AUTHENTICITY

The Mock-ups are made so accurately that it seems a shame to point out minor errors. However for posterity this needs to be done. The overall dimensions are within 1/8″ with some components being made to the original tolerances of around one thousandth of an inch.

From the point of the movie this particular version of a bombe is a little early. The movie is set in early 1943 but the model of Bombe portrayed was not produced until early 1944. The first being delivered to Out-Station Eastcote on the 31 January 1944. We pointed this out at the time but the producers apparently liked the ventilated drums. From our perspective we found that the attention to accurate detail varied a great deal.

The ventilated drums were introduced around June 1943 on the first four wheel (High Speed Keen) machines. The ventilation being required on the very fast drums. However this construction was made standard on all drums and carried forward into the later three wheel machines.

If one looks closely at the photographs one will see that the fast drums are set further forward than the others. This is to accommodate replaceable commutators where another ‘disc’ was fitted to the front of the original commutator. The idea was that this could be changed quickly when the brushes had worn the face down too much. This feature was not fitted to machines built at the time the movie was supposed to portray. However I do not suppose that many people will be concerned about this.

One or two WRNS have spotted that the small pointers that should be fitted to the top right of each drum are missing. These were planned to be fitted but time ran out. The main purpose of these pointers is to allow the fast drums to be rotated to the correct position as defined in the menu prior to a run. They are also important on the indicator drums when it comes to recording a stop condition

Picking on just a small point of detail, the start/stop switch unit, below and to the right of the indicator drums is positioned too far to the right. It should be positioned about 1 1/2″ to the left.

The WRNS who worked on the Bombes often comment when they visit Bletchley Park is that the colours of the drums are wrong. We believe that we supplied the colours as accurately as was possible after 60 years. However the colours were chosen by the filming people who explained that when these appear in the final movie the colour processing can change shade so one has to start with colours that do not necessarily look right.

We have had comments from those involved during WWII that the speed and throw of the drums are not correct in the film. We had little to do with this other than specify the correct speeds and the action of the medium and slow drums. One thing we were told, which makes good sense, was that we were specifying a speed which was close to a sub-multiple of the film frame rate and that strobing was likely. This is the illusion one sometimes sees on old westerns where stagecoach wheels appear to be turning backwards.

The texture of the finish on the covers when viewed at Bletchley Park is far too coarse. Experiments were carried out by Asylum using a near match to the original crackle finish. On film, this apparently looked like a smooth shiny surface. This was solved by using a coarse car underseal overpainted black.

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