RATANA SMASH

Evening Post, Volume CXXV, Issue 144, 21 June 1938, Page 11

RATANA SMASH

TECHNICAL POINTS

WITNESS CROSS-EXAMINED

SPEED FORMULAE

The inquiry into the Ratana derailment, adjourned from yesterday, when the cross-examination of Mr. A. S. Wansbrough, designing engineer of the maintenance branch of the Railways, was not completed after two and a half hours, was resumed today at 10.30 a.m., and was still proceeding at 12.45 p.m.

The Board of Inquiry consists of Sir Francis Frazer (chairman) and Messrs. H. L. Cole and F. W. Furkert.

Mr. H. F. r O'Leary, K.C., with Mr. F. W. Aickin, railway law officer, are representing the Railway Department, and Mr. G. G. Watson the Engine Drivers' Association and the driver of the train, Mr. E. Percival. Mr. F. J. Foot is appearing for the relatives of the late Mrs. E. S. Lewis and Mrs. Esme Webb, two of the passengers, and Mr. N. T. Gillespie for the relatives of the late Mrs. Hazel D. Tullock, another passenger on the train.

Referring to Mr. Wansbrough's evidence, where he had said that he had had experience of many derailments, but knew of no case in which a passenger carriage or engine running on the main line had been derailed, except where there had been excessive speeds or obstacles, Mr. Watson asked the witness if he had since heard or knew of any derailments due to mechanical defects. Mr. Wansbrough replied that he now knew of five derailments due to mechanical defects in ten years. He could not point to any derailment due to excessive speed on the departmental records of the past 12& years, though in ten years there had been 71 derailments.

"Given the particular engine and train under discussion, on this particular curve, what degree of irregularity in cant of track in 18 feet of track would be needed to cause a derailment? —It would have to be well into the second inch in 18 feet. BASIS OF CALCULATION. Questioned on the basis on which in his evidence he had calculated the speed of the train at the time of the derailment, he said that he had never heard of or seen Professor Scott's text book, and had never seen the formula used, until Scott used it himself. The formula depended on variable factors. Scott's formula, on which he had estimated the speed of the train which caused the engine to turn over, depended for accurate results on effective braking and the degree of resistance afforded by the surface over which the train was running. If there were 41b of pressure put on the brakes .by ,the driver immediately before the occurrence there ■ would not be fully effective emergency braking when the Westinghouse pipe broke> unless the driver had tried to pump up full pressure again. Such factors would make for modifications in the results of Scott's formula.

There was room for errors in assumption of fact, and this applied to both Spiller's and Scott's formulae, and such errors might tend to raise the estimated speeds. He did not think the speed could have been estimated- at 60 miles an hour; that would have been a guess. His arrival at the 50 miles per hour speed was by inference.

Sir Francis: An inference is a conclusion you draw through facts admitted, or through what you consider it reasonable to take to be facts, so that an inference is a reasoned decision, and-a guess is something at which you make a shot?— Yes.

Mr. Watson: The assumptions you make in the second portion of your evidence are that this engine proceeded 100 feet on ballast with one side completely in the air?— Yes, for about one second the engine was overbalancing, and for about three seconds it was running on the ballast until it came to rest.

"Do not the marks show that after the engine left the rails it moved forward almost in a straight line, and would not that indicate an extraordinary state of balance?" —"Not balance, exactly. The engine must have commenced to overturn at the overturning speed arrived at when the curve became sufficient."

"This curve is agreed to be one of the sharp curves on the New Zealand railways, sharper* than is tolerated in modern railway construction?"—" Yes."

"If the passengers had gone round that curve in their carriages at 50 miles an hour they would certainly have noticed it?" —"Yes, but I do not think the first car reached the curve at that speed."

To Mr. Aickin: The engine was on a curve on level ground. The speedboard seemed to be accurately placed at 131 miles and in a position that seemed correct. It was not placed exactly at 130.70 miles, the reason being that the board had been there for many years, but from a practical point of view it was at the place where the speed limit should become 20 miles per hour. It was intended to remind the driver that he must slow down to the speed shown in the working timetable. If the. line had not dropped down the hill to Wangaehu, there would not have been a board limiting the speed to 20 miles an hour. In his opinion the engine had not reached the point it was intended to protect before it overturned.

(Proceeding.)