hybrid vehicle is a vehicle that uses two or more distinct power sources to move the vehicle. The term most commonly refers to hybrid electric vehicles (HEVs), which combine an internal combustion engine and one or more electric motors.
Power
Power sources for hybrid vehicles include:
On-board or out-board rechargeable energy storage system (RESS)
Petrol or Diesel fuel
Hydrogen
Compressed air
Liquid nitrogen
Human powered e.g. pedaling or rowing
Wind
Electricity
Compressed or liquefied natural gas
Solar
Waste heat from internal combustion engine.
Coal, wood or other solid combustibles
Electromagnetic fields, Radio waves.
Vehicle type
Two-wheeled and cycle-type vehicles Mopeds, electric bicycles, and even electric kick scooters are a simple form of a hybrid, as power is delivered both via an internal combustion engine or electric motor and the rider's muscles. Early prototypes of motorcycles in the late 1800s used the same principles.
In a parallel hybrid bicycle human and motor power are mechanically coupled at the pedal drive train or at the rear or the front wheel, e.g. using a hub motor, a roller pressing onto a tire, or a connection to a wheel using a transmission element. Human and motor torques are added together. Almost all manufactured models are of this type. See Motorized bicycles, Mopeds and[ for more information. In a series hybrid bicycle (SH) the user powers a generator using the pedals. This is converted into electricity and can be fed directly to the motor giving a chainless bicycle but also to charge a battery. The motor draws power from the battery and must be able to deliver the full mechanical torque required because none is available from the pedals. SH bicycles are commercially available, because they are very simple in theory and manufacturing.The first known prototype and publication of an SH bicycle is by Augustus Kinzel (US Patent 3'884'317) in 1975. In 1994 Bernie Macdonalds conceived the Electrilite SH lightweight vehicle which used power electronics allowing regenerative braking and pedaling while stationary. In 1995 Thomas Müller designed a "Fahrrad mit elektromagnetischem Antrieb" in his 1995 diploma thesis and built a functional vehicle. In 1996 Jürg Blatter and Andreas Fuchs of Berne University of Applied Sciences built an SH bicycle and in 1998 mounted the system onto a Leitra tricycle (European patent EP 1165188). In 1999 Harald Kutzke described his concept of the "active bicycle": the aim is to approach the ideal bicycle weighing nothing and having no drag by electronic compensation. Until 2005 Fuchs and colleagues built several prototype SH tricycles and quadricycles.
Heavy vehicles
Hybrid power trains are used for diesel-electric or turbo-electric railway locomotives, buses, heavy goods vehicles, mobile hydraulic machinery, and ships. Typically some form of heat engine (usually diesel) drives an electric generator or hydraulic pump which powers one or more electric or hydraulic motors. There are advantages in distributing power through wires or pipes rather than mechanical elements especially when multiple drives—e.g. driven wheels or propellers—are required. There is power lost in the double conversion from typically diesel fuel to electricity to power an electric or hydraulic motor. With large vehicles the advantages often outweigh the disadvantages especially as the conversion losses typically decrease with size. With the exception of non nuclear submarines, presently there is no or relatively little energy storage capacity on most heavy vehicles, e.g. auxiliary batteries and hydraulic accumulators—this is changing.
Rail transport
Europe
An is the new Autorail à grande capacité (AGC or high-capacity railcar) built by the Canadian company Bombardier for service in France. This has dual mode (diesel and electric motors) and dual voltage capabilities (1500 and 25000 V) allowing it to be used on many different rail systems.
China
The First Hybrid Evaluating prototype locomotive was designed and contracted by railway research center MATRAI in 1999 and the sample was ready in 2000. it was a G12 locomotive that was converted to hybrid by using a 200KW diesel generator and batteries and also was equipped with 4 AC traction motors (out of retrofited in the cover of the DC traction motors.
Japan
The first operational prototype of a hybrid train engine with significant energy storage and energy regeneration capability was introduced in Japan as the KiHa E200. It utilizes battery packs of lithium ion batteries mounted on the roof to store recovered energy.
North America
In the U.S., General Electric introduced a prototype railroad engine with their "Ecomagination" technology in 2007. They store energy in a large set of sodium nickel chloride (Na-NiCl2) batteries to capture and store energy normally dissipated during dynamic braking or coasting downhill. They expect at least a 10% reduction in fuel use with this system and are now spending about $2 billion/yr on hybrid research.Variants of the typical diesel electric locomotive include the Green Goat (GG) and Green Kid (GK) switching/yard engines built by Canada's Railpower Technologies. They utilize a large set of heavy duty long life (~10 yr) rechargeable lead acid (Pba) batteries and 1000 to 2000 HP electric motors as the primary motive sources and a new clean burning diesel generator (~160 Hp) for recharging the batteries that is used only as needed. No power or fuel are wasted for idling—typically 60–85% of the time for these type locomotives. It is unclear if dynamic braking (regenerative) power is recaptured for reuse; but in principle it should be easily utilized.Since these engines typical need extra weight for traction purposes anyway the battery pack's weight is a negligible penalty. In addition the diesel generator and battery package are normally built on an existing "retired" "yard" locomotive's frame for significant additional cost savings. The existing motors and running gear are all rebuilt and reused. Diesel fuel savings of 40–60% and up to 80% pollution reductions are claimed over that of a "typical" older switching/yard engine. The same advantages that existing hybrid cars have for use with frequent starts and stops and idle periods apply to typical switching yard use.] "Green Goat" locomotives have been purchased by Canadian Pacific Railway, BNSF Railway, Kansas City Southern Railway and Union Pacific Railroad among others.
Cranes
Railpower Technologies Corp. engineers working with TSI Terminal Systems Inc. in Vancouver, British Columbia are testing a hybrid diesel electric power unit with battery storage for use in Rubber Tyred Gantry (RTG) cranes. RTG cranes are typically used for loading and unloading shipping containers onto trains or trucks in ports and container storage yards. The energy used to lift the containers can be partially regained when they are lowered. Diesel fuel and emission reductions of 50–70% are predicted by Railpower engineers. First systems are expected to be operational in 2007.
Road transport, commercial vehicles
Early hybrid systems are being investigated for trucks and other heavy highway vehicles with some operational trucks and buses starting to come into use. The main obstacles seem to be smaller fleet sizes and the extra costs of a hybrid system are yet compensated for by fuel savings,but with the price of oil set to continue on its upward trend, the tipping point may be reached by the end of 1995Advances in technology and lowered battery cost and higher capacity etc. developed in the hybrid car industry are already filtering into truck use as Toyota, Ford, GM and others introduce hybrid pickups and SUVs. Kenworth Truck Company recently introduced a hybrid-electric truck, called the Kenworth T270 Class 6 that for city usage seems to be competitive. FedEx and others are starting to invest in hybrid delivery type vehicles—particularly for city use where hybrid technology may pay off first . Military off-road vehicles since 1985, the U.S. military has been testing serial hybrid Humvees and have found them to deliver faster acceleration, a stealth mode with low thermal signature/ near silent operation, and greater fuel economy.
Ships
Ships with both mast-mounted sails and steam engines were an early form of hybrid vehicle. Another example is the diesel-electric submarine. This runs on batteries when submerged and the batteries can be re-charged by the diesel engine when the craft is on the surface.Newer hybrid ship-propulsion schemes include large towing kites manufactured by companies such as SkySails. Towing kites can fly at heights several times higher than the tallest ship masts, capturing stronger and steadier winds.
Aircraft
Delta Air Lines is going to be turning their Boeing 737NGs into hybrids in early 2010 by mounting the WheelTug ground propulsion system on their fleet of Boeing 737NGs By using the APU, which is powered by a turbine, to power a Chorus Motor mounted on the landing gear for ground movement, Delta Air Lines will be creating a hybrid configuration by ceasing to use the main engines for anything but take off, landing, and flight.
Boeing 737-800
The Boeing Fuel Cell Demonstrator Airplane has a Proton Exchange Membrane (PEM) fuel cell/lithium-ion battery hybrid system to power an electric motor, which is coupled to a conventional propeller. The fuel cell provides all power for the cruise phase of flight. During takeoff and climb, the flight segment that requires the most power, the system draws on lightweight lithium-ion batteries.The demonstrator aircraft is a Dimona motor glider, built by Diamond Aircraft Industries of Austria, which also carried out structural modifications to the aircraft. With a wing span of 16.3 meters (53.5 feet), the airplane will be able to cruise at approximately 100 kilometers per hour (62 miles per hour) on power from the fuel cell
Engine type
Hybrid electric-petroleum vehicles
When the term hybrid vehicle is used, it most often refers to a Hybrid electric vehicle. These encompass such vehicles as the AHS2 (Chevrolet Tahoe, GMC Yukon, Chevrolet Silverado, Cadillac Escalade, and the Saturn Vue), Toyota Prius, Toyota Camry Hybrid, Ford Escape Hybrid, Toyota Highlander Hybrid, Honda Insight, Honda Civic Hybrid Lexus RX 400h and 450h and others. A petroleum-electric hybrid most commonly uses internal combustion engines (generally gasoline or Diesel engines, powered by a variety of fuels) and electric batteries to power electric motors. There are many types of petroleum-electric hybrid drivetrains, from Full hybrid to Mild hybrid, which offer varying advantages and disadvantages .Ferdinand Porsche in 1900 developed the first gasoline-electric series-hybrid automobile in the world, setting speed records using two motor-in-wheel-hub arrangements with a combustion generator set proving the electric power. While liquid fuel/electric hybrids date back to the late 1800s, the braking regenerative hybrid was invented by David Arthurs, an electrical engineer from Springdale, Arkansas in 1978–79. His home-converted Opel GT was reported to return as much as 75MPG with plans still sold to this original design, and the "Mother Earth News" modified version on their website .The plug-in-electric-vehicle (PEV) is becoming more and more common. It has the range needed in locations where there are wide gaps with no services. The batteries can be plugged in to house (mains) electricity for charging, as well being charged while the engine is running.
