Two-axle semi-trailer (fig. 1) for general purposes, with a carrying capacity of 20 tons, with an open platform, with metal folding side and rear walls

In order to protect cargo from atmospheric precipitation, an awning with a frame is installed. The semi-trailer is designed for operation on roads of categories I and II.

Diameter of the kingpin is 50.8 mm.

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

General view of MAZ-5205A semi-trailer

The frame of the semi-trailer is welded, it consists of side members, side beams, cross members, a safety buffer and brackets for attaching nodes.

The I-section spars have the best ratio of bending strength to weight, and the use of welded spars compared to rolled spars, while ensuring strength and reducing weight, makes it possible to reduce the cross section in places with less stress.

Based on these considerations, the spars of the MAZ-5205A semi-trailer were made.

The narrowing of the spars in height above the fifth wheel coupling of the tractor is compensated by the rolling plate, which increases the rigidity and strength of the frame section.

In addition, the very place of transition from the narrowed part of the spar to the middle one is reinforced by welding the lining to the lower shelf.

The crossbars above the rolling plate are welded both to the plate and to the side members, thereby eliminating the possibility of plate deflection from the tractor's fifth wheel coupling.

A socket for fastening the kingpin is welded between the crossbars to the reel plate.

The middle crossbars, which serve to connect the spars and ensure uniform distribution of torsional stresses, simultaneously stiffen the walls of the spars and serve to fix the floor.

Cantilevered, stamped crossbars of variable height connect the spars with the side beams of the frame, for which a rolled channel profile is used, with a section of 140x60x6 mm made of steel 09G2.

Brackets are welded to the frame for mounting support devices, suspension, brake and electrical equipment.

A safety buffer and towing eyes are installed at the rear of the frame.

The front cross member of the frame is stamped, channel section, made of a spherical shape to increase the strength of fastening and rigidity of the front side of the platform.

Before narrowing the spars in height, a frame is welded to them for attaching stationary support devices, consisting of a cross member and longitudinal transverse braces.

The brackets for fastening the spare wheel holder are welded to the right side member in the front.

On the side beams, two sockets are welded for installing platform racks, the sides of which are attached to the beams, front and rear crossbars.

The floor of the platform is attached to the beams and cross members of the frame.

Thus, the frame is also the base of the semi-trailer platform.

The main load-bearing parts of the frame are made of low-alloy steel, which ensures good weldability and performance in all climatic zones.

In the middle part of the frame (along the length), the cross member is welded to the spars only to the walls of the latter, which ensures a reliable connection and torsion performance.

In the rear, on the inside of the spars, towing hooks are welded.

The frame of the semi-trailer in the front part is made with connecting dimensions in accordance with GOST 12105-74, i.e. the contour from the axis of the coupling kingpin forward fits into a radius with a size of 1680 mm, and from the kingpin to the supporting devices it goes beyond the radius with a size of 1900 mm, which ensures the adhesion of the MAZ-5205A semi-trailer with all two-axle truck tractors.

The semi-trailer kingpin is pressed into the socket and secured with a slotted nut with a cotter pin. The diameter of the kingpin for the grips of the tractor's fifth wheel is 50.8 mm.

Maintenance and repair of the frame is similar to maintenance and repair of the frame of the MAZ-5245 semi-trailer.

Spring and balance suspension MAZ-5205

Suspension device

In connection with the increase in the speed of main road trains and a significant increase in carrying capacity, the requirements for the suspension of semi-trailers have increased.

An important role is played by the smoothness of the ride, provided by the suspension for the safety of the transported goods at various degrees of loading.

The specified requirements are met by a four-spring balancing suspension mounted on two-axle semi-trailers (Fig. 2).

The use of asymmetric semi-elliptical springs 1 with sliding ends, which allow the most uniform change in suspension stiffness depending on the degree of loading and road surface irregularities, required the introduction of torque rods 14, 29 to transfer pushing forces to the wheels and braking torques from them to the frame.

the uniformity of the load on the axle is ensured by an equal-arm balancer 26, which includes the short ends of the springs.

When loading a semi-trailer to the maximum allowable overall height, transverse stability is achieved by installing rubber buffers 8 above each spring and stabilizer 2.

The spring bracket and balancer brackets are stamp-welded, welded to the lower shelf of the side members.

