Evaluation of kickback energies in abrasive chain saws and cut-off saws: a theoretical and experimental study

Abstract

Abrasive chain saws and cut-off saws used in construction work are not currently kickback regulated even though fatal kickbacks occur with them. Kickback regulation has been in place for wood chain saws since the 1980's, but it is inadequate for regulating abrasive power saws as they have a different cutting mechanic than wood chain saws. This thesis investigates the different kickback modes analytically and experimentally in order to develop tools for characterizing and predicting them. Simple physics models, numerical integrations, and two test rigs were designed to study them. First the different mechanisms which could cause kickback were considered (kickback modes) and simple physics models were made to describe them. From these, it was found that a pinch based kickback was potentially far more dangerous than a tip-engagement or snag type kickback for abrasive saws.

Using the physics based description for a standard kickback, a "Mark I" kickback rig was made as a variant of the 1980s wood saw kickback machine redesigned to produce high energy kickback events. However, testing found that even under extreme conditions kickback energies were not that high. Consequently, a "Mark II" kickback rig was developed to generate pinch based kickback events and to measure the energy produced. A momentum based mathematical model with only one primary tuning parameter was also created to predict parameter sensitivities and to cross-validate the performance of the rig. It was found that the Mark II rig was able to repeatably generate pinch based kickback events and safely measure the energy produced, measuring kickback events which produced more than 70J of kickback energy. Moreover, the model and rig agreed on the effects of changing the angle of the pinch and the pinch force.

Ultimately the model and rig were meant not only to characterize kickback for academic use, but to proof functional kickback modeling and testing tools which could be further developed to help regulate and design safer abrasive power saws.