Technology – Tubular space frame

AutoZine Technical School – Chassis

Tubular space frame. One of the earliest examples was the post-war Maserati Tipo 61 “Birdcage” racing car. Tubular space frame chassis employs dozens of circular-section tubes (some may use square-section tubes for easier connection to the body panels, though circular section provides the maximum strength), position in different directions to provide mechanical strength against forces from anywhere. These tubes are welded together and forms a very complex structure, as you can see in the above pictures.

For higher strength required by high performance sports cars, tubular space frame chassis usually incorporate a strong structure under both doors (see the picture of Lamborghini Countach), hence result in unusually high door sill and difficult access to the cabin.

In the early 50s, Mercedes-Benz created a racing car 300SLR using tubular space frame. This also brought the world the first tubular space frame road car, 300SL Gullwing. Since the sill dramatically reduced the accessibility of carbin, Mercedes had to extend the doors to the roof so that created the “Gullwings”.Since the mid 60s, many high-end sports cars also adopted tubular space frame to enhance the rigidity / weight ratio. However, many of them actually used space frames for the front and rear structure and made the cabin out of monocoque to cut cost.

Advantage: Very strong in any direction. (compare with ladder chassis and monocoque chassis of the same weight)

Disadvantage: Very complex, costly and time consuming to be built. Impossible for robotized production. Besides, it engages a lot of space, raise the door sill and result in difficult access to the cabin.

Who use it ? All Ferrari before the 360M, Lamborghini Diablo, Jaguar XJ220, Caterham, TVR etc.

Technology – Vehicle Chassis

UNIBODY VEHICLE CHASSIS STIFFNESS STUDY USING ABAQUS

Most street driven cars are manufactured using a construction technique known as unibody spaceframe chassis construction. This means that the body itself provides the stiffness and structure of the vehicle. Many older vehicles had separate stiffening structures and bodies, the body being solely designed as an aesthetic exterior and as a safety and environmental housing for the passengers. This technique is both heavier and requires more materials raising costs. Modern vehicle chassis are made entirely out of formed sheet metal sections which are usually spot welded together to form the structure of the vehicle. Designing these chassis is no easy task, the geometries being incredibly complex. Making these designs both cost effective, lightweight, stiff and safe is always a tradeoff.

Production vehicle chassis vary substantially in the degree to which they maximize the variables previously mentioned. Higher performance vehicles are often designed with maximum stiffness and lightweight in mind. A lighter weight chassis promotes an overall lower vehicle weight and better performance. Chassis stiffness though is also important for vehicle performance.

As a vehicle is driven, various forces are applied by the suspension on the chassis. This occurs under braking, cornering, driving surface variations, or any other vehicle movement. In higher these loads are, the more is demanded of a chassis. The chassis obviously has to be strong enough not to fail under these loads, but beyond that it must not deflect appreciably. Suspensions are carefully designed to position the wheels and tires of the vehicle for optimum performance under all conditions of vehicle use. If the chassis deflects when the forces are high, it causes suspension mounts and attachment points to temporarily shift, which destroys the careful suspension design when it is needed most. Chassis stiffness is most important in high performance or racing cars, where suspension loads are at their highest and suspension adjustment is most critical.

Chassis Development

Through out the development of the motor vehicle, many different types of chassis have been designed and tested. Through the years many advances have been made in chassis technology, and many old technologies have been thrown out as inferior. Here are some of the basic types which were or are in common use.

Ladder Chassis

This is the earliest kind of chassis. From the earliest cars until the early 60s, nearly all cars in the world used it as standard.Major structure of chassis is supported by central rails connected by cross braces. Still used in trucks and SUVs due to good isolation between passenger cabin and road vibration. Since it is two dimensional it is not very stiff, and needs to be built heavier than a good space frame.

Its construction, indicated by its name, looks like a ladder – two longitudinal rails interconnected by several lateral and cross braces. The longitude members are the main stress member. They deal with the load and also the longitudinal forces caused by acceleration and braking. The lateral and cross members provide resistance to lateral forces and further increase torsional rigidity.

Hummer H1& H2 SUV Ladder chassis

57 Chevy Classic Ladder chassis
http://autoweldchassis.com/56chevy.ivnu

Advantage: Well, it has no much advantage in these days … it is easy and cheap for hand build, that’s all.