The ends of the springs slide between the replaceable liners 17, 20, 27 and the bushings 19, in the brackets and the balancer 26, while to prevent slipping of the springs, the third root sheet is bent at the ends.

Replaceable liners are made of steel St. 3, and are designed to protect the side cheeks of the brackets and balancers from abrasion and reduce wear on the upper main leaf of the springs.

The springs are mounted on cushions welded to the axles, and fastening is carried out using two ladders 32 through the upper linings 21, 33 of the springs and the lower linings 22 and 35.

Reaction rods are attached to the lower linings and brackets of the balancer and springs by means of pin 10, nuts and cotter pins.

In addition to transmitting pushing forces, torque rods are designed to adjust the position of the wheel axles relative to the longitudinal axis of the semi-trailer, for which one of the rods on each axle is adjustable.

The complex kinematics of the movement of the torque rods during the operation of the suspension is provided by spherical spherical bearings 16 (ШС-50), pressed into the heads of the torque rods and fixed by locking rings 15.

The horizontal movement of the rod head on the axis is limited by bushings 11. Seals 13, fixed by spring rings 12, protect the bearings from contamination.

The rubbing parts of the reaction rods are lubricated through grease fittings 9 on the mounting axes.

The equal-arm balancer 26 is stamped, welded, is hinged to the bracket on the axis 23 and freely rotates in bronze bushings 25.

To avoid abrasion of the cheeks of the bracket, gaskets 24 are installed on both sides of the balancer.

The lubrication of the bushings and the axis of the balancer is carried out through the grease fitting 22 installed on the axis.

The axis of the balancer is fixed with nuts 6 and lock washer 7, while the balancer must turn by hand.

Stabilizer 2 is installed to increase the lateral stability of the semi-trailer when cornering and changing lanes.

The stabilizer is a shaft with curved ends, which is attached to the upper linings of 33 rear springs by means of pins 3.

It is attached to the semi-trailer frame through levers 4 with cover 34 in rubber-metal bushings 5.

When the left and right sides of the suspension travel at the same time and the same, the stabilizer rotates in the levers and does not affect the operation of the suspension.

With a difference in the strokes of the right and left sides, the end of the stabilizer is twisted relative to the middle part of the shaft, which increases the stiffness of the suspension and reduces the amount of spring travel and, accordingly, the transverse roll of the semi-trailer.

At the same time as the stabilizer, the rubber stops of the spring travel 8 (buffers) have a significant effect on increasing the transverse stability of the semi-trailer.

With increasing loads on the spring, when the semi-trailer rolls or when driving uphill, the rubber buffer reduces the active length of the spring, thereby increasing its rigidity.

The greatest efficiency of the stabilizer and spring buffer is manifested when transporting goods with a high center of gravity.

Suspension maintenance consists in checking the tightening of all threaded connections.

In order to prevent shearing of the center bolt of the springs, it is necessary to periodically tighten the nuts 31 of the ladders, providing a tightening torque of 60-65 kgcm, while the semi-trailer must be fully loaded.

This requirement must also be met in order to reduce tire wear, which increases when the axles are misaligned.

The loosening of the fastening of the ladders also leads to an increase in dynamic loads on the bearings 16 of the torque rods 14, 29, to premature wear of the seating surfaces and the destruction of the bearings.

Loosening the nuts of the bolts that fix the position of the torque rod 29 in heads 28 and 30 can also lead to a change in the position of the axles.

Squeaking in the springs indicates a lack of lubrication between the sheets, which increases the interleaf friction and increases the wear of the sheets.

To avoid creaking in the springs during maintenance, the sheets should be covered with a thin layer of lubricant at the points of contact with each other.

The pins and axles of fastening parts of the suspension are subject to wear during operation, which can lead to dynamic shocks in the joints and to their premature failure.

To increase the durability of the joints, it is necessary to regularly change the lubricant, especially in the axes of the balancers and the fastening pins of the torque rods, and tighten until the axial play is eliminated.

Basic the reason for the breakage of the leaf springs is the overload of the semi-trailer.

It must be remembered that a broken leaf spring does not work and thereby increases the load on the remaining sheets, which can lead to breakage of the entire spring.

It is especially dangerous to break the root sheets, through which there is a direct connection with the frame.

