Marcelo Silveira de Farias

Transmissões presentes em tratores agrícolas no Brasil

The transmission system of an agricultural tractor has a main purpose to transmit the power generated in the hydraulic motor, the power take off and the drive wheels. The gearshift consists of a series of gears that allows the correct selection of speed and torque more appropriate to a particular operation. Then, the transmissions can be classified, basically, in three categories: mechanical, hydrostatic and hydrodynamic, being the mechanical transmissions subdivided in sliding gear and synchronized. Then, the objective of this research was to analyze the different types of transmissions available in 169 models of tractors made in Brazil in order to evaluate the real distribution of them in different power ranges and establish possible correlations. As a result, it was shown a strong tendency for agricultural tractors with power less than 111.8kW possessing mechanical transmission and tractors above 111.8kW possessing the hydrostatic type.

Air and fuel supercharge in the performance of a diesel cycle engine

This paper aimed to evaluate the performance of a Diesel cycle engine, changing the configurations for the air and fuel supply system. Variables analyzed were torque, power, specific fuel consumption and thermal efficiency in four different engine configurations (aspirated, aspirated + service, turbocharged + service and turbocharged). For that, there were dynamometer experiments by power takeoff of an agricultural tractor. The experimental outline used was entirely randomized, in a bifatorial design with three repetitions. Results indicated that the engine supercharge, compared to its original configuration, provided a significant increase of torque and power. Only the addition of turbo does not caused a significant effect in the engine performance. Application of turbocharger provides an improvement in the burning of the air/fuel mixture, which favors the increase of engine power and; consequently, reduced the specific fuel consumption.

Eficiência no consumo de combustível de um trator agrícola equipado com transmissão continuamente variável

The correct choice of modern power transmissions can help farmers decrease production costs. The following research aimed to assess fuel consumption efficiency of an agricultural tractor equipped with continuously variable transmission, at different travel speed and load levels applied on the tractor drawbar. Standard procedure has been applied considering six load levels (30; 40; 50; 60; 70 and 80% of Q0) by means of breaking with a dynamometer car instrumented in a concrete test track, at three travel speeds (5.16; 7.29 and 10.48km h-1). Throughout the experiment, engine speed, traction force and hourly fuel consumption were monitored. The results indicated that there was an average increase of 2.67; 2.82; and 2.61L h-1 in the hourly fuel consumption for each 10% increase in the load level on the tractor, for travel speed of 5.16; 7.29 and 10.48km h-1, respectively. In general, the specific fuel consumption of the tractor decreased as the load levels and the travel speeds were increased.

Metodologia para estimar o número de dias trabalháveis com máquinas agrícolas

No atual modelo de agricultura, e indispensavel que o produtor conheca a real disponibilidade de tempo para a execucao das operacoes agricolas ao longo do ciclo das culturas. Este e o primeiro passo para se planejar e se obter maior eficiencia na execucao dessas operacoes, que estao sujeitas as variacoes do clima. As variaveis meteorologicas de uma determinada regiao influenciam diretamente no numero de dias disponiveis para trabalhar com maquinas agricolas. O objetivo deste trabalho foi estimar as probabilidades de ocorrencia de dias favoraveis para o trabalho mecanizado, utilizando-se informacoes meteorologicas do municipio de Santa Maria, RS, Brasil. As condicoes para se considerar o dia como favoravel para o trabalho com maquinas foram a precipitacao < 5 mm e o armazenamento de agua no solo (ARM) entre 40 e 90% da capacidade de agua disponivel (CAD). O metodo da cadeia de Markov de primeira ordem foi utilizado para estimar as probabilidades condicionais de dias favoraveis ao trabalho com maquinas. Os resultados indicam que a metodologia aplicada para estimar as probabilidades de dias favoraveis ao uso de maquinas agricolas foi viavel, evidenciando as epocas mais apropriadas a execucao de operacoes agricolas mecanizadas no campo, para o municipio de Santa Maria, RS.

NOTA TÉCNICA: CONFORMIDADE DE MANÔMETROS UTILIZADOS EM PULVERIZADORES AGRÍCOLAS

The manometers are important to calibrate agricultural sprayers in order to supply hydraulic pressure required by the kind of spraying nozzles, solution volume and agrochemical used. This study was done to evaluate these devices using five parameters: Operational conditions, external diameter, pressure accuracy, glycerin level in manometers and duration of use on sprayers. Thirty six sprayers were eavluated on-farm through random on-site visits. The results showed mean duration of 16 years of use of sprayers, 8% were without manometers, and more than 30 % had damaged manometers. Among the manometers in good operational conditions (61.1 %), only 31 % had good pressure accuracy (± 10 %). Thus, only seven (19.4%) sprayers equipped with manometers were fit for use.