In spite of the fact that it is common to compare the lubrication system of an internal combustion engine with the blood circulation of the human body, the present-day ingredients of the artificial system took decades to crystallise, in striking contrast to most of the other technical features of both these “prime movers.”
To attempt to describe this process of evolution in a short article of about two thousand words is obviously to ask for trouble, even if an attempt is made to refrain from all but the most brief reference to the question of the quality of the lubricating oil employed, or the influence of the various bearing materials used. Nevertheless, a very large part of the story of the progress in lubrication systems is bound up very closely with the story of the evolution of such “allied” specialist components, and if these are left out, as they must largely be, there remains a comparatively colourless tale of a struggle for control. It is a tale that gradually wends its way through “bags of splash,” low pressure and organised splash, to very little splash, medium pressure and high pressure, with splash as a confounded nuisance. In essence, the story is one of control of the oil that the designer desired to reach a certain point, and then control of the surplus that was left over once the supply had reached that certain portion of the moving parts. In the earlier days, before the coming of the motor car, when such moving parts in the internal combustion engine moved at a rotational speed that could be followed by the human hand and eye, the skilled engineer could and did oil the big-end, for example, literally by eye with an oil can, to the admiration of all the small boys beholding. Very well such a system worked, too, and the writer recalls vividly very many happy hours spent watching such an operation performed on a Crossley paraffin engine engaged on pumping sewage at Southwold, which, he discovered during a recent nostalgic visit there, only ceased to operate in 1942 or thereabouts. But, of course, it was quite unthinkable that such dexterity should be demanded of even the pioneer motorist. It therefore appeared appropriate to the early designers to provide a separate oil tank, and to ensure that by mechanical means, manual plunger or even the pressure in the exhaust system, the oil passed through one or more sight-feed glasses in visible and countable drips to the most important parts of the machinery, the “base chamber” being not the least vital. The base chamber, of course, was always full of goodly supplies of oil, and the sight-feeds served to replace that which slipped past the piston rings, or was burnt in other ways, to say nothing, in some designs, of that which found its way out onto the open road. The oil which the base chamber contained was splashed all over the place by the revolving parts contained therein, and it was this somewhat haphazard procedure that ensured the continued smooth workings of the prime mover. One of the main difficulties, somewhat naturally, was that far to much oil was flung about, and some of the early designers have recorded in the Proceedings of the Institute and elsewhere that, in an endeavour to see what precisely was happening inside, they contrived skilful transparent windows in cunning places around their crank cases, and were rewarded by seeing nothing but an opaque green expanse: oil “mist,” which was commonly supposed to do the actual lubricating, did not exist, quite a few of them averred. Indeed, on this particular subject of lubrication, history is punctuated by a refreshing honesty amongst engineers, which makes the whole study most enchanting! On the subject of manual plungers, the writer has some very happy memories of such a system, wherein the designer ordained that about every ten miles the driver should remove the right hand front the steering mechanism (for which two hands were, without doubt, needed), turn a tap, raise the plunger of a glorified hypodermic syringe slowly, turn a tap again, look down to ascertain that the sight glass was full, and then depress the plunger again. This process was normally repeated as long as a goodly supply of smoke failed to arrive at the exhaust box, and was extremely exciting over the tram-lines at Brixton during the V.C.C. run.
But, happily, the P.V. factor of the various bearings in those far off days was low, and trouble was rare. Even when the loads became quite “modern,” this system, as represented by the classic “Pilgrim” pump, was still more than satisfactory with roller-bearing engines — the 1939 Levis motor-cycle, for example, bears testimony. Indeed, one of the difficulties of this article is that there are many examples of what might be called “old-fashioned” oiling systems working perfectly satisfactorily years after the “leaders” of the industry had adopted something “better.'” The Austin Seven was a first-class example and so was the ‘Model-T’ Ford, neither of which could exactly be described as unsatisfactory motor cars. However, very gradually, the low-pressure system began to replace the splash, but, even so, it was not until after the 1914-18 war that it made real headway. De Dion and Maudslay were in this field by 1906, according to Beamont’s second volume, but at that time, even, the advanced Mercedes still applied exhaust pressure and boasted the usual row of polished sight-feeds. Be that as it may, the drilled crankshaft must indeed have seemed a daring move in those days, but gradually, very gradually, the idea spread, and the passenger and/or driver was relieved of the responsibility of setting the individual sight-feeds, a task that is soul-satisfying to the modern “vintage” or “veteran” type, but which certainly must have persuaded many a prospective motorist of 1906 against purchase. Even by 1910, Mr. H. C. Monkom, who read his paper on “forced lubrication” before the A.I.E., said to his audience : ” … various splash and gravity systems have been very carefully designed for car motors, and the success attained is great, so great that it is easy to argue that the success is good enough …” From a table which he appended to his paper, out of 34 manufacturers, the following is a summary of the types of lubrication systems in use at that date :
- Splash, hand pumps and “auto-level” … 8
- Forced … 18
- Mechanical … 4
- Forced to troughs … 4
Several questioners wanted to know whether some of the schemes that were claimed as “forced” were, in actual fact so, but be that as it may, the average pressure of these systems was about 10 p.s.i., the lowest being Metallurgique with 2 p.s.i. and the highest, Lanchester with 40 (it seems impossible to write a single article without mentioning Lanchester, doesn’t it ?). An average oil consumption of those days was about 600 m.p.g., of which more anon.
