Roberto Lilles Tavares Machado

Análise dos esforços em sulcadores empregados em semeadoras-adubadoras de baixa potência

The furrow openers for no-till system should be easy to penetrate the soil, generate low levels of soil mobilization and require a little traction force. Thus, the aim of this research was to compare six hoe-type furrow openers, four of industrial manufacturing and two handcrafted models, which were used in planters in the region of Pelotas, Brazil. The parameters for comparison among these furrow openers were the horizontal (Fh) and vertical (Fv) forces acting on the tip of the hoe and the cross-sectional area mobilized in the furrow. The experimental design was randomized, with six treatments (furrow openers) from T1 to T6, with four repetitions, constituted by their passage through plots of 20 x 3 m. The force data were collected by load cells and a signal conditioner. The determination of the mobilized area in the furrow was done by a micro soil profilometer. It was concluded that the furrow openers T1, T4 and T6 presented the lowest values of horizontal force (statistically equal and ranging between 1,034 and 1,230 N) and that T1 and T2 produced the highest vertical forces downwards (statistically identical and varying between 749 and 845 N). The furrow openers T1, T2, T4, T5 and T6 generated soil mobilization statistically equal and between 0.006993 and 0.008933 m2.

Validação de um modelo de cálculo por elementos finitos do chassi de uma semeadora de quatro linhas

The static structural behavior of an four row planter experimental frame for family farming was tested using the Finite Element Analysis numerical technique, which took into account the efforts that this machine would be subjected, when suspended over the ground by the three-point hitch of the tractor. To validate the implemented model by SolidWorks Simulation, a real scale prototype was submitted to vertical loads to compare the actual structural displacement to the software calculated displacement. Two studies were made from the calculation model of structural displacement; in the first, it was not included the three- point hitch brackets for calculation, and the measured displacements were not comparable to the calculated ones. In the second study, when hitches were included in the calculation, the results were comparable to those obtained in practice. Therefore, it was concluded that the second study is valid and the frame structure calculations performed by the software are reliable.

Triturador florestal: Determinação da potência de corte necessária ao raleamento da Caatinga

Para execucao do processo de raleamento na Caatinga e muito importante a utilizacao de maquinas do tipo rotores trituradores acoplados em tratores de baixa potencia, visando principalmente maior conforto e diminuicao de tempo e mao-de-obra dos agricultores familiares na implantacao de sistemas de exploracao sustentaveis, chamados de sistemas agrossilvipastoris. O objetivo deste trabalho foi avaliar a minima potencia de corte em funcao dos parâmetros rotacao e velocidade de avanco, utilizando uma metodologia de corte proposta para trituradores florestais. As especies arboreas utilizadas como amostras, foram colhidas da regiao da Caatinga do Ceara. Utilizando um delineamento estatistico inteiramente casualizado no esquema fatorial (4x5), quatro avancos (0,013 Km h -1 , 0,027 Km h -1 , 0,038 Km h -1 e 0,054 Km h -1 ) e cinco rotacoes (447, 638, 882, 1286 e 1792 rpm), com quatro repeticoes, a analise de variância resultou normal segundo os testes estatisticos de Kolmogorov-Smirnov e Lilliefors com o p-valor p > 0.10. Realizou-se entao a regressao na analise de variância aplicando-se um delineamento inteiramente casualizado para as duas rotacoes que consumiram menor potencia. A regressao linear foi significativa para ambas rotacoes e foi possivel estabelecer equacoes lineares da potencia de corte em funcao da velocidade de avanco do mecanismo responsavel pelo corte. Dentre as especies analisadas, determinou-se qual demanda mais potencia de corte , e para esta pode-se determinar a rotacao que consome menos potencia de corte.

Use of walking tractor powered rotary tiller in no-tillage system

Brazilian family farming has at its disposal planters whose furrowing mechanisms, whether disc or shank, require a large vertical force. In smaller planters, this is reflected in low efficiency when opening the furrow or in a high demand for mass (weight). Rotary furrowers require less vertical force for the same operation. This study aimed to evaluate the technical feasibility and performance of rotary furrowers mounted on the powertrain of a walking tractor working under direct seeding, and compare them with shank-type furrowers using bibliographic data. The parameters used in the comparison were the depth and width of the furrow, the area of disturbed soil and the cross-sectional area of the furrow with no soil after the operation. The experiment was carried out on wheat stubble that had lain fallow for six months. Twelve treatments were employed in a factorial design: three models of rotary furrowers, two values for revolutions per unit of linear displacement, and two forward speeds. The variable, cross-sectional area of the furrow with no soil, was statistically affected only by the factor, furrower. However there was significant interaction between the factors, furrower, revolutions per metre and speed, for the variables of depth, furrow width and area of disturbed soil. The values obtained for the variables of width, depth and disturbed area in the cross-section of the furrows, with the three types of rotary furrowers driven by the powertrain of a walking tractor, were similar to those generated by shank-type furrowers.