(d) Not often attempted, but there were a number of good answers and few "shots." The Parsons' turbine was sketched rather more often than the impulse forms. The sketching generally in answer to this question was of a satisfactorily high quality and the proportion of marks given was therefore high, but methods of fastening the vanes do not seem to be known.

Q. 22. Describe, with good sketches, one, and only one, of the following (a), (b), (c), or (d) :

(a) A steam stop valve of the screw-down type.

(b) A locomotive regulator valve of any type.

(c) Three forms of boiler stays, stating the use of each.

(d) The front plate of a Lancashire, Cornish, or return tube marine boiler, showing how the boiler shell and flue

tubes are attached.

(a) This section was about equally popular with the rest, in fact there is little to choose in this respect between any of them. The stop valve was well-known in all its details, the only mistake which occurred at all frequently was, as in Stage 1, the omission of any means for inserting or removing the valve.

(b) This was not an easy sketch to make, and a number of views were commonly found necessary. On the whole, however, the sketches and

descriptions were satisfactory.

(c) Mostly done well. The details of boilers are familiar to most of the students who answered this section.

(d) The sketches here were not of a very high standard, and a number of candidates appeared to be in doubt as to how much they should show.

Q. 23. Answer one, and only one, of the following questions, (a), (b), (c), or (d) :

(a) Describe the testing of any kind of heat engine which you have yourself seen or helped in. What measurements were made and how?

(b) How is an indicator tested? Criticise the method which you describe.

(c) How would you test the calorific power of an oil or spirit? (d) Describe the testing of any kind of boiler for power to

generate steam and for efficiency.

(a) This section and (c) and (d) were equally popular. Most of the candidates who selected (a) were evidently describing something they had seen; in fact in numbers of cases the answers were almost complete. Measurements of I.H.P. and B.H.P. were most popular. Many answers showed electrical knowledge.

(b) Not often done, but from a few schools there were very good answers. (c) Frequently attempted, but the information was often given as though learnt by rote. Thus a whole series of papers described a bomb calorimeter which was to be made of a material "equal to steel as regards tensile strength covered inside with gold or platinum and containing compressed oxygen to the extent of 25 atmospheres"; further, the combustion always required exactly "two ampères at twelve volts" to start it.

(d) Several gave hydraulic tests, and received no marks. There were, however, many excellent answers, and a number of candidates had evidently assisted, sometimes very humbly, at actual tests.

Q. 24. The indicated work of an engine is equivalent to 206 centigrade pound heat units per pound of feed-water; how many pounds of feed-water are required per horse-power hour? If you had a good many examples like this to work out, how would you arrange the work so as to have no unnecessary arithmetic.

Frequently attempted, and although often correctly answered, a number of candidates showed themselves hopelessly confused with their calculations. Not a great number answered the second half of the question completely. Many numerical errors were made.

Q. 25. There is a rule concerning the velocity of a fluid before it enters a turbine wheel and the inclination of the vane and its velocity; what is the rule? Give the reason for it.

Scarcely ever answered. Correct ideas on the subject seemed to be only moderately well grasped by the few that essayed the question.

Q. 26. The moment of inertia of a fly wheel is 9920 in Engineers' units; its speed changes from 10 to 102 radians per second; give in foot-pounds the increase in its kinetic energy. If the acceleration was uniform and the whole change occurred in one quarter of a revolution, what excess turning moment caused it?

Many attempted this who were evidently quite incapable of doing any part of it correctly. In spite of the many attempts hardly any candidates answered the second half correctly. A number of the better-equipped students were doubtful as to "Engineers' units," but this lack of information was not treated hardly, provided that the principles of working were correct. Candidates seem to be familiar only with linear, and not at all with angular motion.

Q. 27. A pound of oil contains 0.85 lb. of Carbon and 0.15 lb. of Hydrogen. What weight of Oxygen is just sufficient to completely burn it? If 1 lb. of oxygen is contained in 4:35 lb. of air, how many pounds of air are needed for complete combustion?

A fair number of correct and thoughful answers were sent up. A few thought the atomic weight of oxygen was 14.

Q. 28. The half travel of a slide valve is 3 inches, advance 30°. How far is the valve from its mid position when the crank has turned through an angle of 35° from a dead point? Prove your method to be right.

