Economize by Engine Governing
Page 52
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"A Service Manager" Endeavours to Dispel Prejudice Against Governors by Explaining Their True Purpose and How they May Be Employed to the Best Advantage
IN the writer's experience there is lmuch misunderstanding on the question of governing engine speed. Many a fleet operator, after experiment with speed governors, has formed a prejudice against them. This has probably been occasioned through a misconception as to their purpose.
The -engine-speed governor is not intended primarily as a safeguard against prosecution. It is not designed for use as a limitation of road speed to 30 m.p.h. or 20 m.p.h., and it is only in rare circumstances and under certain conditions that it can be used as such.
The device is designed to protect owners from abuse of their vehicles by careless drivers. Limiting engine speed to the known correct figure affords this protection with a big saving in upkeep costs, and usually a considerable economy in petrol consumption.
Let us examine the true function of the governor. Rapid wear and tear of an engine are caused almost exclusively by running it at excessive speed. Repeated "revving" at or above the power peak, in intermediate gears, and running "all out" for miles on end are the greatest causes of rapid wear, not only to the engine, but also to the gearbox, transmission, tyres and everything else concerned.
To overcome these evils crankshaft revolutions should be limited, but care must be taken in choosing the limiting point, and it is due to lack of knowledge on this matter that many who have tried engine governors have been disappointed with results. Actually, the full value of the governor would be secured if the limit of engine revolutions were made at the development of
full torque—in other words at that point where the engine gives its greatest wheel-turning capacity, that is, maximum load propulsion. This does not occur at maximum r.p.m., but below.
In practice, the torque peak may represent a road speed in top gear of about 20-25 m.p.h., whereas the maximum road speed of the vehicle may be 50 m.p.h. In such a case, approaching a hill, the vehicle will climb with equal ease, there being no power loss, although not so fast as it would if ungoverned. Obviously, 20-25 m.p.h. is too slow, so a compromise should be made in the majority of cases, and a figure chosen which is as near the torque peak as practicable and, preferably, not above the b.h.p. peak.
A proper realization of this important point will enable any operator to save considerable sums of money in running costs, for driving persistently at excessive engine speeds may easily result in a definite increase of 20 per cent, in fuel consumption and an unassessable advance in maintenance expenditure.