Single-axle frameless semi-trailer-tipper (fig. 1) with rear unloading, with an open platform and an opening tailgate with a carrying capacity of 13.5 tons is designed to transport various bulk construction materials on roads of categories I and II

The main traction vehicle for towing is the MAZ-504G truck tractor.

The axle, hubs, wheels and tires of the dump truck are the same as on the MAZ-5245 semi-trailer.

General view of MAZ-5232V semi-trailer dump truck

Traction frame with roll plate

The coupling of the semi-trailer with the tractor is carried out through the kingpin, pressed into the socket of the plate 3 of the reel (Fig. 2).

Diameter of the kingpin is 50.8 mm.

The transmission of traction occurs through the traction frame 2, connected by axes 1 to the plate 3 reel. The axles are stopped from moving by fingers attached to the brackets.

Traction frame MAZ-5232V

The rolling plate is a welded structure, the basis of which is a metal sheet 6 mm thick.

A kingpin socket with a pressed kingpin is welded to the plate between the longitudinal channel beams and crossbars.

Reliability of fastening of the kingpin is additionally ensured by screwing the shank of the lower cylinder support into it (the thread of the shank is M42x x1.5), while the plane of the support is pressed against the kingpin seat.

Along the axis of the kingpin on both sides of the plate, cast brackets are welded 4 for fastening the reel plate to the platform.

Traction frame 2 is welded from two side members and three crossbars made from channel 14a. At the ends of the side members, forged lugs are welded for connection with the reel plate and the platform.

Inside the spars and along the end of the shelves, creating a box-shaped section, reinforcing strips are welded over the entire length of the spars.

The first cross member is used to attach the platform lift limitation chain, and the chain release spring is attached to the second cross member.

MAZ-5232V traction frame locking mechanism

Maintenance of the rolling plate and the traction frame consists of periodic inspection and tightening of the fastening of the pins for fixing the axles, lubrication of the axles in accordance with the lubrication map.


In case of radial wear of the king pin more than 2 mm, it must be replaced. The king pin must be removed after disconnecting the hydraulic cylinder from the lower support, for which:

  • - install the semi-trailer on support devices, unhook the tractor, disconnect the hoses, brake the semi-trailer with a parking brake and place the goats under the traction frame;
  • - disconnect the locking rod 1 (see Fig. 3) and remove it from the platform brackets and the traction frame. The traction frame with the reel plate will lower onto the trestle;
  • - disconnect the hydraulic lift from the lower support of the cylinder and move it aside, bend the stopper from the lower support and unscrew it from the kingpin, knock the kingpin out of the socket.

Installation of the kingpin is carried out in the reverse order.

If axle 1 (see fig. 2) of the traction frame mounting is worn, it must be replaced. Axle made of steel 40-45 Ø 50-0.17, length 132 mm.

At a distance of 15 mm from the end, a hole Ø 19 mm is drilled perpendicular to the axis of the part to install the locking pin.

In the traction frame mounting bracket, the hole for the axle is made Ø 50 + 0.50 mm, in the lugs of the traction frame, the hole for the axle is made Ø 50 + 0.25 mm.

The axles on the bracket 4 can be replaced, for which the unloaded platform is raised by 20-25 °, the stop 5 is removed and its end with a pin is inserted between the reinforcing ribs of the first cross member of the platform, and the opposite end with the guide tube is inserted into the socket of the right bracket of the plate rolling. Then lower the platform to the stop.

Draft frame locking mechanism

Device. To prevent the lowering of the traction frame with the rolling plate to the ground, when unhitching the tractor from the semi-trailer, the traction frame locking mechanism is used (Fig. 3).

Before disconnecting the tractor from the semi-trailer, it is necessary to lower the support device, which will rotate at a certain angle relative to the axis.

A leash is attached to the body of the support device, connected by a rod 4 to the lever 3 of the locking mechanism.

The lever moves the stop rod 1 with the help of rod 2. The stop rod enters the holes of the lugs of the traction frame and the platform base, and thereby prevents the traction frame with the reel plate from falling.

In the working position of the semi-trailer, the supporting devices must be raised.

Maintenance of the locking mechanism consists in the timely cleaning of the connection of rods and forks from dirt. It is also necessary to monitor the absence of bending of the mechanical rodslocking zma.

