Quote:
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Originally Posted by M. Krass
For the record, that's exactly how a locomotive driver works. 
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Actually, it is not, but it is close. Ken's description maps directly to how a
wobbler engine works. On a steam locomotive, the piston is in a fixed orientation and does not rotate relative to the wheel. The motion of the piston is transferred to the driver by an intermediate drive rod (attached to the piston rod via the crosshead at one end and to the driver bolster at the other). The motion of the drive rod is linear at one end (the piston end) and circular at the other (where it is pinned to the drive wheel). Note the drive rod in the referenced image below (this image is of a model pump engine, but the motion is similar to a locomotive). There is also a nice explanation and animation of this on
How Stuff Works.
-dave
