Interesting Facts
Page 49
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About Oil Engines
ON December 7th, Mr. It. Ricardo, 1.../P.R.S., gave his third and final instalment of the Howard lecture on compression-ignition engines to the members of the Royal Society of Arts, in London.
The principal theme was an outline of the possibilities of the oil engine ; the lecturer particularly stressed the fact that its greatest future lies principally in. the field of high-speed, small units as employed in vehicles. Similar power units will be installed for industrial and marine work ; he visualized exactly the same type of engine, used in batteries, thus permitting easy repair by substitution of a complete unit which is comparatively easy to handle.
This system of unit exchange is becoming widespread in the commercialmotor-operating industry. That is to say, when an engine has run its allotted span it will not be repaired in situ, but will be removed, for repair in mere convenient circumstances, and another engine of duplicate specification will be installed. This system affords many advantages and will permit the employment of more or less standardized designs—possibly those used for vehicles. In turn, this development would benefit the transport man, because the greater numbers of units produced should result in lower prime cost.
Mr. Ricardo's definition of a highspeed engine is one in which the piston speed exceeds 1,500 ft. per . minute, whilst by " small " he refers to a motor having a cylinder bore of less than 8 ins. An interesting estimate of the output of all petrol engines is that 300,000,000 h.p. is developed per annum, and that this total represents about 10 times more than that of all other forms of prime-mover put together.
At present, the petrol engine costs from 11 to £2 per h.p. to produce, and there is no reason according to Mr.. Ricardo, why the oil engine need cost more when bulk manufacture is in Operation.
With regard to maintenance,it was pointed out that the wear on bearings and cylinder liners must always be someWhat greater than that of the petrol engine owing to the increased load—given similar dimensions in both cases—also that greater noise and roughness are always likely to be experienced.
In the lecturer's experience, it is necessary to give a " top" overhaul to an oil engine after about every 1,200 hours' running, and a general overhaul after every 9,000 hours' running. In the case of an engine operating for eight hours a day, this means one day out of action in every six months for a " top " overhaul, and 10 days off for a general overhaul about once in three years.
As has consistently been pointed out by this journal, the present position with regard to the price of oil fuel will not always obtain, and, in the years to come, the compression-ignition engine must depend upon its greater thermal
efficiency for its selling appeal. This efficiency is particularly marked in the case of road vehicles, which are operating for the bulk of the time at about 33 per cent. load.
As is widely realized, Mr. Ricardo's experience is international, and his statement that the present type of British oil engine is in advance of its foreign contemporary must carry a good • deal of weight.
As regards the oil engine for vehicles
• it was pointed out that the present time marks the serious entry of the engine in question into the transport field ; hitherto the vehicles thus equipped have been principally in the hands of enthusiasts who are somewhat apt to gloss over defects and extol virtues. The critical public will soon be able to pronounce its verdict.