Rotary engine: 1 — engine block; 2 — pocket; 3 — rotor

The rotary, or Wankel, engine has no piston, it uses rotors instead (usually two). This engine is small, compact and has a curved, oblong inner shape (known as an «epitrochoid» curve). Its central rotor turns in one direction only, but it produces all four strokes. Dispensing with separate cylinders, pistons, valves and crankshaft, the rotary engine applies power directly to the transmission. Its construction allows it to provide the power of a conventional engine that is twice its size and weight and that has twice asmany parts. The Wankel burns as much as 20% more fuel than the con engine and is potentially a high polluter, but its small size allows the addition of emission-control parts more conveniently than does the piston engine. The basic unit of the rotary engine is a large combustion chamber in the form of a pinched oval (called an epitrochoid). Within this chamber all four functions of a piston take place simultane­ously in the three pockets that are formed between the rotor and the chamber wall. Just as the addition of cylinders increases the horsepower of a piston-powered engine, so the addition of combustion chambers increases the power of a rotary engine. Larger cars may eventually use rotaries with three or four rotors.

Flat (Horizontal-Opposed) Engines.A horizontal-opposed engine is like a V -type engine that has been flattened until both banks lie in a horizontal plane. It is ideal for installations where vertical space is limited, because it has a very low height.

Overhead Camshaft (OHC). Some engines have the camshaft mounted above, for over, the cylinder head instead of inside the block (OHC «overhead camshaft» engines). This arrangement has the advantage of eliminating the added weight of the rocker arms and push rods; this weight can sometimes make the valves «float» when you are moving at high speeds. The rocker arm setup is operated by the camshaft lobe rubbing directly on the rocker. Stem to rocker clearance is maintained with a hydraulic valve lash ad­juster for «zero» clearance.


The body shell is a fairly complex assortment of large steel sections. These sections have been stamped into specific shapes which make up the body of your car. These parts are designed to do many jobs at once; protect the occupants from the elements and in collisions, provide solid mounts for all other systems, and to slice through the air with minimal resistance. The body also has one other job which is usually important to the owner... it has to look good!


Although the zillions of parts that make up a car are all very important, it is also important that the car's body be able to make riding in a car bearable for you. Early cars were so uncomfortable to ride in. The body and the suspension system now give us a smooth ride, and cushion us from the jarring of the road. The idea is that the body of the car should go forward with as little up-and-down and side-to-side movement as possible.

Frame (Chassis) The frame provides a firm structure for the body, as well a good anchor point for the suspension system. There are two types of frames; integral frames or unibody and conventional frames.

A conventional frame is basically a «one-piece» frame, or two «one-piece» frames fastened together. The frame is extremely rigid in order to keep all the other parts of the car in perfect alignment. The manufacturer takes this type of frame and attaches all the other parts of the car to it, like the way a sculptor starts with a wire frame to build his sculpture on and give it shape. To keep things smooth, rubber insulator blocks, or «pads» are placed between the frame and the other car parts. Because the conventional frame is so important to the structure of your car, (without it, your car would be a pile of doors, hoses, seats, wires and metal) it is usually constructed of heavy steel and welded or cold riveted together. Cold riveting keeps the rivets from shrinking.

The integral, or unibody, frame is just the opposite. With this type of frame, the body parts are used to structurally strengthen the entire car, and all of the sections are welded into one piece. Sometimes the parts of the body and the suspension system are attached and reinforced. Also, some unibody frames have partial front and rear frames for attaching the engine and suspension members.

Hood. The car's hood is another type of door. It also consists of an inner and an outer panel. The inner panel provides strength. The outer panel is just a metal cover, or «skin». The underside of the hood is often covered with a sound-absorbing material. Some high performance cars have openings in the hood to allow the engine to «breathe» easier. «Hood scoops» are used to channel outside air directly to the air filter, which gives improved performance and efficiency.

Trunk Lid. The trunk lid is another type of door. It consists of an inner and an outer panel. The inner panel provides strength. The outer panel is just a metal cover, or «skin».

