Mechanical And Towing Systems Flashcards
⚡️Electric trailer brake operations
• Electrically energized magnets are attracted to the brake drum armature
• The rotating armature moves the actuating lever in the direction of drum rotation
• The cam block at the end of the lever forces the primary shoe against the brake drum.
• The primary shoe pushes against the secondary shoe, forcing it against the brake drum. ( servo breaking )
• Increasing the voltage to the magnet increases the force of the brake shoe against the drum
Disk brakes
• Brake pads mounted in the caliper are pushed against the sides of the rotor, creating friction
• Friction or drag slows the momentum of the trailer.
• Disk brakes are not as common on an RV trailer as drum brakes.
Drum brakes
• Brake linings are forced outwards against the brake drum, creating friction.
• Friction or drag slows the momentum of the trailer.
• Return Springs, pull the shoes away from the drum when braking pressure is released.
Brake types
• Drum brakes
• Disk brakes
Factors that govern friction.
• Type of material / composition of lining and drum.
• Temperature
• Amount of force applied
• Weight
• Speed
• Road conditions
• Tire conditions
What are frictional characteristics referred to as?
Coefficient of friction
2 types of friction are?
• Static friction
- Does not perform work
• Kinetic friction
- Does negative work
- Friction in motion
- Resistance to continued movement.
What principle causes brakes to work?
Friction
What are symptoms of improper alignment?
• Uneven or accelerated tire wear
• Worn components or overloading
What is wheel track?
• The ability for the trailer to follow directly in the same track as a tow vehicle.
Incorrect angles may be caused by_____.
Bent axles or loose wheel bearings
Recommended toe angle adjustment is _______.
⅛ inch positive
What does toe angle identify?
• The exact direction tires are pointed compared to the center line of the vehicle when viewed from directly above.
What is the recommended trailer axle camber adjustment?
⅜° positive
How is RV Axel camber adjusted?
• By controlled bending of the axle
What is camber?
• How far the tire slants away from vertical? When viewed directly from the front or back of the vehicle
• Negative when top tilts inward
• Positive when top leans away from center of vehicle
What is independent suspension?
• Independent suspension allows each wheel to move independently of other wheels.
What is non independent suspension?
• Wheels are attached to a solid axle.
• Bumps or movement at one side affects the opposing side
Slipper leaf springs
- Slipper leaf springs
• Eye is formed at one end of the main. leaf
• The eye is attached to the front hanger.
• The rear of the spring slides against the wear surface on the rear hanger or equalizer
Types of suspension
• Steel spring (leaf spring)
• Rubber spring (i.e., Timbren Industries Inc.)
• Rubber torsion (Independent suspension)
Types of rubber Spring.
• Rubber sheer - type springs.
• Straight line load deflection.
Double eye leaf spring.
• Eyes are formed at both ends of the main leaf
• When the spring becomes loaded, it lengthens.
• Double pivot action of the shackle allows the system to move freely
• Multiple axle installations, movement of the equalizer transfers loads evenly between the axles.
What’s determines spring rates?
• Spring widths
• Different rubber compounds.
What is a rubber torsion suspension system?
• Spindle is welded to a lever arm (torsion arm), which is attached to the torsion bar.
• Torsion bar is surrounded by rubber chords encased inside the main axel beam
• As the load is applied, the torsion bar rotates against the rubber chords
• Other than periodic inspection, no other suspension maintenance is required.
What is axle flip?
• Refers to moving the trailer axle from above to below the leaf springs
• Can increase height by about 4 to 6 inches.
• May cause decreased stability because of the higher center of gravity
When replacing an axle, you should look for______________.
• Gross Axle Weight Rating (GAWR)
• Track width
• Spring center measurement.
• Saddle position (over or under the axle)
• Straight or drop, Axel.
Steps for replacing pins and bushings.
• Support the axles
• Remove spring, equalizer bolts, and bushings
• Inspect spring eyes, shackle plates, and equalizer for wear
• Install new bushings and bolts.
• Single axle: 3 bushings per side
• Tandem axel: 7 bushings per side
• Torque nuts to applicable specs
How many bushings per side are on a single axle?
Three bushings per side
How many bushings per side are on a tandem axle?
