Vehicle Power Train and Transmission Systems

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Questions and Answers

What is the primary function of a power train in a vehicle?

To convert high-speed, low-torque rotation into low-speed, high-torque rotation (correct)

To maximize the engine's torque at high speeds

To directly transmit the engine's power to the wheels without modification

To increase the engine's horsepower by changing speed ratios

Which of the following is NOT a typical function of a power train?

Allowing for the selection of speed ratios

Connecting and disconnecting power from the engine

Maximizing fuel efficiency of the engine (correct)

Equalizing power to all drive wheels for turning.

In a friction drive system, what role does friction play in power transmission?

It causes the driven wheel to rotate in the same direction as the driver wheel.

It increases the speed of the driven wheel.

It reduces the torque of the driven wheel compared to the driver wheel.

It transfers power from one wheel to another by the contact between them. (correct)

What is a key limitation of friction drives when compared to gear drives?

They suffer from slippage. Signup and view all the answers

Which of the following is NOT identified as an example of a fluid drive system?

Gearboxes Signup and view all the answers

How do fluid drives transmit power?

By using the flow of hydraulic oil against a turbine Signup and view all the answers

What is a primary advantage of using gear drives for power transmission?

They eliminate slippage between the driver and driven components. Signup and view all the answers

Besides changing speed and direction, what else can gears accomplish in power transmission?

Transfer, increase, or decrease torque Signup and view all the answers

What connects the sprockets in a chain drive?

A continuous chain with links Signup and view all the answers

What happens to torque when using a smaller driver gear in a gear train?

Torque increases Signup and view all the answers

If a driver gear has 20 teeth and a driven gear has 20 teeth, what is the gear ratio?

1 to 1 Signup and view all the answers

A gear train has a 12-tooth driver and a 24-tooth driven gear. If the driver shaft rotates at 500 RPM, what is the speed of the driven shaft?

250 RPM Signup and view all the answers

If a driver gear with 24 teeth rotates at 500 RPM and drives a 12-tooth gear, what is the resulting speed of the driven gear shaft?

1000 RPM Signup and view all the answers

In a gear system, if the input torque is 300 foot-pounds and the driven gear has twice the number of teeth as the driver gear, what is the approximate torque on the driven shaft?

600 foot-pounds Signup and view all the answers

When the power flow is reversed in a gear system, and the larger gear is the driver, how does the speed and torque change on the output shaft?

More speed, less torque Signup and view all the answers

What is the relationship between speed and torque?

Inversely related Signup and view all the answers

What happens when the switch is turned off in a magnetic clutch?

The magnetic field collapses, disengaging the clutch. Signup and view all the answers

In an indirect-action clutch, where is the coil located?

In the driving member of the clutch Signup and view all the answers

What is the purpose of the dry graphite lubricant in an indirect-action clutch?

To allow the driven side of the clutch to 'slip' when a current is applied Signup and view all the answers

How can an indirect-action clutch act as a variable speed clutch?

By controlling the magnetic strength through adjusting current flow. Signup and view all the answers

What is NOT a main purpose of a transmission?

Increasing the torque output of the engine Signup and view all the answers

Which of the following is NOT a major type of transmission?

Electrical transmissions Signup and view all the answers

How are different speed ratios achieved in mechanical transmissions?

By using gears on parallel shafts and having the gears slid along the shafts Signup and view all the answers

In a sliding gear transmission, how are gears shifted?

By sliding gears by hand or foot through mechanical linkage Signup and view all the answers

What is the primary function of the alternating friction disks and plates in a disk and plate type synchronizer?

To lock the driven gear to the driven shifter collar. Signup and view all the answers

Which of the following best describes the operation of a hydraulic assisted transmission?

Hydraulic power is used to engage and disengage gears. Signup and view all the answers

In a hydraulic assisted transmission, what replaces the function of shifter collars?

Friction disk and plate clutch and brake assemblies Signup and view all the answers

What is a key advantage of a hydraulic assisted transmission that allows for shifting 'on the go'?

The functionality of the alternating friction disk and plate clutch and brake assemblies. Signup and view all the answers

How is the power transmitted in a hydraulic assisted transmission?

