Exercise 66: Locomotive Coupling Rod Ends.—A form of knuckle joint used on locomotive coupling rods is shown in fig. 64.
In this case two rods meet and work on the same pin, as shown at (a) fig. 64. Draw, in addition to the views shown in fig. 64, a plan and a vertical section through the axis of the pin. Scale 6 inches to a foot.
Would it be practicable to replace the two rods A B and B C by a single rod working on the crank pins at A, B, and C? Give reasons for your answer.
Exercise 67: Bell Crank Lever.—Draw the plan and elevation of the lever shown in fig. 65. Scale 6 inches to a foot.
Exercise 68: Back Stay for Lathe.—Draw a plan and two elevations of the stay shown in fig. 66. Make all necessary corrections and show all the details in each view. Scale full size.
Exercise 69: Conical Disc Valve and Casing.—Draw, half size, the views shown in fig. 67 of the conical disc valve and casing, and also add an elevation looking in the direction of the arrow.
Exercise 70: Connecting Rod End.—The student should carefully compare this connecting rod end (fig. 68) with those illustrated on pages 50 and 52. The lower part of fig. 68 is a half plan and half horizontal section, and the upper part is a half side elevation and half vertical section. Draw these views and also an end elevation. Scale 6 inches to a foot.
Exercise 71: Engine Cross-head.—The cross-head shown in fig. 69 is for an inverted cylinder marine engine. A is the piston rod, and B B are pins, forged in one piece with C, to which the forked end of the connecting rod is attached. Draw the upper view with the central part in section as shown. Make the right-hand half of the lower view a plan without any section, and make the left-hand half a horizontal section through the axis of the pins B B. Scale 4 inches to a foot.
Exercise 72: Ratchet Lever.—The lever shown in fig. 70 is used for turning the horizontal screw of a traversing screw jack. Draw the two views shown, and from one of them project a plan. Scale full size.
Exercise 73: Steam Whistle.—Draw, full size, the elevation and section of the steam whistle shown in fig. 71. Draw also horizontal sections at A B, C D, and E F.
Exercise 74: Screw Coupling for Railway Carriages.—Draw the three views of the screw coupling shown in fig. 72. Scale 6 inches to a foot.
If the link A is fixed, through what distance will the link B move for two turns of the lever?
Exercise 75: Loose Headstock for a 6-inch Lathe.—Two views of this headstock are shown in fig. 73. On one of these views a few of the chief dimensions are marked. The details, fully dimensioned, are shown separately in figs. 74, 75, and 76.
Explain clearly how the centre is moved backwards and forwards, and also how the spindle containing it is locked when it is not required to move.
Draw, half-size, the views shown in fig. 73, and from the left-hand view project a plan. Draw also the detail of the locking arrangement shown in fig. 74.
APPENDIX A.
SCIENCE AND ART DEPARTMENT, SOUTH
KENSINGTON.
Syllabus.
SUBJECT II.—MACHINE CONSTRUCTION AND
DRAWING.
It is assumed that the student has already learnt to draw to scale, and that he can draw two or more views of the same object in simple or orthographic projection. To pass in machine construction and drawing, he must be able to apply this knowledge to the representation of machinery. He must be acquainted with the form and purpose of the simpler parts of which machines are built up and must have had some practice in drawing them. To test his knowledge, rough dimensioned sketches, more or less incomplete, of simple machine details will be given him, and he will be required to produce a complete drawing in pencil to a given scale. Two or more views of at least one subject will be required, and these must be so drawn as to be properly projected one from the other, in order to show that the student appreciates that he is producing a representation of a solid piece of machinery, and not merely copying a sketch. No credit will be given unless some knowledge of projection is shown. The centre lines of the drawings should be shown, and parts cut by planes of section should be indicated by diagonal shading. Bolts and other fastenings should be carefully shown where required. Any indication that a candidate has merely copied the sketches given, without understanding the part represented, will invalidate his examination.
First Stage or Elementary Course.
