The Case of the Decrepit Diesel

Not all forensic engineering cases involve personal injury, but they almost always involve financial loss one way or the other, and engineering can help resolve technical issues to determine financial liability.

The Scene of the Crime

An attorney representing an aluminum recycling company retained me to examine a fleet of five diesel-powered forklifts to help resolve a dispute between the recycler that had leased the trucks, and the leasing company (a forklift dealer). The lessor's most recent statements included major costs for items worn or damaged beyond normal wear-and-tear. Stunned by these high costs, the recycler refused to pay. The dealer quickly pulled the forklifts from the recycling plant, leaving the recycler scrambling to rent lift trucks from other sources. Without any compromise in sight, the dealer filed a lawsuit to recover the costs of service and allegedly damaged parts.

The Investigation

At the recycler's plant, I saw bundles of flattened drink cans, punched flat sheets and loads of miscellaneous chopped aluminum pieces. Lift trucks ceaselessly zipped back and forth, scooped bundles of scrap and headed over to charge the hungry maws of electric-arc furnaces. Three shifts per day, the furnaces produced a river of molten aluminum that flowed into what seemed to be a continuous sheet caster. Rollers and cooling water sprays converted hot liquid into shimmering sheets rolled to a specified gauge, slit to specified widths and then coiled for storage or shipping. The rapid back-and-forth, three-shift operation with full loads perfectly described the terms, “heavy-duty forklift operation.”

At the dealer's yard, I inspected the five-truck fleet, the sorriest-looking examples of lift trucks I had ever seen. To varying degrees, each machine had chunks of rubber missing from its solid rubber tires, a torn, worn seat, bent steering wheel, damaged lifting mechanism and on and on. With a mechanic and a jumper battery cart, I was to start each machine, inventory its operational and physical condition and render an opinion on each party's claims.

The last two machines represented the largest claimed expenditures. The fourth machine not only didn't start, but wouldn't even crank over. The mechanic and I looked at each other, saying in unison, “seized engine!” We found a bone-dry dipstick. My client was responsible for daily checks — including oil — and failure to do this resulted in a seized engine.

The last forklift cranked easily, starting only when given an ether spritz, but ran poorly. We found plenty of fuel in the tank. The mechanic cracked loose the fuel line at each injector and cranked the engine. Fuel squirted out at each fitting, confirming injector pump operation. The mechanic pulled a glow plug and connected a compression gauge into the port. The gauge needle fluctuated anemically, indicating barely sufficient compression to fire up. So, what could damage this engine that had essentially the same hours of operation as its four companions?

The Smoking Gun

I noticed the recycler had modified each unit. Exhaust systems were re-routed, parking brakes altered, with bits and brackets welded to the forks and carriages. This forklift had a bin to hold some unidentified material installed on the flat engine compartment cover next to the driver's seat. I peered into the innards for some clue and saw a hole in the pipe between the air filter and intake manifold. I also saw a long bolt retaining the bin, in line with the worn-through spot on the intake pipe. Evidently, with a sufficiently heavy load, the fiberglass cover sagged enough to let the bolt's threads act like a file and cut a hole in the intake pipe. It seemed it wouldn't take long for unfiltered, abrasive-loaded air to eat into the engine's cylinder walls and piston rings, drastically reducing compression and performance. My opinion was divided on this issue, as my client had made unauthorized modifications, while the dealer-plaintiff's mechanic failed to observe the hole in the intake pipe during his maintenance checks.

In my opinion report, the final tally of financial liability was about a 50/50 split between plaintiff and defendant. Still, each side chose to go to court. I was called to testify, but while sitting in the courtroom hall with case file materials in-hand, my attorney-client came out during a recess and sent me home. I later learned that with the judge's admonitions, wiser heads prevailed and the case settled. And in just about the proportions I estimated!