By a gear train, while hydraulic clutches and brakes control the power flow. Signup and view all the answers

Which component is NOT a core element in a planetary gear assembly?

Hydraulic Clutch Signup and view all the answers

What is the purpose of the split-second time delay in a hydraulic assisted transmission's shifting mechanism?

To prevent rough or jerky shifts. Signup and view all the answers

What is the primary function of a hydraulic pump in a hydraulic transmission?

To convert the mechanical power from an engine into hydraulic power. Signup and view all the answers

What is the primary function of a tractor's power take-off (PTO)?

To connect the engine's rotating power to auxiliary equipment Signup and view all the answers

What is a key characteristic of a transmission-driven PTO?

It only operates when the engine clutch is engaged and travel is stopped. Signup and view all the answers

What happens when the clutch pedal is depressed halfway in a tractor with a continuous-running PTO?

Only the transmission stops, while the PTO continues running. Signup and view all the answers

Which type of PTO allows the transmission and PTO to operate completely independently of each other?

Independent PTO Signup and view all the answers

At what speed do lower horsepower tractors typically operate their PTOs?

540 RPM Signup and view all the answers

What is a potential risk of attaching a 540 RPM implement to a tractor operating at 1000 RPM?

The implement could be damaged and personal injuries could result. Signup and view all the answers

What year were the industry PTO standards established by the American Society of Agricultural Engineers and the International Standards Organization?

1965 Signup and view all the answers

What feature do many new MFWD (Mechanical Front Wheel Drive) tractors have for engaging and disengaging the front axle drive?

Hydraulically operated clutch assemblies Signup and view all the answers

A Type I PTO has a shaft diameter of what size?

1 3/8" Signup and view all the answers

A Type III PTO uses a shaft with how many splines?

20 Signup and view all the answers

What is the primary function of foam inhibitors in power train lubricants?

To prevent air from mixing with lubricant Signup and view all the answers

Which of the following is NOT a benefit of using power train lubricants that have extreme pressure properties?

Allowing metal surfaces to come in contact Signup and view all the answers

What is the purpose of anti-rust and corrosion inhibitors in power train lubricants?

To reduce scoring and wear between gears Signup and view all the answers

What is the purpose of including seal/gasket conditioners in lubricants?

To maintain the pliability of rubber components Signup and view all the answers

A Type II PTO is designed for equipment requiring what range of PTO HP?

85 to 150 HP Signup and view all the answers

What is the main function of oxide inhibitors in power train lubricants?

To prevent chemical breakdown of the lubricant Signup and view all the answers

Study Notes

Principles of Power Transfer

The most convenient method to move something is often found using simple machines, like levers.
- Early humans used branches as levers to move large rocks. A small rock acted as a fulcrum (pivot point).
Torque is the turning effort causing rotation.
- Measured by force (pounds) multiplied by the distance from the pivot point (feet).
  - Example: 100 lbs of force applied 6 feet from the pivot point equals 600 ft-lbs of torque.
Mechanical advantage of a lever is the ratio of the force side to the resistance side of the pivot.
- Closer to the resistance, the more increased the mechanical advantage.
- The further the force is applied from the resistance, the slower the action is to move the resistance = increased effort.
Simple machines were developed over time.
- Wheel and axle, pulleys, inclined plane, screw, wedge

Introduction to Power Trains

Most modern engines operate most efficiently at about 2,200 RPM.
- A 150-horsepower engine produces about 300 foot-pounds of continuous torque.
A power train converts high-speed, low-torque rotation to low-speed, high-torque rotation of the wheels to pull a load.
- Connects and disconnects engine power.
- Allows selection of different speed ratios.
- Provides a means for reversing vehicle direction.
- Equalizes power to all drive wheels.
- Starts and stops the PTO shaft.
Power transfer methods include friction, moving fluids, and gears.

Friction Drives

Children using a tricycle is an example of friction transfer.
Applied force through the pedals is transmitted to the wheel by friction.
Friction between the wheel and the floor is necessary for the tricycle to move.
Slippage occurs when there is less friction, like on slick surfaces.

