Fifth Wheels

Holland Fifth Wheels

General Information

Holland 3500 and FW8 series fifth wheels ( Fig. 8.1 ) are bracket-mounted to the tractor frame in a position that best distributes the trailer load over the tractor axles.

1. Kingpin Lock Release Handle
2. Kingpin Lock Mechanism

Fig. 8.1, Holland Fifth Wheel

The Type "B" kingpin lock mechanism ( Fig. 8.2 ) utilizes two spring-loaded lock halves. The final forward motion of the kingpin into the open lock halves forces the locks to close in a 360 degree grip around the shoulder and neck of the kingpin, positioning sliding yokes between the lock halves and tapered rib members of the fifth wheel understructure. The kingpin can be released only by manually operating the kingpin lock control handle. The adjustment nut will compensate for wear on the lock or kingpin.

A. Closed Position, Locked
B. Open Position, Unlocked

1. Release Handle and Spring
2. Adjustment Nut
3. Lock Halves
4. Lock Pivot
5. Sliding Yoke

Fig. 8.2, Type B Kingpin Lock Mechanism (bottom view)

The Holland Lockguard ( Fig. 8.3 ) is a device that prevents a false lockup, and is used with Type "B" kingpin lock mechanisms. The Lockguard is a spring-tensioned, smooth-surfaced tongue that the kingpin passes over and depresses when entering the lock mechanism. The Lockguard will prevent the locks from engaging before the kingpin fully enters the locks. If the kingpin enters the fifth wheel incorrectly and does not depress the tongue, the locks are unable to close.

A. Locks open.
B. Locks closed.
C. Kingpin correctly entering the lock. Note how the depressed tongue allows lock halves to close completely around the neck and shoulder of the kingpin.
D. Kingpin incorrectly entering the lock. Note how the steel tongue prevents lock halves from closing, preventing false lockup.

1. Fifth Wheel Plate
2. Trailer
3. Kingpin
4. Lockguard

Fig. 8.3, Lockguard Mechanism (rear view)

The Type "A" kingpin lock mechanism ( Fig. 8.4 ) utilizes a single hinged lock and cam arm. The final forward motion of the kingpin into the open lock forces the hinged lock to pivot on a pin and close around the kingpin. The lock is held in place by a spring loaded plunger. The kingpin can be released only by manually operating the release handle. The adjustment nut will compensate for wear on the lock or kingpin.

A. Closed Position, Locked
B. Open Position, Unlocked

1. Release Arm
2. Release Handle
3. Lock Pin
4. Hinged Lock

Fig. 8.4, Type "A" Kingpin Lock Mechanism

Fifth Wheel Locking Operation

Locking the Fifth Wheel Mechanism

Chock the front and rear of the trailer tires to prevent the trailer from moving.

The kingpin lock mechanism must be fully open, and the fifth wheel plate must be completely lubricated with chassis grease. For lubrication instructions, see Group 31 of the Business Class® Trucks Maintenance Manual .

Keep the fifth wheel plate lubricated to prevent binding between the tractor and trailer. A binding fifth wheel could cause erratic steering and loss of vehicle control, possibly resulting in personal injury or death.

Position the tractor so that the fifth wheel lock opening is in line (both vertically and horizontally) with the trailer kingpin. To prevent a false lockup, the kingpin should be in a position to enter the throat of the locking mechanism. See Fig. 8.3 . Adjust the trailer landing gear to give enough alignment height so that the fifth wheel picks up the trailer on the fifth wheel ramps.

With the fifth wheel lock opening aligned with the trailer kingpin, back the tractor slowly toward the trailer, making sure that the kingpin correctly enters the throat of the locking mechanism. When the trailer is picked up by the fifth wheel, stop the tractor, then resume slow backward motion until positive lockup occurs.

Apply the tractor parking brakes.

Make a visual check for proper kingpin lockup. Release the tractor parking brakes.

Test for kingpin lockup by pulling on the trailer against the chocks. Check for correct maximum clearance between the lock halves. If more than1/8-inch(3.2-mm) clearance exists between the lock halves, the lock must be adjusted. See Group 31 of the Business Class® Trucks Service Manual for adjustment procedures.

