An Investigation of Three Physical Parameters of PTO Entanglements

Journal of Agricultural Safety and Health
  • Schwab, Charles V.;
  • Freeman, Steven A.;
  • Judge, Jon L. P.


The PTO driveline is the most common means of transferring power from a tractor to towed machinery and stationary equipment. While equipment manufacturers install shielding to protect operators and bystanders from coming in contact with operating PTO components (particularly around the knuckle), entanglement is still a cause of some of the most catastrophic agricultural work-related injuries. This study investigated the influence of material type, material length, and angle of material introduction on entanglements with a spinning PTO shaft knuckle. These variables were tested using a laboratory PTO apparatus where 165 entanglements were recorded during the 720 trials conducted. The results indicate that lighter materials, such as cotton thread, have a significantly higher probability of becoming entangled than heavier materials, such as leather bootlaces. Materials that were longer (i.e., extend further below the midline of the PTO knuckle) have higher probabilities of becoming entangled than do shorter materials. The horizontal path that the material traveled across the centerline of the PTO shaft impacted the probability of entanglement. When the angle of intersection of the horizontal path of travel relative to the centerline of the PTO shaft is 90°̊, or close to 90°̊, a higher probability of entanglement occurs. All 165 entanglements occurred on the downward rotational side of the PTO knuckle regardless of which side the horizontal path of travel started from. The results of this study provide the first look at understanding the physical phenomena associated with the initial stages of PTO entanglements and set the stage for future research.

Full article can be found in: Journal of Agricultural Safety and Health
Access this publication at: ASABE Technical Library

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