Disadvantage: Since it is a 2 dimensional structure, torsional rigidity is very much lower than other chassis, especially when dealing with vertical load or bumps.

Who use it ? Most SUVs and all classic cars. I.e 57 Chevy

Technology – Electronic Air Suspension System

Continental Automotive -Electronic Air Suspension System

The Electronic Air Suspension System EAS unleashes the possibilities of electronic engineering to improve the automotive chassis providing drivers with safer driving, better comfort, and sportier handling. EAS automatically adapts damping and spring characteristics, along with the vehicle’s body level to driving conditions and load changes.

Advantages of EAS

• Reduction of roll and pitch movements
• Reduction of other vehicle body movements
• Reduction of variations in wheel loading
• Distinct improvement in driving dynamics and comfort.

Technology – Wheel motor

Siemens wheel motor diag.jpg (JPEG Image, 400×377 pixels)

The Tech Specs
A 7 kilogram (14.4 pound) in-wheel motor forms the heart of the Michelin Active Wheel. Packing in a sophisticated active shock absorption system, with its own dedicated motor, and disk braking brings the wheel to a hefty 43 kg (95 pounds). But Michelin Director for Sustainable Development and Mobility of the Future, Patrick Oliva points out in Die Welt that the sprung weight in the Heuliez Wheel is 35 kg (77 pounds) on the front axle and 24 kg (53 pounds) on the rear.

Together, the two front wheels deliver a steady 41 horsepower, which can spurt up to 82 hp for short sprints. The Will should do 0-100 km (0 – 62 mph) in 10 seconds and will have a max speed of 140 km/h (87 mph).

Lithium ion batteries will be delivered in three modular configurations, offering ranges of 150, 300 and 400 km (93, 186 and 248 miles). Just like hybrids, the Active Wheels recover energy during braking to extend vehicle range. The in-wheel motors are reported to be 90% efficient, compared to about 20% efficiency for a conventional vehicle in city driving.

Technology – Electric Cars vs. Hydrogen Fuel Cell Cars

Google Image Result for http://go635254.s3.amazonaws.com/gas2/files/2008/12/michelin_active_wheel.jpg

To understand the debate between electric cars vs. hydrogen fuel cell cars, it is important to understand that both cars are eventually driven by electric motors. The difference comes in the way the energy is stored. In electric cars the energy is stored in batteries. In hydrogen fuel cell cars the energy is stored in the from of hydrogen gas which is passed through a fuel cell to convert it to electricity.

So essentially, the real debate is between batteries and hydrogen fuel cells. Which one is more effective? That question isn’t easily answered because many factors such as cost, capacity, safety, reliability, accessibility, etc. all affect that decision. Ten years ago, I thought the answer was clear. What I never could have foreseen, though, was the surge in battery technology that would be brought on by the cell-phone craze. It’s left me believing that batteries might become better at storing energy than hydrogen (they’re not there yet).

Each of the two technologies have something going for them. EVs are benefiting from the already existent electrical infrastructure. Car makers aren’t as hesitant to build them knowing that customers will have a way to fuel them. Hydrogen, on the other hand, is simply better at storing large amounts of energy (Toyota’s Highlander Hybrid FCHV gets 80 miles per kg of hydrogen and has a driving range over 500 miles.)

Each technology also has a huge obstacle to overcome: Hydrogen has almost no infrastructure. Battery developers can’t seem to produce a battery that has all the characteristics they are looking for: safe, reliable, light-weight, small, affordable, long-lasting, powerful, etc. Many batteries fulfill a number of these requirements, but none have swept the table.

I don’t know if one will win out over the other, but both have huge potential. Wouldn’t you love to be a part of either industry when its obstacles are finally overcome?

Google Image Result for http://go635254.s3.amazonaws.com/gas2/files/2008/12/michelin_active_wheel.jpg

Imagine a car where the motor, transmission, drivelines exhaust, suspension, and brakes are all inside the wheels. Okay, that’s impossible. But what if there were no need for a transmission, drivelines, and exhaust? Could you put the motor and the suspension inside the wheel? Michelin did.

The entire unit bolts to the car and needs nothing but a brake line and electric connector to enable all its components.