In the elementary stage, a knowledge is required of the simple parts only of machines in common use. Some of these are enumerated in the following list. The student should be practised in drawing them till he recognises their forms, and the object of the arrangement should be explained to him. He should also know the simple technical terms used in describing them.
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 butt 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 flanges 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 flanges and covers.
Shafting.—Forms of shafts and axles and of journals and pivots. Use of collars and bosses. Half-lap coupling. Box coupling. Flange coupling.
Pedestals and Plummer Blocks.—Simplest forms of pedestals and hangers for shafts. Form and arrangement of brass 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. Cock 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 brasses 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 1½ 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.)
2. Connecting rod end. Draw the two views as shown, partly in section (fig. 78). Draw full size. (35.)
3. Hooke's coupling. Draw the three views shown (fig. 79), adding any omitted lines where the views are incomplete. Draw to scale of 1⁄4 full size. (35.)
First Stage or Elementary Examination. 1886.
Instructions.
Read the General Instructions (page 102).
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.) Give sketches showing how the cutting tool of a lathe or other machine is secured in place. (6.)
(b.) Make a sketch of a stud, describe how it is screwed into place, and state some circumstances under which it is used in preference to a bolt. (6.)
(c.) Give sketches showing one method of attaching the valve rod to an ordinary slide valve. (6.)
(d.) Sketch a connecting rod end, with strap, gib, and cotter. Explain the use of the gib. (10.)
(e.) Explain the use of the quadrant for change wheels for a screw-cutting lathe shown in Example 1, fig. 80, by making a sketch showing it in place on a lathe with wheels in gear. (10.)
(f.) Sketch one form of hanger suitable for supporting mill-shafting. (10.)
Examples to be drawn.
1. Quadrant for change wheels for screw-cutting lathe. Draw the two views shown (fig. 80). Scale half-size. (35.)
2. Crank-shaft. Draw the two views as shown, partly in section (fig 81). Scale 1⁄8 full size. (35.)
3. Ball bearing for tricycle. Draw the two views as shown, partly in section (fig. 82). Draw full size. (35.)
First Stage or Elementary Examination. 1887.
Instructions.
Read the General Instructions (page 102).
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.) Explain how the piston rings in Example 1, fig. 84, are made so that the piston may work steam-tight in the cylinder. How are these rings got into place? (8.)
(b.) Give two views of a double riveted lap joint for boiler-plates. (8.)
(c.) Show by sketches how a wheel is fixed on a shaft by means of a sunk key. Explain how the key may be withdrawn when it cannot be driven from the point end. (8.)
(d.) Give sketches showing the construction of a conical metal lift or puppet valve and seating. (10.)
(e.) With the aid of sketches explain how a piston rod is made to work steam-tight through the end of the cylinder. (10.)
(f.) Explain how the slotting machine ram of Example 8, fig. 85, may be made to move up and down when at work. How is the length of the stroke altered, and what is the object of the slotway in the upper part of the ram? (10.)
Examples to be drawn.
1. Piston for steam-engine. Draw and complete the two views shown (fig. 84), the top half of the left-hand view to be in section. Scale 1⁄2 size. (30.)
2. Plan and sectional elevation of a footstep bearing for an upright shaft (fig. 83). Draw and complete these views. Scale 1⁄4 size. (35.)
3. Ram of slotting machine. Draw and complete the two elevations shown (fig. 85). The tool-holders must be drawn in their proper positions in the ram, and not separate as in the diagram. Scale 1⁄4 size. (35.)
First Stage or Elementary Examination. 1888.
Instructions.
Read the General Instructions on p. 102.
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.) Give sketches showing how the separate lengths of a line of shafting may be connected together. (8.)
(b.) What is the object of using chipping or facing strips in fitting up machine parts? Give one or two examples. (8.)
(c.) Give sketches showing how you would grip and drive a round iron bar for the purpose of turning it between the centres of a lathe. (10.)
(d.) Explain the action of the governor shown in Example 1 (fig. 86). (10.)
(e.) Describe in detail how the mud-hole door in Example 2 (fig. 88) is removed for the purpose of cleaning the boiler and how it is replaced and the joint made steam-tight. (10.)
