Jan. 12, 1872.
tory. It was necessary to provide against the
pressure of the metal on the walls of the cope; the
cope was therefore built in the ground of Yin. brick-
work, well rammed up all round to the level of the
surface, for although the core had to be broken down
for each casting, the cope, as far as the brickwork
was concerned, remained permanent, and served for
all the succeeding castings of the same form and
size. When the pit was dug the loam-ring was
laid in position, and upon this the wall was built.
‘These rings were generally cast in one piece, but for
want of space in the foundry at the time, the ring
was made in three segments, and bolted together ;
and as it was proposed to cast the conical cylinders
in the same pit, a strong cast iron cross was pro-
vided, and laid permanently at the bottom of the
pit, with its twelve arms passing under the loam-
ring, so that it could be used to bolt down the coni-
cal cores withont interfering with the cope of the
first cylinders. The loam-ring for the cope was 18in.
wide and 2kin. thick, and cast with twelve lugs
round the cirenmference, to which lugs were
attached the tying-down bolts, consisting of 1Jin.
ronnd rods, forged with stirrups fitting the lugs of
the loam-ring. The weight of metal in the ring
and cross amounts to about seven tons. The cope
was built up of Qin. brickwork, with binding
plates set in the joints at about every six courses.
The plates were jin. thick, and 9in. wide; the walls
were well rammed up all round and thoroughly
dried. Thus far the structure is permanent, and
remains in situ. The walls are faced inside with a
coat of loam struck up in the ordinary way by
means of the loam-boards; these, however, from
their extra weight and size, required to be counter-
balanced, otherwise the process differs in no way
from the general plan adopted in all like cases. In
striking up the cope a seating of about Gin. in
depth is formed at the bottom of the mould; a
similar seating called a dummy is also formed on the
floor where the core is to be built up; this seating
serves for all the succeeding cores; the core being
constructed on this dummy corresponds exactly
with the seating at the bottom of the cope, and
when placed in position is guided by it into the
centre, leaving the desired space all round for the
metal, The core is made on a ring cast rather
smaller than the seating, with eight wrought iron
loops cast in, by which the whole is lifted and placed
in the cope; upon this ring are eight, segmental
plates, which carry the brickwork. These plates
are clamped together, forming one ring, but as soon
as the casting is made the clamps are knocked away,
and the plates set free to allow for the contraction
of the metal in cooling. At every six courses in
the wall are binding plates in segments to strengthen
the work, and the brickwork is 9in. thick all over.
The core thus constructed weighs eighteen tons, In
the first or lowest cylinder a curved moulding is
formed on the bottom edge, for as no flange is here
required it was thought advisable to strengthen the
edge which bears on the ground and carries the
weight of the superstructure; and at the same time
something of the sort was required to equalise the
metal, so as to avoid the chance of a fracture from
any irregularity in the cooling. All these cylinders,
it must be stated, are cast the reverse way to the
position in which tl:ey will stand in the piers, in
order that they may be relieved from the mould
without breaking down the cope. The covering
plate, which is cast in three segments, is struck up
to the form of the bottom moulding of the cylin
ders; this, from their being reversed in the mould,
being at the top, it corresponds with and fits into a
seating formed on the top of the cope, and is cast
with thirty-three holes, thirty of which serve for
the runners, and three for the risers. These seg-
ments were capable of being dried in the stoves;
but in order to dry the rest of the work, “ portable
kettles,” as they are called, are employed: in these,
gas-coke is burnt, and of course this is not so eco-
nomical as drying in stoves; but the stoves at the
Battersea Foundry will not take in a mould more
than 14ft. wide. When the bricks and loam are
dry, the face of the mould is blacked, and then
again dried, and the mould is then put together. A
cast iron cross having twelve arms is laid over all,
and tied down by the twelve 1}in. bolts surrounding
the cope. In making up the mould a sow or trough
is formed, composed of sand and confined between
two rows of jointed plates, called cribs, fixed on
edge all round the top of the mould. In this sow
are thirty runners of about 1iin. diameter, leading
perpendicularly through the holes in the covering
plate down into the mould between the cope and
core. Three other holes of similar size, which serve
as risers, are stopped off from the runners on one
side of the mould. Three basins communicating
with the sow are formed to receive first the metal
from the ladles. The metal when poured is thus con-
THE BUILDING NEWS.