Continuously outboard recharged electric vehicle (COREV)
Given suitable infrastructure, permissions and vehicles, BEVs can be recharged while the user drives. The BEV establishes contact with an electrified rail, plate or overhead wires on the highway via an attached conducting wheel or other similar mechanism (see Conduit current collection). The BEV's batteries are recharged by this process—on the highway—and can then be used normally on other roads until the battery is discharged.This provides the advantage, in principle, of virtually unrestricted highway range as long as you stay where you have BEV infrastructure access. Since many destinations are within 100 km of a major highway, this may reduce the need for expensive battery systems. Unfortunately private use of the existing electrical system is nearly universally prohibited.The technology for such electrical infrastructure is old and, outside of some cities, is not widely distributed (see Conduit current collection, trams, electric rail, trolleys, third rail). Updating the required electrical and infrastructure costs can be funded, in principle, by toll revenue, gasoline or other taxes.
Hybrid fuel (dual mode)
In addition to vehicles that use two or more different devices for propulsion, some also consider vehicles that use distinct energy sources or input types ("fuels") using the same engine to be hybrids, although to avoid confusion with hybrids as described above and to use correctly the terms, these are perhaps more correctly described as dual mode vehicles:
Some electric trolleybuses can switch between an on board diesel engine and overhead electrical power depending on conditions (see dual mode bus). In principle, this could be combined with a battery subsystem to create a true plug-in hybrid trolleybus, although as of 2006[update], no such design seems to have been announced.
Flexible-fuel vehicles can use a mixture of input fuels mixed in one tank — typically gasoline and ethanol, or methanol, or biobutanol.
Bi-fuel vehicle:Liquified petroleum gas and natural gas are very different from petroleum or diesel and cannot be used in the same tanks, so it would be impossible to build an (LPG or NG) flexible fuel system. Instead vehicles are built with two, parallel, fuel systems feeding one engine. While the duplicated tanks cost space in some applications, the increased range and flexibility where (LPG or NG) infrastructure is incomplete may be a significant incentive to purchase.
Some vehicles have been modified to use another fuel source if it is available, such as cars modified to run on autogas (LPG) and diesels modified to run on waste vegetable oil that has not been processed into biodiesel.
Power-assist mechanisms for bicycles and other human-powered vehicles are also included (see Motorized bicycle).
Fluid power hybrid
Hydraulic and pneumatic hybrid vehicles use an engine to charge a pressure accumulator to drive the wheels via hydraulic or pneumatic (i.e. compressed air) drive units. The energy recovery rate is higher and therefore the system is more efficient than battery charged hybrids, demonstrating a 60% to 70% increase in energy economy in EPA testing. Under tests done by the EPA, a hydraulic hybrid Ford Expedition returned 32 miles per US gallon (7.4 L/100 km; 38 mpg-imp) City, and 22 miles per US gallon (11 L/100 km; 26 mpg-imp) highway. UPS currently has two trucks in service with this technology.While the system has faster and more efficient charge/discharge cycling and is cheaper than gas-electric hybrids, the accumulator size dictates total energy storage capacity and requires more space than a battery.
Electric-human power hybrid vehicle
Another form of hybrid vehicle are human power-electric vehicles. These include such vehicles as the Sinclair C5, Twike, electric bicycles, and electric skateboards.
Hybrid vehicle power train configurations
Parallel hybrid
In a parallel hybrid the single electric motor and the internal combustion engine are installed so that they can both individually or together power the vehicle. In contrast to the power split configuration typically only one electric motor is installed. Most commonly the internal combustion engine, the electric motor and gear box are coupled by automatically controlled clutches. For electric driving the clutch between the internal combustion engine is open while the clutch to the gear box is engaged. While in combustion mode the engine and motor run at the same speed.The first mass production parallel hybrid is the Honda Insight.
Mild parallel hybrid
These types use a generally compact electric motor (usually <20 kW) to provide auto-stop/start features and to provide extra power assist during the acceleration, and to generate on the deceleration phase (aka regenerative braking).On-road examples include Honda Civic Hybrid, Honda Insight, Mercedes Benz S400 BlueHYBRID, BMW 7-Series hybrids, General Motors BAS Hybrids and Smart fortwo with micro hybrid drive.
Power-split or series-parallel hybrid
Typical passenger car installations include the Toyota Prius, the Ford Escape, the Lexus Gs450 and LS600.
In a power-split hybrid electric drive train there are two motors: an electric motor and an internal combustion engine. The power from these two motors can be shared to drive the wheels via a power splitter, which is a simple planetary gear set. The ratio can be from 0-100% for the combustion engine, or 0-100% for the electric motor, or an anything in between, such as 40% for the electric motor and 60% for the combustion engine. The electric motor can act as a generator charging the batteries.On the open road, the primary power source is the internal combustion engine, when maximum power is required, for example to overtake, the electric motor is used to assist maximizing the available power for a short period, giving the effect of having a larger engine than actually installed. In most applications, the engine is switched off when the car is stationary reducing curbside emissions.
Series hybrid
series- or serial-hybrid vehicle has also been referred to as an Extended Range Electric Vehicle or Range-Extended Electric Vehicle (EREV/REEV); however, range extension can be accomplished with either series or parallel hybrid layouts.Series-hybrid vehicles are driven by the electric motor with no mechanical connection to the engine. Instead there is an engine tuned for running a generator when the battery pack energy supply isn't sufficient for demands.This arrangement is not new, being common in diesel-electric locomotives and ships. Ferdinand Porsche used this setup in the early 20th century in racing cars, effectively inventing the series-hybrid arrangement. Porsche named the arrangement "System Mixt". A wheel hub motor arrangement, with a motor in each of the two front wheels was used, setting speed records. This arrangement was sometimes referred to as an electric transmission, as the electric generator and driving motor replaced a mechanical transmission. The vehicle could not move unless the internal combustion engine was running.
The setup has never proved to be suitable for production cars, however it is currently being revisited by several manufacturers.In 1997 Toyota released the first series-hybrid bus sold in Japan.[25] Meanwhile, GM will introduce the Chevy Volt EREV in 2010, aiming for an all-electric range of 40 miles,[26] and a price tag of around $40,000.[27] Supercapacitors combined with a lithium ion battery bank have been used by AFS Trinity in a converted Saturn Vue SUV vehicle. Using supercapacitors they claim up to 150 mpg in a series-hybrid arrangement.
Plug-in hybrid electrical vehicle (PHEV)
Another subtype added to the hybrid market is the Plug-in Hybrid Electric Vehicle (PHEV). The PHEV is usually a general fuel-electric (parallel or serial) hybrid with increased energy storage capacity (usually Li-ion batteries). It may be connected to mains electricity supply at the end of the journey to avoid charging using the on-board internal combustion engine.This concept is attractive to those seeking to minimize on-road emissions by avoiding – or at least minimizing – the use of ICE during daily driving. As with pure electric vehicles, the total emissions saving, for example in CO2 terms, is dependent upon the energy source of the electricity generating company.For some users, this type of vehicle may also be financially attractive so long as the electrical energy being used is cheaper than the petrol/diesel that they would have otherwise used. Current tax systems in many European countries use mineral oil taxation as a major income source. This is generally not the case for electricity, which is taxed uniformly for the domestic customer, however that person uses it. Some electricity suppliers also offer price benefits for off-peak night users, which may further increase the attractiveness of the plug-in option for commuters and urban motorists.
Fuel cell, electric hybrid
The fuel cell hybrid is generally an electric vehicle equipped with a fuel cell. The fuel cell as well as the electric battery are both power sources, making the vehicle a hybrid. Fuel cells use hydrogen as a fuel and power the electric battery when it is depleted. The Chevrolet Equinox FCEV, Ford Edge Hyseries Drive and Honda FCX are examples of a fuel cell/electric hybrid.
Hybrid vehicle emissions
Hybrid vehicle emissions today are getting close to or even lower than the recommended level set by the EPA (Environmental Protection Agency). The recommended levels they suggest for a typical passenger vehicle should be equated to 5.5 metric tons of carbon dioxide. The three most popular hybrid vehicles, Honda Civic, Honda Insight and Toyota Prius, set the standards even higher by producing 4.1, 3.5, and 3.5 tons showing a major improvement in carbon dioxide emissions. Hybrid vehicles can reduce air emissions of smog-forming pollutants by up to 90% and cut carbon dioxide emissions in half. Based on the average driving habits of an individual, pollution of these vehicles can be reduced anywhere between 25% to 90%, when you compare them to an everyday gas-powered vehicle.Here is a link showing the amount of CO2 emissions, of hybrid vehicles compared to gasoline vehicles. There are also different pollution numbers when you are comparing different brands of hybrid vehicles. It is also important to note that the emissions are merely transferred to electrical plants for plug-in hybrids; and with many areas of the world burning fossil fuels for electricity, these transferred emissions are quite large.
Environmental impact of hybrid car battery
Though hybrid cars consume less petroleum than conventional cars, there is still an issue regarding the environmental damage of the Hybrid car battery. Today most Hybrid car batteries are one of two types: (1) nickel metal hydride, or lithium ion; both are regarded as more environmentally friendly than lead-based batteries which constitute the bulk of car batteries today. There are many types of batteries. Some are far more toxic than others. While batteries like lead acid or nickel cadmium are incredibly bad for the environment, the toxicity levels and environmental impact of nickel metal hydride batteries—the type currently used in hybrids—are much lower. Nickel-based batteries are known carcinogens, and have been shown to cause a variety of teratogenic effects .The Lithium-ion battery has attracted attention due to its potential for use in hybrid electric vehicles. Hitachi is a leader in its development. Additionally, the market for Lithium-ion batteries is rapidly expanding as an alternative to the nickel-metal hydride batteries, which have been utilized in the hybrid market thus far. In addition to its smaller size and lighter weight, lithium-ion batteries deliver performance that helps to protect the environment with features such as improved charge efficiency without memory effect. In an environment where motor vehicle requirements including lower exhaust emissions and better fuel economy are prevalent, it is anticipated that the practical use of hybrid, electric, and fuel cell vehicles will continue to increase. The lithium-ion batteries are appealing because they have the highest energy density of any rechargeable batteries and can produce a voltage more than three times that of nickel-metal hydride battery cell while simultaneously storing large quantities of electricity as well. The batteries also produce higher output (boosting vehicle power), higher efficiency (avoiding wasteful use of electricity), and provides excellent durability, compared with the life of the battery being roughly equivalent to the life of the vehicle. Additionally, use of lithium-ion batteries reduces the overall weight of the vehicle and also achieves improved fuel economy of 30% better than gasoline-powered vehicles with a consequent reduction in CO2 emissions helping to prevent global warming. The lithium-ion batteries supplied by Hitachi are flourishing in a wide range of different applications including cars, buses, commercial vehicles and trains. Electric vehicles that have the ability to be recharged from an owner’s main power supply are now available in several global automotive markets. When these vehicles are charged overnight, which is less costly than charging the vehicle during the day in Japan, the expense is about one-ninth of the cost for fueling a gasoline powered vehicle.