When the rods are bent, they are subject to mandatory straightening. In case of incomplete entry of the locking rod into the ears of the brackets, it is necessary to carry out the adjustment by rotating the rods in the fastening forks.

Possible malfunctions of the traction frame and reel plate and how to eliminate them

Cause of malfunction - remedy

  • The original position of the traction frame mounting axes is violated

Wear or loss of axle locking pins - Replace pins

  • Perceptible jerks when changing the speed of movement

King pin wear more than 2 mm - Replace king pin

Worn traction frame mounting axles - Replace axles

Working out in the brackets or lugs of the traction frame - Press the repair sleeves into the brackets or lugs


Axle suspension to the semi-trailer frame is carried out using longitudinal semi-elliptical springs - main and additional.

The main spring is divided into two groups:

  • - the first group of springs with a sag of 65-8 mm, the second with a sag of 65+8 mm.

The additional spring is also divided into two groups:

  • -- the first group of springs with a sag of 48+7 mm;
  • - the second one with a deflection arrow 48+1 mm.

Brake system

The brake system of the semi-trailer is similar to the brake system of the MAZ-5245 semi-trailer. The parking brake is similar in principle to the same brake of the MAZ-5206 trailer.

Scheme of separate braking of tractor and semi-trailer MAZ-5232V

A feature of a semi-trailer-dump truck of a frameless design is that when unloading, it is necessary to ensure that the semi-trailer rolls up to the tractor or the tractor to the semi-trailer.

Given this circumstance, the pneumatic brake drive system of the road train as part of the MAZ-504G tractor and the MAZ-5232V semi-trailer provides for the possibility of braking one tractor or one semi-trailer, depending on the unloading conditions (Fig. 4).

Depending on the unloading conditions, braking should be carried out as follows.

When unloading into a dump or bunker, it is necessary to brake the semi-trailer, for which the handle 14 of the release valve 6 installed on the tractor should be moved to a position perpendicular to the longitudinal axis of the crane.

At the same time, the air from the connecting line of the semi-trailer escapes into the atmosphere, as a result of which the air distribution valve 8 is activated and the semi-trailer is braked without pressing the brake pedal 2 in the tractor cab.

After unloading is completed, the handle 14 should be set to its original position.

In the case of unloading a semi-trailer on the site, for better removal of the load from the platform, it is more expedient to brake the tractor, thereby ensuring the semi-trailer rolls up.

To do this, the handle 12 of the valve for manual control of the brakes of the semi-trailer installed on the semi-trailer must be moved to a position perpendicular to the longitudinal axis of the valve using the rod 11, as a result of which the air distribution valve 8 will operate and the semi-trailer will be released.

The tractor is braked by pressing the brake pedal in the tractor cab.

At the end of unloading, the handle 12 should be set to its original position.

In other cases, while ensuring the safety regulations, it is allowed to unload the semi-trailer with the tractor and semi-trailer not braked. At the same time, it is possible to roll both a semi-trailer and a tractor.

It is unacceptable to unload a semi-trailer with the tractor and semi-trailer simultaneously braked, both with a working and parking brake, as this will cause a sharp increase in loads on the tipping and other mechanisms of the road train due to the impossibility of rolling the tractor and semi-trailer, which can lead to their breakdown .

Electrical equipment

Electrical equipment consists of a seven-pin socket, two rear lights that act as stop signals, side lights, direction indicators, a license plate light, and reflectors installed on the sides of the platform.

Scheme of the MAZ-5232V platform lifting mechanism

The platform of the semi-trailer-dump truck is load-bearing, metal, with an automatically opening and closing tailgate.

Internal dimensions of the platform: length 4420 mm, width 2290 mm, height at the front 660 mm, at the back 570 mm; platform volume 7 m3.

The platform consists of the body itself, a visor, a tailgate, a mechanism with a tailgate locking drive and rubber-metal shock absorbers.

The body of the semi-trailer is welded from stamped profiles. The basis is spars made of channel 20a.

The sides are made of 3 mm thick sheet and are reinforced with omega-shaped buttresses, which pass into the cross-beams of the floor fastening.

Bunk floor.

The first tier is a stamped corrugated profile 30 mm high and 2 mm thick welded to the side members, cross members and the lower part of the sides.