Untimely replacement of broken main sheets can lead to axle rotation during movement and to an accident.


For the convenience of disassembling the suspension, it is advisable to place goats under the frame of the semi-trailer, having previously unloaded the springs from the own weight of the frame, for which purpose raise the front part of the semi-trailer with support devices, and the rear part with a jack (from the tractor kit) under the rear buffer.

To remove and disassemble the spring, you must:

  • - unscrew the nuts of the coupling bolts 18 (see Fig. 2) in the balancer, remove the bolts and bushings 19;
  • - unscrew the nuts 31 of the ladders, remove the ladders, the upper linings 21 and 33 of the spring;
  • - unscrew the nuts of the center bolt and clamp bolts, remove the bolts and bushings.

During operation, the spring may have: breakage and cracks of sheets, shearing of the center bolt, breakage and cracks of clamps, wear of the ends of the upper root sheet, wear from the ends of mating sheets, cracks in stepladders or shearing of threads, shearing of coupling bolts in brackets and balancer .

Spring sheets that are cracked or gouged by more than 1 mm should be discarded and may be converted to shorter sheets if possible.

When the end of the upper root sheet is worn more than 60% of its original thickness, the sheet should be replaced or interchanged with the second root sheet.

Sheets with residual deformation (sagging) are straightened to their original size.

Broken center bolts and clamps, as well as spring ladders that have cracks and sheared threads, must be replaced. Cracks in the clamps can be welded with subsequent cleaning flush with the main surface.

To remove the balancer, unscrew the nuts 6 (see Fig. 2) fastening the axles of the balancers, knock out the axle 23, shine the gaskets 24 and the balancer 26.

After disassembly, the bronze bushings of the balancers must be cleaned of grease and cleaned with emery cloth.

The working diameter of the sleeve is 90 + 0.14 mm (it is allowed to use sleeves without repair with a diameter of 90.2 mm). Clean the axis of the balancer from rust and enveloping bronze.

The top and side wear pads in the spring brackets and balancer must be replaced as they wear.

In case of untimely replacement, the walls of the bracket and balancer wear out. Permissible wear of the walls in thickness is not more than 2 mm.

In case of greater wear, the brackets and the balancer must be replaced or can be corrected by welding metal, followed by cleaning to the main plane.

To remove the stabilizer you need:

  • - unscrew the bolts securing the covers 34 to the levers 4, remove the covers and rubber-metal bushings;
  • - unpin and unscrew the nuts of the pins 3 fastening the levers 4 to the brackets on the frame, remove the levers by knocking out the pins 4;
  • - unpin and unscrew the nuts of the stabilizer shaft fastening pins 2 to the upper linings 33, remove the stabilizer shaft.

To remove and disassemble torque rods, you must:

  • - unpin and unscrew the nuts of the pins 10 fastening torque rods 14 and 29, knock out the fingers without damaging the threads, remove the torque rods;
  • - remove the retaining ring 15 of the spherical bearing and press out the bearing 16. This operation is recommended only if the bearing is damaged;
  • - unscrew the heads 28 and 30 of the adjustable rods 29, releasing the tie bolts.

The rubber buffer 8 is removed and replaced when it is delaminated or worn.

Suspension assembly is performed in reverse order. Before assembly, all parts must be washed in kerosene and blown with compressed air or wiped and lubricated with mating parts. Rubber bushings are not lubricated.

When assembling, it is necessary to carefully fix all the parts.

Tighten the nuts of the stepladders of the springs with the springs straightened, providing a tightening torque of 60-65 kgcm, and the nuts of the axles and pins - until the axial play is eliminated. The stabilizer shaft is installed with cut corners on the heads down.

After assembling the suspension, it is necessary to adjust the position of the axles of the wheels relative to the longitudinal axis of the semi-trailer, for which:

  • - place the semi-trailer on a flat horizontal platform;
  • - find and mark on the site the position of the center of the kingpin by means of a plumb line;
  • - mark on the front part of the beam of the first axle the left and right points, remote from the caliper flanges at a distance of 20 ± 1 mm, measure the distance from the found center of the king pin to the marked points. The size difference should not exceed 2 mm;
  • - set the second axis parallel to the first by measuring the distances between them and adjust the position of the axes with adjustable torque rods 29, releasing the coupling bolts of the heads 28 and 80.

