Re-equipment of the basic chassis of the truck by installing a crane-manipulator installation (CMU) is a complex engineering process that requires deep knowledge in the field of sopromat and hydraulics. Commercial vehicle owners often make the decision to upgrade to expand the functionality of the fleet and perform a wider range of work without the involvement of third-party equipment. However, simply welding the supports to the frame can lead to fatal consequences, including the destruction of the spars and loss of controllability on the go.
Literate manipulator-set It begins long before the crane lifts above the body, even at the design and selection stage of components. The distribution of axle loads must be taken into account so as not to exceed the permissible values specified by the chassis manufacturer. Errors in the calculations of the center of gravity can make the operation of the vehicle dangerous not only for the driver, but also for other road users.
In this article, we will discuss in detail all stages of conversion, from the selection of the installation site to the final run-in of the hydraulic system. You will learn about the nuances of strengthening the frame, the correct connection of the pumping group and the legal subtleties of registering changes in the design of the vehicle. Understanding these processes will avoid costly errors and ensure a long service life for both the installation and the vehicle.
Selection of installation site and calculation of loads
The first and most critical step is to determine the mounting point of the crane installation relative to the cabin and the rear axle. Most often, CMUs are installed immediately behind the cabin, which provides better access to the cargo platform, but shifts the center of gravity forward. An alternative is the installation in the rear of the frame, which requires the use of longer retractable supports to compensate for the lever.
When designing, it is necessary to conduct a thorough calculation of loads on each axle of the car in different positions of the boom. Axial loads shall not exceed the maximum permissible values specified in the chassis manufacturer's documentation. Excessive load on the front axle worsens handling and increases tire wear, and overloading the rear axle leads to the destruction of the suspension and frame.
It is important to take into account not only the static mass of the manipulator itself, but also the dynamic loads that arise during operation. At the time of the lift off the load or a sharp turn of the arrow, inertial forces arise, which can be several times higher than the static weight. That is why calculations should be carried out with a margin of safety, taking into account the real conditions of operation.
For accurate positioning, the method of weighing the car on a hornet scale is often used with the imitation of various loading scenarios. This allows empirically confirming theoretical calculations and adjusting the place of installation of the supporting elements. Ignoring this stage often results in the car being undocumented or safely operated.
Frame reinforcement and installation of support elements
The standard frame of a truck is rarely designed for the concentration of loads that a working manipulator creates. Point pressure from the legs of outrigers and the weight of the crane in statics require mandatory frame-up. The most common method is to install sparse linings that distribute the load over a larger area of metal.
The process of strengthening involves welding additional profiles or the imposition of reinforcing plates with a thickness comparable to the thickness of the sparseron. Welds must be made in compliance with technology, often using cutting edges and multilayered surfaces to avoid cracking in the areas of thermal influence. The quality of welded joints directly affects the safety of the entire structure.
⚠️ Attention: It is strictly forbidden to weld the arms of the manipulator directly to the spanger without switchboards or additional amplifiers. This will cause the frame metal to break locally under load.
After installation of reinforcing elements it is necessary to conduct a defectoscopy of welded seams to identify hidden defects. Any microcrack in the high voltage zone can become a source of destruction of the entire load-bearing structure in the future. Professional approach to welding is the foundation of reliability of the converted car.
Use steel of the same brand as the original spars to reinforce the frame to avoid galvanic corrosion and weldability problems.
Hydraulic system and connection of the pumping group
The heart of any crane installation is a hydraulic system that ensures the movement of the boom, the rotation of the column and the work of outriggers. To power hydraulic motors and hydraulic cylinders, a pump group is used, which is most often driven from the power take-off box (COM) of the car's engine or through the drive shaft. The right choice and hydraulics determine the performance and smoothness of the manipulator.
When assembling a hydraulic system, it is critical to keep clean, as even microscopic dirt particles can disable expensive hydraulic equipment. Pipelines shall be laid in such a way as to prevent rubbing, bends and exposure to high temperatures from the exhaust system. For the connection of elements, it is recommended to use high pressure hoses (HVD) with a margin of working pressure.
| Component | Function | Installation requirements |
|---|---|---|
| hydropump | Creating fluid flow | Hard coupling with COM, eliminating vibrations |
| Distributor | Direction of flows | Access to maintenance, protection against dirt |
| Hydrobuck | Storage and cooling of oil | Installation above the support pump, presence of a sapoon |
| RVD (Shlanges) | Transportation of oil | Protection against mechanical damage, reserve length |
Particular attention should be paid to the filtration and cooling system of hydraulic oil. The operation of the manipulator in intensive mode leads to heating of the liquid, which reduces its viscosity and lubricating properties. Installation of the oil cooler allows you to maintain the operating temperature within optimal limits and prevents premature wear of seals.