The second tier is a 6 mm thick sheet welded to the lower floor and sides.

A stamped reinforcement with holes for installing extension boards is welded along the upper edge of the sides.

There is a niche welded into the front side for installing a hydraulic platform lift.

To protect the tractor from getting a load on it, a visor is attached to the front of the body with M10 bolts.

Four shock absorbers are installed in front of the bottom of the spars to support the traction frame.

The tailgate opens around the upper axles in the sideboard brackets.

Opening and closing of the side is carried out automatically depending on the angle of the platform.

If necessary, you can use the manual locking mechanism located on the left side near the tailgate.

Brackets for mounting springs are riveted to the side members of the platform, brackets for supporting devices and brackets for the traction frame are welded.

Brackets for attaching mudguards are welded to the two rear side buttresses. Mudguards are attached to the brackets with M8X20 bolts.

Maintenance of the platform consists of periodic washing and touch-up.

If necessary, adjust the tailgate lock. The adjustment of the manual locking of the tailgate is carried out if there is a gap along the plane of the fit of the side over 6 mm.

The repair of the platform, as a rule, is carried out by welding if the floor or sides are damaged by the cargo.

The damaged places are straightened, and if necessary, welded with the additional installation of reinforcing plates. Reinforcing plates are welded with continuous seams.

Platform lifting mechanism

The dump semi-trailer works together with the MAZ-504G truck tractor, on which special hydraulic equipment is installed, designed to lift the platform of the transported dump truck semi-trailer and driven by the engine (Fig. 5).

The platform lifting mechanism provides lifting of the platform to an angle of 45°, lowering it, stopping in any intermediate position, automatic limiting of the lifting angle, shaking the platform at the end of lifting for better dumping of the load.

In addition, automatic opening and closing of the tailgate of the platform is provided.

The platform lifting mechanism is controlled remotely, pneumatically, carried out from the driver's cab using an air distribution valve.

Pneumatic remote control of the platform lift mechanism and tailgate locks facilitates the driver's work and reduces unloading time.

Hydraulic cylinder MAZ-5232V

The hydraulic cylinder is used to lift the platform. It consists of a fixed pipe body 12 (Fig. 6) and five retractable links telescopically placed in it.

The sealing of the sliding links is achieved by rubber O-rings 10 placed in the grooves of the guide sleeves 9.

The guide sleeves themselves are sealed in the pipes with the same rings 11. From the ingress of dirt and dust from the outside, the sealing rings of the moving links are protected by dirt-removing rubber rings 8.

The direction of the retractable links and the limitation of their travel is achieved with the help of the upper guide sleeves, fixed with locking rings, and the guide half rings 15, which are laid in the moving links located in the lower part.

From below, the cylinder body is closed by a bottom 14 sealed with a rubber ring 13.

The upper support of the cylinder (in the platform) is made in the form of a ball joint.

The ball pin 4 is fixed in the inner retractable tube with the help of a retaining ring 6 and at the same time to the spherical foot 5 of the platform with a nut 3, which is locked with a retaining ring 2.

A similar swivel connects the lower end of the cylinder to the knurling plate.

The articulated fastening of the cylinder to the reel plate and platform relieves all cylinder links from the effects of transverse loads that occur when the platform is skewed.

Oil is supplied to the cylinder through a hole in the lower part of the fixed pipe, closed with plug 17.

The ball joints of the upper and lower cylinder bearings are lubricated through grease fittings 1.

The platform lift limiting mechanism (Fig. 7) is designed to limit the angle of the platform lift and ensure that it shakes at the end of the lift.

The valve 12 for limiting the platform lift is installed in the hole of the cross member and fastened with a bolt 14.

By means of a rod 4 connected to a hinged lever 6, as the platform rises, the tip 7 moves to the right by a gap of 3.0-3.5 mm between the nut 11 and the end to platform lift valve covers (Fig. 8).

When the platform is raised to the set angle, the lever 6 (Fig. 7) acts on the tip 7, which moves the stem 9 (see Fig. 8) of the valve. In this case, the stem rests against valve 5 and tears it away from the socket.

Air under pressure from cavity "A" rushes into cavity "B" and then enters the pneumatic chamber of the control valve installed on the tractor.