A full turn of the rod lengthens or shortens the torque arm by 3 mm. Tighten the bolts after adjustment.

The specified adjustment must be performed to ensure minimal tire wear during operation and to ensure the alignment of the longitudinal axes of the semi-trailer and the tractor during rectilinear movement.

Axles, hubs, wheels and tires

Axles, hubs, wheels and tires are installed on the semi-trailer, the same as on the MAZ-5245 semi-trailer. Tire pressure 4.3 kgf/cm2

Spare wheel holder

The spare wheel (fig. 3) is attached with the holder 7 to the right side member of the frame. The spare wheel is mounted on the plane of the holder and fastened with bracket 5 and screw 2.

In order to reduce the effort required when installing the spare wheel, it is recommended to use the mounting paddles included in the tractor tool kit.

Reference device

The supporting device (Fig. 4) consists of two screw jacks located in the front of the semi-trailer and interconnected by an intermediate shaft.

The right support device jack (Fig. 5) differs from the left one by the presence of an additional two-speed gearbox, which provides accelerated lifting and lowering of the support device rollers at idle (until the rollers touch the ground), as well as lifting and lowering the semi-trailer.

The uppermost position of the support device stand is limited by the nut 5 of the screw and the shoulder of the screw, and the lowermost position is limited by the limiter 2.

Reference device

To lift a semi-trailer, you need (see Fig. 4):

  • - place the semi-trailer on a horizontal platform, put the handle on the shank of drive shaft 2 and - rotate it clockwise, lowering the rollers of the supporting device until they touch the ground;
  • - put the handle on the shank of the shaft 1 of the cargo gear and, turning it clockwise, raise the semi-trailer. A sharp increase in the force on the handle indicates that the support device post is in the limit position.

Lowering the semi-trailer or setting the support device to its original position is carried out in the reverse order.

Right Pole Jack

Working in direct gear after the rollers are in contact with the ground (regardless of whether the semi-trailer is loaded or not) is not allowed.

In exceptional cases, if it is necessary to uncouple the tractor from the semi-trailer on uneven ground (if, when lowering the support devices, the rollers of the left support device came into contact with the ground, and the right support device did not reach the ground by more than 50 mm), the semi-trailer provides for the possibility of mismatched operation of the support devices.

To lower the rollers of the right support device, it is necessary;

  • - remove pin 6 (see Fig. 4) and, turning the handle, lower the right support device until the rollers touch the ground, then set the pin to its original place and cotter pin;
  • - by rotating the drive shaft 11 with the handle, raise the semi-trailer to the required height.

If the rollers of the right support device are in contact with the ground, and the left one does not reach the ground by more than 50 mm, it is necessary to lower the rollers of the left support device in the following order:

  • - remove pin 6 and, turning the shaft 1 with the handle, raise the right support device by an amount equal to the distance between the ground and the rollers of the left support device, then put the finger 6 in place and cotter;
  • - turning the drive shaft with the handle, lower the supporting device until it touches the ground, and then raise the semi-trailer to the required height.

After coupling the semi-trailer with the tractor, it is necessary to raise the rollers of the supporting devices to the transport position, aligning them as described above. It is not allowed to move the semi-trailer with extended support devices, as well as rolling the semi-trailer on the rollers of the support device.

Maintenance of the support device consists in timely lubrication and checking of bolted connections.

In winter, when parking a semi-trailer without a tractor, it is recommended to place wooden linings under the rollers to prevent freezing and subsequent breakdown of the supporting devices.

Possible malfunctions of the support device and how to eliminate them

  • High force on the drive handle or the shaft does not rotate

Lack of play in the meshing of the gears - Adjust the gap

No play in the thrust bearing due to overtightening of the nuts - Adjust bearing tightness


Support device, usually taken apart to replace worn or damaged parts, and to add or replace lubricant.