Sunday, September 26, 2010
Wednesday, September 15, 2010
همه چیز در مورد سیستم انتقال قدرت
کلاچ
کلاچ اصطکاکی
کلاچ دستگاهی است که نیروی موتور را از گیربکس قطع یا وصل می کند یا به عبارت ساده تر عمل کلاچ برای تعویض دنده های گیربکس است این عمل به وسیله پدال که زیر پای چپ راننده قرار دارد انجام می شود به این ترتیب که با فشار به پدال کلاچ صفحه فلایویل جدا می شود و نیرو به گیربکس (جعبه دنده) نمی رسد و در نتیجه چرخ های وسیله نقلیه ازاد می شود بر عکس بارها کردن کلاچ صفحه کلاچ به فلایویل می چسبد ونیروی موتور تابع سرعت و قدرت دنده گیربکس می شود قطعات کلاچ عبارتند از صفحه کلاچ و دو شاخه کلاچ و صفحه فلایویل و بلبرینگ کلاچ و اهرم و شاخک ها صفحه دهنده و دیسک کلاچ که از یک کاسه مانند از نوع چدن تشکیل شده است همانطور که گفته شد کلاچ وسیله ای را برای جدا کردن دستگاه مولد نیرو و از سایر قسمت های استفاده از نیرو تامین می کند کلاچ انواع مختلفی دارد : یک صفحه ای و دو صفحه ای و روغنی و خشک و کلاچ های اتوماتیک قطع کردن نیرو به علل نیرو زیر لازم است- گشتاور حاصل از پیستون یک موتور جرقه ای در سرعت خیلی کم صفر بوده و با زیاد شدن سرعت موتور زیاد می شود تا به حد متوسطی می رسد بنابراین برای وارد کردن گشتاور کافی به قسمت های به حرکت دراورنده خودرو (چرخ ها) در لحظه شروع به حرکت لازم است موتور قبل از انتقال نیروی خود به قسمت مورد استفاده قرار دهنده نیرو با سرعت کم و بدون بار حرکت کند 2- تعویض دنده ها تقریبا برای یک راننده در هنگام ارتباط موتور با دستگاه انتقال نیرو و غیره ممکن است کلاچ باعث قطع شدن انتقال نیرو از موتور به قسمت های حرکت کننده شده و در نتیجه عوض کردن دنده اسان می شود 3- در هنگام راه اندازی موتور بهتر است که گشتاور اینرسی قسمت های دوار را که راه انداز را به در می اورد به حداقل رساند این عمل با قطع کردن قسمت های مورد استفاده قرار دهنده نیرو از میل لنگ به وسیله کلاچ عملی می شود
صفحه کلاچ
این وسیله سبب به حرکت درامدن سایر قسمت های کلاچ می باشد صفحه کلاچ شامل رویه های اصطکاکی (لنت های صفحه کلاچ ) است که به یک صفحه فولادی پرچ شده اند صفحه فولادی حرکت دورانی را توسط فنرهای پیچشی به صفحه داخلی منتقل می کند صفحه داخلی با محور خروجی از موتور که محور ابتدایی دستگاه انتقال حرکت است درگیر است رویه های اصطکاکی بین دو عضو محرک یعنی چرخ طیار و صفحه فشار در اثر نیروی وارد از فنرهای بین روپوش و صفحه فشار کاملا
تحت فشار قرار می گیرد
ازاد شدن کلاچ
برای ازاد کردن کلاچ (جدا کردن دستگاه مولد نیرو از دستگاه انتقال نیرو) کاسه ساچمه ازاد کننده (بلبرینگ کلاچ) به وسیله زائده ای که ان را به پدال کلاچ مربوط می کند به طرف چپ رانده می شود حرکت کاسه ساچمه ازاد کننده باعث می شود که اهرم ازاد کننده مانع از فشار دادن صفحه فشار شده و فنرها را تحت فشار قرار دهد رویه های اصطکاکی کلاچ (لنت های صفحه کلاچ) دیگر بین چرخ طیار و صفحه فشار دهنده تحت فشار قرار نمی گیرد عضو به حرکت درایند یعنی صفحه کلاچ ازاد خواهد بود که مستقل از اجزای متحرک یعنی چرخ طیار و صفحه فشار می چرخد
درگیر شدن کلاچ
به منظور درگیر کردن کلاچ (مربوط کردن دستگاه مولد نیرو به دستگاه انتقال نیرو) نیروی وارد به پدال کلاچ حذف می شود فنرهای صفحه فشار در این موقع سبب فشردن صفحه فشار به رویه های صفحه کلاچ می شوند بنابراین عضو به حرکت درایند بین دو عضو متحرک تحت فشار قرار می گیرد و گشتاور حاصل از موتور به طور مساوی بین چرخ طیار و صفحه فشار تقسیم می شود و بر اثر نیروی اصطکاکی مماسی بین اعضای متحرک و عضو به حرکت درایند به دستگاه انتقال نیرو منتقل می شود پمپ کلاچ برای سهولت کار کلاچ تعبیه شده و دو نوع می باشد یکی پمپ بالا و دیگری پمپ پایین
حذف ارتعاش میل لنگ
به علت فاصله زمانی موجود بین ضربات قدرت منطقه میل لنگ گاهی در میل لنگ ارتعاش های پیچشی شدید به وجود می اید اگر این ارتعاش ها به بدنه منتقل کننده نیرو منتقل شود صدای شدیدی تولید شده و دنده نیز به زودی سائیده می شود برای جلوگیری از این وضع بعضی انواع طرح های حذف کننده ارتعاش لازم است کلاچ بهترین جای تعبیه این طرح هاست این طرح معمولا شامل
فنرهای لوله های و واشرهای اصطکاکی تعبیه شده و در صفحه کلاچ می باشد بنابراین در هنگامی که میل لنگ به طور پیچشی ارتعاش دارد حرکت نسبی بین رویه های اصطکاکی و تیغه محوری به وسیله فنرهای لوله ای امکان پذیر است و نیروی ارتعاشی به وسیله واشر اصطکاکی حذف می شود
معایب سیستم کلاچ 1- لرزش اتومبیل هنگام رها کردن کلاچ
به علت خسته شدن و از فنریت افتادن توپی صفحه کلاچ نیروی وارد به صفحه کلاچ خنثی شده و در نتیجه هنگام حرکت اتومبیل دچار لرزش می شود معیوب بودن فنرهای صفحه فشار دهنده دیسک هم همین عیب را دارد برای رفع این عیب باید صفحه کلاچ به طور کامل تعویض شود 2- بکسواد کلاچ
به علت تمام شدن لنت صفحه کلاچ یا چرب شدن لنت کلاچ بکسواد کرده و در نتیجه نیروی موتور به یکدیگر به طور کامل منتقل نمی شود برای رفع عیب باید اقدام به تعویض لنت و رفع چربی روی لنت کرد نکته : عواملی که باعث چرب شدن لنت می شود معیوب شدن کاسه نمد جلو گیربکس و انتهای میل لنگ است
انواع کلاچ خودرو 1
کلاچ وسيله ايست براي انتقال حرکت چرخشي از يک شفت به شفت ديگر. کلاچ در واقع يک وسيله قطع کردن و يا وصل کردن است که در سيستمهاي انتقال نيرو بکار ميرود. اصولاً در سيستمهاي انتقال نيرو، توان و نيروي توليد شده در موتور براي استفاده به شکلي ديگر و يا استفاده در جايي ديگر نياز به جابجايي و انتقال دارد. حال براي آنکه بتوان بر روي اين انتقال نيرو کنترلي را اعمال کرد. سادهترين راه استفاده از يک کلاچ است تا هر زمان که نياز به توقف انتقال نيرو باشد، اين عمل انجام پذيرد.کلاچ يک اتصال اصطکاکي ميان موتور اتومبيل به عنوان منبع توليد توان و جعبه دنده اتومبيل برقرار ميکند. در حالي که کلاچ اتومبيل درگير است توان از موتور به جعبه دنده و از آنجا به چرخها انتقال مييابد. ليکن گاهي لازم ميشود که دنده مورد استفاده در جعبه دنده ماشين بر حسب شرايط جاده و سرعت حرکت ماشين تغيير کند. براي آنکه بتوان اين تغيير را به راحتي انجام داد، ابتدا لازم است که توان را از چرخ دندههاي موجود در جعبه دنده قطع کرد. براي قطع کردن اين ارتباط تواني ميان جعبه دنده و موتور از کلاچ استفاده ميشود. اين کار براي راننده اتومبيل ميتواند بهراحتي فشاردادن يک پدال به کمک پاي خويش باشد. ليکن فشار دادن اين پدال پايي باعث فاصله گرفتن محور جعبه دنده از صفحه در حال چرخش موتور (فلايويل) خواهد شد. بوجود آمدن فاصله، معادل است با قطع ارتباط و انتقال توان. در اين حالت راننده براي مدت کوتاهي پدال کلاچ را نگه ميدارد و در حالي که جعبه دنده تحت هيچ نيروي خاصي قرار ندارد دنده مناسب را انتخاب کرده و جعبه دنده را در آن دنده مطلوب قرار ميدهد و سپس پدال کلاچ را رها ميکند. در اين حالت انتقال توان از موتور به جعبه دنده دوباره از سر گرفته خواهد شد
◄ويژگيهاي لحاظ شده در طراحي بهينه کلاچ:
جهت طراحي بهينه کلاچ بايد موارد گوناگوني را در نظر گرفت که در زير به آنها اشاره مي کنيم
انتقال ماکزيمم گشتاور : طراحي کلاچ بايد بگونه اي باشد که بتواند 125 تا 150 درصد ماکزيمم گشتاور توليدي موتور را منتقل کند
درگيري و خلاصي تدريجي : کلاچ و سيستمهاي عملگر آن بايد بگونه اي طراحي شوند که حين خلاصي و درگيري صفحات کمترين تکان را به خودرو منتقل کند
- پخش سريع حرارت توليد شده : حين درگيري کلاچ بعلت وجود لغزش در ابتداي امر، گرماي زيادي توليد مي شود که بايد به طرقي دفع شود
- بالانس ديناميکي : چون کلاچ عضو دوار متحرک است، بنابراين در سرعتهاي زياد جهت جلوگيري از بوجود آمدن نيروهاي جانبي بايد از لحاظ ديناميکي بالانس باشد
- استهلاک نوسانات : طراحي کلاچ بايد به گونه اي باشد که سبب از بين رفتن نوسانات انتقالي از موتور به سيستم انتقال قدرت و نوسانات انتقالي از چرخها به موتور شود.
