Biological Systems Engineering


Date of this Version



Smith, B. S. (2015). Fuel Consumption Models for Tractors with Partial Drawbar Loads. Unpublished M.S. thesis, Lincoln, Neb.: University of Nebraska.


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree Master of Science, Major: Mechanized Systems Management, Under the Supervision of Professor Michael F. Kocher. Lincoln, Nebraska: December 2015

Copyright (c) 2015 Bryan J. Smith


Three models for predicting fuel consumption for agricultural tractors with partial drawbar loads were compared. Data were collected from eight John Deere tractors, JD 7230R (e23), 7250R (e23), 7270R (e23), 7290R (e23), 7290R (IVT), 8320R (16 speed), 8345RT (IVT), 8370R (IVT). The tractors were tested with 7 load levels per speed at four different travel speeds as close as possible to 4, 7.5, 10, and 13 km·h-1. The IVT tractors were operated in Auto mode and the geared tractors were shifted up three gears and throttled back to the same travel speeds as the IVT tractors. The 7 loads were selected at 30, 40, 50, 60, 70, 75, and 80% of drawbar pull at maximum power at the selected speed. Model 1 (fuel consumption as a liner function of drawbar power), currently used in OECD Code 2, Section 4.4.8 (OECD, 2014), resulted in a unique equation for each speed. When the slopes for each tractor were compared, 79% of the comparisons were not significantly different. For 80% of the tractors, the second variable in Models 2 and 3 were determined to be significant. For 80% of the tractors, Model 2 was determined to be more accurate than Model 3. . While Model 1 was found to be more accurate than Model 2, the requirement of having a separate equation for each speed limits the practical application of Model 1. Model 2 had only slightly larger error than Model 1, but has the additional flexibility of being applicable over a range of speeds.

Advisor: Michael Kocher