With modern sealing technology, the volumetric efficiency (leakage losses) of a hydraulic cylinder in good condition approaches 100%. But the mechanical-hydraulic efficiency of a hydraulic cylinder varies with seal type and the tolerances between the piston-rod and its wear bands.

Recall that mechanical-hydraulic efficiency refers to the amount of force lost due to mechanical and fluid friction. In a cylinder, these losses are due to friction between the piston-rod and its wear bands and seals, and the friction of the fluid as it’s ejected from the return side of the cylinder at the required velocity. In practice, fluid friction is not significant, provided the cylinder’s ports and its connections are adequately sized.… continue reading »

Rupert Murdoch, the boss of global media giant News Corporation was a neighbor of ours where I grew up. Not that my family was particularly well off. It’s just that my father’s farm happened to be situated close to a group of “sheep stations” the media mogul owned. And compared to the 300,000 acres Mr Murdoch controlled, Dad’s land holding was modest indeed.

In 1981, just in time for the wheat harvest, Dad took delivery of a new combine harvester. It was one of many he owned over the years, but this one was different. It was the first I’d seen equipped with a hydrostatic transmission for the ground drive.… continue reading »

If you’ve read The Hydraulic Troubleshooting Handbook, you’ll recall that I define hydraulic troubleshooting as a logical process of elimination which begins with checking the easy things first.

The emphasis I put on investigating the easy things first may seem so elementary your inclination may be to disregard this advice. Certainly, if you DO follow a logical process of elimination, you will get a result – regardless of whether you check the easy things first or not. It’s just that if you leave anything that’s easy to check until last – you’ll kick yourself for not giving it your attention in the beginning.… continue reading »