ابعاد کلاچ : از لحاظ ابعادي، کلاچ بايد کمترين فضاي ممکن را اشغال کند
اينرسي : قطعات متحرک کلاچ بايد کمترين اينرسي ممکن را داشته باشند
سادگي در تعويض و تعمير : تعويض قطعات و تعمير آنها بايد به سادگي صورت گيرد
- سهولت در عملکرد کلاچ نزد راننده : عمل کلاچ گيري و تعويض دنده نبايد براي راننده حالت خسته کننده و طاقت فرسايي داشته باشد
◄انواع کلاچ:
بدون لغزش : اين نوع کلاچها دو حالت دارند؛ حالت خلاصي و حالتي که کلاچ کاملاً درگير است. بنابراين در اين حالت لغزش يا سايش در کلاچ به هيچ عنوان مشاهده نمي شود
يکطرفه : اين کلاچها در گردش از يک طرف همانند کلاچ بدون لغزش عمل مي کند، اما اگر چرخش در جهت مخالف صورت گيرد دو صفحه کاملاً روي هم سر مي خورند و هيچگونه انتقال نيرويي صورت نمي گيرد؛ بنابراين در اين کلاچها گشتاور تنها از يک طرف منتقل مي شود
اصطکاکي : اساس عملکرد اين کلاچها درگيري دو صفحه داراي ضريب اصطکاک نسبتاً بالاييست که اين درگيري سبب انتقال نيرو از يکي از صفحات به صفحه ديگر مي شود. انواع مورد استفاده اين نوع کلاچها شامل ديسکي، مخروطي، صفحه اي و تسمه اي مي باشد
هيدروليک : در اين نوع کلاچها نيرو از يکي از صفحات به سيال و سپس از سيال به صفحه متحرک مورد نظر منتقل مي شود
از ميان انوا کلاچهاي فق تنه دو نوع آخر در خودروهاي امروزي مورد استفاده قرار مي گيرد
◄کلاچ اصطکاکي
اين نوع کلاچها به پنج نوع عمده زير تقسيم مي شوند
کلاچ مخروطي
کلاچ مخروطي
کلاچ تک صفحه اي
کلاچ چند صفحه اي
کلاچ نيمه گريز از مرکز
کلاچ گريز از مركز
◄کلاچ مخروطي (Con Clutch) :
در اين کلاچها همانگونه که از اسم آن پيداست سطوح اصطکاکي به شکل مخروطي هستند. هنگامي که کلاچ در گير مي شود، گشتاور از طريق فلايويل که سطح داخلي آن به شکل مخروطي است به سطح مخروطي ديگري که درون فلايويل جاي مي گيرد منتقل مي شود. (شکل1-2) براي خلاص کردن کلاچ نيز سطح مخروط خارجي کمي از درون فلايويل بيرون کشيده مي شود تا تماس دو سطح قطع شود.
مزايا : براي فشار يکسان وارده بر پدال، نيروي اعمالي برروي سطوح اصطکاکي در اين حالت بزرگتر از نيروي محوري اعمال شده نسبت به کلاچ صفحه اي است
معايب : اگر زاويه مخروط کوچکتر از حدود 20 درجه انتخاب شود، ممکن است حالت خود قفلي پيش بيايد و جدا کردن دو سطحي که با هم در حالت چرخش هستند مشکل شود
◄کلاچ تک صفحه اي (Single Plate Clutch)
در اين نوع کلاچ، صفحه اصطکاکي بين فلايويل و صفحه فشارنده نگهداشته مي شود و نيروي اعمالي توسط صفحه فشارنده سطوح را به هم مي چسباند. اين نيروي اعمالي از طريق يک پدال که بوسيله پاي راننده فشرده مي شود بوجود مي آيد. (شکل1-3) اين نيرو سبب فشرده شدن انگشتي متصل به صفحه فشارنده مي شود و بدين ترتيب نيرو از پاي راننده به صفحه اصطکاکي منتقل مي شود. (شکل1-
مزايا : در اين نوع کلاچ تعويض دنده نسبت به کلاچ مخروطي آسانتر است، زيرا جابجايي پدال در اين حالت کمتر است و همچنين مانند کلاچ مخروطي مشکل قفل شدن در اين حالت وجود ندارد
معايب : فنرها در اين نوع کلاچ نسبت به حالت مخروطي بايد سختي بيشتري داشته باشند و در نتيجه نيروي فشارنده بزرگتري مورد نياز است
◄کلاچ تک صفحه اي با فنر ديافراگمي (Diaphragm Spring Clutch )
اساس کار اين نوع کلاچها همانند کلاچ تک صفحه اي است با اين تفاوت که در اينجا بجاي فنرهاي پيچشي از فنر ديافراگمي استفاده مي شود؛ اين فنرها در حالت عادي به شکل مخروط ناقص هستند، اما هنگامي که فشرده مي شوند حالت تخت به خود مي گيرند. شکل
مزايا : به علت ذخيره انرژي در امتداد شعاعي طرح نهايي اين کلاچ در امتداد محوري به مراتب کوچکتر و جمع و جورتر خواهد بود. فنر ديافراگمي در مقايسه با فنرهاي تخت کمتر تحت تاثير نيروي گريز از مرکز قرار مي گيرند، لذا براي استفاده در دورهاي بالاتر مناسب تر مي باشند. در اين طرح فنر ديافراگمي هم بعنوان فنر فشارنده و هم بعنوان قطعه ناخني عمل مي کند، لذا اين قطعات از سيستم حذف شده اند و باعث کاهش وزن کل و سر و صداي سيستم مي شوند. در مورد فنر مارپيچي رابطه نيرو و جابجايي فنر خطي است. لذا با سايش صفحات اصطکاکي، به نسبت مقدار نيروي فشارنده آنها نيز کاهش مي يابد. در حاليکه در مورد فنر ديافراگمي اين رابطه غير خطي بوده و مي توان آن را به نحوي طراحي نمود که حساسيت کمتري به سايش داشته باشد
معايب: نيروي فنر نسبت فنرهاي پيچشي کمتر است، بنابراين فقط در ماشينهاي سبک مي تواند مورد استفاده قرار گيرد
عملکرد اين کلاچ همانند کلاچ تک صفحه اي است با اين تفاوت که در اينجا بجاي يک صفحه کلاچ، به تناسب گشتاور انتقالي مورد نظر از چندين صفحه اصطکاکي استفاده مي شود. (شکل1-7) اين امر باعث مي شود که کلاچ بتواند گشتاور بزرگتري را منتقل کند. بنبراين اين کلاچها بيشتر در خودروهاي سنگين يا خودروهاي مسابقه اي که به انتقال گشتاور بزرگتري نياز دارند، مورد استفاده قرار مي گيرد.
