An Introduction to Machine Drawing and Design - LightNovelsOnl.com
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A few very simple questions relating to the arrangement, proportions, and strength of the simplest machine details will be set in the examination paper.
In drawing the examples set to test a student's knowledge and skill in machine drawing, it must be remembered that only a limited time is available. It is only possible to set an example to be drawn in pencil, and the points which will receive attention are (1) accuracy of scale and projection; (2) power of reading a drawing, shown by the ability to transfer portions of the mechanism and dimensions from one view to another; (3) knowledge of machines, as shown by the ability to fill in small details, such as nuts, keys, etc., omitted in the sketches given.
Bearing in mind the limited time available, the student should try to make his outline clear and decisive and complete. But the diagonal lines necessary for sectional parts may be done rapidly, though neatly, by freehand if necessary.
_Riveted Joints._--Forms of rivets and arrangement of rivets in lap and b.u.t.t joints with single and double riveting. Junction of plates by angle and T-irons.
_Bolts, Studs, and Set Screws._--Forms of these fastenings. Forms and proportions of nuts and bolt-heads. Arrangement of f.l.a.n.g.es for bolting.
_Pins, Keys, and Cotters._--Form of ordinary knuckle joint. Use of split pins. Connection of parts by a key. Connection of parts by a cotter. Gib and cotter.
_Pipes and Cylinders._--Forms of ordinary pipes and cylinders and their f.l.a.n.g.es and covers.
_Shafting._--Forms of shafts and axles and of journals and pivots. Use of collars and bosses. Half-lap coupling. Box coupling. f.l.a.n.g.e coupling.
_Pedestals and Plummer Blocks._--Simplest forms of pedestals and hangers for shafts. Form and arrangement of bra.s.s steps. Arrangements for fixing pedestals and for neutralising the effects of wear.
_Toothed Gearing._--Forms of ordinary spur and bevil wheels. Meaning of the terms pitch, breadth of face, thickness of tooth, pitch line, rim, nave, arm. Mode of drawing bevil wheels in section.
_Belt Pulleys._--Forms of belt pulleys for flat and round belts. Stepped speed cones. Drawing of pulleys with curved arms.
_Cranks and Levers._--Forms of ordinary cast-iron and wrought-iron cranks and levers. Modes of fixing crank pin. Modes of fixing crank shaft. Double cranks. Form of eccentrics.
_Links._--Most simple forms of connecting rod ends, open or closed. Use of steps in connecting rods. Use of cotters to tighten the steps.
_Pistons._--Simple forms of piston. Use of piston packing. Modes of attaching piston rod.
_Stuffing-Boxes._--Simple form of stuffing-box and gland. Use of packing. Mode of tightening gland.
_Valves._--Simple conical of puppet valve. Simple slide valve. c.o.c.k or conical sliding valve.
APPENDIX B.
_EXAMINATION PAPERS SET BY THE SCIENCE AND ART DEPARTMENT._
SUBJECT II.--MACHINE CONSTRUCTION AND DRAWING.
_Examiners_, PROF. T. A. HEARSON, M.Inst.C.E., and J. HARRISON, ESQ., M.Inst.M.E.
GENERAL INSTRUCTIONS.
_If the rules are not attended to, the paper will be cancelled._
You may take the Elementary, or the Advanced, or the Honours paper, but you must confine yourself to one of them.
Put the number of the question before your answer.
You are expected to prove your knowledge of machinery as well as your power of drawing neatly to scale. You are therefore to supply details omitted in the sketches, to fill in parts left incomplete, and to indicate, by diagonal lines, parts cut by planes of section.
No credit will be given unless some knowledge of projection is shown, so that at least two views of one of the examples will be required properly projected one from the other. The centre lines should be clearly drawn.
The figured dimensions need not be inserted.
Your answers should be clearly and cleanly drawn in pencil. No extra marks will be allowed for inking in.
All figures must be drawn on the single sheet of paper supplied, for no second sheet will be allowed.
The value attached to each question is shown in brackets after the question. But a full and correct answer to an easy question will in all cases secure a larger number of marks than an incomplete or inexact answer to a more difficult one.
Your name is not given to the Examiner, and you are forbidden to write to him about your answers.
You are to confine your answers _strictly_ to the questions proposed.
A single accent (') signifies _feet_; a double accent (") _inches_.
_The examination in this subject lasts for four hours._
First Stage or Elementary Examination. 1885.
INSTRUCTIONS.
Read the General Instructions above.
Answer briefly any three, but not more than three, of the following questions, and draw two, but not more than two, of the examples.
_Questions._
(_a._) Show two methods by which a cotter may be prevented from slacking back. (6.)
(_b._) Sketch the bra.s.ses for a bearing, and show how they are prevented from turning in the pedestal. (6.)
(_c._) Explain the object of the construction of the connecting rod end shown in fig. 78. Describe how the adjustment must be made and how it is locked. (10.)
(_d._) Show the form of the Whitworth screw thread by drawing to scale a part section of two or three threads taking a pitch of 1-1/2 inches. Figure the dimensions on the sketch. How many threads to the inch are used on an inch bolt? (10.)
(_e._) Make a sketch showing how the adjustment is made in the sliding parts of machine tools: as, for example, in the slide rest of a lathe. (10.)
(_f._) Describe with sketches two methods by which the joints are made in connecting lengths of cast-iron pipes. (6.)
_Examples to be drawn._
1. Jaw for four-screw dog chuck for 5" lathe. Draw the two views as shown (fig. 77). Scale full size.
(Note.--The other three jaws of the chuck are not to be drawn.) (35.)
