504
THE NEW ZEALAND GAZETTE.
{No. 16

SPECIMEN PAPERS FOR MOTOR EXAMINATION.

SECOND CLASS.

First Paper.

The questions are not to be copied. The answers should be written on form Exn. 30. Extra paper will be supplied if required.
Do not deface or make any marks whatever on this paper.

1. Explain how the fuel is ignited in the cylinders (a) of Diesel engines; (b) of semi-Diesel engines; (c) of petrol-engines. State which of these types of oil-engine is the most efficient in regard to fuel consumption, and give reasons for your statement.

2. State the source and the average chemical composition of the fuel commonly used in marine Diesel engines. What, approximately, is the calorific value of this fuel, and what proportion of its heat energy is usefully employed in engines of this type?

3. Give a description of the construction and working of a fuel-pump for a Diesel engine having blast injection. Explain clearly the mechanism of the regulating arrangement, and state the method of “setting” the pump.

4. Explain the meaning of the terms “flash-point” and “burning-point” respectively as applied to oil-fuel. State, approximately, the flash-point and the burning-point of the class of fuel commonly used in Diesel engines. What dangers are associated with the use of fuel of unduly low flash-point in oil-burning vessels?

5. Give a description of any system of lubrication adopted for marine Diesel engines. Explain clearly the method of lubricating (a) the pistons; (b) the main bearings, connecting-rod top and bottom-end bearings, and crosshead guides.

6. Describe, with sketches, the construction of a piston suitable for a four-stroke cycle single-acting Diesel engine. Show clearly the piston cooling arrangement and how the piston is secured to the piston-rod. State what clearance you would allow between the piston and cylinder liner in the case of a cylinder 24 in. diameter.

Second Paper.

7. State the chief duties of an engineer on watch in the engine-room of a motor-ship. What attention should be paid to the main and auxiliary machinery when working, and what observations should be made and recorded during each watch?

8. What is meant by the term “carbonization” as applied to the internal-combustion engine? State the causes and the effects of carbonization, and mention the preventive measures usually adopted.

9. Explain how you would calculate the indicated horse-power (a) of a single-acting four-stroke cycle Diesel engine; (b) of a double-acting two-stroke cycle engine. What is meant by the “mechanical efficiency” of an engine? State approximately the mechanical efficiency of each of the above types of engine.

10. Describe any arrangement for cooling the pistons of internal-combustion engines with which you are familiar. What are the advantages and disadvantages of oil-cooling as compared with water-cooling?

11. Explain what is meant by the “specific gravity” of a body. Describe the construction and use of an instrument commonly employed to determine the specific gravity of oil-fuel, and explain the principle governing its action. What relation does the specific gravity of an oil bear to its temperature?

12. Describe the construction and action of any type of galvanic battery with which you are familiar. State what is meant by “polarization,” and explain how it may be prevented. What, approximately, is the electro-motive force of a single galvanic cell?