The New Zealand Railways Magazine, Volume 2, Issue 4 (August 1, 1927)
The following extracts from a paper read by Lieut.-Col. E. Kitson Clark, T. D., M. A., before the Institute of Mechanical Engineers in April last, describe an interesting experiment in the adoption of the internal-combustion principle to locomotive development. The subject is of particular moment in view of the revolutionary advances which may occur in locomotive and train operating practice, should the experiment prove successful.
Annihilation of time and space and efficient production of power have been accepted as symptoms and reputed as advantages of Western Civilisation. For the last hundred years the steam-locomotive has been a prime minister in these services. Its day is not yet over. Where reliability, versatility, and flexibility are required, where loyalty in lonely places is looked for, there will still be the steam-locomotive; but verstality and flexibility are not necessarily partners with rigid economy. A more complete use of nature's heat units is now called for, together with less human exertion in their application. Under certain circumstances, electricity presents the ideal. An electrical machine demands no physical effort from the operator. Its controls are simple, its power supply is not exhausted at speed, but it requires a land over-flowing with water and crowded with traffic, and postulates for the region thus richly endowed a clientele as abundant in capital.
Where any member of this trinity is absent, designers in all parts of the world who look beyond the steam-engine are turning to the internal-combustion engine for the next step in locomotive development. Oil atomised and expanded by combustion is a more economical vehicle of energy than evaporated water; its machinery-power for power-is less bulky. Its manipulation is a matter of mind rather than muscle and its effort can be maintained at high speeds without exhaustion. So far internal-combustion has merit, but in its usual form it is devoid of flexibility and presents great difficulty in starting against a load.
Therefore, when the Still system came before the author, he was impressed by its unique combination of internal-combustion and steam-power; internal combustion for continuous work, steam for starting, for overload and for auxiliaries, such as brakes, train heating, etc. The problem has been to obtain a machine of moderate cost with all these qualities and at the same time capable of facing the rough usage of a life on the open road.
In a few words the Still system is as follows:-The engine is double acting with internal-combustion at one end of the cylinder and steam at the other end through which the piston rod works. The water in the jacket is in connection with the boiler, and the excess heat from products of combustion assists in the production of steam in the boiler. The boiler is primarily heated by oil burners, and the steam generated is used for starting the engine. The two-stroke experimental engine which has been installed for ten years at the Chiswick Laboratory of the Still Engine Company develops 400 indicated horse-power with the expenditure of 0.345lb. of oil per b. h. p. hour. To obtain such a result on a locomotive would be to save 60 per cent. of the fuel bill, and towards such a result the designs which follow are aimed, but until the final tests with the locomotive are carried out, it is not proposed to make any higher claim than a saving of 10 per cent. on the fuel bill alone.
The locomotive to be described has three coupled axles, is designed to undertake the most ordinary regular work on main line service, and its axle load is 17 tons. The outside dimensions of the locomotive conform to the requirements of the great railways of the country. It is calculated to exert a tractive effort of 24,500lb. from starting to a speed of 6 miles per hour, dropping to 7,000lb. at 45 miles per hour. Its cylinders are disposed horizontally.
The transmission of force is in the first instance via a crank-shaft, mounted in rigid bearings to rotating gearing protected by a page 31 spring and damping device. From this the transmission is by connecting rods which provide the toleration required by the relative movement between the spring-carried superstructure and the driving wheels.
The gearing consists of two pinions incorporated in an engine crank-shaft.
For the fuel supply to the cylinders airless injection has been adopted.
In the course of experiment heavy Diesel oil of 0.95 specific gravity was used, but a lighter oil of 0.86 specific gravity was substituted; an improvement of 5 lb. per sq. in. mean indicated pressure resulted.