Land Transportationcont.

Transmitting Power

» Drive System – A system used to transfer the motion of the engine’s crankshaft into the power that moves the vehicle. Sometimes called power train.

» First Job is to multiply the amount of torque the engine produces.

Transmission Systems» The device that

provides the multiplying, dividing, or reversing of mechanical power and torque coming from the engine.

» Use two kinds of gears» Spur Gears » Helical Gears

Manual Transmission

» Totally controlled by the operator» In a typical 5 speed transmission gears can

be aligned in 6 ways (5 forward, 1 reverse), each with a different gear ratio

» A gear ratio changes the amount of torque. First gear typically 3:1, which means for every 3 times the input shaft spins the output shaft spins once. Fourth gear is typically 1:1, which means both input and output are spinning at the same speed.

Manual Transmission

» A clutch is used to disconnect the engine from the transmission» Allows operator to

start the vehicle smoothly, shift gears, and disengage the engine from the drive train, allowing the motor to continue to run

Automatic Transmission» Not dependant on the

operator» Uses a torque converter

instead of a clutch» It is a type of fluid

coupler, uses fluid to transmit power

» Automatic transmissions can produce unlimited numbers of gear ratios due to the use of planetary gears.

Driveshaft and Axles

» Transmission connected to either a transaxle or driveshaft.

» Power is then sent from the transaxle or driveshaft to the differential

» Differential - Takes rotational power from one source and transfers it to two axles. Also allows wheels to spin at different speeds to make turning easier

Control System

» Braking Systems» Hydraulic Breaking System - A braking

system that links a master cylinder to a brake pedal and to one or two brake cylinders at each wheel.

» When operator depresses the brake pedal, the master cylinder sends pressure via hydraulic fluid to each brake cylinder.

Kinds of Braking systems

» Drum Brakes - Two brake shoes are shaped to fit the inside of the brake drum and expand to create friction when the brake pedal is pressed.

» Disc Brakes - A steel disc called a rotor is mounted to the wheel assembly so it spins freely. The brake caliper straddles the disc and squeezes against both sides when the brake pedal is depressed.

Power Brakes

» Brake system adds a vacuum control valve between the brake pedal and master cylinder.

» The vacuum helps exert force on the master cylinder and allows the driver to use less foot pressure.

Antilock Braking System

» Computer Controlled Braking system. Uses sensors at each wheel to monitor the speed the wheels are turning.

» System used only when tires are spinning at different speeds. (Loss of traction during braking)

» Controller sends pulses to the other wheel to help maintain the same speed, and help maintain control of the vehicle.

Pneumatic Brakes(Air Brakes)

» Uses compressed air to activate the master cylinder.

» The system can be computer controlled to provide a specific amount of pressure for each situation.

» Tractor trailers and trains use air brakes because they can be adjusted to the account for the weight of the cargo there carrying.