Downloaded from SAE International by University of Leeds, Monday, September 24, 2018Off-Highway Power Transmission Systems Wayne H. McGlade LeTourneau-Westinghouse Co. MANY FINE TRANSMISSION systems are available and in use today for various heavy duty, off-highway machine oper­ ations. Some of these independent transmission producers are: Allison Division of General Motors Corp., Clark Tractor and Equipment Co., Cotta Transmission Co., Fuller Trans­ mission Division of Eaton Manufacturing Co., Twin Disc Clutch Co., and the Spicer Transmission Division of the Dana Corp. DESIGNS AND APPLICATIONS Most of these machines, for off-highway operations at least, become a composite of numerous components. The compatibility of the components is not always so easy to achieve as it may seem to be. To a large measure, thep'ro- duct engineer is faced with wisely choosing components in order to come up with the best overall vehicular or machine compromise with which to meet the customer's specific re­ quirements. The marketing and sales department will find many varied and different customer applications for any given product. This imposes again many factors that enter into the deter­ mination of suitable compromise solutions for each product offering. In some instances, any given product --in order to meet all requirements and still be produced and sold as one pack­ age -- may well be compromised to the degree that its total usefulness in performance, reliability, and productivity will not provide proper and adequate values for the customer. The power transmission system becomes one of very vital and critical import in relation to the total vehicle perform­ ance, reliability, and cost of operation. It is specifically with this component in mind that we address ourselves in this paper. In particular, we propose to show the following in some detail: 1. Mechanical, constant mesh, step gear, manual shift designs. 2. Mechanical, constant mesh, step gear, part manual and part power shift designs. 3. Mechanical, constant mech, step gear, power shift, torque converter coupled, countershaft design. 4. Planetary, step gear, manual shift, torque converter coupled design. 5. Electric transmission, stepless range. The objectives for a transmission design maybe to pro­ vide for the following: 1. A smooth and continuous flow of power throughout the speed range to be covered. 2. The simplest and most direct means of taking power from its source, changing its speed and torque to the de­ livery point from the transmission. 3. Design for maximum reliability of the component as a whole. 4. Provide a design simple in its elements in order to be easily maintained and serviced in the field. 5. A design small and compact enough to be practical for the greatest adaptability to machines. 6. In total, to provide for the lowest operating cost per hour of service life. With these objectives in mind, we shall now consider the applications of various transmission systems. Some typical transmission applications are: 1. Motor graders require long continuous runs in a gear at preferably a constant speed. The operator is performing ABSTRACT• Modern off-highway vehicles must perform efficiently and reliably under heavy duty conditions. This requires me­ chanisms that can move and handle material faster and at lower cost. This means bigger powerplants and high capa­city power shifted transmissions. The transmission system is critically important to total vehicle performance, reli­ ability, and cost of operation. This paper reviews the vari­ ous transmissions available and reports the development and experience of the LeTourneau electric drive design. Downloaded from SAE International by University of Leeds, Monday, September 24, 2018vehicle steering, blade control of elevation, one or both ends, and blade angle as well. He may also be shifting the blade laterally. The value of power shifted transmissions versus ma