Re: Leaking packing, CM story, NNG

Vulclain compounds hold a special place in the annals of poorly thought out designs, which explains why they were abandoned so quickly, and why so few survived.

The problem revolves (literally) around the fact that the piston rods are not in line with the wrist pin. If you look are the indicator cards of a Vulclain compound working at long cutoff, you find that the high pressure piston is doing very little work at the start of the stroke but is doing most of the work by the end of the stroke. The result is that the crosshead and pistons assembly is being racked up and down with each stroke, wearing the rod packings egg shaped, and putting large bending stresses on the piston rods at the crosshead. No wonder they constantly leaked, and probably broke piston rods with monotonous regularity,

Did I mention what a terrific salesman Samuel Vulclain was?