Note: The numbers produced of each model would be to some extent dependent upon the type of equipment, the specifications and the Type Approval Tests to be made, but the figures given in the table above are broadly indicative of requirements.
The following describes the project stages in some detail to help explain the principal of each model-classification.
To develop the project a team was set up under the overall control of Jim Irvin with the project leader being Jack Leggett. The other principal team members being Peter Dyer, Alan Evans, Graham Lies and myself.
The A model stage
This stage is a means of proving basic concepts. The distinctive features in the case of the A40 Pack Set were that although simplistically the equipment was a copy of a Canadian prototype, there were many very basic differences inherent in our EKCO unit.
One big reason being that in those days, imported components were not permitted in any military equipment, and therefore virtually all such components in our model were physically different from those in the Canadian counterpart. Also several vital components were unavailable in Britain, including the 'Thermionic' valves, had to be designed and tested on an undesirably short timescale by British firms before much of the meaningful work could be commenced.
A40
Photograph courtesy of i.meulstee@wxs.nl
One of the first things we decided to change was the internal form of construction of the Canadian model, which we felt was inappropriate, primarily because it was felt that many of the original metal parts could be profitably replaced by plastic mouldings in which we (EKCO) had particular expertise.
This came about because Jack Leggett (The Chief Project Engineer) was instrumental in suggesting the use of plastics. We therefore set about producing a representative structure in sheet aluminium and synthetic resin bonded paper (SRBP), the latter simulating the parts in plastic as he envisaged them. This was produced in a matter of a few days on the laboratory bench, using only simple hand tools, but nevertheless provided a very useful indication to everyone of the intended construction.
Another item of note was that on 'A' development models, we engineers would normally be responsible for requesting purchases of all components, and supervising the provision of all piece-parts at this stage. Normally this would be done through the Buying Department who of course had contact with the appropriate engineer in the event of queries, and any technical discussion was automatically deemed a matter for him to deal with.
In the case of the A40 Pack Set, because of the need to re-engineer many of the 'foreign' components, there were high priority requirements for design of these special components by outside suppliers. This was dealt with almost entirely by our team directly, rather than via the Buying Department.
The structural parts were produced mainly by the Model Shop to laboratory sketches complying with dimensions as effectively defined by the Design Specification. However all assembly work was carried out in the laboratory, by a Technician from the Wiring & Assembly shop, and in close collaboration with us.
Initially, non-availability of components prevented completion of the receiver section, but a certain amount of work was possible on the transmitter.
While the physical construction was not representative enough of the intended final form to make vibration testing relevant, electrical performance tests and a check on the stability of transmitter characteristics with temperature variations could usefully be made.
The result of this work was that the A Model provided us with a test bed, which was as representative as possible of the envisaged design, which we produced at a minimum cost, without any of the high expense of formal drawings, which would eventually be required. It also provided a highly efficient way of dealing with many of the earliest and most numerous modifications.
A Ministry requirements of those days was that 'Armed Forces' equipment has to be designed to be 'Rugged', which in simple terms means that it has to be designed to endure rough handling and meet hostile environmental conditions such as a temperature range of minus 40șC to plus 70șC and 100% humidity. Equipment also had to meet a harsh vibration standard.
The A models allowed us to test to this standard early in the program.
The B Model Stage
Despite the great value of the A Model, the eventual aim of this development work was to make sure that there was all the necessary detailed information in order to make 'fully engineered models' and meet the MoD requirement that enable any suitably equipped manufacturer could make the product in quantity in its finalised form, ideally without reference to EKCO. The B Model stage therefore was when the first "engineered" models were produced.
At the B model stage, the importance of the drawing office needs to be explained in a little detail.
It was at this stage that effort was made to produce a full set of drawings covering every detail of construction together with a test specification to prove compliance with the original design requirements.
In practice the process of producing the drawings and translating them into hardware, was not so cut and dried since many drawings were still not finalised at the B Model stage, and could only be finalised following appraisal of information derived from the A models by the development engineers. This gave us a proverbial "chicken-and-egg situation!"
A very close association was maintained with the Drawing Office during this period Jack Leggett tried to visit the D/O at least once a day, discussing details of design or progress with xxxx (the Senior Draughtsman appointed to the project) who became one of the most vital team members because of his intimate knowledge of the work involved.
