I suppose it’s the mechanical engineer in me but ever since I can remember I have always been fascinated by complex curves. It may have been the Spirograph I received as a child, rolling one circle around another to produced a series of intriguing spirals. Or it could have been the Lissajous figures describing complex harmonic motion later on at university. Either way, the complex geometries produced in such a simple way left a major impression.
The geometry of the gerotor oil pump is developed from such a simple approach. Rolling one circle around another, but in the special case when the radius of the smaller circle is exactly half that of the larger, a shape similar to that used in a Roots-type supercharger is produced. Read more…
When I was a lad, my old dad always used to say, “Change your oil regularly, son, and you’ll rarely have any engine problems.” Good advice indeed at a time when the statistic that 90% of all engine wear takes place in the first few seconds of engine life wasn’t even invented.
We live in a world of choice, or so our politicians would have us believe. But when it comes to engine oil systems for racing, is there anything other than a dry sump that can do the job? I would argue not, but despite that there are still authorising bodies or rule setters out there who insist on banning the systems, even though the alternatives are far inferior and these days probably no cheaper. 
It has often been said that I talk an awful lot of hot air. This comment, I hasten to add, is one more frequently voiced from members of my immediate family but this month, somehow and when associated with lube oil systems, the phase has much more of a resounding ring. This month therefore, I want to talk about the scavenge pump in a dry sump system and how big does it really need to be? The answer, as you might expect, is not that simple but let us look at what we are asking the scavenge pump to do. 
Of all the components in a typical oil system, the function and hence usefulness of the oil filter in a modern racing engine must surely be one for review. Designed to separate the larger particles which somehow accumulate in the oil and prevent them from returning back into the engine, there is little doubt that in most roadgoing vehicles some kind of filter may be necessary. In a racing engine however, which is put together under the cleanest of conditions and then assembled into the chassis in workshops where quite frankly, I 
Rather like the blood circulating around our bodies, the lubricating oil in an engine is fairly critical to its well being. For most of the time we don’t give it a second thought but it is only when things go wrong that people start paying attention. And for most of these the first thing they will notice is a reduction in oil pressure.
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.
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 price. And that price on a race engine, is the highest of all – power! So while we are consuming power to pump the oil into the engine 
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 all the sliding components and the power to drive all the auxiliary drive systems - which includes of course, the oil pump. 
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 can be made to pump fluids. A specialised form of this design which, rather than using an involute tooth profile 