Adjust the locks correctly to a maximum clearance of 1/8 inch (3 mm). Incorrect adjustment of the lock could cause the trailer to disconnect, possibly resulting in serious personal injury or death.

After lockup is completed, connect the tractor-to-trailer air system lines and electrical cable to the trailer. Take care to prevent dirt or foreign material from entering the air lines.

Charge the air brake system with air. Make sure that the air connections do not leak.

Retract the trailer landing gear and secure the ratchet handle.

10.

Remove the chocks from the trailer tires.

11.

The load distribution on the front steering axle and rear drive axle(s) will have a direct effect on the steering control of the vehicle.

11.

Determine the front and rear axle weights by weighing the vehicle on scales designed for this purpose.

11.

The maximum axle weight ratings are shown on the Federal Motor Vehicle Safety Standard (FMVSS) label or Canadian Motor Vehicle Safety Standard (CMVSS) label attached to the left rear door post of the tractor. The desired load on the axle is no less than 80 percent of the maximum axle weight rating, but in no instances should the axle load exceed the maximum axle weight rating given on the FMVSS or CMVSS label.

Do not overload any tractor axle by improperly loading the trailer. This could cause erratic steering and loss of vehicle control, possibly resulting in serious personal injury or death.

Unlocking the Fifth Wheel Lock Mechanism

Apply the tractor parking brakes.

Pull the trailer air supply valve to cut off the air supply to the trailer.

Chock the front and rear of the trailer tires to prevent the trailer from moving.

Do not use the trailer air supply for parking trailers not equipped with spring parking brakes. This applies the trailer service brakes only. As air bleeds from the trailer brake system, brake application is lost. This could allow the unattended vehicle to roll away, possibly resulting in serious personal injury or death.

Lower the trailer landing gear until the weight is removed from the fifth wheel.

Disconnect the tractor-to-trailer air system lines and electrical cable. Plug the air lines to prevent dirt or foreign material from entering the lines.

Release the kingpin locking mechanism by pulling the kingpin lock control handle ( Fig. 8.1 ) to the outward position.

Slowly drive the tractor away from the trailer.

Fontaine Fifth Wheels

General Information

On Fontaine fifth wheels, kingpin release is accomplished by activating a manual lock control handle located on the left or right side of the fifth wheel. Kingpin lockup occurs when the kingpin is forced into the jaws and the lock control handle moves to the locked position.

On stationary fifth wheels, the fifth wheel top plate is bracket-mounted to the tractor frame in a position that best distributes the trailer load over the tractor axles.

The sliding fifth wheel mount is used with the Fontaine H5092 series, and the Fontaine 6000/7000 No-Slack II series fifth wheels, and is equipped a with either an air-operated release slide (HAWB or AWB model), or a manual release slide (HMWS or MWS model). The fifth wheel top plate is mounted on a slide assembly, which is attached to slide rails that are mounted on the vehicle frame. The slide rails permit forward and rearward movement of the slide assembly, allowing for optimum weight distribution over the tractor axles.

Slots are evenly spaced along the slide rails, and retractable tapered wedges are positioned through the slots to hold the fifth wheel in the desired position. See Fig. 8.5 or Fig. 8.6 .

The slide portion of the sliding model may be attached to either an air-operated release slide, or a manual release slide.

The air-operated release slide contains an air cylinder that locks and unlocks the fifth wheel slide. See Fig. 8.5 . The air cylinder is activated by a two-position air-control valve in the tractor cab.

1. Locking Wedge
2. Air Cylinder

Fig. 8.5, Air-Operated Sliding Fifth Wheel Mount, AWB Model

1. Locking Wedge
2. Slide Release Pull Handle

Fig. 8.6, Manual Release Sliding Fifth Wheel Mount, MWS Model

The manual release slide contains a slide release pull handle, located on the left side of the fifth wheel, which locks or unlocks the fifth wheel slide. See Fig. 8.6 .

Fifth Wheel Lock Mechanism for Trailer Kingpin

The Fontaine fifth wheel lock mechanism for the trailer kingpin consists of a spring-loaded jaw and a sliding wedge. The jaw and wedge each have a pin permanently attached. The pin on the jaw and the pin on the wedge fit into elongated notches in the lock control handle. The notches in the handle control the limit of movement for both the jaw and wedge. The notches are arranged so that the wedge is actuated first during release of the kingpin.

