Farm tractor safety devices and brake plants

The components sector is able to offer numerous devices, from ROPS to ergonomics and brake plants for the safety of drivers. Especially for brakes, technologies have been developed to keep step with the performance of machines as regards speed and work capabilities

Decause of the type of use and the operational environment, the agricultural tractor can be dangerous, subjected to rolling over and crushing the driver. Without getting into the causes of fatal accidents, it is opportune to consider that simply with the use of tractors equipped with safety devices which have been mandatory by law for years (ROPS), many accidents could be avoided in agriculture for which there is still a correlation between to fatal accidents and the number of operators involved compared to other sectors.

From the point of view of safety and the level of ergonomics, these have been greatly improved over the years in moving from the early tractors of the nineteenth century when, in practice, there were many moving components, mainly the flywheel, and hot parts totally without protection. Since that era, modern tractors are by now equipped with high levels of ergonomics especially designed with consideration for the driver for providing comfort which in many cases is comparable of that in luxury cars.

The first tractors ran on iron wheels, with steel seats sometimes rigid, and these machines were difficult to maneuver because they had no steering wheels. But in little more than one hundred years of building tractors it is now possible to make certain that the operator is comfortably seated in a conditioned environment with components of tires, suspensions designed for tractors along with cabs and seats which dampen vibrations caused by rugged terrain – and for anyone who chooses not to operate the steering wheel, they are now universally equipped with power steering and also the option of buying a machine which, with GPS, steers itself to perform operations which maintaining overlap precision for passage in the field much superior compared to the most expert driver using his own senses.

Again, based on the technologies deployed which allow georeferencing with the assistance of mapping using various parameters to enable operations in the field to be differentiated, many machines with VTR (variable rate technology) can be used for precision farming which, on the basis of choices made, leads to savings of production factors and increased production.

 

Tractor brakes

Also tractor brake plants have made decisive steps to increase the active safety of the farm tractor through great evolution over the years. In fact, in only a few decades there has been a move from very slow machines for which band brakes mounted only on the rear axle were sufficient for type-approved tractors for speeds of up to 30 km/h requiring the installation of powerful oil-bath multi-disk brakes on the rear semi-axles. The following type-approval of 40 km/h required braking on both axles with a double traction insert to transfer braking to the rear axle or equipping both axles with oil-bath disk brakes.

In detail, front axles can be equipped with brakes in a central location which act on the main transmission shaft, before the differential, or peripheral, mounted in this case directly on the lateral reducer box.

The basic work in applying brakes is essential mechanical which are are used for belted specialist tractors with type-approval for maximum speed of 15 km/hr. For this type, the driver works through rigid connecting rods which directly link the brake pedal and the the load device on the disks or friction belt.  The most widespread use of hydraulics works with a piston pump when, when the driver applies the brake pedal, converted to hydraulic pressure through the fluid, wrongly called “brake oil” because the features of density and resistance to low and high temperatures is very different from common oil for lubrication. 

The operation of the hydraulics can be very beneficial in part because it allows applying the braking force to the axles in a very simple way, when the front axle is connected to the brakes. In this case, vacuum servobrakes are appearing also on medium and high power tractors, a common practice in the automotive sector which makes it possible to amplify the force of the driver’s foot on the pedal.

Also medium and low power tractors are now equipped with hydrostatic regenerative brake systems with a hydraulic pump which captures kinetic energy during braking rather than losing it as heat.

Other than the service brake used in driving, tractors are also equipped with a parking brake used to secure the vehicle when parking.

The former is controlled by a floor pedal while the latter is operated manually by the use of a lever or an electrohydraulic control which, on the latest model tractors, operates automatically when the engine is turned off. In addition, there are often air or hydraulic brake systems for towing heavy loads which can reach for or five times the weight of the tractor.

 

Devices for connecting hydraulics

These connectors can be rigid, tubes in metal, or flexible, flexible hoses with rubber coating or, in rare cases, braided metal tubes.  In all cases, connectors should be scrupulously inspected periodically. This is especially called for when metal connectors run under the bottom of the tractor and can come into contact with various types of obstacles to incur damage or crushing or joint seals can be loosened by vibrations to lead to serious safety risks when braking.

Flexible hoses, on the other hand, also require attention for careful visual inspection and an equally careful check of the inside of the hoses. This is difficult to do without dismantling the hoses but can be replaced by an evaluation of maintenance of function to date. Irregular braking is often due to the flexible components which, over time, can be blocked in certain operational locations. In this case, it is a good idea to replace the hose with parts which have the same construction feature and possibly with original spare parts.

The level of fluid in the hydraulic fluid reservoir, usually located over the pump, must also be checked regularly. If the level shows any loss, the inside of the reservoir must be inspected to find the damage causing this loss.

 

The attrition of materials

The attrition of materials has also come through a remarkable evolution, from some basic materials as asbestos, widespread until the close of the 1980s, to components which must ensure the same physical-mechanical performance with lower toxicity for people.

From the seven or eight ingredients used to counter wear based on asbestos there was a sudden move to modern attrition materials made up of more than twenty different components.

 

Further options

There are some countries where it is possible to gain type-approval for tractor speeds of 50, 60 and, in some cases, 65 km/h so at present what is needed is the introduction for agricultural tractors of brake systems similar to those for trucks, that is big outside air-cooled brakes sometimes equipped with ABS. These solutions are becoming mandatory for rigs which travel at high speeds. Correctly so, manufacturers offer these systems as options for those traveling at only 40 km/h but are often towing heavy loads in hilly conditions and need a generous size braking system for braking their own vehicle.

 

Motor brakes

Some tractors are equipped with so-called motor brakes, devices which have been mounted on commercial transport trucks for some time to allow the rig to slow without applying the service brake pedal. These brakes slow or stop the flow of exhaust gas with  the application of a pedal or hand device which controls and closes a butterfly valve to lower the engine rpm. Acting on the control also stops the flow of fuel. This is a control which enables the driver to decelerate without wear on the brakes but works only at high motor rpm.

 

Air brake auxiliary plant

The need to tow increasingly heaver trailers or machinery has led manufacturers to build auxiliary brake systems, air brakes and hydraulic systems. The mixed automatic-air types are generally produced by specialized manufacturers at maximum pressures of 7-8 bar. Their components are a compressor run off a motor by a belt or gears, regulation valves controlling air pressure, a condensation water discharge value, one or two compressed air tanks with capacities of 12-15 liters each, a manometer and a pneumatic clipper distributor.

Widely used in Italy is a combination double coupling pneumatic clipper used on the feed pipe on the left coupling and the control pipe on the right one outside of which is a two-channel component for the yellow coupling to provide air for the trailer and the red coupling to load the tank feeding the brakes. On the other hand, when the trailer plant is equipped with a single-channel component a black coupling is used. These plants also often use an auxiliary clipper to make it possible to inflate tires or use compressed air to clean radiators.

 

Hydraulic brake auxiliary plant

Also available for tractors are brake plants for trailers which work off hydraulic fluid pressure in the circuit for braking the tractor. These systems include a brake actuator proportional to the force applied to the brake pedal by the driver. The degree of the force acting on the trailer can usually be modified by a special regulation valve.

 

Electronics

The greatest evolution, however, has been in the sector of onboard electronics which made their timid appearance in the 1980s. Thanks to the development of dedicated sensors for equipping farm tractors, any special conditions in the surrounding environment can be detected and correlated with the information derived from the tractor operations for warning the driver of imminent danger or of a situation in which performance is not optimal. In some cases, errors or anomalies involuntarily caused by the driver can be “corrected”