502
THE NEW ZEALAND GAZETTE.
[No. 16

THIRD CLASS.

The questions are not to be copied. 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. What materials are employed in the construction of modern marine engines and boilers. State for what parts of the machinery each of these materials is adopted.
2. Explain the fundamental difference between the reciprocating steam-engine and the internal-combustion engine, with respect to the application of the heat energy of the fuel.
3. Describe the construction of a pressure-gauge commonly used by engineers on board ship, and explain the principle on which it acts.
4. Explain why boiler-manholes are generally elliptical. State whether the major axis of the manhole in the shell is placed longitudinally or circumferentially, and give the reason for your statement. Describe with sketches how compensation is made for the loss of strength due to cutting manholes in the shell and end plates of marine boilers.
5. What is meant by the “thrust of a propeller”? Explain how this thrust is produced, and how it is transmitted to the hull of a vessel.
6. Explain what is meant by the expression “thermal efficiency” as applied to a heat-engine. State the approximate thermal efficiency (1) of a modern marine reciprocating steam-engine; (2) of a marine Diesel engine.

SPECIMEN PAPERS FOR ORDINARY 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. Describe the usual method of constructing a built-up crank-shaft for a modern marine steam-engine. Explain how the cranks are set in position on the assembling table, and how the various parts of the shaft are connected together.
2. State the nature, composition, and physical properties of the material commonly employed in the construction of the shells of modern marine boilers. Describe the general conditions and the principal mechanical tests with which this material must comply.
3. Describe the construction of a salinometer used by engineers on board ship. Explain its use, and how it is graduated, and mention the principle involved in its action.
4. What are the chief causes of corrosion in marine boilers? Explain the nature of the actions involved, and mention the preventive and remedial measures generally adopted.
5. Give a brief explanation of the chemical reactions involved in the combustion of coal and fuel-oil. Explain the function of the combustion-chamber, and state the causes of incomplete combustion. What are the indications, respectively, of complete and incomplete combustion?
6. Describe the construction and action of a moving-coil ammeter, and explain the principle governing its action. What is the principal difference between an ammeter and a voltmeter?

Second Paper.

7. State the approximate chemical composition and calorific value (a) of high-grade steam coal; (b) of fuel-oil. Discuss the relative merits of coal and oil-fuel in respect to steam-generation, and mention the approximate evaporative duty of each of these fuels.
8. What is meant by the expression “mean effective pressure” as applied to the steam-engine? Explain clearly how this is determined, and how the horse-power of an engine is calculated.