fbpx

Cart

The cart is empty

Cannot find your purchased courses? Click here to Login!

Before unhooking a semi-trailer, ensure that the ground will support the weight of the landing gear.Before unhooking a semi-trailer, ensure that the ground will support the weight of the landing gear.

 

MUST KNOW

LAP

1) Landing Gear down

2) Air Lines & Electrical (Disconnect)

3) Pin (Pulled & Unlocked)

SHOULD KNOW

 Park the trailer in a safe & preferably secure location.

A safe location is ideally a place away from the flow or path of traffic.

Attempt to park the trailer away from a roadway, or in a yard near the main travel path of other vehicles – ie. employees’ vehicles, forklifts and other trucks.

 Ensure that the ground will support the weight of the trailer – if not, use planking under the dollies or find another location.

If the trailer is equipped with an air suspension dump valve – empty the semi-trailer's air suspension.

 Wind down the landing gear until it just touches the ground - drop or stow the crank handle.

Trailers are parked close together (12-18" (30-45cm); if the crank handle is left in the cranking position another driver may back into it and potentially damage it.

The next driver (usually you) to arrive will find a broken crank handle, and ultimately be delayed.

Disconnect the air lines and electrical chord and stow in the dummy couplers or secure to the deck plate with a bungee chord.

When pulling the fifth wheel handle to release the jaws from the king pin, always use a puller.Pull the 5th wheel handle to release the jaws – preferably using a 5th wheel puller.

If you don't use a 5th wheel puller you're probably going to get grease on your sleeve, and that grease on your sleeve then ends up in your truck - just another sign of professionalism.

Climb in the cab and move the tractor ahead 6-12" inches using “bull” or low gear.

Stop the truck and dump the tractor’s air ride suspension.

Get out and check for daylight between the 5th wheel plate and the trailer apron - this indicator tells you that the ground is supporting the weight of the trailer.

Get back in the cab – pull out completely from under the trailer – you’re done!

COULD KNOW

Dropping the trailer on solid ground

If you don’t inspect the ground before dropping the trailer, it could potentially sink.

If this happens, you—yes you the driver—will be held responsible for negligently dropping a trailer.

Never drop a trailer on pavement without putting wood under the feet.

In some trailer yards, a strip of concrete is poured and the trailer’s dollies must be positioned on the concrete to prevent damage to the pavement.

Dumping the air ride suspension on a loaded trailer before disconnecting prevents potential damage to the landing gear.

Over time as a loaded trailer sits, the air ride suspension bleeds off.

As the air ride suspension gradually deflates, the rear of the trailer sinks; consequently, forward pressure is exerted on the landing gear which potentially bends the legs and struts.

When unhooking the trailer, always, always wind the landing gear down first, otherwise you may get distracted and forget.

By establishing a procedure of doing the landing gear first, you will never risk potentially unhooking a trailer and dropping it on the ground.

Immediately after winding down the landing gear, disconnect the airlines and the electrical chord.

If you wind down the landing gear and then pull the 5th wheel pin, again, you may get distracted and forget to disconnect the lines.

And believe me you: there is nothing that will make you look more amateur than driving away from a trailer and snapping off the air lines and electrical chord.

This error is tantamount to driving away from the fuel pump with the fill spout in your tank.

If you wind down the landing gear and disconnect the lines, but forget to pull the pin, no one will know other than you.

After a bit of embarrassment, you simply get out of the truck and pull the pin.

Before dumping the tractor’s air ride suspension, move the truck forward slightly to disengage the king pin from the 5th wheel jaws.

The trailer’s king pin has a flange on the bottom, and if you lower the truck while the king pin is still inside the 5th wheel , the 5th wheel jaws could potentially “hang up” on the king pin’s flange.

If the king pin hangs up inside the 5th wheel, it could damage both the king pin and the 5th wheel coupling mechanics.

If this undue stress occurs regularly, the 5th wheel may fail altogether.

Finally, don’t just pull out from under the trailer and drive away.

If you pull out only far enough that the trailer comes off the back of the 5th wheel and stops, you can still get the tractor back under the trailer if the ground fails to support its weight.

Otherwise, if you pull the tractor out and the trailer sinks, a crane or heavy fork truck will be required to get the trailer back up to a level that it can be hooked to a truck.

 

Log in to comment
Default Image

Applied Stroke - Check Air Brake Adjustment

Author: Rick
The National Safety Code madates that every driver of a commercial vehicle equipped with air brakes must check push rod travel every day as part of his/her pre-trip inspection. In some jurisdications, drivers must use the applied stroke method; in others, they…
Default Image

Pry Bar - Check Air Brake Adjustment

Author: Rick
The National Safety Code madates that every driver of a commercial vehicle equipped with air brakes must check push rod travel every day. In many jurisdications, drivers are allowed to use the pry bar method; in others , they must use the applied stroke…
Default Image

Compressor or Build-up Test (Air Brakes)

Author: Rick
Depending on which province you're in, the air buildup time or compressor test has somewhat different paramenters. Still, all require that the diesel motor be at a fast idle. A fast idle on a diesel engine is between 900 &1200 rpm.
air brake adjustment

Air Brake Manual Adjustment – Pry Bar Method

Author: Rick
Using the pry bar method, confirm that the brake is in fact out of adjustment. After confirming that the brake is out-of-adjustment and it is equipped with a manual slack adjuster, complete the following steps to bring the brake back into adjustment. If one…
The one-way check valve is primary responsible for the division of the air brake system into a primary and secondary sub-system.

