Safety Files recently featured machines many readers can relate to personally: lawn mowers for home use (“Mower design flaws spark deadly fire,” Machine Design, Sept. 9, 2010, tinyurl.com/MDMowerSafety1 and “Manufacturer negligence or caveat emptor in mower accident?” Machine Design, Oct. 7, 2010, tinyurl.com/MDMowerSafety2).
Several readers commented on the 30-year-old mower in which a fire led to the operator’s death. Ron Amundson questioned whether mower designs have actually changed. “Probably 20% of [new riding mowers I looked at] had unsupported electrical harnesses running right under in-line fuel filters. The insulation is going to be damaged when it rubs on the steel chassis, setting the stage for a repeat of the fire. I would have expected more change over the years.”
Chuck Kelly, P.E., questioned how well the mower had been maintained. “I drove one of these models for 33 years. Sure, it had its faults, but my sons and I examined, diagnosed, and reported problems. We fixed gasoline leaks and sparking wires as common-sense repairs. I consulted the shop manual and the manufacturer’s service center when problems were too difficult.
“Saying the scenario that caused the accident was a design flaw or should have been covered in the owner’s manual is like saying an auto manual should cover what to do if the brake pedal goes to the floor on an expressway on-ramp. Volumes of instruction cannot substitute for common sense.”
Other readers weighed in on whether the manufacturer should have included not-yet-mandated but state-of-the-art safety features in a self-propelled walk-behind mower that injured the operator’s foot.
Paul C. Foley asked, “ Where does manufacturer liability end for obsolete designs that were legal at the time of manufacture? Granted, the manufacturer waited until it was required to make the change, but it had been building the mower without design changes for a number of years. Should liability go back to the design release or back to 1947 when the technology became available?
“Walk-behind lawn mowers are inherently dangerous, and the early manifestations of the blade brake were fraught with poor design and execution. Is the manufacturer liable if an owner tied down the brake with a bungee cord to make restarting easier? Where does litigation stop and common sense come into play?”
Dan Putt took a marketing approach to the question. “Every product has its market strategy, and for this model the manufacturer reduced cost by omitting state-of-the-art features in order to attract a certain market. The consumer would need to consider the feature’s value in making his purchase decision.
“State-of-the-art technology helps manufacturers bring value to their products over the competition. If we mandated every technology, there would be no incentive for companies to innovate. I am sure the first OPC wasn’t designed because the manufacturer was overly concerned with the safety of its product; it was to add value so the consumer would choose the OPC version over the competitors’.”
Lanny Berke, P.E., a Certified Safety Professional and author of Machine Design’s monthly safety column, also gave his thoughts: “In every safety case I’ve seen — not just lawn-mower safety — in-depth thought and good design could keep cost increases low or even cut cost. Designing solely to standards — which address minimal safety issues — is the lazy approach. Instead, a designer’s goal should be to create a safe product that surpasses standards by first performing a hazard analysis and then responding to the hazards identified.
“When this approach is used, each identified hazard results in an in-depth design analysis in the area of the hazard. Such analysis and redesign often show ways to cut cost and still have a safer product.”
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Edited by Jessica Shapiro