To disassemble the support device, you must:

  • - install the semi-trailer with the front part on the gantry, disconnect the supporting devices from the semi-trailer and remove the rollers;
  • - through the hole in the shoe of the rack 6 (see Fig. 5) of the supporting device, unscrew the bolt of the limiter 2, remove the limiter and, turning the drive shaft 11 clockwise, remove the rack 6 from the body 16;
  • - remove the crankcase cover 9 and the bearing caps of the drive shaft 11, remove the drive shaft, after removing the retaining ring;
  • - unscrew the nut of the screw Z of the jack, remove the bevel gear 12 and lightly tapping the hammer from above on the end of the screw to remove it from the housing 16, remove the thrust bearings.

After disassembly, rinse all parts, blow with compressed air, generously lubricate and assemble the support device in reverse order.

After assembly, check the engagement of the gears, adjust with shims if necessary, fill the crankcase cavity with CIATIM-201 grease and close the lid.

Brake system

The semi-trailer is equipped with two brake systems: working and parking. Both systems act on the wheel brake pads.

Pneumatic brake drive diagram

The drive of the brake mechanisms of the working brake system is pneumatic according to a single-wire circuit (Fig. 6), it acts when the brake pedal is pressed in the tractor cab.

Parking brake is mechanical.

The device of the wheel brake mechanism of the MAZ-5205A semi-trailer does not fundamentally differ from the design of the wheel brake mechanisms of the MAZ-8926 trailer.

The difference lies in the increased width of the brake drums and brake linings, a longer expanding fist and a cast caliper mounted on the wheel axle flange.

Oil Moisture Separator

The device of the pneumatic brake drive units and the principle of its operation are the same as those of the MAZ-8926 trailer.

The original unit is a moisture-oil separator (Fig. 7), which performs the function of cleaning the air supplied by the compressor to the pneumatic system of the semi-trailer from oil and water vapors.

The moisture-oil separator is installed in front of the air distribution valve in the supply line.

The impellers 2 of the moisture-oil separator are attached to the body by means of spacer bushings 3 and a coupling bolt 4.

The tap 7 is used to drain the condensate.

Purification of air from oil and moisture vapor in the moisture-oil separator is achieved due to the action of centrifugal forces.

Air through the hole "A" enters tangentially to the inner surface of the housing 1 and, passing through the holes of the impeller 2, acquires a rotational motion.

The centrifugal forces arising from the rotational movement of the air flow and changing the direction of its movement, throw oil and moisture particles to the walls of the housing and onto the surface of the reflector 5.

From these surfaces, moisture and oil drain through the holes in the reflector into the sump 6.

Cleaned air through hole "B" enters the air distribution valve, and then into the air cylinders.

The semi-trailer is equipped with two air cylinders with a volume of 23 and 42 liters, which create a supply of compressed air supplied by the tractor compressor.

The cylinders are attached to the frame with clamps and pads. To remove condensate, there is a tap at the bottom of each cylinder, which should be opened at the end of the working day.

The parking brake drive is similar to the MAZ-8926 trailer drive. The parking brake lever is located on the right side of the semi-trailer.

The parking brake ensures braking of a semi-trailer with a full load in an uncoupled state on a dry paved road on a slope of no more than 20%.

The force on the handle of the parking brake when the semi-trailer is fully braked should not exceed 40 kgf.

Maintenance of the brake system units is the same as for the MAZ-8926 trailer.

Maintenance of the moisture-oil separator consists in periodically disassembling it and washing the parts in gasoline and blowing them with compressed air.

During assembly, pay attention to the correct installation of the impeller 2.

After assembly, it is necessary to check the tightness of the moisture-oil separator under a pressure of 5 - 6 kgf / cm2 air leakage is not allowed.

Repair of the brakes of the MAZ-5205A semi-trailer is similar to the repair of the brakes of the MAZ-8926 trailer.

The following are recommendations for restoring two distinctive parts: the caliper and brake chamber bracket.

The brake caliper is made of 40L cast steel. It is being restored and wear of the hole for the axle of the brake pads and the hole for the bracket of the brake chamber.

When the hole for the axle of the brake pads is worn out to a size of more than 32.1 mm, a repair sleeve is installed.

To do this, the worn hole is drilled to Ø 35.8 mm, the chamfer 1X45 ° is countersinked from the side of attachment to the caliper of the brake shields and the hole is reamed to Ø 36 + 005 mm.

Then, a repair sleeve is pressed into the machined hole, a hole is drilled in the sleeve Ø 8.7 mm through a hole in the caliper for the locking screw of the axle of the brake pads and a thread is cut M10x1 class. 2 in the bushing hole.