(f.) Describe how the parts of the spur wheel in Example 3 (fig. 87) are put together, and explain why the wheel is made in segments. (10.)
Examples to be drawn.
1. Loaded governor for small gas engine. Draw and complete the two views, partly in section as shown (fig. 86). Scale full size. (35.)
2. Mud-hole mouth-piece for Lancashire boiler. Draw and complete the two views shown (fig. 88). Scale 3⁄8ths. (35.)
3. Point for segments of large spur wheel. Draw and complete the views shown (fig. 87). Scale 3⁄16ths.
Note.—As the radius of the wheel is too large for your instruments, the circumference at the joint may be set out straight, as in a rack. (35.)
INDEX
Air-pump bucket, 58
Alloys, 80
Angle irons, 12
Annealing, 79, 80
Axles, 24
Back stay for lathe, 86
Bar stay, 83
Bearings for shafts, 30
Beech-wood, 81
Bell crank lever, 86
Bessemer steel, 79
Bevil wheels, 43
Blister steel, 79
Blooms, 78
Bolt-heads, proportions of, 18
Bolts, forms of, 17
Border lines, 4
Box couplings, 25
— end, connecting rod, 51
Box-wood, 81
Brackets, 33
Brake shaft carrier, 30
Brass, 80
Brasses, 30
Bucket, 58
Built-up cranks, 46
Bush, 30, 49, 51, 54, 56, 63
Butt joints, 10, 11
— strap, 10
Buttress screw thread, 15
Case-hardening, 80
Cast iron, 76
Cast iron flange coupling, 28, 29
— steel, 79
Caulking, 8
Cementation process, 79
Centre lines, 2, 4
Chilled castings, 78
Circulating pump piston, 58
Clearance, cylinder, 74
— of cotter, 49
Cocks, 74
Cogs, 41
— wood for, 81
Collared stud, 18
Collars, 24
Colouring, 3
Colours for different materials, 3
Compasses, 1
Cone keys, 23, 38
Conical disc valve, 70, 71, 89
— head, 7
Connecting rod, locomotive, 51
— — marine, 51
— rods, 49, 89
Construction for rivet heads, 7
Contraction of castings, 77
Copper, 80
Cotters, 48, 49
Countersunk head, 7, 18
Coupling rod ends, 55, 84
— rods, 54
— screw, 96
Couplings, shaft, 25
Cover plate, 10
Cranked axle, 45
Cranks, 43
— built-up, 46
Cross-head pin, 51
Cross-heads, 56, 89
Cross-key, 28
Cup-headed bolt, 17
Decimal equivalents, 6
Dimension lines, 5
Dimensions, 5
— of box couplings, 26
— cast-iron flange couplings, 29
— keys, 24
— stuffing-boxes and glands, 67
— Whitworth screws, 15
Distance lines, 5
Dividers, 1
Draught of cotter, 49
Drawing board, 1
— instruments, 1
— paper, 2
— pen, 1
— pins, 2
Eccentrics, 47
Exhaust port, 71
Eye-bolt, 18
Fairbairn's coupling, 26
Fast and loose pulleys, 37
Feather key, 23
Flange couplings, 27
Flap valves, 68
Flat key, 22
Forge irons, 77
Forging, 79
Form of wheel teeth, 40
Forms of nuts, 16
— rivet heads, 7
— screw threads, 15
Foundry irons, 77
Gasket, 58
Gas threads, 15
Gib, 49
— head, 23
Girder stay, 81
Gland, 64
Grey cast iron, 77
Gun-metal, 80
Gusset stay, 12
Half-lap coupling, 26
Hangers, 34
Hardening of steel, 80
Headstock lathe, 96
Hexagonal nut, 16
Hollow key, 22
Hook bolt, 18
Hornbeam, 81
India-rubber disc valves, 58, 68
Inking drawings, 2
Inside lap of valve, 72