Rocker Panels. A rocker panel is a three or four inch piece of metal that runs along I the bottom of the car body underneath the doors. Rocker panels are usually coated with a рек proof protectant which rubberizes the exterior surface before the car is painted. If you have mud flaps behind your wheels, this protects your rocker panels, as well as your fend­ers and your doors. Rocker panels are often made of chrome plating, and enhance the car.

Wheel Well.The wheel well is either plastic or metal. Metal wheel wells are usu­ally part of the body shell. Metal wheel wells strengthen the structure of the car because of their shape, and because they are strongly welded to the body shell. Most rear wheel wells are made of metal. Wheel wells are coated with a rock-proof, rubberized coating underneath, in order to prevent the rocks kicked up by the wheels from damaging the metal and making a lot of noise when they hit.

Often the front wheel wells are made of plastic. This is because it is harder to mount the engine with the front wheel wells in place. Plastic wheel wells can be removed, and make it easier to mount the engine during the manufacturing of the car.

Front Quarter Panel. The front quarter panel is composed of the body skin, or sheet metal, that runs from the front corner of the hood to the front of the door. It is usually a separate piece that is welded on in a few places. This makes it easy to replace if you get in a «fender bender.» Front quarter panels can usually be replaced relatively inexpensively. Some newer vehicles use a rubber-like plastic for the fenders, which al­lows small impacts to be absorbed without damage.

Windshield. In the 1930s many cars had hinged windshields that could be folded on the hood of the car or opened up. Today, most windshields are stationary. They are fixed in place with a weather-strip made of rubber. The strip has a groove on the inside and a groove on the outside. The inside groove holds the glass; the outside groove holds the metal rim of the windshield opening in place. The glass «floats» in a plastic sealant that is spread out between the edge of the glass and the frame of the windshield.

Windshields are made of laminated safety plate glass, which is a sandwich of glass and clear plastic. The plastic acts as a soft, protective barrier, keeping the glass in place, if it is struck during a collision. The glass sticks to the plastic to eliminate glass from flying around the interior and injuring someone.

Safety glass for windscreens was one of the first passive safety devices introduced into cars, but its use remains a controversial question. North America and Scandinavia favor a laminated glass, which consists of two sheets of annealed glass, separated by a layer of transparent plastic. In recent years, laminated glass has been improved by changes in the properties of the plastic interlayer. Research has demonstrated that this new laminated glass is about 4 times safer than toughened glass, but because it is more expensive, controversy continues as to whether or not toughened glass windscreens |should be banned by legislative action and replaced by laminated glass.

Recent developments have combined the benefits of both laminated and toughened material in that a laminated construction is used, but the sheet next to the inside of the is made of toughened glass.

Seats. There are basically two types of seats: bench seats or bucket seats. A bucket seat is a low, separate seat for one person. Bench seats are a continuous cushion and backrest across the width of the car (although some vans might have them running along the length of the van). Bucket seats are single units with a separation between the left and right seats.

Usually vinyl leather and fabric are used for upholstery. «Flat springs» are used for comfort. A flat spring is a piece of wire that is bent into a zigzag pattern. Both ends of the wire are attached to the seat frame, with additional lengths added every six inches. Foam padding is used to cover the flat springs.

The front seats ride on rails that are bolted to the floor. This arrangement allows eats to move backwards and forwards to suit the driver or passenger. The seat ad-justment lever is attached to a latch that fits into teeth along the rail. Moving the lever releases the seat, and allows the seat to move. At any point of the seat's movement, releasing the lever engages the latch with one of the teeth. Usually there is also a pull-spring; this draws the seat forward when the latch is released. The rear seat usually doesn't move, because it is secured to the floor of the car. Its backrest is attached to the partition between the passenger compartment and trunk.

Having an air bag and wearing an effective seat belt offers the best protection of all. Not only are you protected from frontal crashes by the air bag — you are also protected by the seat belt in all other types of crashes. The benefits of the three-point seat belts have been firmly established: over 50 % of fatal and serious injuries to car occupants would be avoided if all occupants wore their seat belts. Most states now have a law that both passengers and driver must have seat belts buckled while in motion. Those states which do not enforce a seat belt law for all passengers have an effective law for children under five years of age to be strapped in.

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