Fig. 19.
In the following article we propose to explain how this can be accomplished.
Although we would not advise any person to be satisfied with approximate rules or constructions, yet cases do occur where the approximate constructions, being so very near correct, on account of their simplicity, are of greater practical value than the application of the rigid and more difficult theoretical rules.
By these remarks, we do not wish the reader to understand that the following constructions are all done according to the rules of thumb—not by any means; for all, with the exception of a few points, are theoretically correct. At the end of this article, we will point out those points which are, and which are not, approximately found; so that the reader may feel satisfied that our construction may always be relied upon as being correct for all practical purposes.
In what follows, the cylinder will always be regarded as lying on the right-hand side of the axle, the link being between cylinder and axle, and the axle located in the center of pedestal.
To avoid any misunderstanding, we will explain the meaning of some of the terms used.
The length of crank is the distance from center of axle to center of crank-pin.
For convenience, we shall call the total distance from center of eccentric-strap to the center of eccentric-pin in the link the length of the eccentric-rod.
The throw of eccentric is double the distance from center of axle to center of eccentric-wheel.