کلاچ نيمه گريز از مرکز (Semi-Centrifugal Clutch )
در اين نوع کلاچها، فنرها براي انتقال گشتاور در سرعتهاي معمولي طراحي مي شوند، در حاليکه در سرعتهاي بالاتر نيروي گريز از مرکز به انتقال گشتاور کمک مي کند. (شکل1-8) در اين کلاچها نيروي گريز از مرکز از طريق وزنه هايي بوجود مي آيد که همراه ساير اجزا دوار کلاچ مي گردند
کلاچ گريز از مرکز (Centrifugal Clutch )
در اين نوع از کلاچها بر خلاف کلاچهاي نيمه گريز از مرکز، تنها از نيروي گريز از مرکز براي اعمال فشار بر روي صفحات و درگير کردن کلاچ استفاده مي شود. از مزاياي اين نوع کلاچ اين است که به پدال کلاچ نيازي ندارد. کنترل کلاچ بصورت اتوماتيک و توسط دورموتور صورت مي گيرد. خودروهايي که از اين کلاچها استفاده مي کنند، توانايي متوقف شدن با دنده درگير را دارند، بدون اينکه خودرو خاموش شود. بنابراين در اين حالت به مهارت کمتري از جانب راننده نياز است در اين نوع از کلاچها بر خلاف کلاچهاي نيمه گريز از مرکز، تنها از نيروي گريز از مرکز براي اعمال فشار بر روي صفحات و درگير کردن کلاچ استفاده مي شود. از مزاياي اين نوع کلاچ اين است که به پدال کلاچ نيازي ندارد. کنترل کلاچ بصورت اتوماتيک و توسط دورموتور صورت مي گيرد. خودروهايي که از اين کلاچها استفاده مي کنند، توانايي متوقف شدن با دنده درگير را دارند، بدون اينکه خودرو خاموش شود. بنابراين در اين حالت به مهارت کمتري از جانب راننده نياز است
◄ صفحه کلاچ:
صفحه کلاچ شامل يک توپي، صفحه، فنرهاي صفحه کلاچ و فنرهاي لرزه گير صفحه مي باشد. لنتهاي صفحه کلاچ به فنرهاي صفحه کلاچ اتصال دارند. وقتي کلاچ درگير مي شود، فنرهاي صفحه کلاچ اندکي جمع مي شوند و ضربه ناشي از درگيري را جذب مي کنند فنرهاي لرزه گير صفحه يا فنرهاي پيچشي فنرهاي لول کلفتي هستند که روي دايره اي در پيرامون توپي نصب مي شوند. توپي از طريق اين فنرها به حرکت در مي آيد. اين فنرها به کاهش ارتعاشات پيچشي، که ناشي از ضربه هاي توان موتور است کمک مي کند؛ در نتيجه توان بصورت يکنواخت و نرم به جعبه دنده منتقل مي شود. در دو طرف لنتهاي صفحه کلاچ شيارهايي ديده مي شود.در هنگام خلاص شدن کلاچ اين شيارها مانع چسبيدن لنت به چرخ لنگر يا صفحه فشارنده مي شوند. به سبب وجود اين شيارها، ايجاد خلاء بين لنت و چرخ لنگريا صفحه فشارنده و در نتيجه چسبيدن لنت غيرممکن خواهد بود. اين شيارها به خنک کردن لنت نيز کمک مي کنند در نسل اوليه کلاچها جنس لنت را از چرم انتخاب مي کردند. پس از آن لنتهاي بسياري از صفحه کلاچها از پنبه و الياف آزبست (پنبه نسوز) که بهم بافته شده بودند، تشکيل مي شدند. در بعضي از صفحه کلاچها سيم مسي را در لنت مي بافند يا با فشار وارد آن مي کنند تا استحکام بيشتري پيدا کند. اما آزبست آلوده کننده محيط زيست و براي سلامتي زيان آور است. امروزه از مواد ديگري بجاي آنها استفاده مي کنند
ERBIL INTERNATIONAL FIAR 2010 ( 18-21 OCTOBER )
Erbil is the capital and seat of the Kurdistan Regional Government (KRG).It serves as the Northern Gateway to Iraq and is the epicenter of a region.offering all the advantages that matter in the era of globalization.
DOING BUSINESS IN KURDISTAN
The KRG investment law was passed in July 2006 and an Investment
Board was created to manage and promote it. This Investment Law is one of the friendliest to foreign investors looking for lucrative business ventures. Some benefits of this law include:
• Entitlement to buy and own land for investment purposes
• 10 year non-custom tax break
• Ownership of all the capital of any project
• Allocation of free or reduced price land for investment projects
• Repatriation of profits in full.
http://www.ifpiraq.com/
DOING BUSINESS IN KURDISTAN
The KRG investment law was passed in July 2006 and an Investment
Board was created to manage and promote it. This Investment Law is one of the friendliest to foreign investors looking for lucrative business ventures. Some benefits of this law include:
• Entitlement to buy and own land for investment purposes
• 10 year non-custom tax break
• Ownership of all the capital of any project
• Allocation of free or reduced price land for investment projects
• Repatriation of profits in full.
http://www.ifpiraq.com/
Tuesday, September 14, 2010
Thursday, September 9, 2010
Engines : V6
A V6 engine is a V engine with six cylinders mounted on the crankcase in two banks of three cylinders, usually set at either a right angle or an acute angle to each other, with all six pistons driving a common crankshaft. It is the second most common engine configuration in modern cars after the inline four.The V6 is one of the most compact engine configurations, shorter than the straight 4 and in many designs narrower than the V8 engine, and is well suited to the popular transverse engine front-wheel drive layout. It is becoming more common as the space allowed for engines in modern cars is reduced at the same time as power requirements increase, and has largely replaced the inline-6, which is too long to fit in many modern engine compartments. Although it is more complicated and not as smooth as the inline 6, the V6 is more compact, more rigid, and less prone to torsional vibrations in the crankshaft. The V6 engine has become widely adopted for medium-sized cars, often as an optional engine where a straight-4 is standard, or as an economy engine where a V8 is a higher-cost option. It is also becoming a high performance engine, due to its high power and torque output like the classic V8 while still maintaining fuel economy Some examples of this are: Nissan Z-car, Infiniti G, Chevrolet Camaro and the Hyundai Genesis Coupe.Modern V6 engines commonly range in displacement from 2.5 to 4.3 L (150 to 260 cu in), though larger and smaller examples have been produced.
V angles
60 degrees
The most efficient cylinder bank angle for a V6 is 60 degrees, minimizing size and vibration. While 60° V6 engines are not as well balanced as inline-6 and flat-6 engines, modern techniques for designing and mounting engines have largely disguised their vibrations. Unlike most other angles, 60 degree V6 engines can be made acceptably smooth without the need for balance shafts. When Lancia pioneered the 60° V6 in 1950, a 6-throw crankshaft was used to give equal firing intervals of 120°. However, more modern designs often use a 3-throw crankshaft with what are termed flying arms between the crankpins, which not only give the required 120° separation but also can be used for balancing purposes. Combined with a pair of heavy counterweights on the crankshaft ends, these can eliminate all but a modest secondary imbalance which can easily be damped out by the engine mounts.This configuration is a good fit in cars which are too big to be powered by four-cylinder engines, but for which compactness and low cost are important. The most common 60° V6s were built by General Motors (the heavy duty commercial models, as well as a design used in many GM front wheel drive cars) and Ford European subsidiaries (Essex V6, Cologne V6 and the more recent Duratec V6). Other 60° V6 engines are the Chrysler 3.3 V6 engine, the Nissan VQ engine, the Alfa Romeo V6 engine, and later versions of the Mercedes-Benz V6 engine.
90 degrees
90° V6 engines are also produced, usually so they can use the same production-line tooling set up to produce V8 engines (which normally have a 90° V angle). Although it is relatively easy to derive a 90° V6 from an existing V8 design by simply cutting two cylinders off the engine, this tends to make it wider and more vibration-prone than a 60° V6. The design was first used by Buick when it introduced its 198 CID Fireball V6 as the standard engine in the 1962 Special. Other examples include the Maserati V6 used in the Citroën SM, the PRV V6, Chevrolet's 4.3 L Vortec 4300 and Chrysler's 3.9 L (238 in³) Magnum V6 and 3.7 L (226 in³) PowerTech V6. The Buick V6 was notable because it introduced the concept of uneven firing, as a result of using the 90° V8 cylinder angle without adjusting the crankshaft design for the V6 configuration. Rather than firing every 120° of crankshaft rotation, the cylinders would fire alternately at 90° and 150°, resulting in strong harmonic vibrations at certain engine speeds. These engines were often referred to by mechanics as "shakers", due to the tendency of the engine to bounce around at idle speed.More modern 90° V6 engine designs avoid these vibration problems by using crankshafts with offset split crankpins to make the firing intervals even, and often add balancing shafts to eliminate the other vibration problems. Examples include the later versions of the Buick V6, and earlier versions of the Mercedes-Benz V6. The Mercedes V6, although designed to be built on the same assembly lines as the V8, used split crankpins, a counter-rotating balancing shaft, and careful acoustic design to make it almost as smooth as the inline-6 it replaced. However, in later versions Mercedes changed to a 60° angle, making the engine more compact and allowing elimination of the balancing shaft. Despite the difference in V angles, the Mercedes 60° V6s were built on the same assembly lines as 90° V8s.
120 degrees
120° might be described as the natural angle for a V6 since the cylinders fire every 120° of crankshaft rotation. Unlike the 60° or 90° configuration, it allows pairs of pistons to share crank pins in a three-throw crankshaft without requiring flying arms or split crankpins to be even-firing. However, unlike the crossplane crankshaft V8, there is no way to arrange a V6 so that unbalanced forces from the two cylinder banks will completely cancel each other. As a result, the 120° V6 acts like two straight-3s running on the same crankshaft and, like the straight-3, suffers from a primary dynamic imbalance which requires a balance shaft to offset.The 120° layout also produces an engine which is too wide for most automobile engine compartments, so it is more often used in racing cars where the car is designed around the engine rather than vice-versa, and vibration is not as important. By comparison, the 180° flat-6 boxer engine is only moderately wider than the 120° V6, and unlike the V6 is a fully-balanced configuration with no vibration problems, so it is more commonly used in aircraft and in sports/luxury cars where space is not a constraint and smoothness is important.Ferrari introduced a very successful 120° V6 racing engine in 1961. The Ferrari Dino 156 engine was shorter and lighter than the 65° Ferrari V6 engines that preceded it, and the simplicity and low center of gravity of the engine was an advantage in racing. It won a large number of Formula One races between 1961 and 1964. However, Enzo Ferrari had a personal dislike of the 120° V6 layout, preferring a 65° angle, and after that time it was replaced by other engines.Bombardier designed 120° V220/V300T V6 engines for use in light aircraft. The ignition sequence was symmetrical, with each cylinder firing 120° after the previous cylinder resulting in smooth power delivery. A balance shaft on the bottom of the engine offset the primary dynamic imbalance. The straight, pin-type crankshaft journals in the 120° V-6 layout allowed a shorter and stiffer crankshaft than competing flat-6 engines, while water cooling resulted in better temperature control than air cooling. These engines could run on automotive gasoline rather than avgas. However, the design was shelved in 2006 and there are no plans for production.