This invention has HUGE potential! It could be used on EVs, Hydrogen Fuel Cell vehicles, or even hybrids (at least a Chevy Volt type hybrid). It could be used in two or four-wheel-drive, and front or rear-wheel-drive configurations. Car designs could change drastically because the usual space set aside for drive train components could be used for other things.

Technology – Hydrogen production

Production

Hydrogen may also be extracted from water via biological production in an algae bioreactor, or using electricity (by electrolysis), chemicals (by chemical reduction) or heat (by thermolysis); these methods are less developed for bulk generation in comparison to chemical paths derived from hydrocarbons.

The pathway to cleaner Hydrogen production

Water Electrolysis – Hydrogen can also be produced through a direct chemical path using electrolysis. With a renewable electrical energy supply, such as hydropower, wind turbines, or photovoltaic cells, electrolysis of water allows hydrogen to be made from water without pollution. Usually, the electricity consumed is more valuable than the hydrogen produced so this method has not been widely used in the past, but the importance of high pressure electrolysis is increasing as human population and pollution increase, and electrolysis will become more economically competitive as non-renewable resources (carbon compounds) dwindle and as governments remove subsidies on carbon-based fuels. Hydrogen can also be used to store renewable electricity when it’s not needed (like the wind blowing at night) and then the hydrogen can be used to meet power needs during the day or fuel vehicles. This helps make hydrogen an enabler of the wider use of renewables.

Nuclear – One side benefit of a nuclear reactor that produces both electricity and hydrogen is that it can shift production between the two. For instance, the plant might produce electricity during the day and hydrogen at night, matching its electrical generation profile to the daily variation in demand. If the hydrogen can be produced economically, this scheme would compete favorably with existing grid energy storage schemes. What is more, there is sufficient hydrogen demand in the United States that all daily peak generation could be handled by such plants^. However, Generation IV reactors are not expected until 2030 and it is uncertain if they can compete by then in safety and supply with the distributed generation concept.

Other types of production

The molecular hydrogen needed as an on-board fuel for hydrogen vehicles can be obtained through many thermochemical methods utilizing natural gas, coal (by a process known as coal gasification), liquefied petroleum gas, biomass (biomass gasification), by a process called thermolysis, or as a microbial waste product called biohydrogen or Biological hydrogen production. Most of today’s hydrogen is produced using fossil energy resources^, and 85% of hydrogen produced is used to remove sulfur from gasoline. Hydrogen can also be produced from water by electrolysis or by chemical reduction using chemical hydrides or aluminum.Current technologies for manufacturing hydrogen use energy in various forms, totaling between 25 and 50 percent of the higher heating value of the hydrogen fuel, used to produce, compress or liquefy, and transmit the hydrogen by pipeline or truck. Electrolysis, currently the most inefficient method of producing hydrogen, uses 65 to 112 percent of the higher heating value on a well-to-tank basis.

Environmental consequences of the production of hydrogen from fossil energy resources include the emission of greenhouse gases. Studies comparing the environmental consequences of hydrogen production and use in fuel-cell vehicles to the refining of petroleum and combustion in conventional automobile engines find a net reduction of ozone and greenhouse gases in favor of hydrogen.

Hydrogen production using renewable energy resources would not create such emissions or, in the case of biomass, would create near-zero net emissions assuming new biomass is grown in place of that converted to hydrogen. The scale of renewable energy production today is small and would need to be greatly expanded to be used in producing hydrogen for a significant part of transportation needs.

While methods of hydrogen production that do not use fossil fuel would be more sustainable,currently such production is not economically feasible, and diversion of renewable energy (which represents only 2% of energy generated) to the production of “Green” hydrogen for transportation applications is inadvisable.

Tehcnology – Hydrogen storage and Other Considerations

http://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/fuel-cell5.htm

Three hundred miles is a conventional driving range (the distance you can drive in a car with a full tank of gas). In order to create a comparable result with a fuel cell vehicle, researchers must overcome hydrogen storage considerations, vehicle weight and volume, cost, and safety.While PEMFC systems have become lighter and smaller as improvements are made, they still are too large and heavy for use in standard vehicles.

The low density of hydrogen means a hydrogen fuel tank will have to be three times the size of a gasoline tank. Also it must be insulated, and this will add to its bulk. This seems entirely bearable.