At the same time, the discharge line of the platform lifting mechanism is connected to the drain line, and the platform, displacing oil from the cylinder, goes down at a certain angle until the valve 5 is pressed against the seat under the action of the spring 4, and the stem 9 returns to its original position spring force 6.

MAZ-5232V platform lift limiter

The air from the pneumatic chamber of the control valve escapes into the atmosphere through the hole "B" in the stem 9 of the valve, after which the platform begins to rise and the cycle repeats.

Alternately opening and closing the valve ensures that the platform shakes at the end of the lift, which greatly facilitates the dumping of the load.

The tailgate locking mechanism (Fig. 9) is designed to automatically open the tailgate when the platform is lifted and lock it in the transport position.

The mechanism drive is pneumatic with an automatic valve for controlling the side locking mechanism, which directs air into the side locking pneumatic cylinder.

The trunnions 2 of the side are held by two grippers 1 located on both sides of the platform. The grips 1 are connected by rods 15 with levers 11 rigidly fixed on a common shaft 12.

Each of the rods consists of two components connected to each other on the thread in such a way that the total length of the rod can be changed.

When the shaft 12 is rotated at a certain angle in one direction or another, the grippers 1 clamp or release the trunnions 2 of the tailgate.

The shaft 12 is driven by a double-acting oscillating pneumatic cylinder 10.

The covers and the cylinder body are tightened with four studs.

The piston and rod are sealed with rubber o-rings.

The cylinder is hinged with a pin 9 to the cross member 8 of the platform, and its rod is connected with a fork 6 by means of a pin 5 with a lever 4 fixed rigidly on the shaft 12 in its middle part.

MAZ-5232V platform lift limit valve

Air is supplied to the pneumatic cylinder through the holes in the covers through air ducts connected to the automatic valve for controlling the side locking mechanism.

When air is supplied to the cavity "A" (Fig. 5) of the cylinder, the piston will move to the right, turn the shaft 12 by means of lever 4 (see Fig. 9). will be released.

When air is supplied to cavity “B” (see Fig. 5) (in this case, cavity “A” is connected to the atmosphere through a valve), the movement of all links of the mechanism will occur in the opposite direction and the grippers, turning clockwise, will clamp the bead pins .

When the semi-trailer is moving, the cavity "B" of the cylinder is under air pressure and thus the piston is forcibly held in the position corresponding to the closed board.

Even in the absence of air pressure, spontaneous opening of the side is excluded, since the rods 15 (see Fig. 10) with the position of the links of the mechanism corresponding to the closed side, are located above the axis of the shaft 12 (pass through the dead center), which prevents the rotation of this shaft clockwise.

To be able to control the side grabs in case of any malfunction of the pneumatic drive, a handle 13 is installed on the shaft 12 on the left side of the semi-trailer, with which the driver can open or close the side.

The end of the handle in the closed position of the board rests against the rear buttress of the side board, which allows you to unload the pneumatic cylinder from the loads that appear when the load is applied to the tailgate.

The bead locking mechanism is automatically controlled by valve 5 (see Fig. 5).

Air from the semi-trailer air tank is supplied to the valve through the hole in the bottom cover 1 (Fig. 10) of the valve.

When the platform is raised, the traction frame hook acts on the lever 6 of the valve installed on the platform cross member, which, turning around the axis, presses on the pusher

Down, the pusher presses the rubber valve 12 from the socket.

Air rushes from the lower cavity into the space between the pusher and the drilling in the body and through the hole 1 in the body through the pipeline is supplied to the side locking pneumatic cylinder.

When lowering the platform, the hook of the traction frame acts on lever 6, which, turning around the axis, presses on the other pusher.

Process It occurs in the same way as described, but air is supplied to another cavity of the cylinder.

The air pushed out of the cylinder is released into the atmosphere through a hole in the pusher.

The safety stop of the platform is located on the right side of the semi-trailer.

To install the stop, it is necessary to raise the platform at an angle of 20 - 25˚, then remove the stop and insert the end with the pin into the cross member of the platform between the ribs.

MAZ-5232В tailgate locking mechanism

The guide tube should be lowered into the reel plate bracket seat, then the platform should be lowered to the stop.

It is forbidden to use the stop when the platform is loaded.

