Plate XLIII. Details:—
Figs. 36, 37, Eccentric-strap and rod for valve-gear.
Fig. 38, Side connecting-rods.
Figs. 39-43, Pump-rod, guide, and plunger.
Figs. 44-49, 51, Traverse-shaft, levers, side links, crosshead, and
Figs. 50, 52-54, Piston-rod, crosshead, crosstail, and slides.
c, Table-head, or entablature.
E, Stuffing-box for piston-rod.
e', Plug to close the bottom of cylinder.
P, Guides for crosshead.
H, Steampipe and throttle-valve-casing,
J, J, Connecting-rods.
N, Eccentric for valve-gear.
0, Traverse shaft, valve-gear.
р, Counterweight for valve-gear.
Q, Governor-spindle, hollow.
s, t, Brackets to carry governor-spindle.
it, Mitre-wheels to drive governor.
v, Traverse-rod to work throttle-valve.
w, Eccentric to work force-pump.
a, a’, Plummer-blocks for crankshaft.
b, Arch brackets to bind the columns.
с, Flanges on columns to join the brackets.
e, Cover of stuffing-box.
/', Eod to bind the guides F.
1, i, Steam-ports.
I, Lever on traverse-shaft, worked by eccentric.
V, Levers on traverse-shaft, to work the valve.
m, Side-rods to valve-crosshead.
n, Detent to keep eccentric-rod in gear.
o, o', Governor-rods and links.
p, p , Sockets sliding on governor-spindle, and joined by a rod.
2> rli ri s) t, v, Lever from governor, and adjustable link, lever,
and set-screw for throttle-valve.
Hand-Sketching, and Drawing from the Object.
Mechanical drawings are made entirely with instru-
ments, by the aid of which the exact forms and dimensions
of the objects are literally represented; but, where a draw-
ing of a piece of mechanism is to be made from the work
itself, wholly or partially, it is usual to do so by the me-
dium of free hand-sketching of the machine. In the ope-
ration of sketching, an exact figure is not to be looked for,
though it may of course be much the better of a good eye
and a steady hand; an intelligible representation checked
by a sufficiency of dimensions, obtained by actual measure-
ment, and written on the sketch, affords the materials for
constructing an exact drawing to scale. Indeed, hand-
sketches, though useful and expedient, are not essential, if
the drawing be made in the presence of the object, for the
measurements may be read off, as taken, and at once set
off by scale. The hand-sketch is, in general, however,
advisable, as it expedites the operation, and enables the
draughtsman to check his operations at any stage.
Before commencing the hand-sketches of a machine, it
should be examined sufficiently to ascertain the design and
mode of operation, that the functions of the parts of the
machine may be understood, and that the draughtsman
may simplify the operations by well-chosen views.
In hand-sketching, it is best and most expeditious to
complete each view, or, at least, each outline, in one ope-
ration, before taking and writing on dimensions: the
sketching and the measuring are distinct processes, and
when each is done consecutively, a better sketch is made,
and the dimensions are likely to be better chosen.
With respect to details, we do in sketching as in exact
drawings : detail sketches are made of particular parts, of
a larger size, and roomy enough to admit all the figures
and notes that may be necessary.
Hand-sketches, in short, should be as minute as the
drawings intended to be made from them; should comprise
as many views; and should exhibit the whole construc-
tion as completely.
Working Sketches of a Pillar-Drill.—Plate XLIY.
The contents of this plate are designed to illustrate the
usual style of sketching, and to show how the labour may
be economized consistently with the completeness of the
sketches. The Fig. A is a pictorial view of the pillar-
drill selected as the subject of the sketches, fitted up and
in working order. One of the columns or pillars of the
building constitutes the base or foundation of the machine.
The drill-spindle is carried vertically by cast-iron brackets
bolted to the pillar. It derives its revolving motion, by
means of a pair of bevil wheels, from the cone-pulley fixed
on a horizontal spindle passing through the colmnn, and
supported by a bracket on the other side. The lower end
of the spindle is socketed to hold the drilling bit, and on
the upper end is formed to clasp the lower end of the
screw by which the elevation of the bit is adjusted. The
screw works through a nut fixed in the uppermost
bracket, and has a spur wheel on the upper end, which
gears with a pinion on the upright spindle carrying
at its lower end the hand wheel by which the screw is to
be worked. The table for carrying the object to be
drilled, is made with a bracket to embrace the column;
its level is adjusted by a rack and pinion motion, the rack
being fixed to the column; and, when so adjusted, a set-
screw at the back fixes the table. The object to be drilled
is screwed upon the table between vice-jaws.