CAR NEW MODELS: control arm or wishbon

CAR NEW MODELS: control arm or wishbon: In automotive suspension, an automobile's  control arm  or wishbone (aka. A-arm or A-frame) is a nearly flat and roughly triangular su...

Advantages and disadvantages of MacPherson strut

Although it is a popular choice, due to its simplicity and low manufacturing cost, the design has a few disadvantages in the quality of ride and the handling of the car. Geometric analysis shows it cannot allow vertical movement of the wheel without some degree of either camber angle change, sideways movement, or both. It is not generally considered to give as good handling as a double wishbone or multi-link suspension, because it allows the engineers less freedom to choose camber change and roll center.

Another drawback is that it tends to transmit noise and vibration from the road directly into the body shell, giving higher noise levels and a "harsh" feeling to the ride compared with double wishbones, requiring manufacturers to add extra noise reduction or cancellation and isolation mechanisms.

Despite these drawbacks, the MacPherson strut setup is still used on high performance cars such as the Porsche 911, several Mercedes-Benz models and lower BMWs models (including the new Mini but excluding the 2007 X5, 2009 7-series, 2011 5-series and 5-series GT).

The Porsche 911 up until the 1989 model year (964) use MacPherson strut designs that do not have coil springs, using a torsion bar suspension instead.

control arm or wishbon

In automotive suspension, an automobile's control arm or wishbone (aka. A-arm or A-frame) is a nearly flat and roughly triangular suspension member (or sub-frame), that pivots in two places. The base of the triangle attaches at the frame and pivots on a bushing. The narrow end attaches to the steering knuckle and pivots on a ball joint.

The upper control arm can clearly be seen at the top portion of the suspension components in the attached photo, where it is the silver part horizontally attached to the frame inside the red body portion and connecting to the steering knuckle near the side of the tire's wheel rim. Note the roughly A-shaped design with the top of the A near the tire and the bottom two points connected to the frame inside the body's space. In the photo, the A-shape is reinforced with a solid triangular plate near the top of the A.

Two such devices per wheel make up a double wishbone suspension, while one control arm per wheel makes up a part, usually the lower part, of a MacPherson strut suspension or of various other configurations.

Intermittent wipers

The inventor of intermittent wipers might have been Raymond Anderson who, in 1923, proposed an electro-mechanical design. (US Patent 1,588,399). In 1958 Oishei et at. filed a patent application describing electro-mechanical, thermal and hydraulic designs. (US Patent 2,987,747). Then in 1961 John Amos, an engineer for the UK automotive engineering company Lucas Industries, filed in the UK the first patent application for a solid-state electronic design. (See US patent 3,262,042).

In 1963, another form of intermittent wiper was invented by Robert Kearns, an engineering professor at Wayne State University in Detroit, Michigan. The road to his intermittent wipers began earlier, on his wedding night in 1953, when an errant champagne cork shot into Kearn's left eye, which eventually went almost completely blind. Nearly a decade later, Kearns was driving his Ford Galaxie through a light rain, and the constant movement of the wiper blades irritated his already troubled vision. He got to thinking about the human eye, which has its own kind of wiper, the eyelid, that automatically closes and opens every few seconds. Finally in 1963, Kearns put his idea into action, building his first intermittent wiper system using off-the-shelf electronic components. Kearns showed it to the Ford Motor Company, and proposed manufacturing the design.

In the Kearns design, the interval between wipes was determined by the rate of current flow into a capacitor. When the charge in the capacitor reached a certain voltage, the capacitor was discharged, activating the wiper motor for one cycle. After extensive testing, Ford executives decided to offer a design similar to Kearns’ intermittent wipers as an option on the company's Mercury line, beginning with the 1969 models. Kearns and Ford became involved in a multi-year patent dispute that eventually had to be resolved in court. A fictionalized version of the Kearns invention and patent lawsuit was used for the 2009 film Flash of Genius, which is billed as "based on the true story", but does not claim to be historically accurate in all respects.

In March 1970, Citroën introduced rain-sensitive intermittent windscreen wipers on their SM model. When the intermittent function was selected, the wiper would make one swipe. If the windscreen was relatively dry, the wiper motor drew high current, which set the control circuit timer to delay the next wipe longest. If the motor drew little current, it indicated that the glass was wet, setting the timer to minimize the delay.

Rain-sensing Wipers

In the past, automakers have tried to either eliminate the wipers or to control their speed automatically. Some of the schemes involved detecting the vibrations caused by individual raindrops hitting the windshield, applying special coatings that did not allow drops to form, or even ultrasonically vibrating the windshield to break up the droplets so they don't need to be wiped at all. But these systems were plagued by problems and either never made it to production or were quickly axed because they annoyed more drivers than they pleased.

However, a new type of wiper system is starting to appear on cars that actually does a good job of detecting the amount of water on the windshield and controlling the wipers. One such system is made by TRW Inc., here is a PDF describing their rain sensor system. TRW Inc. uses optical sensors to detect the moisture. The sensor is mounted in contact with the inside of the windshield, near the rear view mirror.