Jack Leggett took a close interest in drawings and his signature was required anyway on all the drawing before they could be officially issued and anything manufactured from it.
This did not mean that engineering checked all the dimensions on a drawing. Though ultimately important, this was too time consuming to carry out generally, and was seconded to drawing office staff. Nevertheless it is also important to realise that a major reason for producing models from drawings, was in fact simply to verify those drawings, and particularly the dimensions given on them.
Drawings were initially produced in pencil on tracing paper, thus providing for ease of modification, and an alphabetical order of issue was used. For those who might imagine development work to be a one-step design process, at the end of the B Model stage, only a few of the simplest drawings would be expected to be at the original issue "A". On the other hand the alphabet was on occasions too short, to cover the more than 26 changes to a few of the most complex drawings.
A record of every change was kept through a procedure called a 'Change Note'; this enabled us to keep track of design changes as the units evolved.
Incidentally, our design team had authority to 'mark-up' advance prints to enable rapid modifications to parts already in manufacture thus saving the time normally required waiting for the formal issue of a revised drawing.
Concession notes were another useful piece of paperwork, which enabled a piece-part not strictly to drawing to be used, provided the performance or structural strength of the part was not adversely affected, or could be tolerated for the purposes of a particular model.
Inevitably the B Model stage became a compromise where the overall effectiveness of the compromise was very dependent upon the quality of the engineering skills at all levels. The big difference between A and B was that in order to fulfil the major purpose of proving drawings at this stage, models were built in the Assembly Shop, from the information provided by the drawings. However it was still our responsibility to ensure that order cover was provided for any components to be purchased, with the priority given to items with longest delivery time.
Assembly of the B models was commenced as early as possible not only to validate the drawings through careful inspection but also to look for modifications, which were needed to piece parts, as were changes to circuitry, component and wiring layout. Some of these changes became apparent during electrical testing due to the dense packing of components where we also had to ensure that components could be changed when required.
In line with this, we discovered that some major structural changes were required as the material used for the plastic mouldings had to be changed due to unsatisfactory results during low temperature testing. Additionally changes were needed to the metal cast front panel.
At the B model stage it was also found that additional internal screening was required, which incidentally took several man months of laboratory testing to resolve.
Due to the time taken to build each 'B' Model, we were able to absorb changes progressively as they were built with each unit being progressively better that the last the result being that at the end of the B Model phase, we were getting close to the finalised design.
Once these modifications were made, testing again took place, which simulated some of the Type Approval Tests, which would be applied at the C Model stage. Non-destructive vibration testing formed an important part of this testing since we were looking for resonance's, which could be ultimately damaging to the basic structure.
Another test, which took place at the end of the B model stage, was called the 'systems test'. The objective of this test was to establish that two A40 sets could operate as a two-way radio over the design specification range and conditions. This was somewhat difficult to achieve simply because no two B models were exactly the same, but nevertheless we got good results.
The C Model Stage
The C Model stage was the final one in which our Development Section was involved and largely employed the same team and the same facilities, which dealt with the B Models.
The manufacture of the C Models should have been a formality since they should have been "fully engineered" units made entirely to finalised drawings approved by MoD, principally in order to provide for Type Approval Tests and general evaluation of the finished product.
In practice the situation was much nearer to the B Models since a few outstanding modifications still need to be dealt with, but broadly a full set of drawings was in existence, tracing in ink onto linen blanks being the only remaining Drawing Office requirement left, in order to comply with the original contract.
Completion of the Type Approval Tests to MoD satisfaction was the main objective of the C models, and our principal concern during this stage. Failure here could have been expensive, involving not only design modification, but also a repeat of all the tests, however due to the care taken during the B Model stage, these were successful and led to MoD recognition of the conclusion of the Development Contract, and authorisation for the pilot production run of D Models.
The D Model Stage
The production of the D Models was outside the realm of the Development Section since these were made to production standards. The techniques used in production obviously differed from those employed during development and our role was to liase with the Production team to help ease the units into production.
In a final twist, despite 4 years of detailed development and hard work, we did not in fact get the full production contract and Jack Leggett left the company to work for the Canadian version of our MoD (SRDE) fairly early on in the development program.
