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Of all the parts used on crawler-type construction equipment, the track bushings in the undercarriage of large bulldozers are subjected to particularly severe load conditions. A new and innovative heat treatment technology has been developed in order to improve the durability of these bushings from the point of their wear and fatigue crack characteristics. A new steel material has also been specified to match this heat treatment technology. The bushings thus developed have been extensively tested on bulldozers in customer service and proved to be successfully applied for production. They also offer a possibility for considerable reduction in manufacturing cost.

The paper provides mechanical and performance specifications for a giant 650 PS bulldozer and cites the outstanding features of this machine. The new bulldozer offers improvements in dozing, ripping, and pushing. It has an electropneumatic system employing solenoid valves and air cylinders, and it can be controlled by radio for unmanned operation in dangerous sites.

KOMATSU has successfully developed and marketed the HYPER GX series computer-controlled, intelligent hydraulic excavators. The development concepts of the HYPER GX series are as follows: 1. To improve safety at construction sites by use of measuring functions which reduce the number of ancillary workers. 2. To improve working environment and the quality of work by use of automatic functions which reduce operator fatigue and time required to complete a job. 3. To solve the problem of shortage of experienced workers by the use of operator support functions which allow easy operation even for inexperienced or older operators. Representative of these is the fully automatic grading function, with which the movement of boom, arm and bucket is computer-controlled to enable automatic excavation at a predetermined gradient.

This paper introduces a laboratory-developed tester for the front suspension of off-highway dump trucks. In dump truck movement at jobsites, the front suspension system is subjected to three-way load, i.e. in the vertical, horizontal and turning (steering) directions. Using three actuators, controllers and a computer, we conducted a lab simulation of such loads. With this tester, various quality assurance tests were carried out to provide reliable data in a short period of time. These tests were as follows: (1) Performance test to measure suspension characteristics such as spring stiffness, damping coefficient and internal friction (2) Stress measurement test to confirm structural strength (3) Endurance test to confirm durability and longevity of parts subject to wear, such as seals and bushings (4) Temperature environmental test to confirm sealing performance across a very low to high temperature range (5) Dust environmental test to confirm sealing performance against dust