The construction and the proof were very commonly known. Many gave a Zeuner construction which was not really necessary, but S.H.M. principles do not seem to be too well known.

Q. 29. The entropies of a pound of water and of dry saturated steam at 150° C. are 0'442 and 1623 respectively. The volume of the dry steam would be 6'168 cubic feet.

Now there is a pound of wet steam at 150° C. whose entropy is 1.235. What is its dryness fraction? that is, how much of it is steam, how much water? What is its volume? Neglect the volume of the water.

Often attempted and generally accurately done. A few attempts were made via Total Heat, and after much arithmetic a successful result was obtained. When the first part was done, the second seemed to present little difficulty. The volume of the wet steam was almost always correctly given.

Q. 30. A boiler furnace fire is about 12 inches thick. What do we know as to the way in which combustion is going on at various places in the coal and above it, and in the space just on the furnace side of the flues? Does it depend upon the time that has elapsed since the furnace was last fed with coal? If so, say in what state the fire is, to which your description applies.

Comparatively few complete answers were made, in spite of the number of times the question was attempted. Numbers merely discussed the matter, and seemed concerned at the thickness of the fire. Knowledge of simple chemical principles is greatly needed.

Q. 31. When the outward radial force on each ball of a motionless Watt Governor required to keep it in equilibrium at the distance feet from the axis is equated to the centrifugal force which would exist if it were revolving, we find the following result. W lb. is a load, w lb. the weight of each ball; ƒ friction; n revolutions per minute

speeds corresponding to r = 0*5.

If you had to do this for other values of r and for other values of W, how would you arrange the work so as to have least trouble?

This being only arithmetical, a number attempted it, but many slips have to be recorded. Those that used slide rules did best. The most frequent mistake was to neglect the second square root to be taken in the h term. The arithmetic shown in this question was of a low order. Methods of saving work were seldom well known.

Q. 32. In a gas engine cylinder where v = 22 and p=1472 it was known that the temperature was 130° C. What is the temperature when p= 122 and v = 12?

In doing this you have assumed the stuff to behave as a perfect gas. Why is this not correct?

Was often attempted, but nearly half forgot to add 273 to the initial temperature. Otherwise the first half of the question was commendably free from arithmetical error. Answers to the second half of the question were very interesting and showed not a little ingenuity. Unhappily, however, they also showed the most widespread errors as to the understanding of what laws a perfect gas is supposed to follow. Some thought a perfect gas was unaffected by temperature, others thought that the p v/t formula was not obeyed if the gas received or lost heat in any way, or if there was a mixture of gases. The answers to the second part were very feeble.

Q. 33. Steam 90 per cent. dry at 2033 lb. per square inch passes through a non-conducting reducing valve or throttle valve; and lowers in pressure to 1019 lb. per square inch; what is its dryness at the lower pressure? Use the following information :

(Remember that H

=

195

165

468'0

489-9

+ where is temperature and L is latent heat and x is the coefficient of dryness of the steam. Remember that H is the same for the steam on the two sides of the valve.)

Was often done and usually correctly. Many who failed to get the correct answer often did so owing to faulty algebra. As a rule, however, when the correct answer was not given the candidate was hopelessly confused.

Q. 34. Air is at 1600° C. in a vessel, and at the pressure p; it escapes through an orifice which expands outside into an atmosphere of pressure 1. Its temperature as it passes without shock into a wheel outside is not to exceed 500° C., what is p? Assume the adiabatic law.

Most rarely attempted, but a few answers were sent in that got full marks.

STAGE 3.

Results 1st Class, 29; 2nd Class, 75; Failed, 135; Total, 239. The number of candidates in this state was 239, compared with 176 last year, thus showing an increase of 63, or nearly 36 per cent. The work on the whole was satisfactory, and in the case of a few candidates was very good indeed. The sketches in answer to Questions 41 and 42 were generally in good proportion and exhibited a close observance of practical details. But the divorce of this kind of knowledge from that of a mathematical nature was very marked in this as in the other stages, and is specially referred to in Honours. The answers are now criticised in detail.

Q. 41. Describe, with good sketches, one, and only one, of the following, (a), (b), (c), or (d) :—

:

(a) A crank shaft bearing of a large horizontal or vertical engine, giving the diameter of the bearing.

