Online Cdl Training Combination Vehicles Flashcards
What two things are important to prevent rollover?
Keep cargo as close to the ground as possible and drive slowly around turns.
When you turn suddenly while pulling doubles, which trailer is most likely to turn over?
the rear trailer
Why should you not use the trailer hand brake to straighten out a jackknifing trailer?
The brakes on the trailer wheels cause the skid -- release so the trailer wheels will grip the road again.
What is off tracking?
the rear wheels follow a different path than the front wheels
Why should you not turn wide all the way into the left lane?
So cars don't pass you on the right side
Why should you not use the trailer hand valve while driving?
The trailer hand valve should only be used to test the brakes.Do not use it in driving because of the danger of making the trailer skid.
Describe what the trailer air supply control does.
push it in to supply the trailer with air, pull it out to shut the air off and put on the emergency brakes
What is the trailer air supply control on newer vehicles?
A red eight sided knob which you use to control the tractor protection valve
Describe what the service line is for
They provide the air pressure used to operate trailer brakes
What is the emergency air line for?
The emergency air line (also called the supply line) has two purposes. First, it supplies air to the trailer air tanks and secondly, the emergency line controls the emergency brakes on combination vehicles
Why should you use chocks when parking a trailer without spring brakes?
to keep it from rolling if the air leaks out and the emergency brake lets go
What are shut-off valves?
Used in the service and supply air lines at the back of trailers used to tow other trailers. These valves permit closing the air lines off when another trailer is not being towed. You must check that all shut-off valves are in the open position except the ones at the back of the last trailer, which must be closed
How to test the trailer hook-up with independent brake control
1. Depress the clutch2. Shift into the lowest gear 3. Put on the independent trailer brakes 4. Release the clutch to the friction point5. Pull gently forward against the locked trailer brakes6. Disengage the clutch7. Repeat the whole procedure
How to test the trailer hook-up without independent brake control
1. Push in the clutch2. Shift into the lowest forward gear3. Switch the tractor protection valve from normal to emergency4. Partly engage the clutch5. Gently pull forward against the locked trailer brakes6. Repeat the whole procedure
If the tractor is not secured what is the result?
Damage to brake lines
If the trailer brakes aren't function what is the result?
Trailer pushed into obstruction
If jaws are not securely fastened what is the result?
Trailer breaks loose on the road
If the ground is not girl for uncoupling what is the result?
Trailer falls and is damaged
What could happen if climbing on tractor?
Fall from slippery surface
What could happen if you work undersupported trailer?
Injury when landing gear collapses and trailer drops to the ground
What might happen if the trailer is too high when you try to couple?
it may not couple correctly, the trailer may strike the back of the tractor and cause damage
After coupling, how much space should be between the upper and lower fifth wheel?
Inspect coupling, use flashlight if necessary.. Make sure there is no space between
True or false: to drive you need to raise the landing gear only until it just lifts off the pavement
False
Which shut-off valves should be open and which closed?
You must check that all shut-off valves are in the open position except the ones at the back of the last trailer, which must be closed
How can you test that air flows to all trailers?
Wait for air pressure to reach normal, then push inbred trailer air supply knob. This will supply air to the emergency (supply) lines. Use the trailer handbrake to provide air to the service line. Go to the rear of the rig. Open the emergency line shut-off valve at the rear of the last trailer. You should hear air escaping, showing the entire system is charged. Close the emergency line valve. Open the service line valve to check that service pressure goes through all the trailers, then close the valve. If you do not hear air escaping from both lines, check that the shut-off valves on the trailer(s) and dolly(s) are in the open position
How can you test the tractor protection valve?
Shut the engine off, step on and off the brake pedal several times to reduce air pressure in the tanks. The trailer air supply control should pop out (or go from normal to emergency) when the air pressure falls into the pressure range specified by the manufacturer, usually within the range of 20-45 psi
How can you test the trailer emergency brakes?
charge the trailer air brake system and check that the trailer rolls freely. stop and pull out the trailer air supply control valve , pull the trailer gently to see that the trailer emergency brakes are on
How can you test the trailer service brakes?
check for normal air pressure, release the parking brake, move forward slowly and use the trolley valve to engage the trailer brakes
You can prevent a roll over by keeping the cargo as close to the ground as possible and:
Going slow around curves
Why are "bobtail" tractors harder to stop?
The vehicle is lighter
On a combination vehicle, to stop a jackknife:
Do not use the trailer hand brake
Offtracking is:
When the rear wheels follow a different path than the front wheels
The trailer air supply:
Supplies the trailer with air
The service line:
Carries air to the trailer brakes
Why should you connect the air hose couplers together?
To keep dirt and water out of the lines
What happens when you cross the air lines of an older trailer without spring brakes?
You could drive away, but have no trailer brakes
Why do many trailers built before 1975 have no parking brakes?
They do not have spring brakes
If the service line comes apart while driving but the emergency line is okay, what happens immediately?
Nothing is likely to happen until you press the service brake pedal
You should always grease the fifth wheel because:
It prevents steering problems
What should you do just before the tractor is coupled?
Connect the emergency and service air lines
In coupling, where should the tractor be lined up?
Directly in front of the trailer
In coupling, the trailer is at the right height when:
The trailer is lifted slightly when the tractor connects
During coupling, how do you lock the trailer brakes before you back under the trailer?
Pull out the trailer air supply knob
To make sure that the kingpin and the fifth wheel connection are secured, what should you do?
Slowly pull forward with the trailer brakes locked
When coupling is complete, how much space should there be between the upper and lower fifth wheel?
No space
When the fifth wheel locking lever is almost in the locking position but will not lock, what should you do?
Have it repaired before driving.
After the tractor is coupled, you should not move it until you push in the air supply knob and:
Wait until the air pressure is normal
After coupling, you can make sure the air lines are not crossed because:
When you pump the brake you will hear the brakes move and air escape
When the engine and brakes are off, the air leakage rate for combination vehicles must be less than:
3 psi per minute
The maximum leakage rate for a combination vehicle with the engine off and brakes on is:
4 psi per minute
You should use the trailer hand valve:
To test the trailer brakes
Why do you need a tractor protection valve?
It keeps air in the tractor if the trailer breaks away or develops a bad leak.
The tractor protection valve will close automatically when:
The air pressure is low (20-45 psi)
When testing the trailer emergency brakes, you should charge the air brakes system, check that the trailer rolls freely and?
Pull out the trailer air supply control.
After you have turned the hand brake on, how do you check the trailer brakes?
Bring the air pressure up to normal, turn the parking brakes off and move slowly forward to see if the trailer slows down