The illustrations in this chapter are in most cases not drawn to scale;
they are also in some parts incomplete, and in others some of the lines
are purposely drawn wrong. The student must keep to the dimensions
marked on the drawings, and where no sizes are given he must use his own
judgment in proportioning the parts. All errors must be corrected, and
any details required, but not shown completely in the illustrations,
must be filled in.
EXERCISE 62: _Single Riveted Butt Joint with Tee-iron Cover
Strap._--Two views, one a side elevation and the other a sectional
elevation, of a riveted joint are shown in fig. 60. Draw these
views, and also a plan projected from one of them. Show the rivets
completely in all the views. Scale 4 inches to a foot.
[Illustration: FIG. 60.]
[Illustration: FIG. 61.]
EXERCISE 63: _Girder Stay for Steam Boiler._--The flat crown of the
fire-box of locomotive and marine boilers is generally supported or
stayed by means of girder stays, an example of which is shown in
fig. 61. A B is the side elevation of a portion of one of these
girders. Each girder is supported at its ends by the plates forming
the vertical sides of the fire-box. The flat crown is bolted to the
girders as shown. Observe that the girders are in contact with the
crown only in the neighbourhood of the bolts. Consider carefully
this part of the design, and then answer the following questions:
(1) What objections are there to supporting the girders at the ends
only without the contact pieces at the bolts? (2) What objections
are there to having the girders in contact with the crown plate of
the fire-box throughout their whole length?
Draw the views shown in fig. 61, and from the right-hand one
project a plan. Scale 4 inches to a foot.
[Illustration: FIG. 62.]
EXERCISE 64: _End of Bar Stay for Steam Boiler._--On page 12 one
form of stay for supporting the flat end of a steam boiler is
described. Another form of stay for the same purpose is shown in
fig. 62. A B is a portion of the end of a steam boiler. C D is one
end of a bar which extends from one end of the boiler to the
other. The ends of this bar are screwed, and when the bar is of
wrought iron the screwed parts are generally larger in diameter
than the rest of the bar. When made of steel the bar is generally
of uniform diameter throughout. In the case of wrought-iron bar
stays the enlarged ends are welded on to the smaller parts.
Welding is not so reliable with steel as with wrought iron. Write
out answers to the following questions: (1) What is the advantage
of having the screwed part of the bar larger in diameter than the
rest? (2) Why are steel bar stays not generally enlarged at their
screwed ends?
Draw the views shown in fig. 62, and project from one of them a
third view. Scale 4 inches to a foot.
EXERCISE 65: _Knuckle Joint._--Draw the plan and elevation of this
joint shown in fig. 63, and also draw an end elevation looking in
the direction of the arrow. The parts at A and B are octagonal in
cross section. Scale 4 inches to a foot.
[Illustration: FIG. 63.]
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.
[Illustration: FIG. 64.]
EXERCISE 67: _Bell Crank Lever._--Draw the plan and elevation of
the lever shown in fig. 65. Scale 6 inches to a foot.
[Illustration: FIG. 65.]
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.
[Illustration: FIG. 66.]
[Illustration: FIG. 67.]
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.
[Illustration: FIG. 68.]
[Illustration: FIG. 69.]
[Illustration: FIG. 70.]
[Illustration: FIG. 71.]
[Illustration: FIG. 72.]
[Illustration: FIG. 73.]
[Illustration: FIG. 74.]
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.
[Illustration: FIG. 75.]
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?
[Illustration: FIG. 76.]
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.