For a long time, crawler bulldozers were considered one of the most difficult types of earthmoving equipment to manage. However, in recent years, thanks to the introduction of a number of new technologies, it has become much easier to manage them, and the bulldozers themselves are acquiring more and more versatile, versatile capabilities.
One of the main reasons for this, of course, can be considered the increasingly popular hydrostatic transmission (HST). Some experts even call the ongoing changes a “hydrostatic revolution”.
Let’s start with some statistics. Over the past 10 years, the proportion of bulldozers with a hydrostatic transmission type (at least among machines with a power of up to 130 hp) has constantly grown. According to the World Construction Equipment Directory, hydrostatic bulldozers currently dominate the market.
Such changes in the ratio are by no means accidental: freed from the gearbox, bulldozers have become more versatile machines with a wide range of action.
Companies – manufacturers of earth-moving equipment at different rates were moving towards the recognition of the feasibility of using hydrostatic transmission.
So, despite the fact that Caterpillar Corporation has been considered the world leader in the production of crawler bulldozers for more than 100 years, another American company, John Deere, became the initiator of the “hydrostatic revolution”. It was its developers who, back in 1976, created the first two-disc bulldozer with a hydrostatic transmission.
Among domestic manufacturers of dozers, there is an enterprise specializing in the creation of equipment exclusively using hydrostatic transmission. The Chelyabinsk plant ” DST-URAL ” switched to the GTS. Every year the designers of the plant improve this scheme and produce world-class bulldozers.
Hydrostatic transmissionused on bulldozers, today it is predominantly common on medium and heavy-duty special equipment: hydrostatic transmission is used by all leaders in the excavator equipment market.
The use of HTS in excavators is associated with the performance of their main work by actuators with hydraulic force transfer. The spread of HTS was also facilitated by the improvement of machining technologies and the widespread use of synthetic oils produced for predetermined use parameters, and in addition, the development of microelectronics, which made it possible to implement complex HTS control algorithms.
Hydrostatic transmission is a hydraulic drive with a closed (closed) circuit, which includes one or more hydraulic pumps and hydraulic motors. Designed to transfer the mechanical energy of rotation from the motor shaft to the executive body of the machine, by means of a stepless flow of working fluid regulated in magnitude and direction.
The main advantage of a hydrostatic transmission is the ability to smoothly change the gear ratio over a wide range of rotational speeds, which allows much better use of the machine’s engine torque compared to a stepped drive. Since the output speed can be brought to zero, smooth acceleration from a standstill is possible without the use of the clutch. Low speeds are especially needed for various construction and agricultural machines. Even a significant change in load does not affect the output speed, since there is no slip in this type of transmission.
The great advantage of hydrostatic transmission is the ease of reversing, which is provided by a simple change in the inclination of the plate or hydraulically, by changing the flow of the working fluid.
This allows you to get a gain in reliability, because often, with a heavy load on the car, the cardan shafts do not withstand and you have to repair the car. In northern conditions, this occurs even more often at low temperatures. By simplifying the mechanical wiring, it is also possible to free up space for auxiliary equipment. The use of a hydrostatic transmission can make it possible to completely remove the shafts and bridges, replacing them with a pumping unit and hydraulic motors with gearboxes built directly into the wheels.
Another important advantage of the hydrostatic transmission experts call the ability to select a specific electronic program on the monitor display in the cab of the machine. Depending on the working situation and the schedule of the bulldozer operator, for example, the frequency of breaks, the degree of sensitivity of the levers, the brake pedal and the steering modulation can be adjusted.
Experienced construction machine operators know that among the most difficult jobs for a bulldozer is laying pipes in trenches . And in this case, it is precisely the hydrostatic system that contributes to their safe transport at a controlled speed and precise laying.
Use of electroproportional control and special electronic systems allows to reach the most optimum distribution of power between the drive and executive mechanisms, to limit loading of the engine, to reduce fuel consumption. Engine power is used to the maximum even at the lowest speeds of the car.
allows you to use additional power strictly as needed during a particular maneuver. The use of hydrostatic transmission ensures the stabilization of the engine speed at the optimum level and obtaining tangible fuel savings in conditions of high maneuverability of the bulldozer and continuity of tractive effort. Good traction with the ground and reduced vibration loads are achieved thanks to the oscillating suspension of the guide wheels and track rollers. The optional satellite remote blade tilt system allows you to visualize the progress and degree of completion of the work. All movements of the bulldozer undercarriage are controlled from a single proportional joystick. Hydraulic transmission pumps and motors are maintenance-free and highly reliable; oil change intervals have been significantly extended (up to 8,000 hours), which can significantly reduce operating costs.
This happens due to the fact that at the time of manual gear shifting, you have to release and press the gas pedal.All this negatively affects both speed and fuel consumption. In a hydrostatic transmission, this process is smooth and the engine runs more economically, which increases the durability of the entire system.
Speaking about the benefits of the increasing use of bulldozers equipped with hydrostatic transmission in combination with GPS, experts remind that one of the permanent problems of the industry is the lack of highly qualified bulldozer operators. And in this sense, the current hydrostatic bulldozers are just a gift.
Equipped with state-of-the-art equipment, these machines allow experienced operators to fine-tune them to suit the job ahead. But no less important is the fact that it takes less time for young bulldozer operators under the guidance of mentors to master the once capricious technique.
The choice of HTS with electronic control, taking into account all the advantages described, prompted the DST-URAL plant to develop a fully electronic control system for all other machine systems, which made it easy to implement and implement any machine control programs, get remote access and control parameters, significantly simplify machine control, adapt it to the operator. All this helped to significantly reduce the requirements for the qualification of the bulldozer operator, and now he only needs two joysticks to control the machine: the left one is responsible for all movement, the right one for attachments.
As a result, all the advantages described above allowed DST-URAL equipment to firmly occupy its niche in the road construction market of the CIS, every year the plant increases the production of competitive products and introduces advanced technologies for monitoring and controlling machines.