ARS | Publication request: Overlap loss of manually and automatically guided mowers

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 29, 2011
Publication Date: March 8, 2012
Citation: Shinners, T.J., Digman, M.F., Panuska, J.C. 2012. Overlap loss of manually and automatically guided mowers. Applied Engineering in Agriculture. 28(1):5-8.

Interpretive Summary: Overlap loss in harvesting machinery has been observed as a necessary inefficiency for many years. Each time a non-row-crop machine (such as a hay mower) makes a pass in the field, it is favorable for the operator to overlap slightly into the previous pass (where the crop has already been cut) as opposed to undercutting and leaving a strip of crop standing. In this study, overlap loss was explored through a controlled experiment as well as an on-farm survey. In the controlled experiment, we tested how driver experience and cutting speed influenced the amount of overlap. The cutting speeds tested were 4, 6, and 8 miles per hour (mph). The experienced driver had been cutting at the research farm for over five years and the second driver was new to the job. We conducted the experiment in first and second cutting with the farm's donated self-propelled windrower with a disk cutterbar. Surprisingly, speed didn't play much of a role in overlap and neither did experience. However, when the two factors interacted (particularly high speeds and low experience levels), the overlap loss increased. In the second part of the experiment, we measured pass-to-pass overlap on 15 farms. The machines included pull-type, mounted, and self-propelled mowers with operating widths varying from 10 to 32 feet. The operating speeds varied from 5.5 to 12.5 mph. The overlap varied from 0.5 to 16% with the average around 5%. That's 5% of the cutting width wasted with each pass. Overlap averaged slightly higher for the pull-type at 6.6% than for the mounted and self-propelled machines at 5.2 and 5.0%, respectively. The other interesting fact gleaned from the study was that the observed machines that utilized automatic steering with signal correction were able to cut overlap in half from 5 to 2.5%. This information will help forage producers improve the efficiency of their harvest.

Technical Abstract: Overlap loss in harvesting machinery has been observed as a necessary inefficiency for many years. Each time a non-row-crop machine makes a pass in the field, it is favorable for the operator to overlap slightly into the previous pass (where the crop has already been cut), as opposed to undercutting and leaving a strip of crop standing. In this study, overlap loss was explored through a controlled experiment as well as an on-farm survey. The experimental portion employed a factorial design to study the influence of two drivers and three cutting speeds (6.4, 9.7, and 12.9 km/h) of a self-propelled windrower. Driver experience and mowing speed were not found to have a significant effect on overlap. However, the interaction of inexperienced operators and higher mowing speeds increased overlap. The on-farm survey included three mower configurations: pull-type, self-propelled windrower, and mounted, as well as cutting widths ranging from 4.01 to 9.60 m and a variety of field conditions on 15 farms. Three of the mounted mowers and one self-propelled windrower utilized automatic guidance. Surveyed overlap ranged from 0.4 to 16.13% of machine cutting width. Average loss was 5% of cutting width. Automatic guidance has been purported to improve efficiency by eliminating time spent covering already mowed ground, reducing operator fatigue, and ensuring a uniform cutting pattern and swath density. The use of a GNSS-based guidance system to steer the mower was shown to reduce overlap loss from 5.03% to 2.34%.