Ch 15-17 Flashcards
1
Q
greatest concern for w/ tractor-trailer operations
A
jackknife
- when some of the tires lose traction
2
Q
the different jackknife circumstances
A
- front tires of tractor lock: lose steering control, will usually skid in straight line
- rear tires of tractor lock: rear of tractor will want to spin around, causing jackknife
- rear tires of tractor lose traction due to sudden acceleration: drive axle will lose traction causing spinout and jackknife
- Rear tires of tractor lose traction b/c engine brake is on in wet weather
- trailer tires lock: trailer at risk of swinging out, usually slower than tractor so driver has time to correct it
3
Q
Causes/Preventing jackknifes
A
- over acceleration
- failure to turn of engine brake on wet roads
- aggressive braking: drive appropriate speed, smooth braking, anticipate hazards
- driving on 2 dif. surfaces
4
Q
Tiller lader skid control
A
- 1st step is to let off offending pedal
- if its the tractor skidding, let off offending pedal, look where you want the vehicle to go, steer in that direction
- when trailer is swinging out, tiller operator may be able to steer back in line, but don’t rely on them to regain control
5
Q
trailer rollovers
A
- drive will not sense warning signals of the trailer braking traction or starting to roll
- 1st warning will be by watching the trailer or worse, starting to feel the tractor roll as the rolling trailer pulls it
- tiller operator must stay in constant contact w/ driver, advising if driving too fast
- driver must keep tiller operator aware of planned route and upcoming turns
- Communication is key
- helpful to maintain teams on a regular basis
6
Q
backing operations
A
- tiller operator is a set of eyes in the rear
- must be aware of blindspots associated w/ sitting high on top of vehicle
- backup camera still recommended
7
Q
turning a tiller ladder
A
- excessive speed may force the tiller operator to oversteer or lose control because they won’t have enough time to correct steering angle and bring back in line
- after the turn, driver must ensure tiller op has brought trailer back in line and wheel straightened
- tiller op must remember to disengage the 5th wheel lockout (provides stability for aerial device) prior to leaving scene. It may put a bend in the truck, causing poor handling as all tires won’t be in full contact w/ the road
- w/ appropriate speed and proper positioning, tiller op will have to make minimal steering corrections and should only be done when there’s a need
- ensure enough space for overhang
8
Q
overhang
A
- portion of the vehicle from rear axle to rear of the truck
- tiller operator must ensure enough space for the trucks overhang
9
Q
Statistics on 15-passenger vans
A
- b/t 1990-2002: 1,576 fatal van crashes, 1,111 fatalities were occupants, 86% of those were not wearing seatbelts, 92% wearing seatbelts survived
- rollover 2.2x more likely if loaded to more than half capacity
- 5x when fully loaded compared to only driver
- 5x when on high speed road (greater than 50mph)
- 2x on a curved road
10
Q
Rollovers in 15-passenger vans
A
- more occupants = center of gravity higher and toward rear
- most common 3 scenarios:
1. goes off a rural road
2. driver fatigue
3. overcorrection as a panic reaction to a roadway emergency or wheel dropping off pavement
11
Q
implementing safety procedures for 15-passenger vans
A
- age requirements: there are age requirements for large apparatus but not smaller vehicles. Should be over 21 y/o
- number of passengers: 9 max, in front of rear axle
- speed
- seatbelts
- fatigue: switch every 2 hours and avoid overnight travel
- distractions
- tire pressure: 74% of the fatal accidents did not have properly inflated tires
12
Q
selecting a tow vehicle/damage resulting from an oversized load
A
- knowing how much weight the tow vehicle can pull is the first step in trailer safety
- tow packages typically include heavy-duty engine w/ trans cooler, oversized mirrors, heavy-duty rear suspension, and wiring for the trailer
- damage resulting from an oversized load
1. brake components
2. transmissions: excess heat breaks down trans fluid, lack of lubrication, causes breakdown of trans mechanical components or total failure if it seizes
3. suspension components
13
Q
selecting a hitch
(terminology)
A
- tongue: v-shaped portion of trailer including the coupler
- tongue weight: transferred to tow vehicle at hitch point, should be 9%-15% of total trailer weight. Too light will cause sway,
- gross trailer weight: total trailer weight
- gross combined vehicle weight rating: total weight of vehicle, trailer, passengers and equipment
- gross vehicle weight rating
- Hitch ball: coupler latches to it. Ensure proper size for coupler, 3 sizes:
1. 1 7/8” - up to 2k lbs
2. 2” - 3,500-8,000lb(most common
3. 2 5/16” - 6,000-30,000 lbs - Draw bar: ball mount, 2 sizes (1 1/4”, 2” square)
- coupler: drops over hitch ball, 4 types:
1. weight carrying hitch: carries all tongue weight on ball and receiver
2. weight distributing hitch: across tow vehicles entire frame w/ “spring bars”
3. 5th wheel hitch: mounted on bed of truck forward of rear axle
4. gooseneck hitch: similar to 5th wheel, uses ball hitch instead of locking pin
14
Q
Electromagnetic trailer brakes
A
- electrical current is sent through an electromagnet found inside brake drum
- brake controller determines how much electricity/force is applied
- advantages
1. ability to engage separately from vehicle
2. alleviate trailer sway
3. helpful when descending hills - disadvantages
1. problems when used infrequently, rust
2. requires brake controller installation - can be applied manually and/or brake pedal
- 2 types of brake controllers:
1. time delay: preset amount of force
2. proportional: applies at same intensity as brake pedal
15
Q
surge braking systems on trailers
A
- activated by momentum of decelerating trailer
- trailer pushes against hitch and engages hydraulic master cylinder, engaging brake system on trailer
