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The annexed engravings are a front view I (figure 1) and a side section (figure 2) of a very simple and ingenious variable eccentric, by C. A. Holm, a London mechanic, and published irom drawings in the London Artisan: It is designed for the throw ot a crank or eccentric where there is not room for the ordinary slotted crank, a is the shaft from which the motion is communicated, on this, shaft is keyed the eccentric disc, b. In the centre of this disc is a stud, c, which is screwed into the centre of another disc, d d. This latter disc has a pin, c, fixed in it, eccentric, from sing the shaft, a, to revolve, it is clear that the stroke given to the pin, e, will be double the iadiu#bm centre 6F a to centre of e. But, if the screw, be slackened, the disc, d d, can V turned round until the centre of c is brought over the centre of a, when e will have no motion at all. And any point between these two will give a different stroke, as ? shown by the dotted lines in figure 1. Lines are engraved on theedge of the disc as 1, 2, 3/4, 5,6, and 7, which give the different ranges of stroke. Every engineer and person acquainted with a steam engine will at once perceive that this is a very simple device for setting the throw of an eccentric and crank. Its value will at once be appreciated by the fraternity. It is a on any engine, and it is equally applicable to various forms of expansion gear as well as the eccentrics of steam engines.