The arguments against the new idea were many. Some said that the tortuous drilled passages in the crankshaft would easily clog up, and some that when the brass bearings wore a bit, the pressure would drop anyway! One confirmed “splash” enthusiast even went so far as to say that if the bearing fit and oil pressure were correct for an engine in the cold state, then there was bound to be no pressure at all and far too much flung off the rotating parts when hot, which seems rather classic from someone who should have known something about flinging. The same person was equally convinced that even if the pressure system were suitable for constant speed engines, splash was the very thing for the variable speed motor-car engine. All the modern types of oil pumps, relief valves and breathers were represented, but, of course, they improved in detail during the ensuing years. Apropos of the low-pressure pump supplying troughs under the big-ends, a system which, for light cars, at any rate, lasted well into the ‘twenties, it is certainly amusing to read of someone, not, it is believed, unconnected with the original Wolseley Company, who, after listening to all the theories about the best shapes that big-end dippers might take, stated that his worked just as well when the rods were fitted the wrong way round. Our second example of refreshing honesty! It is interesting, too, to ponder that a cogent argument in favour of the forced system at about 1910 was that engines so equipped ran quieter than those with the older schemes.
In the post-war period during which low pressure and dippers competed for popularity, it should be borne in mind that piston and piston-ring design greatly affected the issue inasmuch as an oil consumption of about 800 m.p.g. or thereabouts pre-supposed not only frequent replenishing of the oil to replace that which passed the piston rings upwards, but also frequent changing of the oil due to the high degree of dilution caused by the amount of fuel which passed the same piston rings downwards. Carburation played a large part in this problem, especially in those cases where the period of operation with the choke out had not received sufficient attention.
As late as 1929, Laurence Pomeroy, senior, then with the Daimler Company, declared that the pressure system was by no means an unmixed blessing, stating that cold starting was the weak point, wherein the walls were starved for a period long enough to affect seriously the life of the engine, unless special measures were taken to deal with the point. Going back to the earlier ‘twenties, however, there is great difficulty in assessing exactly what the actual seriousness of this problem was, as two similar series models from a given factory could well differ as regards oil consumption by as large a variation as 3:1. The dilution problem was serious, however, whatever the degree, and it was by no means uncommon for the percentage of fuel in the lubricating oil to reach 20 after quite short running periods. For example, a test carried out by the U.S. Standardisation Committee showed that a typical mineral oil lowered its flash point by as much as 310 deg. F. after only five hours’ test running. The coming of aluminium pistons achieved a saving in oil consumption of up to 45 per cent. over their cast-iron predecessors, and we approach the days when a large part of the progress in the motor car lubrication system begins to be seriously affected by the specialist in other spheres. Some consideration must therefore be given to these allied “trades” if the story is to make any sense at all. Space, as has been acknowledged at the commencement of this article, does not permit of more than the briefest reference. Pistons and rings, for example, have passed through the stage of research for suitable working clearances, ring spacing and radial pressure. Oil control rings, “slippers,” bi-metal and self-compensating types have all been tried, rejected, accepted and tried again, and our modern pistons and rings are superb examples of the noble art of engineering compromise. The oil companies, likewise, have probed the hoary questions of mineral versus vegetable oils, graphite additives, oils for combating acid action, oils which keep their “oiliness” at elevated temperatures, oils which do not absorb fuel, and those which would the better stand the constantly increasing mechanical and thermal loading demanded by the motor car and aeroplane engine.
Bearings were undoubtedly the “Achilles heel” of the early pressure lubrication systems. They wore out pretty quickly and the whole system was “let down” thereby, thus adding an argument in favour of the retention of the old splash or semi-splash systems, which were relatively immune from bearing condition. Through hand-fitting and grooving, through boring in-line to the modern “thin-wall” type the story of the bearing is itself a fascinating one. Again, the messy piece of felt surrounded by a piece of chicken-wire is now replaced by oil filters and purifiers that really double the useful life of the lubricating oil itself. One could continue to multiply such examples indefinitely. Gradually, however, with these aids the designer began to get real control over the in the standard pressure system. It is not to escape the idea that in part, at any rate, the dry sump system, which had some popularity during the “vintage” period, was born of the desire to attain this control. Admittedly, especially where air-cooling is used, as in modern motor-cycle practice, there was the added argument that the oil could be used as an aditional heat remover, but as no doubt some vintage enthusiasts would agree, both these ideas sometimes failed, and the result was a sump full of oil and a pen’orth of froth and hot smell its the oil tank!
But that was forgiveable as even today oil has an infuriating habit of appearing not to follow the proper procedure, especially in small drilled passages and adjustable restrictors.
Not so long ago, some engineers stood round a certain engine and decided that oil would come up that drilling under so much pressure, would have its pressure reduced by that opening and then would flow out of that hole at a controlled and predictable rate. Nothing of the sort happened in fact, a perfect flood appearing out of the hole, seemingly defying all the natural laws, and no doubt any honest engineer could tell of a similar experience. Did not Sir Henry Birkin write, in 1932: “… oil continues to puzzle” ? But today, with pressures continuing to rise, with oil consumptions literally negligible and the whole system fool-proof, there is no doubt that most of the problems have been overcome. But perhaps a vintage soul may be allowed to indulge in a final nostalgic memory of the Austin Seven, and its lubrication system, which was sheer genius, as was the whole motor car it graced. In its “context,” as a car for the Great British Public, it surely owed much of its ability to motor and go on motoring to those two little jets that must surely have been drawn originally when a certain pencil slipped down a crack in the top of a billiard table under some immortal influence. — “A.B.C.”