Hydrogen has a very low volumetric energy density at ambient conditions, equal to about one-third that of methane. Even when the fuel is stored as liquid hydrogen in a cryogenic tank or in a compressed hydrogen storage tank, the volumetric energy density (megajoules per liter) is small relative to that of gasoline. Hydrogen has a three times higher energy density by mass compared to gasoline (143 MJ/kg versus 46.9 MJ/kg). Because of the energy required to compress or liquefy the hydrogen gas, the supply chain for hydrogen has lower well-to-wheel efficiency but a higher tank-to-wheel compared to gasoline IC‘s.^[33] Some research has been done into using special crystalline materials to store hydrogen at greater densities and at lower pressures. A recent study by Dutch researcher Robin Gremaud has shown that metal hydride hydrogen tanks are actually 40 to 60-percent lighter than a equivalent energy battery pack on an electric vehicle permitting greater range for H2 cars

Technology – Fuel Cell Problems

http://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/fuel-cell5.htm

Fuel cells might be the answer to our power problems, but first scientists will have to sort out a few major issues.

Cost

among the problems associated with fuel cells is how expensive they are. Many of the component pieces of a fuel cell are costly. For PEMFC systems, proton exchange membranes, precious metal catalysts (usually platinum), gas diffusion layers, and bipolar plates make up 70 percent of a system’s cost. in order to be competitively priced (compared to gasoline-powered vehicles), fuel cell systems must cost $35 per kilowatt. Currently, the projected high-volume production price is $73 per kilowatt

Durability

Researchers must develop PEMFC membranes that are durable and can operate at temperatures greater than 100 degrees Celsius and still function at sub-zero ambient temperatures. A 100 degrees Celsius temperature target is required in order for a fuel cell to have a higher tolerance to impurities in fuel. Because you start and stop a car relatively frequently, it is important for the membrane to remain stable under cycling conditions. Currently membranes tend to degrade while fuel cells cycle on and off, particularly as operating temperatures rise.

Infrastructure

In order for PEMFC vehicles to become a viable alternative for consumers, there must be a hydrogen generation and delivery infrastructure. This infrastructure might include pipelines, truck transport, fueling stations and hydrogen generation plants. The DOE hopes that development of a marketable vehicle model will drive the development of an infrastructure to support it.

Technology – Hydrogen Fuel Cells

HowStuffWorks “How Fuel Cells Work”

You’ve probably heard about fuel cells. In 2003, President Bush announced a program called the Hydrogen Fuel Initiative (HFI) during his State of the Union Address. This initiative, supported by legislation in the Energy Policy Act of 2005 (EPACT 2005) and the Advanced Energy Initiative of 2006, aims to develop hydrogen, fuel cell and infrastructure technologies to make fuel-cell vehicles practical and cost-effective by 2020. The United States has dedicated more than one billion dollars to fuel cell research and development so far.

Fuel cells generate electrical power quietly and efficiently, without pollution. Unlike power sources that use fossil fuels, the by-products from an operating fuel cell are heat and water.  If you want to be technical about it, a fuel cell is an electrochemical energy conversion device. A fuel cell converts the chemicals hydrogen and oxygen into water, and in the process it produces electricity.But how does it do this?

Polymer exchange membrane fuel cell (PEMFC)

The Department of Energy (DOE) is focusing on the PEMFC as the most likely candidate for transportation applications. The PEMFC has a high power density and a relatively low operating temperature (ranging from 60 to 80 degrees Celsius, or 140 to 176 degrees Fahrenheit). The low operating temperature means that it doesn’t take very long for the fuel cell to warm up and begin generating electricity. We?ll take a closer look at the PEMFC in the next section.The (PEMFC) is one of the most promising fuel cell technologies. This type of fuel cell will probably end up powering cars, buses and maybe even your house. The PEMFC uses one of the simplest reactions of any fuel cell. First, let’s take a look at what’s in a PEM fuel cell.

In the above image you can see there are four basic elements of a PEMFC:

• The anode, the negative post of the fuel cell, has several jobs. It conducts the electrons that are freed from the hydrogen molecules so that they can be used in an external circuit. It has channels etched into it that disperse the hydrogen gas equally over the surface of the catalyst.

• The cathode, the positive post of the fuel cell, has channels etched into it that distribute the oxygen to the surface of the catalyst. It also conducts the electrons back from the external circuit to the catalyst, where they can recombine with the hydrogen ions and oxygen to form water.

