These notes give a detailed step-by-step procedure for a complete disassembly and reassembly of the Original-Odhner Model 239 mechanical calculator. They are also applicable, with suitable modifications, to the other models in the 200 series, and in principle to any Odhner machine from the 1920s to the 1970s.
The notes have been prepared and refined during the rebuilding of a significant number of Odhner machines, and may provide a useful guide to anyone faced with a similar task. The sequence of operations described works well for me, but comes with no guarantees. No responsibility will be taken for any consequences arising from the use of these notes by others.
These notes are intended to be read in conjunction with two other documents in this section: the Technical Description of the Odhner pinwheel mechanism, which gives an illustrated description of the construction and operation of the basic Odhner mechanism, and the additional features in the Model 239, and the Notes on overhauling a mechanical calculator, which describe general techniques for disassembly, cleaning, and rebuilding. Please study this material carefully before commencing your overhaul and refer frequently as you proceed, especially to the illustrations in the Technical Description.
If you use these notes to rebuild an Odhner I would appreciate receiving your feedback, comments, or suggestions for improvement via the enquiry form.