Maintenance. During operation, it is necessary to systematically control the attachment of the hydraulic cylinder to the frame and to the platform, monitor the tightness of its seals and regularly lubricate the ball joints of its upper and lower supports through oilers.

It is recommended to check the fastening of the cylinder at TO -1. In this case, it is necessary to check the reliability of the locking of the nuts of the upper and lower supports of the cylinder.

After a long period of operation, slight oil smudges may appear on the surfaces of the sliding links of the hydraulic cylinder, which are the result of scraping off the oil film by the sealing rings.

They should be removed with a clean, dry cloth. Abundant oil leaks indicate wear on the O-rings.

In this case, the sealing rings must be replaced, since the presence of oil on the working surfaces of the cylinder links leads to contamination and, consequently, to accelerated wear of the parts.

Automatic valve for controlling the side lock mechanism MAZ-5232V

Under normal operating conditions, the service life of sealing rings corresponds to 80-100 thousand km of semi-trailer run, however, with a significant overload of the semi-trailer and when using contaminated oil, the service life of the rings is sharply reduced.

Frequent replacement of the O-rings on the hydraulic cylinder extenders under normal operating conditions indicates wear and the need to replace the upper guide sleeves.

In order to avoid breakage of the lower guide half rings of the cylinder links, it is necessary to avoid lowering an unloaded or even partially unloaded platform, since when the platform is lowered rapidly, the guide half rings are subjected to sharp shock loads.

For the normal operation of the hydraulic cylinder, a correctly set limit of the maximum platform angle is of great importance, which is achieved by adjusting the mechanism for limiting the platform angle.

A properly adjusted mechanism should not allow the platform to rise more than 45°.

At such an angle of elevation of the platform, the stroke of the cylinder is somewhat less than the maximum possible and, as a result, the cylinder does not work by surprise.

Maintenance of the tailgate locking mechanism is reduced to systematic monitoring of the tightness of the connections, pipelines and hoses supplying air to the cylinder, the tightness of the cylinder itself, and periodic checking of the adjustment of the mechanism.

Significant air leaks through air line connections, pneumatic cylinder cover seals and its stem are usually determined by ear.

Minor air leaks can be detected with a soap solution. The tightness of the system should be checked at TO-1.

It is recommended to adjust the mechanism only if necessary, when a malfunction of its operation is noticed.

Adjustment of the tailgate locking mechanism consists in the correct selection of the length of the rods 15 (see Fig. 9) and the length of the pneumatic cylinder rod 10.

The length of the rod 15 is changed by moving the nuts 14 along the thread of the rod. The length of the rod is changed by screwing or screwing the fork 6 onto the cylinder rod.

It is recommended to adjust the bead locking mechanism in the following order:

  • - bleed air from the tractor pneumatic system, unpin and remove pin 5 that fastens the cylinder rod to lever 4 and push the cylinder rod until the piston stops in the bottom cover;
  • - pressing the handle with the free end to the buttress, bring the length of the left rod 15 by turning the nuts 14 to a value that ensures a reliable clamping of the bead trunnion between the bracket 3 and the grip 1.

Also adjust the length of the right gripper rod;

- check the operation of the bead lock mechanism manually. To do this, open and close the locks 2-3 times with handle 13.

If the force required to move the link through the dead center is too great, the length of the rods should be increased. Tighten nuts 14;

  • - extend the cylinder rod by 5 mm, loosen the nut 7 and rotate the fork in the required direction to bring the holes of the fork until aligned with the hole in the lever 4, while firmly pressed against the bracket at the end of the handle;
  • - insert and cotter pin 5. Lock nut 7;
  • - start the engine, bring the pressure in the pneumatic system to 4 kgf / cm 2 and raise and lower the empty platform several times, checking the operation of the side locking mechanism.

A properly adjusted locking mechanism should ensure reliable clamping of the trunnions by the grips, the absence of spontaneous opening of the side and the gripping of the grips by the trunnions of the side when it is opened and closed during the lifting and lowering of the platform.

Opening and closing of the tailgate should take place at a platform lift angle of 10 - 15˚.

