emulsions are used, because, when
9951-406: 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 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
10058-521: 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 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
10165-591: The traditional chromed-steel levers. With the decline of the British motorcycle industry, the use of Amal carburettors declined, but they are still produced under different ownership as spares for the classic market. Besides carburettors for light-applications such as types 308 and 355 for Pedal Cycle Motors , Amal historically had three popular carburettor designs: 'Standard' fitted up to 1955, 'Monobloc' fitted from 1955 and 'Concentric' fitted from 1967. The most historic - 76 & 276 Series (Amal 'Standard' series) can be spigot or flange fixing with adjustment screws on
10272-428: The valve allows extra fuel into the engine, then at a certain engine RPM it closes to reduce 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
10379-489: Was Amal's first carburettor specifically designed for racing machines, and was based on AMAC's TT carburettor that had been introduced in 1924. A jet block and hollow slide were used. The body, jet block and slide were assembled and then machined as one unit to ensure perfect matching and unobstructed flow through the carburettor. No needle or needle jets were fitted. For starting a pilot jet and bypass were used. To reduce fuel surge when cornering, two float chambers were used with
10486-492: Was available in the same sizes as the original GP. A smoothbore version of the 2000 series Mark Concentric was made available for racing used. To obtain the "smoothbore", a jet block and hollow slide were fitted. Although the carb was never used as an OEM part, it was popular with smaller specialist racers. The AMAL company was formed in the late 1920s when three manufacturers amalgamated – Amac, Brown and Barlow, and Binks – to manufacture carburettors and associated products under
10593-532: Was corrected by varying the jet size. The orientation of 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
10700-477: Was expensive to produce and limited production throughput. To reduce production costs and time, die cast zinc alloy bodies were introduced in 1932. These were designated types 74, 75, 76 and 89 and were virtually identical to the previous types, most of the components were interchangeable. Ingress of dust and dirt caused premature wear to the carburettor, which was partially resolved by fitting air filters. The idle and air bleed circuits still drew air from outside
10807-525: 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 the Carter Carburetor WCFB and
10914-517: Was introduced, designated 689, which was a mirror image of the 389. This allowed twin carb installations with each carb having its own float chamber. Production ended in 1967 when the Concentric was introduced. The Monobloc was reintroduced in 2014, the 375 body being cast in aluminium alloy . Replacement hard anodised slides to reduce wear were made available. To reduce the technical and manufacturing problems of previous carbs and with pending emission controls requiring more accurate fuel metering,
11021-408: Was not very effective, it did lead the manufacturer of the Acurad machines, Ube Industries , to discover that it was just as effective to apply sufficient pressure at the right time later in the cycle with the primary piston; this is indirect squeeze casting. When no porosity is allowed in a cast part then the pore-free casting process is used. It is identical to the standard process except oxygen
11128-461: Was of 400, 600 and 900 series Concentrics. The Spanish motorcycle manufacturers required a better cold starting system so Amal and Talleres Arreche jointly designed modifications to the concentric to provide a separate enrichment circuit. These carburettors, introduced in 1973, were available in both flange and spigot mountings to suit the Spanish manufacturers requirements. To distinguish this variant from
11235-484: Was slightly larger than any previous Monobloc, and all were flange-fitting with stud-holes at two-inch centres. The Concentric design with non-protruding float chamber was both slimmer and shorter, enabling easier mounting to two-port cylinder heads. Left or right sided carburettors could be produced from basically the same die-casting, and the design was compatible with up to 40 degrees of downdraught. Eventually three variants were produced: Mk1, Mk1.5 and Mk2. Following
11342-446: Was taken from the outside of the carb through a drilling. The GP was available in four body sizes and in flange mounting only: Initially the GP was produced in zinc alloy but in the late 1950s the material was changed to aluminium ally. The GP suffered from pilot systems, partly due to dust and dirt entering through the air drilling. The pilot system also limited the carb from being used with more than 20° downdraft otherwise flooding of
11449-429: Was the first done for any casting process. This was done by creating an electrical analog of the thermal system. A cross-section of the dies were drawn on Teledeltos paper and then thermal loads and cooling patterns were drawn onto the paper. Water lines were represented by magnets of various sizes. The thermal conductivity was represented by the reciprocal of the resistivity of the paper. The Acurad system employed
#150849