The sensor projects infrared light into the windshield at a 45-degree angle. If the glass is dry, most of this light is reflected back into the sensor by the front of the windshield. If water droplets are on the glass, they reflect the light in different directions -- the wetter the glass, the less light makes it back into the sensor.

The electronics and software in the sensor turn on the wipers when the amount of light reflected onto the sensor decreases to a preset level. The software sets the speed of the wipers based on how fast the moisture builds up between wipes. It can operate the wipers at any speed. The system adjusts the speed as often as necessary to match with the rate of moisture accumulation.

The TRW system, which is found on many General Motors cars, including all Cadillac models, can also be overridden or turned off so the car can be washed.

For more information on windshield wipers and related topics, check out the links on the next page!

Applications of roots type supercharger

The Roots-type supercharger is simple and widely used. It can also be more effective than alternative superchargers at developing positive intake manifold pressure (i.e., above atmospheric pressure) at low engine speeds, making it a popular choice for passenger automobile applications. Peak torque can be achieved by about 2000 rpm. Unlike the basic illustration, most modern Roots-type superchargers incorporate three-lobe or four-lobe rotors.

Accumulated heat is an important consideration in the operation of a compressor in an internal combustion engine. Of the three basic supercharger types, the Roots design historically possessed the worst thermal efficiency, especially at high pressure ratios. In accordance with the ideal gas law, a compression operation will raise the temperature of the compressed output. Additionally, the operation of the compressor itself requires energy input, which is converted to heat and can be transferred to the gas through the compressor housing, heating it more. Although inter coolers are more commonly known for their use on turbochargers, superchargers may also benefit from the use of an inter cooler. Internal combustion is based upon a thermodynamic cycle, and a cooler temperature of the intake charge results in a greater thermodynamic expansion and vice versa. A hot intake charge robs the engine of efficiency and produces diminishing returns from the compression process, while an inter cooling stage adds complexity but can improve the efficiency by releasing some of the unneeded heat. Above about 5 psi (0.3 bar) the inter cooling improvement can become dramatic. With a Roots-type supercharger, one method successfully employed is the addition of a thin heat exchanger placed between the blower and the engine. Water is circulated through it to a second unit placed near the front of the vehicle where a fan and the ambient air-stream can dissipate the collected heat.

The Roots design was commonly used on two-stroke diesel engines (popularized by the Detroit Diesel [truck and bus] and Electro-Motive [railroad] divisions of General Motors), which require some form of forced induction, as there is no separate intake stroke. The Rootes Co. two-stroke diesel engine, used in Commer and Karrier vehicles, had a Roots-type blower but the two names are not connected.

The superchargers used on top fuel engines, funny cars, and other dragsters, as well as hot rods, are in fact derivatives of General Motors Coach Division blowers for their industrial diesel engines, which were adapted for automotive use in the early days of the sport of drag racing. The model name of these units delineates their size; i.e. the once commonly used "4–71" and "6–71" blowers were designed for General Motors diesels having four or six cylinders of 71 cubic inches each. Current competition dragsters use aftermarket GMC variants similar in design to the −71 series, but with the rotor and case length increased for added pumping capacity, identified as the 8–71, 10–71, 14–71 etc.

Roots blowers are typically used in applications where a large volume of air must be moved across a relatively small pressure differential. This includes low vacuum applications, with the Roots blower acting alone, or use as part of a high vacuum system, in combination with other pumps.

Some civil defense sirens used Roots blowers to pump air to the rotor (chopper). The most well known are the Federal Signal Thunderbolt Series, and ACA (now American Signal Corporation) Hurricane. These sirens are known as "supercharged sirens".

Roots blowers are also used in reverse to measure the flow of gases or liquids, for example, in gas meters.

Construction of fuel injection pump

Earlier diesel pumps used an in-line layout with a series of cam-operated injection cylinders in a line, rather like a miniature inline engine. The pistons have a constant stroke volume, and injection volume (i.e., throttling) is controlled by rotating the cylinders against a cut-off port that aligns with a helical  slot in the cylinder. When all the cylinders are rotated at once, they simultaneously vary their injection volume to produce more or less power from the engine. Inline pumps still find favour on large multi-cylinder engines such as those on trucks, construction plant, static engines and agricultural vehicles.

Distributor diesel injection pump

For use on cars and light trucks, the rotary pump or distributor 

pump was developed. It uses a single injection cylinder driven from an axial cam plate, which injects into the individual fuel lines via a rotary distribution valve. Later incarnations such as the Bosch VE pump vary the injection timing with crank speed to allow greater power at high crank speeds, and smoother, more economical running at slower revs. Some VE variants have a pressure-based system that allows the injection volume to increase over normal to allow a turbocharger or supercharger equipped engine to develop more power under boost conditions.

Inline diesel metering pump

All injection pumps incorporate a governor to cut fuel supply if the crank speed endangers the engine - the heavy moving parts of diesel engines do not tolerate overspeeding well, and catastrophic damage can occur if they are over-revved. Poorly maintained and worn engines can consume their lubrication oil through worn out crankcase ventilation systems and 'run away', causing increasing engine speed until the engine destroys itself. This is because most diesel engines only regulate their speed by fuel supply control and don't have a throttle valve to control air intake.