The chamfer 1x45° is countersunk in the hole of the bushing on the side of attachment to the caliper of the brake shields and the hole in the bushing is expanded to Ø 32+005 mm.

The holes for the brake chamber bracket, worn out to a size of 56.1 mm, are also restored by installing a repair sleeve.

The worn hole is drilled to Ø 59.8 mm, the chamfer 1X45 ° is countersinked from the side of attachment to the brake shield caliper and the hole is reamed to Ø 60 + 0.05 mm.

A repair sleeve is pressed into the machined hole, a 1 x 45 ° chamfer is countersinked in the sleeve hole from the side of attachment to the brake shield caliper and the hole is expanded to Ø 56 + 006 mm.

When drilling holes for the axle of the brake pads and for the bracket of the brake chamber, the surface of the hole Ø 172 +0.08 mm is taken as the base.

The axes of the holes for the bracket of the brake chamber and for the axle of the brake shoes, as well as the mounting hole Ø 172 + 0.08 mm, must be parallel to each other and perpendicular to the mating surface with the flange of the trailer axle with an accuracy of 0.1 mm over a length of 100 mm.

Brake chamber bracket. The bracket tube is made of steel 35, and the bushings for the support necks of the expander knuckle are made of KMTs-3-1 bronze.

The bracket is restored when the holes in the bushings for the support necks of the expander fist and the holes in the flange for the bolts of fastening to the caliper are worn out, the support flange is bent and the welds are broken.

When the holes in the bushings for the bearing journals of the expanding fist are worn out to a size of more than 38.10 mm, the bushings are replaced.

To do this, the worn bushings are pressed out and new ones are pressed in: one from the side of the socket under the sealing rings flush with the end of the socket and the second flush with the end of the bracket.

Then the bracket is installed in the jig and holes in the bushings up to Ø 38 mm are deployed on a vertical drilling machine.

The runout of the landing surface in the caliper relative to the axis of the surfaces of the holes of the bushings for the support necks of the expanding fist should not exceed 0.1 mm.

When the holes in the support flange for the mounting bolts to the caliper are worn out to a size of more than 15.3 mm, they are drilled out to Ø 17.0 mm, welded with a continuous seam with an UONI-13/45 electrode Ø 3 mm, both surfaces of the support flange are turned until removed weld metal and drill holes Ø 15 mm, having previously marked the centers of the holes according to the template.

The plane of the flange must be perpendicular to the surface of the holes in the bushings for the support necks of the expanding fist with an accuracy of 0.2 mm over a length of 100 mm.

Disturbed welds are restored by welding them in places of violation with an electrode UONI-13/45 Ø 3 mm.

The electrical equipment of the semi-trailer is made according to a single-wire circuit (Fig. 8). There is a seven-pin socket for connection to the tractor on the semi-trailer.

Electrical scheme

Semi-trailer platform (fig. 9) onboard.

Rear and side boards open downwards on hinges, side posts are removable.

The front board is permanently installed. An awning frame and an awning are installed on the platform.

 MAZ-5205 platform

The floor of the platform is wooden, the sides are metal. Awning frame made of tubular profiles with wooden gratings.

The base of the platform is the frame of the semi-trailer, on which the floor cassettes are installed.

The cassettes are assembled from boards 34 mm thick, interconnected into a tongue and groove, enclosed at the ends in a stamped square with a section of 85x29x2 mm.

The boards are attached to the fittings with M6 bolts. Cassettes consist of two parts - right and left, and during assembly are joined along the longitudinal axis of symmetry of the platform.

The outermost floor boards are milled, which ensures installation under the profile of the side beam of the frame.

The cassettes are attached to the frame crossbars through the end fitting with M8 bolts. The floor boards on the frame are located in the longitudinal direction and are attached to the frame crossbars with M8x55 bolts.

The front three boards, machined along the semicircular profile of the front cross member of the frame, are installed across the frame and brought under the front cross member. They are fastened with M8 bolts to the squares on the frame.

To provide access to the semi-trailer's removable kingpin, the front floor cassette has a hatch closed with aastin. The plate is attached to the boards with M6x30 screws.

