DEPARTMENT OF ENGINEERING. FIRST YEAR EXAMINATION. APPLIED MECHANICS. HONOURS. 1. Make a neat dimensioned sketch of a roof-truss suitable for a span of 50 feet; the roof principals are spaced 14 feet centre to centre. If the dead load is equivalent to 12 pounds per square foot of area covered, and the wind load 25 pounds per square foot acting at right angles to the principal rafter on one side, calculate the panel point loads, and draw the reciprocal figures for the dead load only, and for the wind on the left. Check the results obtained by the method of moments on any two members. 2. Referring to the above question, make sketches giving dimensions of the principal points and connections. State what material you would employ and the tests you would specify. 3. Determine the stresses in the subjoined truss ► 20 ́ 20′ + 20 ́ 20′ 20′ 20 ́ 20 30 一中 * Assuming the three left hand loads increased to 20 tons each, determine the stresses. State whether the frame as sketched is suited to endure them without modification, and, if not, suggest the required modification. 4. Show how to design one of the two main girders of a single line railway bridge of 50 feet span to carry a dead load of 0.4 ton, and a live load of 1.2 ton per foot run on each main girder. 5. Write an essay on one of the following subjects (a) The determination of the safe working stresses in bridges of structural steel. (b) The design of timber viaducts and trestles suitable for the New South Wales Railways. 6. Describe the apparatus you would use to determine the elastic and plastic properties, also the ultimate strength of a circular bar of steel subjected to torsional stress. Investigate fully the equations of resistance to torsion, and the coefficient of rigidtty Calculate the horsepower transmitted by a shaft 3 inches in diameter, subjected to torsional stress only, having given revolutions per minute 200; safe working stress, 10,000 pounds per square inch. FOURTH YEAR EXAMINATION. MECHANICAL ENGINEERING III. HONOURS. Thorough answers to a few questions are expected. Not less than THREE questions should be attempted. 1. (a) Discuss, in as precise a manner as possible, the question of the combustion of fuel and its relation to smoke prevention. (b) Describe, by means of sketches, any automatic CO2 recorder with which you are acquainted. 2. Discuss one of the following: (i.) The phenomenon known as the "whirling" of shafts; or (ii.) The torsional vibrations of shafts. In connection with the latter, describe the principle of action of any two forms of torsional indicator with which you are acquainted. 3. Give a brief account of one or other of the following: (i.) Rotary air compressors; or (ii.) High-lift centrifugal pumps. It is essential that your answer be illustrated by accurate sketches. 4. Draw a diagram to scale showing completely the stresses developed throughout a double-riveted lap joint. Discuss the bearing of these on the design of boiler drums, and state under what conditions, if any, you would still advocate the use of lap joints. Various methods have been adopted to "reinforce" such a joint. Discuss these. 5. Some makers of producer gas engines guarantee a development of 10 B.H.P. at a cost of 1d. per hour; under what conditions would this be possible? In the course of your answer deal precisely with the questions of the thermal and mechanical efficiencies of the plant, size of the unit, and the cost and quality of fuel. Scheme out a diagram to enable the cost per B.H.P. to be readily ascertained for any specified set of conditions. 6. Discuss the question of engine friction, and in particular give a full account, accompanied by the necessary analytical investigation, of the method of determining engine friction by a no-load retardation test. 7. In a weigh shaft suitable for a naval engine, and under the conditions indicated in the accompanying diagram, determine the correct size for the shaft, paying due regard to the questions of compound stress and of stiffness. LP Drog Rods 4000lbs 3500 lbs ENGINEERING DESIGN AND DRAWING. HONOURS. Candidates are required to attempt ONE only of the following designs. The designs are to be sketch layouts to such a scale as may be found convenient, but sufficient detail is to be given to show exactly what is meant by the candidate, and the method of attack is to be clearly explained. 1. A winch is required for hauling logs in the bush; it must be capable of giving an effective pull on the rope of 5 tons, at a maximum speed of 100 ft. per minute. The power is supplied by an electric motor run at 600 revolutions per minute. The winch must be provided with two drums, and arrangements must be made by means of a friction clutch, preferably on the drum, such that the effect of the haul does not interfere with the running of the motor. A brake should also be provided, so that the winch drum will not run back under the spring of the rope. 2. An hydraulic rivetter is required for driving rivets in boiler plate up to 72 inches wide and 1 inch thick, the largest rivet used being 14 inches diameter. You may assume that the load required to drive the rivet satisfactorily is equal to 100 tons. Design the machine. 3. Design a small steam pump suitable for boiler feeding and general service. The pump to be single acting, and of the crank shaft type, with slotted cross head. It should be capable of supplying 500 gallons per hour against a pressure of 180 pounds. 4. Design an overhead travelling crane suitable for dealing with a load of 5000 pounds on a span of 30 ft. All motions to be hand worked from the floor of the building, and the main feature of the design to be simplicity and cheapness. 5. It is required to obtain by means of a water tower a pressure of water of not less than 25 pounds per square inch, and not more than 30 pounds per square inch. A circular tank, having a capacity of 30,000 gallons, is to be provided, built of steel plates, and carried on a steel frame. Design the tank and structure. |