If this happens at a greater or lesser platform elevation angle, it is necessary to move the automatic valve for controlling the bead locking mechanism in the slots of the bracket so that at a platform elevation angle of 10-15 ° valve lever 6 (see Fig. 7) can come into contact with hook on the cross member of the traction frame, and thereby open the access of air to the pneumatic cylinder of the bead locking mechanism.

Adjusting the platform lift limit mechanism. With the platform lift properly adjusted, the platform lift limit valve should operate at a platform lift angle of 45°.

In this case, the last retractable tube of the cylinder should extend 250-300 mm and the platform should be automatically shaken.

If, with the platform fully raised, the last pipe protrudes more than 300 or less than 250 mm; it is necessary to carry out the adjustment in the following sequence:

  • -raise the platform with a lifting mechanism and set the safety stop;
  • - make sure that the distance from the end of the valve cover to the end of the nut 11 (see Fig. 7) is 3-3.5 mm and, if necessary, adjust the value of this dimension with the nut 11 and tighten the lock nut 10;
  • - by changing the working length of the rod 4 with the help of nuts 2 and 3, achieve such a position that the valve is activated when the last cylinder pipe is extended by 250-300 mm. With an increase in the working length of the rod 4 (when loosening the nuts), the lifting angle of the platform increases, and with a decrease in the length of the rod, it decreases. After completing the adjustment, tighten the lock nut 3.


To remove the hydraulic cylinder, you must:

  • - raise the platform using a lifting mechanism or an external lifting device, securely lock it with a safety stop and drain the oil from the system;
  • - remove the circlip of the nut of the upper cylinder support, unscrew the nut, disconnect the discharge line hose from the cylinder, remove the circlip of the nut of the lower cylinder support and unscrew the nut;
  • - remove the cylinder from the semi-trailer.

The sequence for disassembling the hydraulic cylinder is as follows:

  • - unscrew the bottom of the cylinder body, remove the sealing ring from the bottom, push each retractable link down from the body in sequence from the link of the smallest diameter to the largest. From each extracted link, remove the guide half rings;
  • - from the cylinder body, as well as from the first, second, third and fourth retractable links, remove the retaining rings for fastening the upper guide sleeves, and then the guide sleeves themselves;
  • - remove the outer and inner sealing rings and wiper rings from the grooves of the guide sleeves.

Rinse all parts of the cylinder and carefully inspect. Replace worn parts. The most worn parts of a hydraulic cylinder are the moving link O-rings and wiper rings.

If the tightness of the cylinder sealing rings before disassembly was insufficient, the rings should be replaced.

Carefully inspect the guide half rings.

If there are chips or cracks on them, which could appear as a result of lowering a loaded platform, the half-rings must be replaced.

After a long operation of the hydraulic cylinder (after approximately 80 - 100 thousand platform lifts), it may be necessary to replace the upper guide sleeves, which is usually indicated by increased clearances between the guide and the corresponding link, which cause accelerated wear of the sealing rings.

The hydraulic cylinder is assembled in the reverse order of disassembly.

This requires:

  • - thoroughly rinse all parts of the hydraulic cylinder, blow with compressed air, lubricate the sealing rings and the inner surface of the guide sleeves with grease before assembly;
  • - assemble the hydraulic cylinder carefully, being careful not to damage the sealing rings.

After assembly, the cylinder must be checked for smooth running and tightness. To do this, oil is brought to the cylinder until it is completely expanded and then the pressure is brought to 50 kgf / cm2.

A properly assembled cylinder should, under the influence of the oil pumped into it, move apart smoothly, without markets kov, and upon reaching the full stroke must withstand without leakage an oil pressure of 150 kgf / cm2 for 5 minutes.

Install the cylinder on the semi-trailer in the reverse order of removal.

After installing the cylinder, carefully lock the nuts of the upper and lower supports with a retaining ring.

Possible malfunctions of the hydraulic cylinder and how to eliminate them

Cause of malfunction - Remedy

  • The extension of the cylinder links occurs out of sequence, the links are extended jerkily, the platform does not completely lower

Jamming of sliding links of the cylinder - Disassemble the cylinder, eliminate the causes of jamming

  • Excessive oil leakage through the sliding link seals

Damage or wear of link O-rings or guide sleeves - Replace O-rings

  • Oil leaking from the bottom of the cylinder

Damage of the sealing ring of the bottom of the cylinder - Replace the sealing ring