Paper 7: Ground-Drive Systems for High-Powered Tractors

Attempts to solve the problem of transmitting high engine power to the drawbar have resulted in a variety of tractor designs. Measured rates of work on two- and four-wheel drive tractors and a tracklayer showed that while the four-wheel drive had the highest output, the tracklayer was more efficient for heavy draught operation. The two-wheel drive machine has a higher rolling resistance than the four-wheel drive and methods of measuring rolling resistance are described. The paper discusses the reasons that different performances are obtained from two- and four-wheel drive vehicles of the same engine power, and highlights some of the advantages to be gained. Previous theoretical work on two- and four-wheel drive tractor performance and on transmissions for four-wheel drive is also discussed, together with practical limitations on tyre size for operation under certain conditions. A small survey to measure tyre and track wear is described and a method is suggested of relating tyre wear to work done by quoting tyre costs per gallon of fuel used. The paper concludes with a few comments on soil compaction.