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Know-how 41: Preventive maintenance (26)—cab drill

8th September 1967
Page 45
Page 45, 8th September 1967 — Know-how 41: Preventive maintenance (26)—cab drill
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Which of the following most accurately describes the problem?

ATER our look at accident damage and its effect on planned work, and still with prevention very much in mind, let us look at another aspect which has a very considerable bearing on costs and unscheduled repair. I refer now to the engine unit that has failed expensively, the actual cause of the trouble having been some simple feature that could have meant only a slight delay at little expense.

In earlier years, we had fewer instruments than today, and such a thing as a coolant "temp" gauge was very much a luxury and rarely a standard fitting on goods vehicles.

So right

In fact one famous firm discarded the oil pressure gauge on their goods vehicle, and once when the question was raised personally with their engineer, he smiled and said: "You would only worry if I fitted one; keep your sump full and you will come to no harm"! And my 30 years' experience has not proved him wrong.

Nevertheless, in this day of more power, noise and speed, we have become instrument minded. It could be that there are now too many things to watch while driving on congested roads.

Just the same, the older driver had a great respect for his oil gauge, and night trunk men all had their own torch to periodically check that all was normal, and it is indeed true that few of those drivers were unaware of failing oil pressure, etc., and as a rule called a halt before damage could be caused.

Today, however, things are very much different, and more and more engines are driven on when in trouble, until they lock up, or tear something apart, yet in each cab there are instruments to tell the tale and little will get out of hand if a watch is maintained on them.

With hundreds of miles of motorways and near flat-out driving, boredom is one of the enemies of trunk drivers. Whereas in earlier days the driver would have a quick look at his oil gauge during and immediately after a stiff climb, this practice has somehow disappeared, and failing oil pressure or rising temperature has an increasing habit of passing unnoticed until the "crunch", by which time a lot of expense has been caused with many days' loss of use.

Every engineer has experienced these complete failures, and each will have heard the stock explanation—"there was one large bang" or, "it just pulled up quickly 'without any warning".

Yet on stripping down it is all too clear that either top or bottom end had been in trouble for many miles, with excessive noise, smell, smoke and failing power evident. Pistons do not grip their rings, lose all compression, or break up unnoticed, and a "blue" crank, with turned and burnt out shells, has screamed loudly before grabbing hold for the last time, yet for some reason, the ever-increasing warnings have been ignored until the final halt.

As stated, these failures are a real body blow to productivity and programmes. It is part of any engineer's task to ensure that all drivers are made aware of the value of cab drill—the daily oil and coolant check— and that instruments show normal readings before moving off. The instruments are useful but must be glanced at regularly.

The weakness can be that non-mechanically minded drivers may not be fully aware of safe and unsafe readings; one driver admitted that he thought the gauges were just there for the engineers to check.

Many drivers questioned after some "blow-up" blame small dials, or that the spokes of the wheel cut the line of vision, others that vibration distorts true vision at a four feet distance from dial to eye. I agree that there is something in all these claims; in fact on higher speed vehicles, with more attention needed through the screen, we may have to think in terms of audible oil and coolant tell-tales rather than visual.

But what concerns the engineer with existing vehicles is that all drivers should be educated in cab drill, before they are given a modern vehicle, to make sure that they understand how to read gauges correctly and can recognize the earliest symptoms or signs of mechanical distress.

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