During lockup, the jaw is moved first with the spring-loaded wedge being allowed to slip into place against the jaw. A timing bracket ensures that the wedge and jaw are moved at the correct time.

Placing the lock control handle in the unlocked position moves the wedge away from the jaw. This action unlocks the jaw so that it can be moved by the trailer kingpin. When the tractor is moved out from under the trailer, the kingpin moves the jaw until the kingpin is out of the mechanism. With the jaw in the unlocked position, the lock control handle will remain in the unlocked position until manually moved by the operator.

During coupling ( Fig. 8.7 ), the motion of the kingpin entering the jaw will actuate the jaw and wedge. The jaw will move behind the kingpin, followed by the wedge. The purpose of the wedge is to reinforce the jaw and take up slack around the pin. Any wear on the jaw is immediately taken up by the wedge so there is no slack in the connection.

NOTE: Kingpin correctly entering the lock. Note how the steel tongue allows lock halves to close completely around the neck and shoulder of the kingpin.

A. Unlocked Position
B. Locking
C. Locked

1. Wedge
2. Jaw
3. Trailer Kingpin

Fig. 8.7, Fontaine Kingpin Lock Mechanism

Fifth Wheel Locking Operation

Locking the Fifth Wheel Lock Mechanism

Before attempting to lock or unlock the fifth wheel lock mechanism of a sliding type fifth wheel, the slide release pull handle, if so equipped, and the slide locking wedges must be in the locked position. This prevents the sliding member from moving rapidly to the far forward or rearward position, which could damage the fifth wheel member or kingpin.

Chock the front and rear of the trailer tires to prevent the trailer from moving.

The kingpin lock mechanism must be fully open, the fifth wheel plate must be completely lubricated with chassis grease. For lubrication instructions, see Group 31 of the Business Class® Trucks Maintenance Manual .

Position the tractor so that the fifth wheel lock opening is in line (both vertically and horizontally) with the trailer kingpin. The kingpin should be in a position to enter the throat of the locking mechanism, as shown in Fig. 8.7 . Adjust the trailer landing gear to give enough alignment height for positive kingpin lockup.

With the fifth wheel lock opening aligned with the trailer kingpin, back the tractor slowly toward the trailer, making sure that the kingpin enters the throat of the locking mechanism. Continue backward motion until positive lockup occurs.

Apply the tractor parking brakes.

Make a visual and physical check for positive kingpin lockup. When lockup has occurred, the fifth wheel control handle will have moved to the locked position. Make sure that the safety latch is down over the lock control handle. See Fig. 8.8 . This will hold the control handle in the locked position.

NOTE: Make sure the safety latch is down when the control handle is locked.

A. Unlocked
B. Locked

1. Lock Control Handle
2. Safety Latch

Fig. 8.8, Fontaine 5000 Series Fifth Wheel, Locking and Unlocking

Release the tractor parking brakes. Test for kingpin lockup by pulling on the trailer against the chocks.

After lockup is completed, connect the tractor-to-trailer air system lines and the electrical cable to the trailer. Take care to prevent dirt or foreign material from entering the air system lines.

Charge the air brake system with air. Make sure that the air connections do not leak.

10.

With the trailer wheels chocked and the brakes set, check for clearance between the kingpin and the fifth wheel jaws by moving the tractor forward and backward against the locked kingpin. There should be no slack between the tractor and the trailer. If slack is present, uncouple the trailer.

10.

For adjustment instructions, refer to the applicable manufacturer's service information.

Incorrect fifth wheel lock adjustment could cause the trailer to disconnect, possibly resulting in serious personal injury or death.

11.

Retract the trailer landing gear, and secure the ratchet handle. Remove the chocks from the trailer tires.

12.

The load distribution on the front steering axle and rear drive axle(s) will have a direct effect on the steering control of the vehicle.

12.

Determine the front and rear axle weights by weighing the vehicle on scales designed for this purpose.

12.