Fluid Drives

Water wheels are a simple form of fluid power transfer.
Water force causes paddles to turn the wheel.
Modern fluid drives include fluid couplings, torque converters, and hydrostatic transmissions.
- Fluid drives use hydraulic oil movement to turn turbine wheels.

Gear Drives

Gears are the most common way to transfer power.
- Gears meshing eliminates slippage.
Gears change speed and direction of power; also, increase or decrease torque.
- Chain drives are a variation of gear drives.
Sprockets (gears) are connected by a chain to eliminate slippage.
- Driving sprocket transfers power to the driven sprocket.

Gear, Pulley, and Sprocket Ratios and Shaft Speeds

Gear ratio is the tooth count ratio of two gears.
- 1:1 ratio means no speed or torque change.
- A smaller driver gear produces less speed and more torque. -Example: If a smaller driver gear with 12 teeth turns at 500 RPM, the driven gear with 24 teeth turns at 250 RPM (resulting in 600 foot-pounds of torque).
Larger driver gear produces more speed and less torque.

Purpose of the Clutch

The clutch connects and disconnects the engine and transmission.
Used to gradually apply load to the power source.
Most clutches use friction to transfer power.

Operation of a Basic Clutch

Two disks are mounted on separate shafts with a space/clearance between the shafts.
When the surfaces contact, friction causes them to turn together.
Engaging positions release the clutch pedal and the clutch disk turns with the flywheel.
Disengaging positions depress the clutch pedal, compressing springs and breaking the frictional contact between disks.

Types or Classifications of Clutches

Disk/plate clutches, wet or dry
- Many modern clutches use plates and disks instead of single disk units.
- Dry clutches operate through linkages.
- Wet clutches operate in an oil bath.
Overrunning Clutch—only engages in one direction.
Magnetic Clutch—uses magnetic forces to hold together/engage.

Major Ways in Which Clutches Operate

Mechanically operated clutches use linkages and springs.
Hydraulically operated clutches use a master and slave cylinder. Hydraulic fluid controls the clutch.
Electrically operated clutches use electromagnetism to engage/disengage the clutch.

Final Drives

Final drives provide a final reduction in speed and increase in torque.
- Different types of final drives exist (pinion drives, planetary drives, chain drives).
This reduction is vital to transmit power at lower speeds, but higher torque levels.

Torque Dividers

Component added to power trains to divide torque to front and rear drive axles.
Useful in vehicles with true four-wheel drive or mechanical front wheel drive.
Used when front and rear drive tires are different sizes or for other variations in the power train system.
- Torque divider clutch/shifting options and use for varying situations.

Power Take Off (PTO)

PTO is an extension of the power train in tractors—connects engine power to auxiliary equipment.
- Classifications: transmission-driven, continuous-running, and independent.
- Includes speed and torque considerations, and safety precautions.

Transmission Features

Mechanical transmissions use gears for various speed ratios, reverses.
- Types of mechanical transmissions (sliding, collar, synchromesh).
Hydraulic transmissions use hydraulic fluids for power transmission; types include hydrodynamic, and hydrostatic.
Uses a gear and piston assembly to transmit power; this is different than power transmissions that rely on gears or chains.

Power Train Lubricants

Gear oils, automatic transmission fluids, transmission/hydraulic fluids, lubricating greases are vital.
- Viscosity ratings, foam inhibitors, extreme pressure, and other critical additives.
- Manufacturers' recommendations for types and amounts differ by application, operating conditions, and equipment (i.e. tractor).
Oil additives for safety and efficiency and prevent oxidation/damage.

Gear Oil Classifications

SAE classification by viscosity ratings
- Higher numbers mean higher viscosity.
API classification by operating conditions
- GL-1 to GL-6. Use different oils depending on engine capabilities.
Different ratings for different functions in the power train system.

Lubricating Greases

Grease types (calcium, sodium, lithium).
Grease additives to handle high temperatures, moisture, and other varying conditions.

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Description

Test your knowledge on the power train components and functions in vehicles. This quiz covers friction drives, fluid drives, gear drives, and chain drives. Understand how these systems transmit power and their advantages and limitations.