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The nature of the damage incurred by the master rod bearings, crankpins, and other parts of the engines indicates that over-revving in excess of 3000 rpm took place on each engine. This is borne out by the testimony of an expert witness during the hearing that the slight indication of heating on the master rod bearings, knuckle pin bushings, piston pin bushings and knuckle pins was caused by overspeeding of the engine rather than by lack of lubrication. This testimony was later corroborated by an independent examination of the parts of one engine by an expert agency.
The expert who testified that over-revving in excess of 3000 rpm took place based his opinion on experience with similar engines which had been over-revved on a test stand. He found that marks made on various rotating parts of the engine, especially the crankpin, varied both in magnitude and direction in proportion to the amount of overspeeding. Data obtained from overspeed tests on master rod bearings of this type of engine indicates that the oil film will remain intact for bearing loads imposed by an engine speed of at least 3000 rpm.
From test experience with other bearings which were damaged in a manner very similar to the damage incurred by these bearings it is estimated that the duration of the over-revving was from five to eight seconds and furthermore it appears that rotation of the engines was stopped very shortly after the over-revving occurred because certain marks on the crankpins which were caused by overspeeding would have been erased if the engines had again been operated at normal speed.
Witnesses near the scene of the accident also presented testimony which indicated over-revving. Several witnesses heard a loud roar of engines for varying periods of time. Mr. Garland Jacobs, who was 300 yards west of the scene of the accident, thought that the roar lasted for about 30 seconds. By retracing Mrs. Thompson's movements the estimated duration of the noise she heard was 19 seconds at 400 yards west of the scene of the