The maximum axle weight ratings are given on the Federal Motor Vehicle Safety Standard (FMVSS) label or Canadian Motor Vehicle Safety Standard (CMVSS) label attached to the left rear door post of the tractor. The desired load on the axle is no less than 80 percent of the maximum axle weight rating, but in no case should the axle load exceed the maximum axle weight rating given on the FMVSS or CMVSS label.

Do not overload any tractor axle by improperly loading the trailer. This could cause erratic steering and loss of vehicle control, possibly resulting in serious personal injury or death.

Unlocking the Fifth Wheel Lock Mechanism

Apply the tractor parking brakes.

Pull the trailer air supply valve to cut off the air supply to the trailer.

Chock the front and rear of the trailer tires to prevent the trailer from moving.

Lower the trailer landing gear until the weight is removed from the fifth wheel.

Disconnect the tractor-to-trailer air system lines and electrical cable. Plug the air lines to prevent dirt or foreign material from entering the lines.

Release the kingpin locking mechanism by lifting the safety latch and pulling the lock control handle to the unlocked position. See Fig. 8.8 .

Slowly drive the tractor away from the trailer.

Fifth Wheel Slide Operation

Connect the trailer kingpin to the tractor fifth wheel. For instructions, refer to Fontaine "Fifth Wheel Locking Operation," in this chapter.

After positive lockup of the fifth wheel lock mechanism has been accomplished, release the slide using one of the following methods:

2.1

For air-operated release models, set the cab-operated control switch ( Fig. 8.9 ) to UNLOCK.

Fig. 8.9, Cab Control, Fifth Wheel Slide

2.2

For manual release models, lift the slide release pull handle to disengage it from the guide plate. Then, pull out the handle ( Fig. 8.10 ) until it is in the unlocked position and can be positioned against the guide plate to hold it out. The slide release pull handle will stay in the unlocked position until it is manually disengaged from the guide plate.

Fig. 8.10, Fontaine Sliding Fifth Wheel Manual Release

Lower the trailer landing gear just enough to remove the weight from the tractor.

Pull the trailer air supply valve to cut off the air supply to the trailer.

Chock the front and rear of the trailer tires to prevent the trailer from moving.

After moving the fifth wheel to the desired position, be sure the trailer landing gear will not, at any time, come in contact with the tractor frame or other components. Make sure that the front of the trailer will not come in contact with the rear of the cab or with other components if they extend beyond the rear of the cab.

Slowly move the tractor forward or backward until the fifth wheel is in the desired location.

Apply the tractor parking brakes.

NOTE: The fifth wheel may have to be moved slightly to enable the locking wedges to enter the fully locked position.

Lock the sliding member in position using one of the following methods:

Check to be sure that the lockpins are seated in the holes. Failure to achieve complete lockup may cause the trailer to detach from the tractor, possibly resulting in serious personal injury or death.

8.1

For air-operated release models, set the cab-operated slide control switch to LOCK. Visually inspect the locking wedges to make sure that they are fully inserted in the slide rail slots.

8.2

For manual release models, disengage the slide release pull handle from the guide plate. The slide release pull handle is spring-loaded in the locked position and will seek the locked position when disengaged from the guide plate. The fifth wheel may have to be moved slightly to enable the locking wedges to fully enter the locked position. When the slide release pull handle returns to the fully locked position, visually and physically check the locking wedges to make sure they are fully inserted into the slots in the slide rails. Make sure the slide release pull handle is locked in position against the guide plate.

The amount of load distribution on the front steering axle and rear drive axle(s) will have a direct effect on the steering control of the vehicle.

Determine the front and rear axle weights by weighing the vehicle on scales designed for this purpose.

The maximum axle weight ratings are given on the Federal Motor Vehicle Safety Standard (FMVSS) label or Canadian Motor Vehicle Safety Standard (CMVSS) label attached to the left rear door post of the tractor. The desired load on the axle is no less than 80 percent of the maximum axle weight rating, but in no instances should the axle load exceed the maximum axle weight rating given on the FMVSS or CMVSS label.

Adjust the fifth wheel slide correctly, and do not overload any tractor axle by incorrectly loading the trailer. Incorrect slide adjustment or improper axle loading could cause erratic steering and loss of vehicle control, possibly resulting in serious personal injury or death.