In the side beam of the frame, the upper shelf of which is in the same plane with the floor boards, there are five holes with welded tubular guides for installing awning frame racks.

The side boards are made up of three parts, each 3070 mm long, metal, welded, and consist of a corrugated panel 1.5 mm thick with a longitudinal arrangement of corrugations.

The rigidity of the board is given by a frame welded from square pipes 40x40x2 with two vertical posts.

Four stamped hinges are welded to the bottom tube of the frame, to which the sides are hung with the help of axes.

An amplifier with windows for installing extensions is welded to the upper tube of the frame.

In front of the windows, brackets are welded to the side panel. The clear size of the window and bracket is 72x34 mm.

At a distance of 410 mm, a plate with arcuate loops is welded to the side panel at a distance of 410 mm from above, through which the platform awning is attached. The distance between the loops does not exceed 200 mm, the size of the loop in the clear is 35x13 mm.

Below the hinges, three stamped hooks are welded to the panel between the uprights for attaching the awning tension cord.

At a distance of 285 mm from the top, brackets with lugs for fastening the 15 locking bracket are welded to the side panel near the extreme racks of the frame.

A pin 14 with a locking bar is attached to the bracket on a chain.

Bracket 15 of the lock, fixed on the rack 18, is inserted between the ears, into which the pin 14 is inserted and fixes the bracket.

The pin is protected from falling out by a locking bar, which rotates with eccentricity on a rivet in the pin groove 14 and under its own weight always tends to take a perpendicular position relative to the pin.

A stamped square is welded to the lower edge of the board, closing the gap between the boards and the frame, preventing moisture from getting inside the platform.

The rear side board differs from the front board in that the bracket of the constipation ladder is welded to the extreme post adjacent to the rear board at a distance of 260 mm from above.

The rear board 1 is structurally different from the side boards with locks, two brackets welded to the upper reinforcement for easy lifting into the body, and a folding support step on the inside of the board.

When the tailgate is open, the step rotates under its own weight around the axis and is installed perpendicular to the sideboard.

Step-ladder-type tailgate lock

Closing occurs due to the tension of the ladder 25, fixed to the bracket on the side board on the axle 24 with nuts.

Nuts not only fasten the ladder, but also adjust it relative to the axis (lengthening or shortening).

The handle 23 of the lock is attached with an axis to the ears of the lock bracket welded to the side post of the tailgate.

Turning the handle perpendicular to the board panel, grab the stepladder 25 of the side board with the curly cutout of the handle and then return the handle 23 to its original position, pressing it firmly against the board panel.

In this case, the axis of the ladder will move beyond the center of the attachment axis and, due to the eccentricity, will ensure reliable locking of the lock.

Additional fixation of the handle 23 in the closed position is carried out by the latch 20, which is fixed in the handle with a pin 21 and is pressed from the handle by a leaf spring 22.

The hinged sides are fastened with fingers to the stamped ears 16 through the loops.

The lug is attached to the frame beams with two bolts, while the position of the lug along the beam can be adjusted using elliptical holes on the beam.

To prevent damage to parts and assemblies of the tractor and semi-trailer, as well as tailgates, rubber stops 19 are bolted on the frame beam and on the rear cross member.

The front semicircular side is similar in design and method of fastening to the front side of the MAZ-5245 semi-trailer.

The side boards are connected to each other and to the front board through the front pillar and middle pillars. The front pillar is attached with M10 bolts to the front wall panel and frame beams.

The post has an omega-shaped unequal section.

One of the shelves is attached to the front board, the second goes over the side board from the inside of the platform.

The middle pillar 18 has an omega-shaped equal-arm section, both shelves of which extend beyond the side walls, closing the gap between the side and the pillar.

The lower part of the B-pillar is sloped so that it fits into the slot on the side beam of the frame.

On the inside, the rack is reinforced with a welded metal strip, creating a box-shaped section in the most stressed places.

Square cutouts are made in the outer corners of the rack, into which the clips 15 of the constipation are inserted. The brackets are attached with a pin 13 to the ears welded to the uprights.

To increase the transverse rigidity of the platform and protect the cargo being transported from displacement in the longitudinal direction, tie chains are installed between the opposite posts 18, fixed to the brackets of the posts on one side with a hook, and on the other - with the same lock as on the semi-trailer MAZ-5245.