Apart from the accidental ingress of debris, the greatest danger to any design of oil pump, particularly one of the gear tooth design, is that of cavitation. Commonly found in centrifugal pumps also, the presence of this phenomenon and the resulting surface erosion is often confusing to the uninformed. A complex process having one of many causes, for an adequate explanation we need to understand and explore some of the more basic principles of fluid mechanics. In particular if we consider...
It is surely an obvious statement of fact that what goes in, will eventually come out again – somewhere! Filling the bath with water and then watching it drain away again afterwards is an example. The joy of watching the bank balance rise at the end of the month and then tearfully watching it ebb away again in the weeks following, is another. But unlike these examples, which would appear to happen without any effort at all, the task of extracting the oil out of an engine comes at a...
The science of engine development is one of incremental steps; small but measurable increases in power over a period of time. Improvements in port flow, increasing the engine rev limit or changes in intake or exhaust system sizes will, no doubt, help. But while that is undoubtedly the high profile, glamorous part of development, as far as engine performance goes, it is only half the story. The other, perhaps less glamorous part is that of minimising the parasitic losses; the friction in...
Last month we looked very briefly at gear pumps, in particular, external gear pumps when two gears sit side-by-side. A particular derivation of the gear pump however, sometimes referred to as an internal gear pump or internal-external gear pump is when one external gear fits inside a rotor consisting of an internal gear. With the centres of each gear offset from one another and a differing number of teeth on each of the gears, rather like its external counterpart, the resulting cavities...
Having established that a positive displacement pump is the only practical way of supplying lubrication to our engine, the question remains as to which of these many types is most suited. And to understand this it is necessary to examine the engine’s demands on the oil. In any high performance unit the oil has two primary functions: to lubricate (obviously) and to cool. For more mundane applications we can also include things like ‘to protect against corrosion’ or ‘...