Seven bushings per side
What can a loose U bolt cause?
It can cause a broken center bolt.
Broken rebound clips may cause_______.
Main leaf breakage
Improper tracking is referred to as________.
Dog tracking
Track can be effected by__________.
• Worn suspension components
• Axel adjustment
• Bent frames
Torque requirements
• Start all bolts or nuts by hand.
• Tighten in stages following a cross or star pattern.
• Retorque after 50 miles and again at 100 miles.
Types of tire wear
• Tow in wear
• Tow out wear
• Heel and toe wear
Wheel selection
• Bolt circle
• Capacity ( LR )
• Off set
• Center bore (important for center cap)
• Stud diameter and lug design.
• Tire size ( width in mm - Side wall hieght in mm - R Diameter of interior of wheel )
How to identify tires size
• Cross section in millimeters.
• Aspect ratio in percentage.
• Radial or bias-ply
• Load rating
Tire sizing
Example: 225 / 75R16D
• Cross section in millimeter ( 225 )
• Sidewall height in millimeter (75)
• Wheel diameter (R16)
• Load rating (D)
Types of wheel offset
• Positive offset
• Zero offset
• Negative offset
What can unbalanced wheels and tires cause?
Tire and suspension wear.
Types of wheel balancing
- Dynamic unbalanced
• Wieght of the wheel and tire is uneven towards the edges of the wheel. (causes wheels to wobble) - Dynamic balancing
• Equal distribution of weight on each side of the tire center line. - Static unbalancing
• Heavy spot exist on one area of the tire and wheel assembly.
• Centrifugal force pulls the tire off-center as it rotates.
• Produces radial vibration (wheel tramp) - Static balancing
• Equal distribution of weight around the center of the wheel
What is the purpose of shock absorbers?
To control, bounce, and maintain tire to road contact
Warn suspension components may cause___________.
• Tire wear
• Poor handling
• Noise
GVWR
Gross vehicle weight rating
• Maximum weight a vehicle is designed to carry, including net weight, vehicle with accessories, passengers, fuel and cargo.
GAWR
Gross Axel weight rating.
• Specified by vehicle manufacturer as the load carrying capacity of a single axle system, measured at the tire - ground interface.
• Maximum weight an axle is designed to carry
6-Way Connection wires
• Green - right turn/brake light
• Yellow - left turn/brake light
• Black - 12 VDC charge line.
• White - ground.
• Brown - tail /running lights
• Blue - electric break control.
4-Way Connection Wires
•Yellow - left turn and stopped lamp.
•Green - right turn and stop lamp.
•Brown - running lamps.
• White - ground wire.
7-Way Connection Wires
• Red - left turn and stop lamp.
• Brown - right turn and stop lamp.
• Green - running lamps and taillights.
• Blue - electric breaks.
• Black - 12 VDC charge line.
• White - groundwire.
• Yellow - backup lights/ Auxiliary use.
Class 4 hitches
No color but labeled with proof of load rating.
Net weight (Curb Weight)
Is the full weight of the vehicle, including a full tank of fuel and all standard operational equipment
GVW
-Gross vehicle weight
• Actual weight of fully loaded vehicle GVW is derived by adding the weight on all the axles of the loaded vehicle.
GCWR
Gross combination weight rating
• Maximum weight of the tow vehicle and trailer combined.
Class 1 hitches.
Silver
Class 2 hitches
Brass
Class 3 hitches
Black
CMVSS 108
• Document that specifies requirements for lights, reflective devices, and associated equipment on vehicles in Canada.
• CMVSS 108 Vehicles must have adequate illumination and signals. In order to reduce accidents. Applies to travel trailers, folding trailers and fifth wheels.
Folding camping trailer
An RV that is built on its own chassis, has a rigid or canvas top and side walls that can be folded or otherwise stowed for transit and is designed to be towed behind a motor vehicle
Fifth-wheel trailer
An RV designed to be coupled to a towing vehicle by a fifth-wheel type coupler ( King pin box ), through which a substantial part of the trailer weight is supported by the towing vehicle.
Truck camper
RV designed to be loaded onto ( and unloaded from ) the bed of a pickup truck.
Travel trailer
RV designed to be towed behind a motor vehicle by means of a bumper or frame hitch