33
ducted into the mould in thirty small streams, which ensures a uniform flow to all parts at once. The calculated weight of th2 casting is about nine tons, but as it is always desirable to have metal enough, and to spare, it is run from three ladles, a six ton, a four ton, and a three ton, making in all about thirteen tons of metal. The arrangement adopted of pouring the metal out at three founts is very satisfactory. The largest ladle is served by the traveller, and the other two by the cranes, one being close to the work, and the other about twelve feet off, from which the metal flows to the mould along a trough. The metal is melted in two cupolas, one 3ft. internal diameter, and the other 2ft. 6in, The largest cupola has three tuyeres, the smaller one two. A pressure of Tin. of blast was got with one of Lloyd’s 30in. fans, driven by an eight horse- engine, and the thirteen tons of metal was run down in about an hour and a half. A mixture of one-fourth pig iron and three-fourths best machine scrap is employed, which produces a metal extremely strong and suitable for the purpose. The conical cast- ings forming that portion of the piers of the bridge which reduces the diameter from 21ft. to 15ft. require rather a different arrangement with regard to the building-up of the core. The angle of the cone is so great, contracting as the cylinders do 3ft. on each side in a height of 4ft. 6in., that it would be impracticable to lay on the loam overhead, as it were; it would not have adhered to the brickwork, but would have fallen off as soon as the board left it. The plan was therefore adopted of thicknessing up the cope and building the core within it. The cope of the conical cylinders is built inside that of the parallel ones, as there are some more to cast after these are done. When the cope is struck up in loam and dried, a thickness of wet sand, cor- responding with the thickness of the casting, is laid on and struck up with the core-board and dried. The core is then built inside the cope, and when dry is lifted out and dressed, and the thickness of sand re- moved ; in all other respects the casting is conducted as usual, except that as these castings present more surface on plan, they require extra holding down, which was effected by means of cast iron clamps on the inside, in addition to the twelve external tie- bolts. The 15ft. cylinders are made in every re~ spect ina similar way to the 21ft. ones, allowance being made for the difference in size only. They weigh only about 7 tons, and it takes a week to prepare each mould. Mr. Kingsford concluded his paper by some remarks on the estimation of the several strains that are set up in the moulds during the time of pouring in the metal for these large cast- ings. In the case of the 21ft. cylinders the width of the flange was 4in., the circumference being 66ft., giving an area of 22 square feet, multiplied by 4ft. 6in., the height of the evlinder; this equals 99 cubic feet of displacement, and as a cubic foot of iron weighs 4ewt. there is about 20 tons exerting itself to lift the core. In the conical castings the flotation is considerably more. The difference of areas between the cylinder at the bottom and top of the mould represents about 190 square feet; this, multiplied by 4ft. 6in., the height, gives 855 cubic feet of dis- placement, being equal to 170 tons. From this we must deduct about 20 tons for the weight of the core, which represents a vessel floating in liquid iron, and 150 tons is the upward pressure on the tying- down bolts. There are twelve 1}in. bolts, equal to 27 circular inches, 10 tons to a circular inch being generally considered safe. This gives 270 tons, which should be sufficient; but in order to be on the safe side, the mould is clamped on the inside, which greatly adds to its rigidity, the object being to guard against the mould straining as much as possible. Besides the actual strain from the pressure of the metal exerted to float the core there is the lateral pressure on the walls of the core and cope. The cope being in the ground and well rammed up may be passed by as safe ; but the core requires very careful construction. Eight of these cylinders, out of about thirty, have been cast. The core of the first, as before stated, was not sufficiently strong enough to bear the weight of the metal against its sides, and it gave way. The second strained so much that instead of its thickness averaging 1gin., as it ought to have done, it averages 2in., and weighs 12 tons. The succeeding ones have not strained much, but the lightest is fully Jin. thicker than it ought to be, and Mr. Kingsford believed that in order (o cast them without straining in the least the walls of the core would have to be 18in. thick, and the core would weigh upwards of 30 tons. Now that it is possible from practice, however, to judge the amount of the strain in the castings it was allowed for, and the remaining cylinders will be nearly correct as to thickness. Another cause of straining is the pres- sure of the suddenly heated air in the mould as soon as the melted iron isrun in, ‘This is not so easily
calculated, but it is necessary, in order to have a
good sound casting, free from scabs, that the air
should be thus confined, The metal enters by thirty
Tunners, and the same quantity of air, greatly
augmented in bulk, has to escape through three
risers, which it does, in all probability, at a pressure
of nearly 15Ib. to lin. If so, it would just about
double all the strains, for one inch of iron, 4ft. 6in.
high, equals about 14 tons or 15 tons.
