F - Coupling Units Fundamentals and Service

Question 1

Fifth wheel couplings are used to connect a semi-trailer to:

Answer 1

A tractor, a convertor dolly, or the lead trailer of a B train combination.

Question 2

The fifth wheel component that provides the bearing surface for the weight of the front of the semi-trailer is the:

Answer 2

Top plate.

Question 3

True or False: The purpose of the coupling jaws in a fifth wheel is to engage and secure the trailer kingpin.

Answer 3

True.

Question 4

Fifth wheel assemblies are rated based on four considerations. What are they?

Answer 4

Towed vehicle weight (TVW), maximum expected drawbar load, vertical load to be carried by the fifth wheel, and type of operation.

Question 5

Four advantages of sliding over stationary fifth wheels are:

Answer 5

Weight can be transferred between tractor axles, trailers with different kingpin settings can be accommodated, vehicle length can be varied, and additional manoeuvrability can be gained.

Question 6

Which if the fifth wheels is the most commonly used fifth wheel?

Answer 6

Semi-oscillating type.

Question 7

Pintle hooks designed to remove the clearance between the hook and the drawbar eye are called:

Answer 7

No-slack pintle hooks.

Question 8

The function of the safety restraint on a trailer unit coupled with a pintle hitch is to:

Answer 8

Ensure that the trailer remains attached to the towing unit int he event of a trailer hitch separation.

Question 9

List four faults that can be identified by visually inspecting a fifth wheel.

Answer 9

Cracked, bent, broken, or damaged components; Missing parts, Loose or missing fasteners, Condition of locking devices such as cotter pins, Top plate wear or warpage, Rusting or corrosion.

Question 10

Excessive clearance between the fifth wheel jaws and the lock tester kingpin is a result of:

Answer 10

Improper jaw adjustment and/or excessive jaw wear.

Question 11

The amount of wear in fifth wheel oscillating pins and bushings can be checked by:

Answer 11

Barring the top plate up and down as well as back and forth.

Question 12

True or False: A distorted or cracked fifth wheel top plate must be straightened or welded before it can be rebuilt.

Answer 12

False; A top plate must not be welded or straightened because it will weaken.

Question 13

The contact surface of the fifth wheel top plate is lubricated with:

Answer 13

Water resistant lithium-based grease.

Question 14

What two fifth wheel components should be lubricated with a light lubricating oil?

Answer 14

Cam track path and pivot point; Rack and slide path on sliding fifth wheels.

Question 15

True or False: A trailer kingpin must be replaced if it is bent more than 1 degree.

Answer 15

True.

Question 16

A trailer kingpin must be replaced if its diameter is worn more than:

Answer 16

3 mm (0.125 in)

Question 17

Before backing a tractor into a semi-trailer, you must:

Answer 17

Inspect the fifth wheel for damage, ensure that slider plungers are engaged, and check that the lock jaws are open,

Question 18

True or False: Trailer air and electrical connections can be made after the trailer is securely coupled to the fifth wheel.

Answer 18

False; Trailer connections must be done before coupling in order to set the trailer brakes.

Question 19

What test must be performed after the trailer is coupled to the fifth wheel?

Answer 19

A pull test must be performed by gently pulling against the trailer parking brakes.

Question 20

The first step in uncoupling a tractor/semi-trailer combination is to:

Answer 20

Position the unit o firm, level ground.

Question 21

True or False: When operating the landing gear to disconnect a semi-trailer, use high speed until the skid pads contact the ground and then shift t low speed for 4 to 8 additional turns.

Answer 21

True.