Other angles
Narrower angle V6 engines are very compact but can suffer from severe vibration problems unless very carefully designed. Notable V6 bank angles include:
The 10.6° and 15° Volkswagen VR6, which is such a narrow angle it can use a single cylinder head and double overhead camshafts for both cylinder banks. With seven main bearings, it is more like a staggered-bank in-line six rather than a normal V6, but is only slightly longer and wider than a straight-4. The 45° Electro-Motive 6 cylinder version of their model 567 Diesel locomotive engine. The 54° GM/Opel V6, designed to be narrower than normal for use in small front-wheel drive cars. The 65° Ferrari Dino V6. A 60° angle limited the size of the carburetors which originally used in the engine, while a 65° angle allowed larger carburetors at the expense of a slight increase in vibrations. The 75° Isuzu Rodeo and Isuzu Trooper V6 of 3.2 and 3.5 L in both SOHC and DOHC versions. The 80° Honda RA168-E Formula One engine in the McLaren MP4/4
Odd and even firing
Many older V6 engines were based on V8 engine designs, in which a pair of cylinders was cut off the front of V8 without altering the V angle or using a more sophisticated crankshaft to even out the firing interval. Most V8 engines share a common crankpin between opposite cylinders in each bank, and a 90° V8 crankshaft has just four pins shared by eight cylinders, with two pistons per crankpin, allowing a cylinder to fire every 90° to achieve smooth operation.Early 90° V6 engines derived from V8 engines had three shared crankpins arranged at 120° from each other, similar to an inline 3-cylinder. Since the cylinder banks were arranged at 90° to each other, this resulted in a firing pattern with groups of two cylinders separated by 90° of rotation, and groups separated by 150° of rotation, causing a notorious odd-firing behavior, with cylinders firing at alternating 90° and 150° intervals. The uneven firing intervals resulting in rough-running engines with unpleasant harmonic vibrations at certain engine speeds.An example is the Buick 231 odd-fire, which has a firing order 1-6-5-4-3-2. As the crankshaft is rotated through the 720° required for all cylinders to fire, the following events occur on 30° boundaries:
Angle 0° 90° 180° 270° 360° 450° 540° 630°
Odd firing 1 6 5 4 3 2
Even firing 1 4 5 6 3 2
More modern 90° V6 engines avoid this problem by using split crankpins, with adjacent crankpins offset by 15° in opposite directions to achieve an even 120° ignition pattern. Such a 'split' crankpin is weaker than a straight one, but modern metallurgical techniques can produce a crankshaft that is adequately strong.In 1977, Buick introduced the new "split-pin crankshaft" in the 231. Using a crankpin that is 'split' and offset by 30° of rotation resulted in smooth, even firing every 120°. However, in 1978 Chevrolet introduced a 90° 200/229 V6, which had a compromise 'semi-even firing' design using a crankpin that was offset by only 18°. This resulted in cylinders firing at 108° and 132°, which had the advantage of reducing vibrations to a more acceptable level and did not require strengthening the crankshaft. In 1985, Chevrolet's 4.3 (later the Vortec 4300) changed it to a true even-firing V6 with a 30° offset, requiring larger crank journals to make them adequately strong.In 1986, the similarly-designed 90° PRV engine adopted the same 30° crankshaft offset design to even out its firing. In 1988, Buick introduced a V6 engine that not only had split crankpins, but had a counter-rotating balancing shaft between the cylinder banks to eliminate almost all primary and secondary vibrations, resulting in a very smooth-running engine.
V angles
60 degrees
The most efficient cylinder bank angle for a V6 is 60 degrees, minimizing size and vibration. While 60° V6 engines are not as well balanced as inline-6 and flat-6 engines, modern techniques for designing and mounting engines have largely disguised their vibrations. Unlike most other angles, 60 degree V6 engines can be made acceptably smooth without the need for balance shafts. When Lancia pioneered the 60° V6 in 1950, a 6-throw crankshaft was used to give equal firing intervals of 120°. However, more modern designs often use a 3-throw crankshaft with what are termed flying arms between the crankpins, which not only give the required 120° separation but also can be used for balancing purposes. Combined with a pair of heavy counterweights on the crankshaft ends, these can eliminate all but a modest secondary imbalance which can easily be damped out by the engine mounts.This configuration is a good fit in cars which are too big to be powered by four-cylinder engines, but for which compactness and low cost are important. The most common 60° V6s were built by General Motors (the heavy duty commercial models, as well as a design used in many GM front wheel drive cars) and Ford European subsidiaries (Essex V6, Cologne V6 and the more recent Duratec V6). Other 60° V6 engines are the Chrysler 3.3 V6 engine, the Nissan VQ engine, the Alfa Romeo V6 engine, and later versions of the Mercedes-Benz V6 engine.
90 degrees
90° V6 engines are also produced, usually so they can use the same production-line tooling set up to produce V8 engines (which normally have a 90° V angle). Although it is relatively easy to derive a 90° V6 from an existing V8 design by simply cutting two cylinders off the engine, this tends to make it wider and more vibration-prone than a 60° V6. The design was first used by Buick when it introduced its 198 CID Fireball V6 as the standard engine in the 1962 Special. Other examples include the Maserati V6 used in the Citroën SM, the PRV V6, Chevrolet's 4.3 L Vortec 4300 and Chrysler's 3.9 L (238 in³) Magnum V6 and 3.7 L (226 in³) PowerTech V6. The Buick V6 was notable because it introduced the concept of uneven firing, as a result of using the 90° V8 cylinder angle without adjusting the crankshaft design for the V6 configuration. Rather than firing every 120° of crankshaft rotation, the cylinders would fire alternately at 90° and 150°, resulting in strong harmonic vibrations at certain engine speeds. These engines were often referred to by mechanics as "shakers", due to the tendency of the engine to bounce around at idle speed.More modern 90° V6 engine designs avoid these vibration problems by using crankshafts with offset split crankpins to make the firing intervals even, and often add balancing shafts to eliminate the other vibration problems. Examples include the later versions of the Buick V6, and earlier versions of the Mercedes-Benz V6. The Mercedes V6, although designed to be built on the same assembly lines as the V8, used split crankpins, a counter-rotating balancing shaft, and careful acoustic design to make it almost as smooth as the inline-6 it replaced. However, in later versions Mercedes changed to a 60° angle, making the engine more compact and allowing elimination of the balancing shaft. Despite the difference in V angles, the Mercedes 60° V6s were built on the same assembly lines as 90° V8s.
120 degrees
120° might be described as the natural angle for a V6 since the cylinders fire every 120° of crankshaft rotation. Unlike the 60° or 90° configuration, it allows pairs of pistons to share crank pins in a three-throw crankshaft without requiring flying arms or split crankpins to be even-firing. However, unlike the crossplane crankshaft V8, there is no way to arrange a V6 so that unbalanced forces from the two cylinder banks will completely cancel each other. As a result, the 120° V6 acts like two straight-3s running on the same crankshaft and, like the straight-3, suffers from a primary dynamic imbalance which requires a balance shaft to offset.The 120° layout also produces an engine which is too wide for most automobile engine compartments, so it is more often used in racing cars where the car is designed around the engine rather than vice-versa, and vibration is not as important. By comparison, the 180° flat-6 boxer engine is only moderately wider than the 120° V6, and unlike the V6 is a fully-balanced configuration with no vibration problems, so it is more commonly used in aircraft and in sports/luxury cars where space is not a constraint and smoothness is important.Ferrari introduced a very successful 120° V6 racing engine in 1961. The Ferrari Dino 156 engine was shorter and lighter than the 65° Ferrari V6 engines that preceded it, and the simplicity and low center of gravity of the engine was an advantage in racing. It won a large number of Formula One races between 1961 and 1964. However, Enzo Ferrari had a personal dislike of the 120° V6 layout, preferring a 65° angle, and after that time it was replaced by other engines.Bombardier designed 120° V220/V300T V6 engines for use in light aircraft. The ignition sequence was symmetrical, with each cylinder firing 120° after the previous cylinder resulting in smooth power delivery. A balance shaft on the bottom of the engine offset the primary dynamic imbalance. The straight, pin-type crankshaft journals in the 120° V-6 layout allowed a shorter and stiffer crankshaft than competing flat-6 engines, while water cooling resulted in better temperature control than air cooling. These engines could run on automotive gasoline rather than avgas. However, the design was shelved in 2006 and there are no plans for production.
Other angles
Narrower angle V6 engines are very compact but can suffer from severe vibration problems unless very carefully designed. Notable V6 bank angles include:
The 10.6° and 15° Volkswagen VR6, which is such a narrow angle it can use a single cylinder head and double overhead camshafts for both cylinder banks. With seven main bearings, it is more like a staggered-bank in-line six rather than a normal V6, but is only slightly longer and wider than a straight-4. The 45° Electro-Motive 6 cylinder version of their model 567 Diesel locomotive engine. The 54° GM/Opel V6, designed to be narrower than normal for use in small front-wheel drive cars. The 65° Ferrari Dino V6. A 60° angle limited the size of the carburetors which originally used in the engine, while a 65° angle allowed larger carburetors at the expense of a slight increase in vibrations. The 75° Isuzu Rodeo and Isuzu Trooper V6 of 3.2 and 3.5 L in both SOHC and DOHC versions. The 80° Honda RA168-E Formula One engine in the McLaren MP4/4
Odd and even firing
Many older V6 engines were based on V8 engine designs, in which a pair of cylinders was cut off the front of V8 without altering the V angle or using a more sophisticated crankshaft to even out the firing interval. Most V8 engines share a common crankpin between opposite cylinders in each bank, and a 90° V8 crankshaft has just four pins shared by eight cylinders, with two pistons per crankpin, allowing a cylinder to fire every 90° to achieve smooth operation.Early 90° V6 engines derived from V8 engines had three shared crankpins arranged at 120° from each other, similar to an inline 3-cylinder. Since the cylinder banks were arranged at 90° to each other, this resulted in a firing pattern with groups of two cylinders separated by 90° of rotation, and groups separated by 150° of rotation, causing a notorious odd-firing behavior, with cylinders firing at alternating 90° and 150° intervals. The uneven firing intervals resulting in rough-running engines with unpleasant harmonic vibrations at certain engine speeds.An example is the Buick 231 odd-fire, which has a firing order 1-6-5-4-3-2. As the crankshaft is rotated through the 720° required for all cylinders to fire, the following events occur on 30° boundaries:
Angle 0° 90° 180° 270° 360° 450° 540° 630°
Odd firing 1 6 5 4 3 2
Even firing 1 4 5 6 3 2
More modern 90° V6 engines avoid this problem by using split crankpins, with adjacent crankpins offset by 15° in opposite directions to achieve an even 120° ignition pattern. Such a 'split' crankpin is weaker than a straight one, but modern metallurgical techniques can produce a crankshaft that is adequately strong.In 1977, Buick introduced the new "split-pin crankshaft" in the 231. Using a crankpin that is 'split' and offset by 30° of rotation resulted in smooth, even firing every 120°. However, in 1978 Chevrolet introduced a 90° 200/229 V6, which had a compromise 'semi-even firing' design using a crankpin that was offset by only 18°. This resulted in cylinders firing at 108° and 132°, which had the advantage of reducing vibrations to a more acceptable level and did not require strengthening the crankshaft. In 1985, Chevrolet's 4.3 (later the Vortec 4300) changed it to a true even-firing V6 with a 30° offset, requiring larger crank journals to make them adequately strong.In 1986, the similarly-designed 90° PRV engine adopted the same 30° crankshaft offset design to even out its firing. In 1988, Buick introduced a V6 engine that not only had split crankpins, but had a counter-rotating balancing shaft between the cylinder banks to eliminate almost all primary and secondary vibrations, resulting in a very smooth-running engine.