Joggles, 33
Joint, knuckle, 84
Journals, 24
— length of, 32
Junk ring, 61
Keys, 22
— proportions of, 23
Kinghorn's metallic valve, 70
Knuckle joint, 84
— screw thread, 15
Lancaster's piston packing, 61
Lap joints, 8, 9, 10, 12
— of slide valve, 72
Lathe headstock, 96
Lead of valve, 74
Lever, bell crank, 86
— ratchet, 96
Lignum-vitæ, 81
Locking arrangements for nuts, 21, 62
Lock nuts, 19
Locomotive connecting rod, 51
— cranked axle, 45
— cross-head, 56
Locomotive eccentric, 47
— piston, 60
Lubricator, needle, 32
Malleable cast iron, 78
— iron, 78
Marine connecting rod, 51
— coupling, 28
— crank-shaft, 46
— piston, 61
Merchant bars, 78
Mortise wheels, 41
Mottled cast iron, 77
Muff couplings, 25
Muntz metal, 80
Needle lubricator, 32
Nuts, forms of, 16
— lock, 19
— proportions of, 18
Oil-box, 54, 65
Outside lap of slide valve, 72
Overhung crank, 43
— cranks, proportions of, 45
Packing, 63
Pan head, 7
Pedestal, shaft, 30
Pencils, drawing, 1
Phosphor bronze, 80
Pillar bracket, 34
Pillow block, 30, 32
Pin, cross-head, 51, 54
— split, 21
Piston rod, 57
Pistons, 57
Pitch circle, 40
— of wheel teeth, 40
— surfaces of wheels, 39, 43
Pivots, 24
Plummer block, 30
Plunger, 57
Printing, 4
Proportions of bolt-heads, 18
— keys, 23
Proportions of lap joints, 9, 10
— marine engine pistons, 62
— nuts, 18
— overhung cranks, 45
— pillow blocks, 32
— rivet heads, 7
— wheel teeth, 40
Puddled bars, 78
Puddling process, 78
Pulley, eccentric, 47
Pulleys, 36
Pump bucket, 58
Ramsbottom's packing, 60
Ratchet lever, 96
Riveted joints, 8
Rivet heads, forms of, 7, 8
— — proportions of, 7
Riveting, 7
Rivets, 6
Rope pulley, 39
Round key, 23
Saddle key, 22
Scales, 5
Screw coupling, 96
Screwed gland and stuffing-box, 65
Screw threads, 14, 15
Screws, representation of, 16
Sellers V screw thread, 14
Set screw, 21, 49
— squares, 1
Shaft couplings, 25
— hanger, 34
Shafting, 24
Shear steel, 79
Sheave, eccentric, 47
Shingling, 78
Shrinking, process of, 44
Siemens-Martin steel, 79
Slide blocks, 56
— valves, 68, 71
Sliding key, 23
Snap head, 7
Snug, 17
Spiegeleisen, 80
Spring bows, 1
Spur wheel, 41
Square nut, 16
— screw thread, 14
Stay, back, for lathe, 86
— bar, 83
— girder, 81
— gusset, 12
Steam ports, 71
— whistle, 96
Steel, 79
Steps, 30
Strap, 49
— eccentric, 47
— end of connecting rod, 49
Stud bolts, 18
Studs, 18
Stuffing-boxes, 63
Sunk key, 22
Taper bolt, 18, 27
— pin, 23
Tee-headed bolt, 18
Tee-iron cover strap, 81
Tee square, 1
Teeth of wheels, form and proportions of, 40
Teeth, pitch of, 40
Tempering of steel, 80
Throw of crank, 44
— eccentric, 47
Toothed wheels, 39
Valve Kinghorn's metallic, 70
— slide, 68, 71
Valves, 68
— conical disc, 70
— india-rubber, 58, 68
Velocity ratio in belt gearing, 36
Wall boxes, 34
Washers, 19
Welding, 79
Whistle, steam, 96
White cast iron, 77
Whitworth screws, dimensions of, 15
— V screw thread, 14
Wood, 81
Working drawings, 4
Wrought iron, 78
Yellow pine, 81