Readers letters
While Barnes Wallis's bombs were subjected to the laws of gravity and friction, sinking and exploding at the end of their run, the stories and fascination with the project evidently are not. On May 2nd, Channel 4 devoted 2 hours to Dr Hunt of Cambridge University Engineering Department's very expensive experiments to try and re-establish data of the original trials on the basis that it had been lost in a flood. Much of this could, I suspect, have been done with CFD. Who paid, I wonder, particularly for the construction of the quarter scale dam and DC4 flights in Canada?
I well remember Wallis's CEI lecture on Future British Transport in Portsmouth Guildhall in October 1968, a wonderful demonstration of the 82 year old engineer's brilliance, enthralling us with his development of the supersonic swing wing and throwing us a challenge for marine engineers to develop a re-cycle gas turbine to propel cargo carrying submarines beneath the polar ice cap, and thus shorten the distance for exports to the Far East. He first apologised for having to speak from memory: his notes in the ground floor of his Brooklands office, had been flooded the previous day when the River Wey burst its banks. He had recovered his films and slides from the first floor by rowing boat. (Perhaps tit for tat, in retrospect).
Hunt was shown briefly looking at Science Museum records. Development is described in 65 files available in the PRO/National Archive, (listed in Source Sheet 34). In particular the main trials that the programme glossed over and by-passed are summarised; those of the GOLFMINE prototypes dropped from the Wellington bomber. File AVIA15/3933 is of particular interest. The key parameter that Wallis emphasised several times, but which did not appear in the programme, was that the bomb's density must be 75lbf/ft3 (pounds per cubic foot). Two of the recovered remains are on display at Brooklands, and a third near complete GOLFMINE is in Dorchester. Some of the film clips shown in the programme were of a Mosquito bomber of 618 squadron dropping the half-ton anti-ship HIGHBALL version, which was never used in action.
The programme's title, The Men Who Built the Bomb, did not mention the very difficult problems of their construction and strength, originally spherical, like the marble tests; and the repeated failure of the casings. That fell to the Oxley Engineering Company of Leeds, who had pioneered welded fabrication of steel tanks and gas holders before the war. Examples of their patent spiral guided gas holders can be seen at Fulham, Sale, Ascot and Dover. The plates are laid at 45 degrees, in line with the spiral guides. Their task was made difficult by the secrecy of the Dams project and the drawings that initially required the external surfaces to be ground smooth. There is some discussion of this and welding procedures in the minutes of the meeting of 19th December 1942.
A further problem was that some of the GOLFMINES had dimpled casings, like golf balls. Credit for overcoming these problems is due to Oxley's Chairman, H.H.Hollis, a brilliant welding engineer. My father, (a civil engineer) in Oxley's London office and his co-directors, eventually managed to extract the information that their products were being dropped onto water, spinning, from an aeroplane. The casings were back-welded. My late cousin Peter Barnes (who became a member of the Institution after the War) was a welder in Oxleys at that time, awaiting his call-up. A photo of the Oxley Board is attached below. Hollis is seated 2nd from the right, my father seated at the left end. Sidney Stansfield, Managing Director, is standing on the left. Herbert Savill, (a gas engineer), who became Chairman after Holllis's sudden death in 1947, is on his right.
Vickers then made the full sized UPKEEP bomb, and Oxley continued making HIGHBALLs.
Clearly, Cambridge is catching up fast with applied science; and I very much hope that Dr Hunt will be publishing an Institution paper on his research project in the near future. Barnes Wallis became an Honorary Member in 1966.
(* - Yorkshire Post original)
Bob Barnes
Next letter: Taking fun out of engineering