GENERAL ENGINEERING I.

1. A standard test piece of steel o.8 in. in diamete is found to stretch 0.0054 in. under a load of 10,000 lbs. in a length of 8 in. Find (a) The co-efficient of elasticity. (b) If the coefficient of linear expansion is 0.0000065, find the increase or decrease of tensile stress caused by a fall of 20° in temperature.

2. A steel boiler shell, 36 in. diameter, 1⁄2 in. thick, has a longitudinal double rivetted lap joint, the diameter of rivets being I in., and the pitch 3 in. If the allowable stresses are: shear 10,000 lbs., tension 15,000 lbs., and compression 20,000, find the safe internal pressure to which the boiler might be subjected.

3. A bow-string truss of the Pratt type has a parabolic upper chord; there are 8 panels; the span is 160 ft. and the rise 40 ft. Find the stress in the diagonal member of panel L, L2, that is to say, the member U1 L2.

(a) When all the panel points of the lower chord are loaded with 20,000 lbs. each.

(b) When all the panel points of the lower chord except L1 are loaded with 20,000 lbs. each.

4. A standard 12 in. I-Beam weighs 40 lbs. per ft., with a moment of inertia of 246, and a sectional area of 11.8. It rests upon two supports 24 ft. apart, and bears a uniformly distributed load of 8,000 lbs., including its own weight, and also a concentrated load of 4000 lbs. 8 ft. from end and a concentrated load of 5000 lbs. 8 ft. from the other end.

(a) Find the position and amount of the maximum bending moment.

(b) The maximum fibre stress.

(c) The maximum shear.

(d) State whether in your opinion the beam is safely loaded.

(e) Find the maximum deflection due to the uniformly distributed load.

GENERAL ENGINEERING II.

1. A masonry retaining wall 20 ft. high is rectangular in section, the masonry weighing 150 lbs. per cu. ft. The backing weighs 100 lbs. per cu. ft. and has an angle of repose of 11⁄2-1. The back of the wall is vertical. There is no friction between earth and wall. The finished surface is level. Find the proper thickness of the wall.

2. Find the safe uniform load for a 12" I-beam weighing 55 lbs. per ft. with a moment of inertia of 321, which spans 3 openings of 12 ft. each. Find also the reactions at the 4 supports. Safe fibre-stress 15,000 lbs. per sq. in.

3. Determine the safe uniform load for a reinforced concrete beam 12 in. wide and 18 in. deep, reinforced with 2 rods 1⁄2 in. square and 2 rods 3/8 in. square, placed 2 in. from the bottom of the beam, allowing 500 lbs. for concrete and 15,000 lbs. for steel, and the ratio of elasticities 10.

4. Determine the size of a hollow steel shaft whose inside diameter is one-half the outside, to transmit 10,000 H.P. at 120 revs. per min., allowable shearing stress 9,000 lbs., coeff. of elasticity in shear 12,000,000. If the shaft is 50 ft. long, find the angle of twist.

5. Find the crown thrust of a parabolic arch of 60 ft. span and 15 ft. rise, loaded with a uniform load of 2,000 lbs. per lineal foot horizontally.

6. Two steel I-beams, similar to that of question 2, are latticed together to serve as a column, with fixed ends, the length being 30 ft. Neglect area of latticing and find (a) the proper spacing c. to c, (b) the safe load, taking S=50,000 in Gordon's formula with a factor of safety of 4. Moment of inertia about axis parallel to web, 17.5.

GENERAL ENGINEERING V.

One hour.

1. Explain the difference in the explosion of a mechanical mixture and a chemical preparation.

Give

2. Is the percentage of nitro-glycerine that a compound contains an indication of its safeness for handling? reason for answer and an example.

3. Give the different ways in which nitro-glycerine, that shows signs of decomposition, may be destroyed.

4. Why is the fulminate in a cap or primer adulterated, and what substances are used?

5. Give the twelve general rules for the handling of explosives on the works.

6. Describe the methods used in testing the strength of explosives which are to be used on engineering works.

7. Give generally the precautions to be taken in preparing charges, charging and firing the charges, when electricity is used.