Saturday, September 4, 2010
Wheel Alignment
In its most basic form, a wheel alignment consists of adjusting the angles of the wheels so that they are perpendicular to the ground and parallel to each other. The purpose of these adjustments is maximum tire life and a vehicle that tracks straight and true when driving along a straight and level road.This article begins with information that any motorist should know; however, if you are interested in learning more about this topic, click on the underlined words for more detailed explanations of each term. We will cover various levels of detail with the deepest levels containing information that even a wheel alignment technician will find informative.Wheel Alignment is often confused with Wheel Balancing. The two really have nothing to do with each other except for the fact that they affect ride and handling. If a wheel is out of balance, it will cause a vibration at highway speeds that can be felt in the steering wheel and/or the seat. If the alignment is out, it can cause excessive tire wear (1)and steering or tracking problems.
If you know anything about wheel alignment, you've probably heard the terms Camber, Caster and Toe-in.
Camber
Camber is the angle of the wheel, measured in degrees, when viewed from the front of the vehicle. If the top of the wheel is leaning out from the center of the car, then the camber is positive ,if it's leaning in, then the camber is negative. If the camber is out of adjustment, it will cause tire wear on one side of the tire's tread. If the camber is too far negative, for instance, then the tire will wear on the inside of the tread.
If the camber is different from side to side it can cause a pulling problem. The vehicle will pull to the side with the more positive camber. On many front-wheel-drive vehicles, camber is not adjustable. If the camber is out on these cars, it indicates that something is worn or bent, possibly from an accident and must be repaired or replaced.
Caster
When you turn the steering wheel, the front wheels respond by turning on a pivot attached to the suspension system. Caster is the angle of this steering pivot, measured in degrees, when viewed from the side of the vehicle. If the top of the pivot is leaning toward the rear of the car, then the caster is positive, if it is leaning toward the front, it is negative. If the caster is out of adjustment, it can cause problems in straight line tracking. If the caster is different from side to side, the vehicle will pull to the side with the less positive caster. If the caster is equal but too negative, the steering will be light and the vehicle will wander and be difficult to keep in a straight line. If the caster is equal but too positive, the steering will be heavy and the steering wheel may kick when you hit a bump. Caster has little affect on tire wear.
The best way to visualize caster is to picture a shopping cart caster. The pivot of this type of caster, while not at an angle, intersects the ground ahead of the wheel contact patch. When the wheel is behind the pivot at the point where it contacts the ground, it is in positive caster. Picture yourself trying to push the cart and keep the wheel ahead of the pivot. The wheel will continually try to turn from straight ahead. That is what happens when a car has the caster set too far negative. Like camber, on many front-wheel-drive vehicles, caster is not adjustable. If the caster is out on these cars, it indicates that something is worn or bent, possibly from an accident, and must be repaired or replaced.
Toe-in
The toe measurement is the difference in the distance between the front of the tires and the back of the tires. It is measured in fractions of an inch in the US and is usually set close to zero which means that the wheels are parallel with each other. Toe-in means that the fronts of the tires are closer to each other than the rears. Toe-out is just the opposite. An incorrect toe-in will cause rapid tire wear to both tires equally. This type of tire wear is called a saw-tooth wear pattern as shown in this illustration.
If the sharp edges of the tread sections are pointing to the center of the car, then there is too much toe-in. If they are pointed to the outside of the car then there is too much toe-out. Toe is always adjustable on the front wheels and on some cars, is also adjustable for the rear wheels.
Four-Wheel Alignments
There are two main types of 4-wheel alignments. In each case, the technician will place an instrument on all four wheels. In the first type the rear toe and tracking is checked, but all adjustments are made at the front wheels. This is done on vehicles that do not have adjustments on the rear. The second type is a full 4-wheel alignment where the adjustments are first made to true up the rear alignment, then the front is adjusted. A full 4-wheel alignment will cost more than the other type because there is more work involved.
Other facts every driver should know about wheel alignments.
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A proper wheel alignment should always start and end with a test drive. -
The front end and steering linkage should be checked for wear before performing an alignment. -
The tires should all be in good shape with even wear patterns. If you have a tire with excessive camber wear, for instance, and you correct the alignment problem that caused that wear, the tire will now be making only partial contact with the road. (see illustration on right) -
Pulling problems are not always related to wheel alignment. Problems with tires (especially unequal air pressure), brakes and power steering can also be responsible. It is up to a good wheel alignment technician to determine the cause.
Advanced Wheel Alignment Information.
While Camber, Caster & Toe-in are the settings that are always checked when doing a wheel alignment, they are not the only settings. Below is a list of the alignment settings that are important for a wheel alignment technician to know about in order to diagnose front end problems.To find out more about each of these measurements, click on them. -
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Camber
When camber specifications are determined during the design stage, a number of factors are taken into account. The engineers account for the fact that wheel alignment specifications used by alignment technicians are for a vehicle that is not moving. On many vehicles, camber changes with different road speeds. This is because aerodynamic forces cause a change in riding height from the height of a vehicle at rest. Because of this, riding height should be checked and problems corrected before setting camber. Camber specs are set so that when a vehicle is at highway speed, the camber is at the optimal setting for minimum tire wear.
For many years the trend has been to set the camber from zero to slightly positive to offset vehicle loading, however the current trend is to slightly negative settings to increase vehicle stability and improve handling.
Caster
Positive caster improves straight line tracking because the caster line (the line drawn through the steering pivot when viewed from the side) intersects the ground ahead of the contact patch of the tire. Just like a shopping cart caster, the wheel is forced behind the pivot allowing the vehicle to track in a straight line.
If this is the case, then why did most cars have negative caster specs prior to 1975 ? There are a couple of reasons for this. In those days, people were looking for cars that steered as light as a feather, and cars back then were not equipped with radial tires. Non-radial tires had a tendency to distort at highway speed so that the contact patch moved back past the centerline of the tire (Picture a cartoon car speeding along, the tires are generally drawn as egg-shaped). The contact patch generally moves behind the caster line causing, in effect, a positive caster. This is why, when you put radial tires on this type of car, the car wanders from side to side and no longer tracks straight. To correct this condition, re-adjust the caster to positive and the car should steer like a new car.
Toe
Like camber, toe will change depending on vehicle speed. As aerodynamic forces change the riding height, the toe setting may change due to the geometry of the steering linkage in relation to the geometry of the suspension. Because of this, specifications are determined for a vehicle that is not moving based on the toe being at zero when the vehicle is at highway speed. In the early days prior to radial tires, extra toe-in was added to compensate for tire drag at highway speed.
On some older alignment machines, toe-in was measured at each wheel by referencing the opposite wheel. This method caused problems with getting the steering wheel straight the first time and necessitated corrective adjustments before the wheel was straight. Newer machines reference the vehicle's centerline by putting instruments on all four wheels. For more information on this see Steering Center and Thrust angle.
Steering Axis Inclination (SAI)
SAI is the measurement in degrees of the steering pivot line when viewed from the front of the vehicle. This angle, when added to the camber to form the included angle (see below) causes the vehicle to lift slightly when you turn the wheel away from a straight ahead position. This action uses the weight of the vehicle to cause the steering wheel to return to the center when you let go of it after making a turn. Because of this, if the SAI is different from side to side, it will cause a pull at very slow speeds. Most alignment machines have a way to measure SAI; however it is not separately adjustable. The most likely cause for SAI being out is bent parts which must be replaced to correct the condition. SAI is also referred to as KPI (King Pin Inclination) on trucks and old cars with king pins instead of ball joints.
Included Angle
Included angle is the angle formed between the SAI and the camber. Included angle is not directly measurable. To determine the included angle, you add the SAI to the camber. If the camber is negative, then the included angle will be less than the SAI, if the camber is positive, it will be greater. The included angle must be the same from side to side even if the camber is different. If it is not the same, then something is bent, most likely the steering knuckle.
Scrub Radius
Scrub radius is the distance between where the SAI intersects the ground and the center of the tire. This distance must be exactly the same from side to side or the vehicle will pull strongly at all speeds. While included angle problems will affect the scrub radius, it is not the only thing that will affect it. Different wheels or tires from side to side will cause differences in scrub radius as well as a tire that is low on air. Positive scrub radius is when the tire contact patch is outside of the SAI pivot, while negative scrub radius is when the contact patch is inboard of the SAI pivot (front wheel drive vehicles usually have negative scrub radius).
If the brake on one front wheel is not working, with positive scrub radius, stepping on the brake will cause the steering wheel to try to rip out of your hand. Negative scrub radius will minimize that effect.
Scrub radius is designed at the factory and is not adjustable. If you have a vehicle that is pulling even though the alignment is correct, look for something that will affect scrub radius.
