to change their minds; if public money had been spent upon an article for the ship, into the ship it had to go. A few months before the first flight of the R.101 her designer urged his superiors to fit petrol engines in the ship as we had done in R.100, on account of the excessive weight of the diesel engines. This petition was refused by some high civil servant in the Air Ministry whose name is now forgotten, perhaps fortunately; the diesel engines had been developed for R.101 and they had to be used. It is interesting to note these relative restrictions imposed on the two staffs; our work was hampered by the paucity of research dictated by the fixed price contract, and theirs by the inflexibility of the official system.
My own work in the calculating office led at times to a satisfaction almost amounting to a religious experience. The stress calculations for each transverse frame, for instance, required a laborious mathematical computation by a pair of calculators that lasted for two or three months before a satisfactory and true solution to the forces could be guaranteed. To explain this for the benefit of engineers, I should say that each transverse frame consisted of a girder in the form of a stiff, sixteen-sided polygon with the flats at top and bottom; this girder was twenty-seven inches deep and up to a hundred and thirty feet in diameter. Sixteen steel cables ran from the centre of the polygon, the axis of the ship, to the corner points, bracing the polygonal girder against deflections. All loads, whether of gas lift, weights carried on the frame, or shear wire reactions, were applied to the corner points of the polygon, and except inthe case of the ship turning these loads were symmetrical port and starboard. One half of the transverse frame, therefore, divided by a vertical plane passing through the axis of the ship, consisted of an
encastré
arched rib with ends free to slide towards each other, and this arched rib was braced by eight radial wires, some of which would go slack through the deflection of the arched rib under the applied loads. Normally four or five wires would remain in tension, and for the first approximation the slack wires would be guessed. The forces and bending moments in the members could then be calculated by the solution of a lengthy simultaneous equation containing up to seven unknown quantities; this work usually occupied two calculators about a week, using a Fuller slide rule and working in pairs to check for arithmetical mistakes. In the solution it was usual to find a compression force in one or two of the radial wires; the whole process then had to be begun again using a different selection of wires.
When a likely-looking solution had at last been obtained, deflection diagrams were set out for the movements of the various corners of the polygon under the bending moments and loads found in the various portions of the arched rib, and these yielded the extension of the radial wires under load, which was compared with the calculated loads found in the wires. It was usual to find a discrepancy, perhaps due to an arithmetical mistake by a tired calculator ten days before, and the calculations had to be repeated till this check was satisfied. When the deflections and the calculated loads agreed, it was not uncommon to discover that one of the wires thought to be slack was, in fact, in tension as revealed by the deflection diagrams, which meant that the two calculators had to moisten the lips and start again at the very beginning.
The final check was to take vertical and horizontal components of the forces in every member of the frame to seethat they equated to zero, that your pencil diagram was not sliding off the paper into the next room. When all forces were found to be in balance, and when all deflections proved to be in correspondence with the forces elongating the members, then we knew that we had reached the truth.
As I say, it produced a satisfaction almost amounting to a religious
My own work in the calculating office led at times to a satisfaction almost amounting to a religious experience. The stress calculations for each transverse frame, for instance, required a laborious mathematical computation by a pair of calculators that lasted for two or three months before a satisfactory and true solution to the forces could be guaranteed. To explain this for the benefit of engineers, I should say that each transverse frame consisted of a girder in the form of a stiff, sixteen-sided polygon with the flats at top and bottom; this girder was twenty-seven inches deep and up to a hundred and thirty feet in diameter. Sixteen steel cables ran from the centre of the polygon, the axis of the ship, to the corner points, bracing the polygonal girder against deflections. All loads, whether of gas lift, weights carried on the frame, or shear wire reactions, were applied to the corner points of the polygon, and except inthe case of the ship turning these loads were symmetrical port and starboard. One half of the transverse frame, therefore, divided by a vertical plane passing through the axis of the ship, consisted of an
encastré
arched rib with ends free to slide towards each other, and this arched rib was braced by eight radial wires, some of which would go slack through the deflection of the arched rib under the applied loads. Normally four or five wires would remain in tension, and for the first approximation the slack wires would be guessed. The forces and bending moments in the members could then be calculated by the solution of a lengthy simultaneous equation containing up to seven unknown quantities; this work usually occupied two calculators about a week, using a Fuller slide rule and working in pairs to check for arithmetical mistakes. In the solution it was usual to find a compression force in one or two of the radial wires; the whole process then had to be begun again using a different selection of wires.
When a likely-looking solution had at last been obtained, deflection diagrams were set out for the movements of the various corners of the polygon under the bending moments and loads found in the various portions of the arched rib, and these yielded the extension of the radial wires under load, which was compared with the calculated loads found in the wires. It was usual to find a discrepancy, perhaps due to an arithmetical mistake by a tired calculator ten days before, and the calculations had to be repeated till this check was satisfied. When the deflections and the calculated loads agreed, it was not uncommon to discover that one of the wires thought to be slack was, in fact, in tension as revealed by the deflection diagrams, which meant that the two calculators had to moisten the lips and start again at the very beginning.
The final check was to take vertical and horizontal components of the forces in every member of the frame to seethat they equated to zero, that your pencil diagram was not sliding off the paper into the next room. When all forces were found to be in balance, and when all deflections proved to be in correspondence with the forces elongating the members, then we knew that we had reached the truth.
As I say, it produced a satisfaction almost amounting to a religious
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