THE ABC OF THE AUTOMOBILE: THE CHASSIS

foreign [Music] take the body off a car and you know what's left the chassis the frame the wheels and the Machinery including me the engine I really drive the chassis and the body comes along for the ride I'd like to show you how the power I generate gets from here to here where moving the car really begins I'll have a little more than just that to show you but let's begin you could just hook up the end of my crankshaft to a drive or propeller shaft so they turn together at the rear you'd need some kind of gear system so that the rear axle would turn and turn the wheels but there would be some practical problems with this arrangement for one thing as soon as you turn on my starter the car would start to go because I'd be connected straight through to the wheels and when you put on the brakes you'd not only stop the car you'd stop me too dead so you have to have a way of separating me from the drivetrain as we call it the clutch does it this friction type acts like plates that are held in contact by Springs and pulled apart by a pedal with the clutch disengaged like this my crankshaft does not turn the drive shaft when you're ready to go you let upon the clutch pedal and the Springs bring the plates together because of the friction between them my crankshaft turns the drive shaft you have to disengage the clutch before stopping so that you won't kill the engine clutches can be operated automatically by hydraulic components a hydraulic clutch looks like two halves of a donut each half with a set of blades the two halves are set close together but do not touch they are surrounded by a case filled with a special fluid when you start me and let me idle at low speed nothing happens in the clutch except that the fluid begins to move a little between the two halves but when you speed me up fluid is moved with enough Force to turn the second half and the drive shaft with it slowly at first then faster until the two halves turn together and act as a nearly solid connection but you have another problem to solve at slow speeds I'm not able to put out much power but as I increase my RPM that's revolutions per minute I get stronger so I have to go fast in order to start moving the heavy car what I need is a transmission it may be automatic such as this one or the manual type such as this in either case a transmission is a gearbox it has a hood shaft that is turned by the engine and clutch and an output shaft that turns the drive shaft the gear shift lever changes the ways the various gears turn each other in low gear it takes about three turns of the input shaft to produce one turn of the output shaft once it's underway the gears can be shifted to second operates with about two input turns to one output turn in high or third gear input one turn output one turn some manual transmissions may have four or more forward speeds of course there's also a reverse setting so that you can back up the car when you have to and neutral in which there is no connection between input and output the clutch works with the transmission it is always disengaged when the gears are shifted so there won't be any strain on them an automatic transmission uses a hydraulic clutch and a set of planetary gears the gears resemble the planet circling the Sun hydraulic valves operate to lock the gears separately or in combinations so that my driving power or Torque which means twisting force goes through the gear system as needed for starting up accelerating cruising and reversing the operation of an automatic transmission depends on the setting of The selector lever the position of the accelerator pedal and the speed of the car now let's have a look at the drive shaft if the car had no springs we could simply put the drive shaft in place connected directly to the transmission in the rear axle but with springs as the car goes over bumps the wheels move up and down with relation to the frame and the shaft would be bent the problem is solved by the universal joint it may be installed at the front or at both ends of the shaft each joint is made up of two yolks connected together by a cross on which they can pivot so even though the shafts may be out of alignment The Joint transmits the rotation but now we have another problem that of transferring the shaft torque to the rear axle we could use a small pinion gear on the shaft and a ring gear on the rear axle but when the car makes a turn the outside wheel travels farther than the inside one in the same amount of time so one of the wheels would have to Skid around the turn the solution to this problem is to use a differential it is a gear system that lets the wheels rotate at different speeds when making a turn that's what differential means the axle is divided into two axles each carries a gear called differential or side gear the ring gear is not fastened to the axle but is free to turn on it the differential pinion gear turns freely on a pin fastened to the ring gear and meshes with both side gears to give the system greater strength a duplicate pin and pinion gear are added thus sharing the load when the car travels Straight Ahead the wheels turn at the same speed but when you make a turn the differential gear system divides the torque going through the differential gear to the two axles and the axles and wheels can turn at different speeds now let's look at the brakes which are operated by hydraulic pressure a hydraulic part of the system gets its pressure from a dual master cylinder or pump that you operate with your brake pedal the master cylinder with its two Chambers is a definite safety feature if there should be a pressure failure only one pair of brakes will be affected the other will stop your car for you the rear brakes are usually the drum type the drums are attached to the wheel and axle combination in this type brake shoes with special lining material on them are moved into contact with the revolving brake drum thus slowing it and ultimately stopping it and the wheels and the car many front brakes are now the disc type like the drums they are attached to the wheel and axle combination the Linings are held in what looks like a pair of pincers or calipers and the operation is squeezing them together the clearances are actually very small but are shown wider here for clarity the pincers tighten the Linings against the disc and stop the wheels one big advantage of disc brakes is their ability to cool very quickly power brakes are like the manual types except that they use vacuum power from me the engine so that it takes less work or exertion on your part with power brakes a 90 pound grandmother can stop a car as easily as can a 240 pound football player the same goes for power steering for which I Supply the boosting Force it makes the car much easier to maneuver particularly when parking in both power and non-power steering the steering poster column turns a worm gear which is engaged with the steering gear rods form a linkage to the wheels which moves them in response to the Turning of the steering wheel safety steering columns or posts were first introduced on GM's 1967 models these columns are designed to telescope in a collision greatly lessening the possibility of injury to the driver now let's take a look at Springs at the front end of the car coils are usually used to support the frame for the rear wheels either coils or leaf springs are normally used shock absorbers snub or check the spring action to prevent bouncing when the wheels hit a bump or drop into a pothole I'd like to say one more thing about the car's equipment the highly important electrical system as you undoubtedly know the battery and alternator Supply me with the electricity for my starter and ignition systems over 600 feet of wire bring power to the more than 36 lights and the many gauges motors and accessories including the radio and the air conditioning system well that's the basic story of the automobile chassis now we know that some people are more aware of the body of a car but what's underneath gets more interesting every year put it all together as they say and you've got something that provides Dependable comfortable and safe transportation you look to your car for satisfaction and for safety I have just one more thing to say do your best to take care of us and we'll do our best to take care of you