A brief discussion ensued, and the thanks of the
members having been voted to Mr. Kingsford for his
interesting paper, the proceedings terminated.
——_ @—____
THE TIMBER TRADE OF 1871.
(From Churchill and Sim's Circular.)
Te gross imports of 4,000,000 loads of wood,
which we last year commented on as the
largest ever known, has this year again increased 10
per cent., or a total of 4,500,000 loads, and this in-
crease is entirely in the import from the North of
Europe, that from Canada having been stationary
for some years. It is not surprising that the
Canadian trade should not increase in the same ratio
as the European, when we consider—firstly, the
difference of freight from America, which is nearly
double that from the Baltic, and in an article of
small value in comparison with its bulk, freight is
a large item of cost; and, secondly, the large and
ever-increasing demand in the United States, by
which the value of wood in Canada is being enhanced
every year. The proprietors of saw-mills in the North
of Europe propose to take full advantage of this
increase of trade, and of the competition of English
buyers for the well-known stocks, and are asking
largely-advanced prices for this season’s shipments.
The increase of production likely to be stimulated
by these advanced prices, however, will sooner or
later overtake the increase of demand, and the
inevitable reaction from high to low prices will
follow. It must, however, be remembered that the
prices of wood will in course of years be aways
rising, as the cost of labour is always increasing.
The wood growing in the most convenient situations
for shipment is being exhausted, and for the trans-
port from greater distances, the navigation of rivers
has to be improved, or railways have to be made
to being the blocks to the saw-mills, or the sawn
wood to the shipping ports, The London importa-
tion has not kept pace with that to outports, but it
appears to have been just sufficient for the consump-
tion, the stocks on the whole being about the same as
at the beginning of last year, showing, however,
some increase in foreign deals, counterbalanced by a
decrease in colonial deals. We look forward with
confidence that the consumption in the year 1872
will continue on alarge scale, and that if the cost of
wood be not too much enhanced, there is a good pros-
pect of a year of prosperity for the importers and
dealers.
eee ne ees
DAMP HOUSES.
[ is by no means easy (says the Field) to pre-
vent damp from rising from the soil to the
house ; it is a much easier thing to prevent moisture
(the cause of the damp) from lodging and remaining
in the soil, and it is worth knowing that it is so. If
it had been known earlier, and when known acted
upon, the number of damp houses would be
much less than it is now. Let the site of the
house—and the larger the area operated upon the
better—be drained precisely after the fashion a field
is drained, and there will be little moisture in the
soil from which damp can arise. Let the whole
area be surrounded by catch drains, and the area in
the direction of its length or breadth, aceording to
the fall or inclination of the ground, be divided into
spaces by parallel drains, all of which discharge
their water in the main drain leading to the outfall.
We need scarcely say that the drains should be
placed deep, not less in heavy soils than 4ft. 6in.
The drains, or rather the trenches, may be filled up
with stones, if these be plentiful, or, better still,
the ordinary field-drain tube. A good deal depends
also upon the position of the site; some pay so
little attention to this that they build on the spot
the best calculated to catch the water and retain it.
Let the ground be rising, or on a slope, so that the
drainage of the soil will be easily carried out; never
build in a hole. This advice, ought, we think, to be
unnecessary; it is not so, seeing how often houses
are built in holes or depressions, Further, build the
house pretty well off the gronnd, so as to rise to the
ground-floor level by three steps at the least. Some
like to burrow so much that they will actually
descend to their houses—a most pernicious system.
Where expense is no object, but having a house as
comfortable as possible is the aim, we should recom-
mend the whole house to be cellared under, and all
the cellar floors laid with Portland cement concrete,