• The electrolyte is the proton exchange membrane. This specially treated material, which looks something like ordinary kitchen plastic wrap, only conducts positively charged ions. The membrane blocks electrons. For a PEMFC, the membrane must be hydrated in order to function and remain stable.

• The catalyst is a special material that facilitates the reaction of oxygen and hydrogen. It is usually made of platinum nanoparticles very thinly coated onto carbon paper or cloth. The catalyst is rough and porous so that the maximum surface area of the platinum can be exposed to the hydrogen or oxygen. The platinum-coated side of the catalyst faces the PEM.

The Fuel cell

The pressurized hydrogen gas (H₂) entering the fuel cell on the anode side. This gas i­s forced through the catalyst by the pressure. When an H₂ molecule comes in contact with the platinum on the catalyst, it splits into two H⁺ ions and two electrons (e^–). The electrons are conducted through the anode, where they make their way through the external circuit (doing useful work such as turning a motor) and return to the cathode side of the fuel cell.

Meanwhile, on the cathode side of the fuel cell, oxygen gas (O₂) is being forced through the catalyst, where it forms two oxygen atoms. Each of these atoms has a strong negative charge. This negative charge attracts the two H⁺ ions through the membrane, where they combine with an oxygen atom and two of the electrons from the external circuit to form a water molecule (H₂O).

This reaction in a single fuel cell produces only about 0.7 volts. To get this voltage up to a reasonable level, many separate fuel cells must be combined to form a fuel-cell stack. Bipolar plates are used to connect one fuel cell to another and are subjected to both oxidizing and reducing conditions and potentials. A big issue with bipolar plates is stability. Metallic bipolar plates can corrode, and the byproducts of corrosion (iron and chromium ions) can decrease the effectiveness of fuel cell membranes and electrodes. Low-temperature fuel cells use lightweight metals, graphite and carbon/thermoset composites (thermoset is a kind of plastic that remains rigid even when subjected to high temperatures) as bipolar plate material.

Fuel Cell Efficiency

P­ollution reduction is one of the primary goals of the fuel cell. By comparing a fuel-cell-powered car to a gasoline-engine-powered car and a battery-powered car, you can see how fuel cells might improve the efficiency of cars today.If the fuel cell is powered with pure hydrogen, it has the potential to be up to 80-percent efficient. That is, it converts 80 percent of the energy content of the hydrogen into electrical energy. However, we still need to convert the electrical energy into mechanical work. This is accomplished by the electric motor and inverter. A reasonable number for the efficiency of the motor/inverter is about 80 percent. So we have 80-percent efficiency in generating electricity, and 80-percent efficiency converting it to mechanical power. That gives an overall efficiency of about 64 percent. Honda’s FCX concept vehicle reportedly has 60-percent energy efficiency.

Gasoline Power Efficiency

T­he efficiency of a gasoline-powered car is surprisingly low. All of the heat that comes out as exhaust or goes into the radiator is wasted energy. The engine also uses a lot of energy turning the various pumps, fans and generators that keep it going. So the overall efficiency of an automotive gas engine is about 20 percent. That is, only about 20 percent of the thermal-energy content of the gasoline is converted into mechanical work.

Battery Power Efficiency

A battery-powered electric car has a fairly high efficiency. The battery is about 90-percent efficient (most batteries generate some heat, or require heating), and the electric motor/inverter is about 80-percent efficient. This gives an overall efficiency of about 72 percent. Being the more efficient out of the three.

But that is not the whole story. The electricity used to power the car had to be generated somewhere. If it was generated at a power plant that used a combustion process (rather than nuclear, hydroelectric, solar or wind), then only about 40 percent of the fuel required by the power plant was converted into electricity. The process of charging the car requires the conversion of alternating current (AC) power to direct current (DC) power. This process has an efficiency of about 90 percent.

So, if we look at the whole cycle, the efficiency of an electric car is 72 percent for the car, 40 percent for the power plant and 90 percent for charging the car. That gives an overall efficiency of 26 percent. The overall efficiency varies considerably depending on what sort of power plant is used. If the electricity for the car is generated by a hydroelectric plant for instance, then it is basically free (we didn’t burn any fuel to generate it), and the efficiency of the electric car is about 65 percent.