Riding Height
Riding height is measured, usually in inches, from the rocker panel to the ground. Good wheel alignment charts provide specs, but the main thing is that the measurements should be within one inch from side to side and front to rear. Riding height is not adjustable except on vehicles with torsion bar type springs. The best way to fix this problem is to replace the springs (Note: springs should only be replaced in matched pairs). Changes in riding height will affect camber and toe so if springs are replaced or torsion bars are adjusted, then the wheel alignment must be checked to avoid the possibility of tire wear. It is important to note that the only symptom of weak coil springs is a sag in the riding height. If the riding height is good, then the springs are good.
Set Back
Set back is when one front wheel is set further back than the other wheel. With alignment equipment that measures toe by using only the front instruments, any setback will cause an uncentered steering wheel. Any good 4-wheel aligner will reference the rear wheels when setting toe in order to eliminate this problem.
Some good alignment equipment will measure set back and give you a reading in inches or millimeters. A set back of less than 1/4 inch is considered normal tolerance by some manufacturers. More than that and there is a good chance that something is bent.
Thrust Angle
Thrust angle is the direction that the rear wheels are pointing in relation to the center line of the vehicle. If the thrust angle is not zero, then the vehicle will "dog track" and the steering wheel will not be centered. The best solution is to first adjust the rear toe to the center line and then adjust the front toe. This is normally done during a 4-wheel alignment as long as the rear toe is adjustable. If the rear is not adjustable, then the front toe must be set to compensate for the thrust angle, allowing the steering to be centered.
Steering Center
Steering center is simply the fact that the steering wheel is centered when the vehicle is traveling down a straight and level road. A crooked steering wheel is usually the most common complaint that a customer has after a wheel alignment is performed. Assuming that the steering wheel stays in the same position when you let go of the wheel (in other words, the car is not pulling), then steering center is controlled by the front and rear toe settings. When setting steering center, the rear toe should be set first bringing the Thrust Angle as close to the vehicle centerline as possible. Then the steering wheel is locked in a straight ahead position while the front toe is set. Before locking the steering wheel, the engine should be started and the wheel should be turned right and left a couple of times to take any stress off the power steering valve. After setting the toe, the engine should be started again to be sure that the steering valve wasn't loaded again due to the tie rod adjustments. Of course, you should always road test the vehicle after every alignment as a quality control check.
Another problem with steering center has to do with the type of roads that are driven on. Most roads are crowned to allow for water drainage, and unless you drive in England, Japan or another country where they drive on the wrong (sorry) left side of the road, you usually drive on the right side of the crown. This may cause the vehicle to drift to the right so that the steering wheel will appear to be off-center to the left on a straight road. The best way to compensate for this is as follows:
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If there is a difference in caster, it should be that the left wheel is more negative than the right wheel, but not more than 1/2 degree. Check the specs for any specific recommendations on side-to-side differences. -
If there is a difference in camber, then the left wheel should be more positive than the right wheel. Check the specs to see what the allowable difference is.
Toe Out on Turns
When you steer a car through a turn, the outside front wheel has to navigate a wider arc then the inside wheel. For this reason, the inside front wheel must steer at a sharper angle than the outside wheel.
Toe-out on turns is measured by the turning angle gauges (turn plates) that are a part of every wheel alignment machine. The readings are either directly on the turn plate or they are measured electronically and displayed on the screen. Wheel alignment specifications will usually provide the measurements for toe-out on turns. They will give an angle for the inside wheel and the outside wheel such as 20� for the inside wheel and 18� for the outside wheel. Make sure that the readings are at zero on each side when the wheels are straight ahead, then turn the steering wheel so that the inside wheel is at the inside spec. then check the outside wheel.
The toe-out angles are accomplished by the angle of the steering arm. This arm allows the inside wheel to turn sharper than the outside wheel. The steering arm is either part of the steering knuckle or part of the ball joint and is not adjustable. If there is a problem with the toe-out, it is due to a bent steering arm that must be replaced.
Tire wear (1) and Alignment & Balance
Wheel alignment and Wheel Balancing are two totally different things, but many people often get them confused. In a nutshell, wheel alignment consists of adjusting the angles of the wheels so that they are perpendicular to the ground and parallel to each other. The purpose of these adjustments is maximum tire life and a vehicle that tracks straight and true when driving along a straight and level road. Wheel Balancing, on the other hand allows the tires and wheels to spin without causing any vibrations. This is accomplished by checking for any heavy spots on the wheel-tire combination and compensating for it by placing a measured lead weight on the opposite site of the wheel from where the heavy spot is.
The symptoms of a car that is out of alignment are:
At each tire, take a coin and insert it in the tread at the inside, center and outside.
Another indication of an out-of-alignment condition is a car that continuously drifts or pulls to one side of the road when you let go of the wheel. A car that is hard to keep in a straight line without constant steering corrections is also a candidate. These conditions may or may not also contribute to premature tire wear.
A wheel alignment cannot be done on a car with loose or worn front end parts. The technician will first check for worn parts and inform you of any problems before beginning the alignment.
The best type of wheel alignment is a four wheel alignment. Many cars today have adjustable rear alignment settings, but even for cars without adjustments in the rear, a four wheel alignment will allow the technician to identify any rear tracking problems and compensate for them with adjustments to the front.
After the wheel alignment is finished, you should drive the car on a straight and level road and check that the car goes straight and that the steering wheel is in the proper position with the spokes level. If you notice a problem, take the car back and have the technician drive it and fine-tune the alignment settings.
Click Here for more information on Wheel Alignment
Wheel Balance: Out-of-balance tires will cause a car to vibrate at certain speeds, usually between 50 and 70 mph. A tire is out of balance when one section of the tire is heavier than the others. One ounce of imbalance on a front tire is enough to cause a noticeable vibration in the steering wheel at about 60 mph. To balance a wheel, the technician will mount it on a balancing machine which spins the wheel to locate the heavier part. He will then compensate for the heavy part by attaching a lead weight on the opposite side. Many people are pleasantly surprised at how smooth their car drives after balancing all four wheels.
Most high quality tires will hold their balance fairly well and go out of balance very gradually. If you notice a vibration that wasn't there the day before, it is possible that one of the lead balancing weights fell off. If you feel the vibration mostly in the steering wheel, the problem is most likely in a front wheel. If the vibration is mostly in the seat, the problem is probably in the rear.For those of you who are very sensitive about vibrations and your shop can't seem to get that last bit of vibration out, check to see if you have locking wheel lugs. Some locking lugs are as much as 1.5 ounces heavier than the other lug nuts which translates to about 1/2 ounce at the wheel rim . Try putting a 1/2 ounce weight opposite the locking lug and see if it helps.
Wheel alignment and Wheel Balancing are two totally different things, but many people often get them confused. In a nutshell, wheel alignment consists of adjusting the angles of the wheels so that they are perpendicular to the ground and parallel to each other. The purpose of these adjustments is maximum tire life and a vehicle that tracks straight and true when driving along a straight and level road. Wheel Balancing, on the other hand allows the tires and wheels to spin without causing any vibrations. This is accomplished by checking for any heavy spots on the wheel-tire combination and compensating for it by placing a measured lead weight on the opposite site of the wheel from where the heavy spot is.
The symptoms of a car that is out of alignment are:
- Uneven or rapid tire wear
- Pulling or drifting away from a straight line
- Wandering on a straight level road
- Spokes of the steering wheel off to one side while driving on a straight and level road.
- Vibration in the steering wheel at certain highway speeds.
- Vibration in the seat or floorboard at certain highway speeds.
- Scalloped or cupped wear pattern on the tires
At each tire, take a coin and insert it in the tread at the inside, center and outside.
- a -If the tread is deeper on the edges than in the center, the tire is over inflated.
- b -If the tread is deeper in the center than the edges, the tire is under inflated.
- c -If the tread is deeper on one side than the other, have your wheel alignment checked soon.
- d -Run your hand back and forth across the tread, being careful not to cut yourself on any debris or exposed steel belt wire. If the tread is smooth in one direction, but jagged in the other you have what is called a "saw-tooth" wear pattern which is caused by a toe-in problem. Have the alignment checked as soon as possible as this condition causes rapid tire wear.
Another indication of an out-of-alignment condition is a car that continuously drifts or pulls to one side of the road when you let go of the wheel. A car that is hard to keep in a straight line without constant steering corrections is also a candidate. These conditions may or may not also contribute to premature tire wear.
A wheel alignment cannot be done on a car with loose or worn front end parts. The technician will first check for worn parts and inform you of any problems before beginning the alignment.
The best type of wheel alignment is a four wheel alignment. Many cars today have adjustable rear alignment settings, but even for cars without adjustments in the rear, a four wheel alignment will allow the technician to identify any rear tracking problems and compensate for them with adjustments to the front.
After the wheel alignment is finished, you should drive the car on a straight and level road and check that the car goes straight and that the steering wheel is in the proper position with the spokes level. If you notice a problem, take the car back and have the technician drive it and fine-tune the alignment settings.
Click Here for more information on Wheel Alignment
Wheel Balance: Out-of-balance tires will cause a car to vibrate at certain speeds, usually between 50 and 70 mph. A tire is out of balance when one section of the tire is heavier than the others. One ounce of imbalance on a front tire is enough to cause a noticeable vibration in the steering wheel at about 60 mph. To balance a wheel, the technician will mount it on a balancing machine which spins the wheel to locate the heavier part. He will then compensate for the heavy part by attaching a lead weight on the opposite side. Many people are pleasantly surprised at how smooth their car drives after balancing all four wheels.
Most high quality tires will hold their balance fairly well and go out of balance very gradually. If you notice a vibration that wasn't there the day before, it is possible that one of the lead balancing weights fell off. If you feel the vibration mostly in the steering wheel, the problem is most likely in a front wheel. If the vibration is mostly in the seat, the problem is probably in the rear.For those of you who are very sensitive about vibrations and your shop can't seem to get that last bit of vibration out, check to see if you have locking wheel lugs. Some locking lugs are as much as 1.5 ounces heavier than the other lug nuts which translates to about 1/2 ounce at the wheel rim . Try putting a 1/2 ounce weight opposite the locking lug and see if it helps.
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