ENGINEERING FOR RURAL DEVELOPMENT TRACTOR MFWD BRAKING DECELERATION RESEARCH BETWEEN DIFFERENT WHEEL DRIVE

Abstract. The article presents and analyses the reasons of the braking parameter in 4×4 tractor. It is noted that the wheeled tractors are working in transport, cargo, driving with implements and without them in the fields, etc. for most of the time. The contact area with the road surface during braking decreases when increasing the driving speed and the overall dynamic stiffness of the tire changing increases the rolling resistance. However, it is worth mentioning that the tire contact with the road surface area is also dependent on the tire air pressure and improperly selected or uneven tire air pressure to increase the vehicle rolling resistance, increasing the frontwheel lead, which reduces the braking efficiency. The change of the front-wheel lead increases kinematic discrepancy between the drive wheels. These factors have negative effect for the tractor performance parameters, the transmission is loaded heavily, the power losses are increased, tires wear faster, the fuel consumption is increased. This article shows and analyses tractor deceleration between different wheel drive (4×2 and 4×4) with different driving speed. Keywords: inflation pressure, deceleration, braking, agricultural tractor. Introduction Tractors are identified as MFWD (Mechanical Front-Wheel Drive) tractors, when the front axle is driven by a mechanical drive and the front drive wheels are smaller than the rear wheels. Today, MFWD tractors are extensively used for transportation work when connected to the tractor trailer or semi-trailer. The latter considerably increases the tractor rear wheel vertical load and the rear tire deformation, but reduces the front-wheel vertical load and tire deformation. Increasing and decreasing the rear of the front tire deformation increases the actual size of the front wheel advance. This change has no harmful effects on the tractor vehicle dynamics while working, because when running a good road and at higher speed, the front wheel drive is generally unplugged. However, front-wheel accelerates change effects of the MFWD tractor braking dynamics, since the braking front axle is always automatically enabled Brake and steering systems in vehicles are the most effective gear, which directly affects the vehicle dynamics. In general, the brake system is running in the longitudinal vehicle dynamics and driving dynamics system running side. However, their effects combine when the vehicle is braked on uneven surfaces. The yaw moment braking compensates for steering control on the road. To avoid improper steering compensation vehicles have been equipped with the wheels being driven in rotation angle of the controller, designed to mitigate the impact of asymmetric braking forces and stabilize the angular deviation in vehicles Freight transportation tractors are combined with various trailers or semi-trailers. Almost 75 % of kinetic energy of the tractor-trailer combination is acquired from the trailer, so it is very important that the brake system of the trailer is sufficient to defeat the emerging kinetic energy. The stability of the compound depends on the coordination of the tractor and trailer braking systems, and also their braking efficiency. If the tractor brake system works better than the trailer brake system, the braked tractor can be pushed, and the tractor is pulled, the trail braking efficiency is better. The braking process is the best when the tractor-trailer brake efficiency is the same [4; 8; 9]. The necessity to use the brake system can occur in various situations. However, all braking systems are divided into two categories The maximum braking force developed by the vehicle wheel depends on the wheel grip to the road and vertical road reaction affecting the wheel. Operational braking intensity is always less than the maximum possible braking efficiency. Emergency braking does not exceed 5-10 % of all braking situations. However, this is a very important condition, which is important in emergency situations

ENGINEERING FOR RURAL DEVELOPMENT PERFORMANCE OF 4 WD TRACTOR ON GRAVELED ROAD

Abstract. The distribution of the vertical loads of the axles and the air pressure in the front and rear tires have an influence on the kinematic discrepancy between the front and rear driving wheels during the exploitation of the 4 WD tractor. The kinematic discrepancy between the front and rear driving axle has an influence on fuel efficiency on the 4 WD driven tractors, too. The performance of 4 WD driven tractors during transport work on the graveled road is analyzed in this paper. The interaction of the different air pressure of the front and rear driving wheels with the road surface is analyzed in this paper. There are shown the results of the experimental investigation of the kinematic discrepancy influence on fuel efficiency during exploitation of the 4 WD driven tractor on the graveled road in this paper

ENGINEERING FOR RURAL DEVELOPMENT INTERACTION BETWEEN DRIVING WHEEL AND ROAD SURFACE OF ALL WHEELED DRIVEN TRACTOR

Abstract. Interaction between the tires of a 4x4 wheeled driven tractor and the road surface, the influence on the slippage of the vertical load of the wheels and air pressure of the tires, the theoretical speed of the front and rear wheels and their influence on interaction between the surface of the road are analyzed in this article. The driving torque of the 4x4 wheeled drive tractor has been distributed in proportion to the friction coefficient between the wheel-road surface and the distribution of the vertical load and dynamic radius of the wheel. The results of the experimental investigation on the interaction between the road surface, vertical load and the air pressure in the tires of the 4x4 wheeled drive tractor which is operating with the front loader are presented. The optional air pressures are found in the front and rear tires of the 4x4 wheeled driven tractor, which is operating with the front loader. Keywords: tractor, driving wheels, slippage, slid, air pressure in the tires, the vertical load of the wheel, front loader. Introduction There are all driving wheels in the tractor (4x4). Tractors with all driving wheels are more advantaged in the work on the fields, damp and light soils, because they are more terraining. However, in dry and hard road surfaces a lot of energy is wasting in the front driving axle [1; 2]. Wheeled tractors are used for a whole year in agriculture. There are three groups of operation modes of the tractor by specification of work: work on the fields, when tractor is loaded by a big tractive force (plugging cultivation, sowing etc.); work at a big friction efficiency in high speed (work of transport); work with the tractor when the driving wheels are loaded unproportionally on the driving axles (work with front loader etc.) [3; 4]. Most of the tractors with 4x4 driving wheels are made that they would have 55-60 % of the total tractor weight on the rear axle in the static state. To keep these proportions in the exploitation period is recommended. To keep the vertical loads of the driving axles should not deviate more than 10 % if it impossible. The main condition is that the load of the front driving axle is not less than 20 % of the total weight of the tractor to keep good handling and safety during exploitation [5; 6]. The driving wheels of the tractor in all cases slip, when the tractor is loaded on tractive force. In this case, the factual speed v f is less than the theoretical speed v t of the tractor. These loses are evaluated by slippage δ, % [7; 8]. The ways to reduce slippage are: usage wider or dual wheels, to force the driving wheels to the road surface. The contact area of the wheel-road surface and the tractive force increases by 20 % by decreasing air pressure in the tires The exploitation period of the tire, economical effect, and tractive force of the tractor depend on the air pressure in the tires. The air pressure in the tires must be increased on the road. The air pressure in the tires must be about 1.4-1.6 bar on the road in higher speed It was found that correct air pressure in the tires reduces the power loses in association with the tire and road surface contact area. In this case the controlled air pressure in the tires is increasing the friction between the tire road surface. As a result of it -increased driving force of the wheel of the vehicle [1; 2]. The contact area of the front and rear wheels can be increased or decreased twice by varying the air pressure in the tire