Surviving wartime 'Earthquake' Bombs

I clearly remember both Grand Slam and Tallboy casings standing vertically outside the Brooklands clubhouse in the BAE days.
Painted in a neutral grey.

A couple of photos taken in the early 50's at Brooklands of a reunion with Barnes Wallis with some of his wartime team and possibly ex Dambusters aircrew.

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Kevin ~ thanks for the link to newforsetheritage pdf file as that appears to answer most of my questions.

Dave.

Both Tallboy and Grand Slam casings were cast at English Steel Limited, Sheffield.

Paper No 853 of Volume XXXIX 1945-1946 Proceedings of the Institute of British Foundrymen (the excitement mounts:)) states that although the paper describes one method of making this somewhat unusual casting that ' it has also been made successfully by more normal methods in another foundry in Scotland and also a foundry in the USA' It continues, 'It has also been made in the USA from a welded tube to which castings were welded to form the nose and base. Nevertheless, there is little doubt that if the job had to be started again little alteration in method would be made in he foundry whose work is described.

The interior of the castings were dressed by shotblasting via a feed nozzle inside the casing as it was rotated vertically via electrically driven friction belts. Little dressing was required due to the smooth finish of the built-up core that could be used just once and this was a work of art from a patterman and mouldmakers point of view.

The paper does not report the machining operations but refers to a photograph (Plate 15) as being the Machine Shop. The photo shows two GS side-by- side undergoing hydraulic testing!

So, if only Nairn did the machining, then cases would have gone from Sheffield to Nairn and then to the Filling Factory.

PETERTHEEATER;157722 wrote:

So, if only Nairn did the machining, then cases would have gone from Sheffield to Nairn and then to the Filling Factory.

Secret Scotland states:

'The casings for some of the 12,000lb and 22,000lb "earthquake bombs" were finished there.'

There are many sub elements to finishing as I found out when my employer purchased some 3M long by 2M Diameter castings for a special project.

Finishing

Fettling - the removal of feeders and excess material from a casting - is the first stage of finishing a casting. The metal removal is often achieved using manual cutting or grinding. However, more emphasis is being placed on automatic fettling, whereby the casting is placed in a machine programmed to remove materials from specific areas. The method of fettling must be taken into account at the initial casting design stage, so that the process is fast and efficient.

Blasting - abrasive particles, such as sand, grit or steel shot, are propelled at high velocity to impact the casting surface to remove surface contaminants. It can also be used to provide a uniform surface finish to castings. Propulsion of the abrasive particles is usually achieved using a centrifuge or compressed air nozzles.

Heat Treatment - the application of heat to a casting to alter the material properties making them suitable for the finished product or for subsequent processing. Heat treatments can be achieved in a number of ways, including induction heating, furnace heating and localised flame heating, amongst others.

Cleaning - non-mechanical removal of surface contaminants. Parts are submerged in different solutions, depending on the requirements of the cleaning process and any subsequent operations. Typical treatments are: molten salt baths used for electrolytic cleaning, acid baths for pickling, chemical cleaning and organic solvent cleaning.

Coating - application of a surface coating aesthetic purposes or to impart resistance to corrosion, wear and erosion. Coating techniques include electroplating, hot dip coatings, hard facing, thermal spraying and painting.

The above was copied from a reference book while I attempted to understand what the mechanical engineers were discussing.

I discovered that all of the machining categories also covered as many if not more sub categories etc.

If any one can locate the original specifications for bomb castings it would give you an idea as to what they referred to as finishing.

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Another one on display at the Pakistan Air Force Museum, Karachi.