Improved Means for Determining the Expansion of Solids.
Year: 1896

page_text: PROVISIONAL SPECIFICATION.
Improved Means for Determining the Expansion of Solids.
I FRANK CHARLES WEEDON Alleyn's School, Dulwich S.E. Teacher of Science,
do hereby declare the nature of this invention to be as follows:-
A bar of the solid to be experimented on, is placed on a platform, in, and running
nearly the whole length of, a trough, which is slightly longer than the bar. Each
end of the trough is pierced by stuffing boxes, in each of which works horizontally
a short plunger of small diameter. Outside the trough at each end is a micrometer
screw gauge held in a vice, secured to a heavy moveable base. The jaw of each gauge
is pierced by a cylindrical hole slightly larger in diameter than the plungers.
Melting ice surrounds the bar. The plungers are adjusted so as to be in contact
with the ends of this experimental bar, and the vices are so placed that the lengths
of the gauges are continuous with that of the bar, and the plungers while in contact
with the bar pass through the hole in the jaw of the gauge, and are also in contact
with the micrometer screw.
The reading of the gauge is taken and the screw turned back a few revolutions
The length of the bar is observed. Heat is applied to the trough, the ice is melted
& the water formed is raised to the boiling point. The bar thus heated
expands.
The gauges are screwed up so as to be in contact as before and the difference of
the reading due to the expansion, is observed at both ends.
The sum of these readings is the expansion of the bar.
This invention is specially adapted for use in the laboratories of schools and
colleges.
It takes up less room than the classical methods. It is capable of yielding accurate
determinations.
It is educational in its simplicity-There are no confusing complications, nor does
it assume previous knowledge, which junior students are not likely to be in possession
of; such as the relation of similar triangles, or the law of incident and reflected ray
with a rotating mirror.
It requires the knowledge of the micrometer screw gauge, an instrument which
is now generally used by beginners in practical physics. It thus utilises the
previous knowledge of the student. It is economical, since the complete apparatus
is comparatively inexpensive, and the separate parts can be utilised for many other
laboratory exercises.
Dated this 21st day of November 1896.

page_text: Improved Means for Determining the Expansion of Solids.
I, FRANK CHARLES WEEDON, of Alleyn's School, Dulwich in the County of
Surrey, Science Teacher, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement:-
This invention relates to apparatus for measuring the linear expansion of solid
bodies when heated, and the said invention has for its object to provide for the
aforesaid purpose apparatus specially adapted for use in schools and colleges for
educational purposes. It will be understood that the apparatus employed by skilled
physicists for determining the linear expansion of solid bodies is not suitable. for the
use of junior students by reason of its great delicacy of adjustment and its costliness,
and hence it is necessary to employ a modified form of apparatus which shall be
comparatively cheap but which shall be capable of yielding a degree of accuracy at
least as great as the limits of accuracy of a junior student so as to be of real value
as an educational instrument. My improved apparatus fulfils these requirements.
It comprises a trough for containing ice or water or other medium by which the
temperature of the body whose expansion is to be measured is determined,
and a sliding pin passing through each end of the trough and making contact
internally with the body under test and externally with the screw of a micrometer
gauge. These two micrometer gauges hy which the expansion is measured are held
in suitable rigid clamps external to the trough so that neither the gauges nor the
clamps are in contact with the trough.
In order that iny invention may be readily understood I will now describe the
same with reference to the accompanying drawing which shows in perspective one
end of my improved apparatus adapted for measuring the expansion of rods or bars,
a portion of the trough hereinafter described being broken away to show the interior
thereof. It should be understood that the other end of the apparatus is precisely the
same as that shown in the drawing.
A is a trough for containing ice or water or other medium by which the temperature
of the body under test is determined. The said trough is supported on standards B
fixed to a strong base C which carries the whole of the apparatus. D is the body
to be tested, the same being in the form of a bar or rod somewhat shorter than
the trough and resting on a platform or in a channelled support E that stands on
legs E. Near each end of the trough I preferably provide a guide E2 secured to
the base of the trough and notched at the top to receive the rod D and to prevent
lateral movement of the rod. F is a gas burner for heating the contents of
the trough to any desired temperature; Fi is a flexible gas tube connected to the
burner. G is a shallow tray resting on the base Cand containing water or
preferably arranged for water to continuously flow along it to prevent the conduction
and radiation of heat to the base C. It will be understood that the heat radiated
from the bottom of the trough if allowed to impinge on the base C would cause a
slight expansion of the base and vibrate the readings thus impairing the accuracy
of the apparatus. At each end of the trough in line with the bar or rod to be
tested is a stuffing-box H through which passes a pin or plunger J. The packing
in the box is pressed sufficiently to prevent the escape of liquid from the trough
but not so as to prevent the free sliding of the pin through it. K is a micrometer
screw gauge of ordinary construction having the usual stationary pin removed.
The said gauge is secured in a clamp L which is fixed to the base C and is sufficiently
rigid to prevent any movement of the guage. The gauge is arranged in line with
the pin J and the said pin passes through the eye left by the removal of the

page_text: stationary screw pin of the gauge and forms the abutment against which the end of
the micrometer screw is adjusted before the readings are taken. There is a
micrometer gauge at each end of the trough. M, M are two screens to protect the
clamps and screw gauges from thermal radiation.
The apparatus is used as follows, that is to say, the bar or rod D to be tested is
placed upon the platform or support E in the ice or liquid in the trough and when
the experiment does not begin from the freezing point of water, the temperature
is taken by thermometers placed in the liquid. The pins Jare then carefully pushed
in until their inner ends touch the ends of the rod or bar, and the micrometer screws
are screwed forward until their ends touch the outer ends of the pins J.
The readings on the two gauges are then observed, and the length of the rod or bar
D is measured. Tire micrometer screws are now screwed back and the burner Fis
then lit to heat the liquid in the trough to the boiling point or to any lower
temperature which temperature is maintained for a sufficient length of time to allow
things to assume a state of equilibrium. The micrometer screws are then again
screwed forward until they abut against the pins J and a second set of readings is
taken. The sun of the first two readings deducted from the sum of the second
two readings gives the linear expansion of the rod, and that amount divided by
the length of the rod measured at the lower temperature gives the expansion
per unit length between the limits of temperature adopted in the experiment.
For very accurate determinations a correction can be applied for the expansion
of the pins J but as this correction amounts but to a small fraction of the total
expansion it can be neglected by junior students. The position of the gauges can
be adjusted initially as may be desired after simply unscrewing the clamps.
I have found that this apparatus gives very accurate results and can be used
readily by very young students. It takes up less room than the classical apparatus
employed for a like purpose, and is not confusing in use nor does it assume any
previous knowledge which junior students are not likely to possess such as the
relations of similar triangles or the law of incident and reflected rays from a rotating
mirror. It requires merely a knowledge of the micrometer screw gauge, an
instrument which is now very generally used by beginners in practical physics.
It thus utilises the previous knowledge of the student, and is economical since
the complete apparatus is comparatively inexpensive and the separate parts can be
utilised for many other laboratory exercises, and hence it will form a valuable
adjunct to the physical laboratories of schools and colleges.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is :-
1. The pins sliding through stuffing-boxes in both ends of the heating trough
in combination with micrometer screw gauges held in clamps external to and
independent of the heating trough, substantially as, and for the purposes,
specified.
2. An apparatus constructed substantially as described with reference to the
accompanying drawing and operating as, and for the purposes, specified.
Dated this 20th day of August 1897.
GEORGE HARRISON,
35 Therapia Road, Honor Oak, S.E., Agent for the Applicant.