The timing cams used in the Bombe were originally used on Punched Card equipment. Some of the original BTM (not Bombe specific) drawings were missing. These were regenerated from the specification data by John Keen. No original cams were located in used BTM machines so new cams were produced. Paul Kellar made these in his private workshop.

BTM Cams are designed to either ‘Make’ or ‘Break’. Depending on the contact type used different timings can be produced from the same cam. A variety of cam shapes provide the full range of timing requirements

Below are two views of the unit in place in the frame. Here the cams have yet to be aligned and set up.

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