Why is oil foaming in hydraulics?
The foam in the hydraulic tank usually indicates air sucking through leaky joints on the suction line of the pump or a low level of liquid. Also, the reason may be the use of oil of the wrong brand or mixing different types of liquids.
Electrical equipment and control system
Modern manipulators are controlled by electrohydraulic proportional valves, requiring reliable power supply and a high-quality signal line. Management system includes an operator remote (often radio controlled), logic unit, position sensors and end switches. Errors in the installation of the electrician can lead to a failure of the security system or spontaneous movement of the boom.
Laying wire harnesses should be carried out in corrugated pipes or metal hose to protect against moisture, oil and mechanical damage. All connections must be made using moisture-proof connectors that comply with the IP67 standard or higher. Reliable contact and lack of oxidation are the key to stable electronics operation in conditions of vibration and temperature changes.
An important element is the installation of load limiters (CRPs), which automatically block dangerous operations. These sensors must be properly calibrated and connected to the control system so that the operator receives timely overload warnings. Ignoring the operation of security systems is unacceptable when operating lifting equipment.
☑️ Electrical checks
Legal aspects and registration in the traffic police
Installation of the CMU on a truck is a change in the design of the vehicle, which requires a mandatory registration procedure in accordance with the technical regulations of the Customs Union. The owner must obtain a preliminary opinion on the possibility of making changes in the accredited testing laboratory. Without this document, any conversion work is considered illegal.
After the installation work, it is necessary to undergo a technical examination, which will confirm the compliance of the installed installation with safety requirements. On the basis of a positive conclusion of the laboratory and the diagnostic card, the car is inspected at the traffic police, where a mark is made in the CTS and PTS. Only then can the vehicle legally be used on public roads.
⚠️ Note: Operation of a car with an installed, but unregistered manipulator threatens a large fine and putting the vehicle on the parking lot. Traffic police officers check the compliance of the design with the data in the documents.
The registration process can take anywhere from a few weeks to several months, depending on the workload of laboratories and certification bodies. Pre-prepared package of documents, including certificates for the CMU and the act of work performed, significantly speeds up the procedure. It is recommended to trust the design of specialized organizations with experience in the conversion of commercial vehicles.
Running-in and maintenance of the KMU
After the installation and registration is completed, the run-in stage begins, during which the work of all nodes under load is checked. First launch shall be carried out at idle speed to remove air from the hydraulic system and to check the leakproofness of the joints. Gradual increase in load allows to reveal hidden defects of installation or production of components.
Regular maintenance is a key factor in the durability of the manipulator. It includes monitoring the level and quality of hydraulic oil, lubrication of rubbing vapors (fingers, bushings, hinges) and visual inspection of metal structures for cracks. The frequency of maintenance is determined by the manufacturer's regulations, but at least once a month during intensive operation.
Particular attention should be paid to the condition of the retractable supports and their anchorages, as they experience maximum loads. Any backlashes in the connections should be eliminated immediately, as they lead to accelerated wear and reduced crane stability. Timely replacement of worn seals will prevent oil leakage and pollution of the environment.
Regular lubrication of hinge joints and replacement of hydraulic system filters increase the life of the manipulator by 40-50% and prevent expensive breakdowns.
Maintenance logs help to track repair history and plan replacement resources. This is especially important for commercial vehicles, where simple machinery leads to direct financial losses. Professional approach to maintenance ensures the readiness of the equipment to work at any time.
Can I install a manipulator in the garage?
Theoretically, this is possible with welding equipment, lifting mechanisms and deep knowledge of hydraulics. However, legally to issue such an installation without certificates from a specialized organization will be extremely difficult or impossible. In addition, errors in the calculation of the strength of the frame can lead to emergency situations.
How often should a manipulator be examined?
A full technical inspection of the lifting mechanism is carried out at least once every 12 months. In addition, there is the concept of a partial survey, which can be carried out more often depending on the intensity of use and working conditions.
Does the CMU installation affect the car warranty?
Yes, making design changes, such as welding the frame and connecting to the COM, almost always leads to a loss of warranty on the affected units and assemblies. If the car is new, it is recommended to consult the dealer before starting work.
What type of hydraulic oil is best to use?
It is necessary to use the oil of the viscosity and grades recommended by the manufacturer of the hydraulic pump and the entire system. Usually these are special hydraulic oils with anti-wear additives. Mixing oils of different brands and types is not recommended.