A horizontal cross-section of the apparatus is shown in fig. 7, and a
vertical cross-section facing the front is given in fig. 8. Other
details of structural steel are seen in fig. 9.
In constructing the new chambers, the earlier wood construction, with
its tendency to warp and its general non-rigidity, was avoided by the
use of structural steel, and hence in this calorimeter no use whatever
is made of wood other than the wood of the chair.
To avoid temperature fluctuations due to possible local stratification
of the air in the laboratory, the calorimeter is constructed so as to be
practically suspended in the air, there being a large air-space of some
76 centimeters between the lowest point of the calorimeter and the
floor, and the top of the calorimeter is some 212 centimeters below the
ceiling of the room. Four upright structural-steel channels (4-inch)
were bolted through the floor, so as to secure great rigidity, and were
tied together at the top with structural steel. As a solid base for the
calorimeter chamber two 3-inch channels were placed parallel to each
other 70 centimeters from the floor, joined to these uprights. Upon
these two 3-inch channels the calorimeter proper was constructed. The
steel used for the most part in the skeleton of the apparatus is
standard 2-1/2-inch channel. This steel frame and its support are shown
in fig. 10, before any of the copper lining was put into position. The
main 4-inch channels upon which the calorimeter is supported, the
tie-rods and turn-buckles anchoring the framework to the ceiling, the
I-beam construction at the top upon which is subsequently installed the
large balance for weighing the man, the series of small channels set on
edge upon which the asbestos floor is laid, and the upright row of
channel ribs are all clearly shown.
[Illustration: FIG. 10
Photograph of framework of chair calorimeter. In the photograph are
shown four upright channels and the channels at the top for supporting
the calorimeter. The smaller upright 2-1/2 inch channels and angles are
shown inside of this frame. In the lower part of the figure is seen the
asbestos board for the bottom of the calorimeter and underneath this a
sheet of zinc.]
[Illustration: FIG. 11
Photograph of portion of framework and copper shell. The finished copper
shell is seen in position with some of the thermal junction thimbles
soldered into it. A portion of the food aperture and the four brass
ferrules for conducting the water pipes and air pipes are shown. A
section of the zinc outside is shown in the lower part of the figure.]
A photograph taken subsequently, showing the inner copper lining in
position, is given in fig. 11.
The floor of the chamber is supported by 7 pieces of 2-1/2-inch channel
(N, N, N, fig. 8), laid on top and bolted to the two 3-inch channels (M,
fig. 8). On top of these is placed a sheet of so-called asbestos lumber
(J', fig. 8) 9.5 millimeters thick, cut to fit exactly the bottom of the
chamber. Upright 2-1/2-inch channels (H, fig. 8) are bolted to the two
outside channels on the bottom and to the ends of three of the long
channels between in such a manner as to form the skeleton of the walls.
The upper ends of these channels are fastened together by pieces of
piping (P, P, P, fig. 8) with lock-nuts on either side, thus holding the
whole framework in position.
The I-beams and channels used to tie the four upright channels at the
top form a substantial platform upon which is mounted a large balance
(fig. 9). This platform is anchored to the ceiling at four points by tie
rods and turn-buckles, shown in fig. 4. The whole apparatus, therefore,
is extremely rigid and the balance swings freely.
The top of the chamber is somewhat restricted near the edges (fig. 8)
and two lengths of 2-1/2-inch channel support the sides of the opening
through which the subject enters at the top (fig. 7).
Both the front and back lower channels upon which the bottom rests are
extended so as to provide for supports for the outer walls of asbestos
wood, which serve to insulate the calorimeter. Between the channels
beneath the calorimeter floor and the 3-inch channels is placed a sheet
of zinc which forms the outer bottom metallic wall of the chamber.
In order to prevent conduction of heat through the structural steel all
contact between the inner copper wall and the steel is avoided by having
strips of asbestos lumber placed between the steel and copper. These are
shown as J in fig. 8 and fig. 12. A sheet of asbestos lumber beneath the
copper bottom likewise serves this purpose and also serves to give a
solid foundation for the floor. The supporting channels are placed near
enough together to reinforce fully the sheet of asbestos lumber and
enable it to support solidly the weight of the man. The extra strain on
the floor due to tilting back a chair and thus throwing all the weight
on two points was taken into consideration in planning the asbestos and
the reinforcement by the steel channels. The whole forms a very
satisfactory flooring.
_Wall construction and insulation._--The inner wall of the chamber
consists of copper, preferably tinned on both sides, thus aiding in
soldering, and the tinned inner surface makes the chamber somewhat
lighter. Extra large sheets are obtained from the mill, thus reducing to
a minimum the number of seams for soldering, and seams are made tight
only with difficulty. The copper is of standard gage, the so-called
14-ounce copper, weighing 1.1 pounds per square foot or 5.5 kilograms
per square meter. It has a thickness of 0.5 millimeter. The whole
interior of the skeleton frame of the structural steel is lined with
these sheets; fig. 11 shows the copper shell in position.
For the outer metallic wall, zinc, as the less expensive metal, is used.
One sheet of this material perforated with holes for the attachment of
bolts and other appliances is shown in position on the outside of the
wall in fig. 11. The sheet zinc of the floor is obviously put in
position before the channels upon which it rests are laid. The zinc is
obtained in standard size, and is the so-called 9-ounce zinc, or 0.7
pound to the square foot, or 3.5 kilograms to the square meter. The
sheet has a thickness of 0.5 millimeter.
[Illustration: FIG. 12.--Cross-section in detail of walls of
calorimeter, showing zinc and copper walls and asbestos outside (A);
hair-felt lining (B); cross-section of channel iron (H); brass washer
soldered to copper (K); asbestos insulation between channel iron and
copper (J); bolt holding the whole together (I); heating wire (W) and
insulator holding it (F) shown in air-space between zinc and hair-felt;
section of one of the cooling pipes (C) and its brass support (G);
threaded rod (E) fastened into H at one end and passing through asbestos
wall with a nut on the outside; and iron pipe (D) used as spacer between
asbestos and zinc.]
In the cross-section, fig. 7, A represents the copper wall and B the
zinc wall. Surrounding this zinc wall and providing air insulation is a
series of panels constructed of asbestos lumber, very fire-resisting,
rigid, and light. The asbestos lumber used for these outer panels is 6.4
millimeters (0.25 inch) thick. To further aid in heat insulation we have
glued to the inner face of the different panels a patented material
composed of two layers of sheathing-paper inclosing a half-inch of
hair-felt. This material is commonly used in the construction of
refrigerators. This is shown as E in fig. 7, while the outer asbestos
panels are shown as F.
A detail of the construction of the walls, showing in addition the
heating and cooling devices, is given in fig. 12, in which the copper is
shown held firmly to the upright channel H by means of the bolt I,
screwing into a brass or copper disk K soldered to the copper wall. The
bolt I serves the purpose of holding the copper to the upright channel
and likewise by means of a washer under the head of the screw holds the
zinc to the channel. In order to hold the asbestos-lumber panel A with
the hair-felt lining B a threaded rod E is screwed into a tapped hole in
the outer part of the upright channel H. A small piece of brass or iron
tubing, cut to the proper length, is slipped over this rod and the
asbestos lumber held in position by a hexagonal nut with washer on the
threaded rod E. In this manner great rigidity of construction is
secured, and we have two air-spaces corresponding to the dead air-spaces
indicated in fig. 7, the first between the copper and zinc and the
second between the zinc and hair-felt.