Supreme Court presses Not Calculated In Mower Manufacture

Press, Volume XCVIII, Issue 28896, 16 May 1959, Page 17

Supreme Court presses Not Calculated In Mower Manufacture

Production of the Pyramid hydraulic mower had been embarked upon by W. H. Price and Son, Ltd., without calculations of the stresses on the machine or any proper critical analysis, said William Stuart Turnbull, the firm’s design engineer, in the Supreme Court yesterday. He was being cross-examined before Mr Justice Adams during the hearing of the claim over the Pyramid mower. This had been done because the job was “apparently satisfactory’* —otherwise production would not have been started. Turnbull said. Turnbull's cross-examination lasted all day. and was not completed when the Court adjourned. At one stage he was told by Mr R. W. Edgley, counsel for Pyramid Machines, Ltd., that his time in the witness-box would be much shorter if he would answer the questions put to him. “Were not Price’s depending on you to ascertain that all proper calculations had been made?” asked Mr Edgley. Turnbull: It was never put to me that way. “Didn’t it occur to you that they might be? You did all the drawings, didn’t you?” Turnbull said he made the sketches for the drawings. Questioned further, he admitted the sketches were “the whole basis” of the drawings from which final production of the mower was made Calculations of Stresses Turnbull said he could not recall making calculations of stresses at no-load and said he could not remember making calculations of stresses with the knife blocked. “Do you consider that greater stresses are at no-load and when the knife is blocked?” asked Mr Edgley. “I would not say that without having full details of possible knife loads,” said Turnbull. “At any rate, you’ve made no calculations in either of those loads?” said Mr Edgley. Turnbull: I have not calculated either. Is it not a fact that the greatest stress encountered is on no-load? —That is open to doubt. Can you point to any engineering authority that says other than that the greatest stress is at no-load? “I haven’t seen any engineering authority dealing with the subject of stresses in powerdriven mowers,” said Turnbull. Mr Edgley: We are dealing with stresses generally on mechanism. “Isn’t it customary for qualified engineers to keep calculation sheets of what calculations they make?” asked Mr Edgley. “If you did make any calculations regarding this mower and its motor, it would be rather careless not to keep them, wouldn’t it? Wasn’t it a casual way to approach the matter?” Turnbull: It could be careless, but even now I don’t keep all the calculations in respect to the jobs I do. Turnbull said that after apparently satisfactory field trials, it appeared that certain calculations were correct. Mr Edgley: As a result of what happened to the production mowers, it appears now that the calculations weren’t correct? Turnbull: Yes. Engineering Qualifications Cross-examining Turnbull about the drive of the mower, and the cutting knife. Mr Edgley suggested they presented no serious problems. Turnbull: They did present problems. His Honour: Would a competent engineer have any difficulty in providing for them? Turnbull: I don’t think so. “Were you not trained to do this type of job, design, or drive?” asked Mr Edgley. “If all the practical considerations had been known,” said Turnbull. “Was your course of training such as to qualify you to design this drive? Will you answer the question directly, please.” said Mr Edgley. “I don’t think it can be answered directly,” said Turnbull. “There were many factors which no-one who does the mechanical engineering degree course would necessarily know about.” Mr Edgley: Do you say then you weren’t qualified to design this drive?—l would have been qualified had I also had some experience of farm machinery His Honour: Then you weren’t qualified? Turnbull: I would not say fully, sir. Reliance by Pyramid In questioning Turnbull about the necessity of a heavier drive shaft, Mr Edgley asked: “Who would make the decision about that?” Turnbull: It wouldn’t require an engineer to make that one. Mr Edgley: Would you answer my question please. Who made the decision? Turnbull did not reply. “Did anyone in Pyramid tell you a heavier shaft was necessary?” asked his Honour. Turnbull: I can’t remember the exact instructions, sir. “Wouldn’t you agree, Mr Turnbull, that Pyramid Machines were relying on you as an engineer about this?" asked Mr Edgley. “I wasn’t told that at the time,” Turnbull said. “But such a thing need not be expressed in words. They looked to you, didn’t they, to let them know what sort of drive they could have?” said Mr Edgley. Turnbull: I said previously they didn’t actually say that they were looking to me. His Honour: Did you understand they were looking to you to say what would be the proper form of drive to use? Turnbull: Not the final selection. sir. I did give alternative forms. “Did you understand they were looking to you for advice as to w’hat would be an appropriate alternative form?” asked his Honour. Turnbull: Yes, sir. Design of Mower Shaft "You’ve said you knew the drive shaft bent. Would it not be obvious to you as an engineer that a heavier one was required?” Mr Edgley asked. Turnbull: Yes. As an engineer would you have let Pyramid Machines have another one as light and as inadequate without at least warn-

