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This paper addresses a commercial mobile tree chipper with a mechanical infeed system that is manually fed. OSHA records associated with commercial tree chipper accidents indicate tree workers have alleged that their arms have been pulled into the chipper feed wheels by branches during the feeding process. An infeed extension pan has been proposed to prevent a tree worker’s arm from being pulled into the chipper feed wheels if his gloved hand gets caught in the branches being fed into the chipper feed wheels if his gloved hand gets caught in the branches being fed into the infeed hopper. Experiments performed with human test subjects and an anthropomorphic dummy are presented under arm pull-in scenarios to study the safety implications of the proposed infeed extension pan.

A fatal accident occurred when a right angle gear box on an auger elevator disintegrated freeing the outboard end of a rotating PTO shaft. The tractor, acting as a stationary power source, flailed the PTO shaft which then struck and killed a farmer. No similar occurrences have been reported for the nearly 2000 similar units which have been used for over a decade. This paper studies a number of fundamental failure modes in order to determine which failure modes created the accident. Systematic analysis showed that the accident was caused by unusual misuse of the product. Known safety control concepts do not preclude this unforeseeable event.

Ancient Egyptians allegedly moved large stone blocks by placing cylindrical rollers beneath them and manually urging them along. This rolling procedure required that the rollers emerging from the rear of the stone be manually lifted and replaced in front. This roller replacement protocol has been automated in commercially available roller units that allow continuous movement of heavy machinery under the action of pry bars, come-a-longs, winches, or manual push efforts. Unfortunately, when slopes or asperities are encountered these heavy loads may accelerate uncontrollably or steer themselves in unsafe directions when the roller units become reoriented. This paper describes two inventions that cause the locomotion of the machinery to proceed in inchmeal fashion by intermittently braking the system while the roller units are manually reset.

A two year old child strangled to death when the drawstrings of her jacket became lodged in a catch point hazard at the top of a residential sliding board. Approaches utilized in the safety analysis include accident reconstruction, safety literature review, standards research, an accident statistics survey, and an evaluation of alternative jacket and sliding board designs. Results of the analysis indicate there are technically and economically feasible design alternatives which prevent the child strangulation hazard associated with the jacket drawstrings and sliding board.