WHAT MAKES THE WHEELS GO ROUND?
Page 14
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By "The Inspector."
IDO NOT KNOW what the experience of other people is generally, but I find very often, when I am talking to prospective users of mechanical transport, users who have had nothing but the smallest experience of the kind before; that one of the first things—and sometimes the only thing—upon which they ask for enlightenment is, "How much petrol does the machine use I' It is certainly a commonly-held opinion amongst the uninitiated that the cost of petrol represents the bulk of the expense of running a motor vehicle. Assuming that a 10-cwt. van—shall we say1—will do 20 miles to the gallon on the average, and assuming the price of petrol at as. 6d. per gallon, the mileage cost, of course, for petrol works out at a small fraction over 2d. per mile. Now, although in the bulk this amounts to a considerable charge, there are other factors, such as the cost of tyre maintenance, the depreciation of the machine, and the repair charge, which, of course, jointly bulk very much more largely.
One itern to which the new user gives very little thought, perhaps, is the cost of lubricating oil and grease, which, although it does not i9proach the cost of the liquid fuel on a mileage basis, may easily, in certain circumstances, yield, a cost factor of very considerable proportions. Indeed, on a machine which is badly looked after, or on which the lubricating system was either originally, or has since become, wasteful, the cost of oil and grease may easily amount to a flgure not far short of that for which the petrol is accountable. In almost all new models, and in the published descriptions of them, we., as a rule, even to this day, find that great emphasis Is laid upon the embodiment of newly-designed and economical lubrication systems. We are quite certainly not yet near finality.
I well recall in this connection the very great interest that was aroused when the first trough system was introduced on commercial vehicles—the system by which troughs positioned below the big ends of the connecting rods were kept filled to overflowing by suitably-driven eireulating pump arrangements, into which receptacles the big ends on their paths round the crankshaft dipped their scoops. This was an infinitely preferable arrangement over the older method by which the. bottom of the crankcase held a great reservoir of oil at levels which, of course, varied with the consumption. It was also considered to be a considerable improvement on the forced method by which oil was pushed through elaborately-contrived ducts and passage ways carved out of the crankcase fabric and through the pins, webs and journals of the crankshaft.
There have been many variations since. those days, and, undoubtedly, considerable economy has been effected by the skilful employment of modern combined pump and circulatory systems of careful design. With it all, however, the average engine, after a certain amount of wear has taken place, and when the designer's original care has been negatived considerably on that-account, uses a good deal more oil than it should do. It is, of course, by no means an easy task to avoid exceptional waste of oil up the cylinder walls past the pistons, and although baffles and auxiliary piston rings do much to check this, a lot more oil is burnt hp than is desirable. We have yet got to arrive at a system which will provide that the whole of the lubricating oil used in the motor vehicle internal-combustion engine is used solely for lubri 534 eating and for no other purposes. There is room for a lot of improvement yet in respect. of the engine.
But it is not only the engine which is a wasteful unit on motor-vehicle chassis. Only a few machines have the design so effective as to avoid considerable, waste of lubrication from the gearbox, the back axle, and, indeed, from the innumerable joints on all auxiliary parts of the chassis. Ball bearings have, of course, worked wonders in reducing the lubricatiug troubles with which designers were at one time all too familiar, when they had to depend on plain bronze or white-metal-lined 'bearings, into which lubrication had to be inserted through erratically-cut channels. It was a hard job to keep such bearings thoroughly lubricated, and yet, at the same time, to avoid loss of oil through their ends. Axle ends, again, have been and are, in many cases, still a difficulty. Everyone knows of the trouble that is frequently experienced duo to the leakage of oil through axle ends, such oil finding its way with diabolical persistence on to the brake surfaces of the back wheels. Indeed, the brakes will frequently, in accordance with the general cussedness of things (particularly on several models on which I can recall the details), become More amply lubricated and certainly with more facility than a number of the surfaces which require such help, and which the designer had fondly hoped would receive it.
It is admitted that we have not reached finality in respect of such main units as the engine, the gearbox, and the live axle; but there are also many other moving parts on the chassis on which we are faced with another aspect of this lubrication problem, an aspect no less fertile of difficulty and one still calling for hard thinking on the part of the designer. I refer, of course, to those many parts which require the considerable aid of some sort of lubrication, and which, as a rule, are considered to be sufficiently cared for if a Stauffer lubricator or its equivalent is provided for its surface. As a rule, grease applied in this way to steering joints, spring shackles, brake and similar joints and other small movable parts on the ordinary chassis is, in the long run, very inefficient indeed. Only in certain cases are such lubricators used. Over and beyond the inherent drawback of Stauffers in respect of the attention required, there is the fact that grease is by no means a satisfactory medium for these odds and ends of joints. It refuses tap feed in very cold weather, it liquefies all too early in the hot.
Generally speaking, I think it will be admitted that there is still plenty of room for improvement in the design of strictly economical lubrication systems for the engine, gearbox, back axle and the many small joints on the average chassis. I read last week of an effort which is being made in this direction to improve the lubrication of the brake, steering and other auxiliary gear joints of a certain chassis. It consists, primarily, of an arrangement of wicks and small oil reservoirs, of which I have much hope. It is an American idea, but I remember quite well much wonderful economical lubrication which has served its purpose excellently for years on locomotive engines, " portables " and " stationaries," in which oil, sometimes with a little tallow mixed, and wicks or pads have been the principal features. I must admit that it makes me go cold every time I hear people scheming new devices to scrape carbonized oil off the top of the pistons. It sounds almost as bad as providing a stunp in the oil tray under the chassis to catch petrol. In any case, that's something that should not happen.