One-Way Check Valves

Author: Rick
A cattle chute with one-way gates allows the cows to only move in one direction – forward. A one-way check valve in an air brake system works exactly the same – it allows air to only move in one direction – forward through the system. The one-way check valves…
Default Image

Air Brake Chambers

Author: Rick
Convert air pressure into a strong mechanical force to apply the foundation brakes.
Default Image

Air Gauge(s)

Author: Rick
The gauges are in either pounds per square inch (psi) or Kilopascals (kPa). These measure the amount of air pressure in the primary and secondary air tanks.
Default Image

Automatic Front Wheel Limiting Valve

Author: Rick
To reduce application pressure to the steering axle brakes during most braking situations. Reduced pressure to the steer axle brakes occurs for most braking applications. Only during hard braking is there equivalent pressure delivered to both the front and…
A bobtail proportioning valve will move most of the braking to the front steer axles when there's not trailer attached.

Bobtail Proportioning Valve

Author: Rick
A bobtail proportioning valve great increases braking safety owing to different weight distribution.
Brake fade is the only reason that a modern air brake system will fail.

Brake Fade

Author: Rick
Brake faide is the only reason that a modern air brake system will fail.
Default Image

Brake Linings & Drums

Author: Rick
To stop the vehicle, brake linings rub against the brake drum. This action creates friction, converting the vehicle's forward energy of motion into heat energy, which stops the vehicle’s tires. If the tires have traction, the vehicle will come to a stop. The…
A caging bolt is used to release the emergency brakes in the event of an emergency (life or death situation).

Caging Bolt

Author: Rick
Allows the spring brakes to be manually released in an emergency - a dire emergency.
Default Image

Compounding Air Brakes

Author: Rick
OBSOLETE Making a heavy service brake application while the parking brakes are applied. This is often an error of truck driving school students.
Air Brakes Simply Explained is a comprehensive manual that guarantees that you will pass your air brake ticket first time.

Brake Pedal - Foot Valve OR Treadle Valve

Author: Rick
MUST KNOW The brake pedal applies the service brakes - truck, or truck and trailer brakes. In other words, the brake pedal brings the vehicle to a stop when it it depressed. SHOULD KNOW The foot valve operates the secondary and primary sub systems…
You must know what a manual front wheel limiting valve is for your CDL air brake test. These are no longer found on modern trucks.

Manual Front Wheel Limiting Valve

Author: Rick
OBSOLETE To reduce application pressure to the steering axle by 50 % compared to the drive axle brakes, when required by reduced road conditions (rain, snow or ice). The system consists of a dash switch with 2 positions: Dry Road: 100% front wheel braking; in…
After a brake application, air is exhausted from the air brake system via the quick release valve to reduce brake lag.

Quick Release Valve

Author: Rick
The quick release valve moves to reduce brake lag in the air brake system.
Default Image

Relay Emergency Valve

Author: Rick
OBSOLETE Fills the trailer air tanks (reservoir) and applies and releases the trailer service brakes. The relay emergency valve also applies the trailer emergency brakes in the event of a trailer breakaway or normal disconnect. Knowledge Test Question: In the…
The relay valve takes a message from the brake pedal and draws air directly from the air tank to the brake chamber, thus reducing brake lag.

Relay Valve

Author: Rick
Several relay valve throughout the air brake system reduce brake lag, thus allowing the brakes to apply faster.
Default Image

Air Tanks (Reservoirs)

Author: Rick
Stores compressed air for braking and for other air operated accessories. The air tanks are the first fail-safe in the air brake system. In the unlikely event that the air compressor fell of the side of the engine, the air tanks (reservoirs) store enough air…
Default Image

Slack Adjuster

Author: Rick
Slack adjusters have three purposes: 1) To convert the forward linear motion of the push rod into rotary motion of the camshaft. The slack adjuster works on exactly the same principle as a box end wrench on a nut. 2) To act as a lever, thus generating greater…
Default Image

Spring Brake Modulator (Inversion) Valve

Author: Rick
OBSOLETE Used on some vehicles with dual air systems. This device provides a means of using the force of the spring brakes to assist in stopping a vehicle in an event of a failure in the rear (primary) air system.
Default Image

Spring Parking Brake (Emergency)

Author: Rick
Applies the parking brakes of the air brake equipped vehicle indefinitely – if needed of course. The parking brakes are held in the “ON” position by the mechanical force of the springs; these spring parking brakes are held in the “OFF” position by system air…
Default Image

Stop Light Switch

Author: Rick
Activates the brake lights when a service brake application is made by the driver.
On most trucks, the air lines to the trailer are plumbed into the tractor protection valve.

Tractor Protection Valve

Author: Rick
The tractor protection valve protect the tractors air supply from being depleted in the event of a trailer breakaway.
Default Image

Trailer Hand Control (Spike)

Author: Rick
OBSOLETE Independently applies and releases the trailer service brakes. Knowledge Test Question: This air brake control is not to be used for parking. Although most tractors are still equipped with hand valves, beyond a trailer service tug test, these air…
Default Image

Two-way Check Valves

Author: Rick
Must be used whenever two sources of air are used to operate a single device or system. For CDL air brake test, the driver must know there are 2 in the system.
Always, always check the jaws are closed around the king pin to ensure that the trailer is in fact hooked to the truck.

Hooking a Semi-Trailer

Author: Rick
Always check with a flashlight that the 5th Wheel jaws are locked around the king pin.
blog image

Brake Fade | Air Brakes

Author: Rick
Although air brakes are more-or-less buletproof these, like all braking systems, have one failing: BRAKE FADE.

© Smart Drive Test Inc. 2024.

Contact Us: [email protected]