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Multi body simulation of agricultural vehicles such as tractors has relied on the representation of tires by equivalent spring-damper combinations. Historically, the stiffnesses assigned to various modes of deflection have been established on the basis of tests on a limited population of tires. Vehicle accelerations obtained by simulations of transport over typical terrain and rectangular obstacles using these parametric characterizations have deviated significantly from measurements. This paper reports on an attempt to develop finite element tire models, which are capable of generating quasi-static spindle forces and moments for prescribed displacements over irregular terrain and capture phenomena such as enveloping of obstacles. Though based on the tire manufacturers knowledge of constructional details, they are presented as ‘black boxes’ to the vehicle analyst for imposition of boundary conditions and loads, including inflation pressures.

The product line of 4WD tractors offered by John Deere has been updated as part of the continuous improvement process to meet customer needs and provide a product with maximum value to our customers. The new model lineup is 250, 300, 350 and 400 engine HP. Per customer requests a new model has been added to the prior model lineup at 350 HP. The new models expand the usage of electronic engine control, enhance the engine power curves for increased productivity, provide improved operator comfort, enhance conveniences available to the operator, provide added improvements for serviceability and revises the options available for the customer so that he can purchase the product of maximum value for his needs.

Intense worldwide competition of the 1980's is forcing U.S. corporations to greatly improve product value with scarce resources and short lead time. While these are difficult challenges, they also are opportunities for imaginative managers. The paper describes an approach for product development which is based on three key factors. Developing customer oriented product goals and aligning them with corporate business goal of profitability. Implementation of these goals by an integrated multidisciplinary team effort. A simultaneous or parallel execution of all activities rather than a sequential approach.

The 9000T track-type agricultural tractors mark John Deere's entry into the high-horsepower, track tractor market. The 360-HP 9300T and the 425-HP 9400T tractors were designed with input from customers to meet customers' needs. Through customer input, on-farm research, and common sense, these tractors have been designed to work light in the spring, heavy in the fall, handle steep hillsides, turn under load and pull like a locomotive. Incorporating many of the already-market-dominating features of the 9000 wheel tractors plus innovative track vehicle features such as the wide stance, long wheel base, controllability, power, and versatility, these machines are truly amazing.