ing them of the danger they would run?—l don’t think so, but my position at Price’s then was draughtsman. So you used for this motor a one-inch shaft without making any calculations of stresses? That may have been so. “Is it not so?” asked Mr Edgley. “I can’t remember exactly what happened four or five years ago,” Turnbull said. You heard from Julian he’d seen a motor with a broken shaft?—Yes. Did you then make calculations of the stress on the shaft?— No. Would it not have been wise to do so, as an engineer?—lt might have been. In effect, you just guessed that a one-inch shaft was adequate?— That might be the case, but it was not proved inadequate in the 1955 field trials. “Did you tell Mr Price your design was a guess?” asked Mr Edgley. Turnbull: I don’t recall doing so. You wouldn’t be very pleased to do it. would you? “I would not be ashamed of it,” said Turnbull. Experience of Hydraulics Asked what was his experience of hydraulic motors. Turnbull said it consisted of his experience with the Pyramid Machines project, and what he had later learned from other makers of hydraulic equipment in Christchurch. Mr Edgley: What other makers of hydraulic equipment have you acquired knowledge from? Turnbull: C. W. F. Hamilton. Couldn’t you have acquired knowledge from them in 1955 and 1956?—1t might have bben possible but commercial firms are not usually willing to pass on information they have obtained themselves about their own products. Turnbull detailed hydraulic equipment Hamilton’s made in 1955 and 1956.

And Hamilton’s to your knowledge have done other hydraulic equipment since—more allied to the Pyramid Machine hydraulics? Yes. “Then if Hamilton’s could acquire such hydraulic knowledge to make such machines, why shouldn’t W. H. Price and Son not have acquired it?” asked Mr Edgley. “Because in 1954-55, there was little general knowledge of hydraulic equipment, and very much less technical information available than there is now.” Turnbull said Have you seen Hamilton’s hydraulics on the Pyramid mower?—Yes. I think you’ll agree that Hamilton's have put their knowledgc of hydraulics to better use than Price’s on this Pyramid mower? —I don’t think I can fairly answer that question, not knowing all the information that Hamilton’s are likely to possess. But you know that the Hamilton hydraulic motor was not made specially for that mower?—Yes. It’s a stock job—l also know.. “Will you please answer, is that so?” interrupted Mr Edgley. Turnbull: Yes. it’s a standard stock line Changes in Motors Questioned on the testing of 1955 production run motors. Turnbull said the test “may not have been adequate by proper engineering standards.” Pressed for an admission that the tests were inadequate. Turnbull said that was so, “Otherwise, we wouldn’t have gone to the trouble of providing the test rig in 1956. The tests were inadequate because more power was required from the motors than that originally asked for.” Turnbull said Turnbull admitted that after field trials with the experimental motor and mower, the motor was changed. “So that the motor that had been tested and proved was not used again?” said Mr Edgley. Turnbull: No, but the changes were to features which would not alter the power output or flow requirements. It’s correct that the change was made by Price’s on their own initiative??— Yes, but it could only be a change for the better. They were accepted as a result of tests. Did it make the parts easier to manufacture?—Yes.

Were you aware early in 1957 that the modified mowers almost al! broke down?—l was aware that only a small proportion of those sent out were still working. Were you satisfied that thev weren’t satisfactory and that the job was a failure?—Not entirely, because there are still some mowers working. Are #ou not satisfied that the hydraulic components supplied by Price’s were inadequate? Or do you think they were adequate?— Yes. If carefully used under light conditions.

CAR CONVERSION CHARGE

Man Gaoled For Six Months Appearing for sentence in the Supreme Court yesterday on a charge of converting a motor-car valued at £lBO, Terrence Desmond Bradshaw, aged 25, was imprisoned by Mr Justice Haggitt for six months. The main cause of the crime was excessive drinking by Bradshaw, said his counsel (Mr P. G S. Penlington). The prisoner had been off work for long periods as the result of a succession of injuries and had developed a propensity for liquor. He had been convicted of the same offence on two previous occasions and had been admitted to probation. It was a proper case for a substantial monetary penalty followed by probation, said counsel. Sentencing Bradshaw,' his Honour said that on his release from prison he would continue the probation he was already serving and would be ordered to take out a prohibition order.