Hydraulic?

Hydraulic?
by: Seamus Dolly


This may sound a little strange, but one day a man called in looking for  some water for his car. That was not unusual, until he started to put  it into his hydraulic reservoir for the braking system of his car. I was  young and curious, but he explained that water would suffice.  Many years later and some hydraulic experience, it seems that he was  right. Or partly so! 
It should be remembered that twenty-five years ago, and anywhere from  there back, the properties of rubber seals were different. Not deviating,  but going some way to explain where the hydraulic oil/brake fluid,  actually went. The fluid and indeed all oils were much different and had  little agreement with the rubbers available at the time. Leakages were  commonplace. 
Though many may frown upon it, water is still efficient as a medium for  hydraulic pressure, in the very short term, and especially in the case  of a braking system in a general performance automobile. It is the  purity of the water that changes its usability, but anything will do in  an emergency. Incidentally, pure water is an insulator, though I wouldnt  have the confidence to test the theory on a personal level, with four  hundred volts. Lol! Seriously though, this would be a reason why battery  top-ups, should be done with distilled or pure water. Water hasnt been  simply, water, for some time, or since it was chemically analysed. 
Modern hydraulic oils have anti-foaming, anti-wear (component-wise),  anti-corrosive, lubrication, and heat dissipation properties. They also  have special properties that limit their ability to compress, which is  the area that hydraulic excels over pneumatic. Higher control comes with  the solidity of the fluid, much as that sounds like a contradiction. 
Indeed, pneumatic control is favoured where there are risks of  contamination, from the oil itself, and this is one of the reasons that  air is preferred to oil in a lot of production systems. 
Friction does exist, even with fluid, and this as well as compressive  forces, is the cause of heat generation. Any such heat generation, can  result in a change in the liquids viscosity, thickness/thinness, ability  to flow. It can also have a negative effect on the various sealing  arrangement, whether steel on steel, rubber/plastic and its composites (sometimes  brass or bronze impregnated polymers), or indeed, where cast iron  replaces steel. Incidentally, dissimilar materials in juxtaposition and  dynamically, are better than similar ones. 
Steel on cast iron, generally, is better that steel on steel. 
So, while this man went for the only resource available at that point in  time, the pressure generated should be similar, or the difference  negligible, he would have been missing the lubrication properties that  oils achieve. His saving, was the short piston movement, the relatively  slow speed of his vehicle, and the limited time of usage. 
Hydraulics are exceptional at what they do, and large forces can be  transmitted through tight radii, and indeed, returned through 180  degrees, such is its theory with respect to acting equally in all  directions. Hydraulic systems have replaced the numerous and purely  mechanical applications, where the moving parts are essentially and  consistently lubricated. This is even better in a corrosive atmosphere,  where for example, salty air will compromise all exposed parts. 
On a lighter note, if such an improvising individual was thirsty, then  he would have a choice between his brake fluid reservoir, his window  washer reservoir, or indeed, his radiator.




About The Author


Seamus Dolly is at http://www.countcontrol.com/.