Drawing of a 'going barrel' type mainspring barrel in a watch, sectioned through the axis. The mainspring is shown fully wound, tight around the winding arbor. The wheel attached with screws at top is the ratchet, to prevent the mainspring from unwinding. This was from a keywind pocketwatch; the winding arbor (axle) extended to a squared off section (not shown) accessible through a hole in the back. A key was inserted through the hole, fitted on the shank, and turned to wind the watch. Besides the arbor, this is similar to a mainspring barrel in a modern watch. Alterations: removed caption, sharpened, converted to PNG.
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{{Information |Description=Drawing of a 'going barrel' type watch mainspring barrel. The drawing is a section through the axis. Alterations: removed caption, sharpened, converted to PNG. |Source=downloaded from [http://books.google.com/books?id=5SYJAAAA