(b) The crank axle of an inside cylinder locomotive, with the eccentric-discs, inserting approximate dimensions.

(c) The piston and connecting rod of a gas or petrol engine. State the diameter of the piston.

(d) The wheel of a Parsons' or other steam turbine, showing how the vanes are fixed, and how it is balanced axially against steam pressure. Also the arrangement which prevents leakage.

The choice generally fell on (a) or (c). In the answers to (a) bearings stated to be for horizontal engines were sometimes shown in which there was only provision for vertical wear. In (c) the answers revealed a wide acquaintance with small petrol engines. The sketches to (b) were evidently confined to students from locomotive works, and were for the most part excellent. In regard to (d) a few of the sketches were from practical experience of turbines, but many were apparently from books.

Q. 42. Describe, with good sketches, one, and only one, of the following, (a), (b), (c), or (d) :— .

(a) A large steam stop valve of good design.

(b) A locomotive regulator valve of any type, showing the pipe by which steam is led from the steam dome to the cylinders.

(c) Four forms of boiler stays, stating the use of each.

(d) The front plate of a Lancashire, Cornish, or return tube marine boiler, showing how the shell, the flue tubes and the stays are attached.

Here again (a) and (c) were generally chosen. In answering (a) the candidates not infrequently spoiled an otherwise good sketch by showing a design in which it was impossible to get valve and seating either in or out of the casing. The regulator valve was not very well sketched, and its construction could seldom have been thoroughly made out from the sketch by a person who did not possess a previous knowledge of its form.

Q. 43. Answer one, and one only, of the following questions, (a) or (b) :— (a) How is an indicator tested? Criticise the method which you describe.

(b) Describe the testing of any kind of boiler for strength and power to generate steam and for efficiency.

The boiler test was usually the one described, and many of the answers showed that the writers had themselves seen such tests. In other cases the candidates said, vaguely, measure this or measure that with no hint of a practical way of doing it. The efficiency of a boiler was better understood than its power to generate steam.

Q. 44. Why is it, that the steam turbine seems to take more advantage of a very perfect vacuum in its condenser than a reciprocating engine? What are the defects of any turbine you know? Why do we obtain so little mechanical energy as compared with what is shown on the Rankine Cycle?

Some knowledge of the defects of the steam turbine was shown, but in regard to the other parts of the question the answers were nearly always worthless. The question was not very often attempted.

Q. 45. For any radial valve gear we have a figure which enables us rapidly to find the half travel of the valve and the advance for any position of the gear. Show how this is arrived at and prove the method to be correct. Assume motions to be simple harmonic.

Was seldom attempted, and with poor results. Candidates had some knowledge but lacked the power to present it in a coherent and logical form. Sometimes a proof of the Zeuner diagram was given, the travel and advance being supposed known. In other cases Stephenson's link gear was described.

Q. 46. Crank 1 foot, connecting rod 45 feet, what are the accelerations at the ends and some other point in the stroke, if the engine makes 200 revolutions per minute? The piston and rod and cross head are 420 lb.; draw a diagram to show the force in pounds required to produce the motion. State the scale clearly. This was a favourite question, and it was often well answered. A rather common error was to take the middle of the piston stroke to correspond with the crank position half way between the dead points.

Q. 47. Prove the formula connecting latent heat, temperature, pressure and change of specific volume when there is a change from liquid to vapour.

This question, when attempted, which was not very often, was nearly always completely answered, and indicated good book knowledge.

Q. 48. It has been proposed, instead of much superheating in the usual way, to have less of this and to superheat in the receivers between the cylinders. Assuming that the thing can be done in a good practical way, what is your opinion of its merits? Of course you will give your reasons.

Was answered more frequently than the knowledge possessed by the candidates justified. One or two condemned the method outright. A few pointed out how the difficulties arising from a high degree of superheat would be materially lessened, several using the diagram very effectively in their explanation.

Q. 49. In the following Table u is the volume in cubic feet of 1 lb. of dry saturated steam. v is the actual volume of a pound of wet steam (neglect the small volume of the water). What is the dryness fraction in each case?

0

In the table we give the entropy of 1 lb. of water and 4. the entropy of 1 lb. of dry saturated steam. Make a temperature entropy diagram. Mark the three points where the volume is 3.2 cubic feet and draw a curve through them.