Evening star. [volume] (Washington, D.C.) 1854-1972, 1904-09-20
AN IMPORTANT PATENT
ISSUED TODAY TO PROF. ALEX.
GRAHAM BELL.
His Invention Of "An Aerial Vehicle
or Other Structure''-His
Explanation

A patent was issued to Prof. Alexander
Graham Bell today covering the invention
Of IAN aerial vehicle or other structure"
device which has become well known scien-
tifically as the tetrahedral unit and tetrah-
edral kite. Application was filed for patent
in June 1903 and the issue was made to-
day.
This latest invention of Prof. Bell Is the
result of investigations conducted with a
view, more particularly, to the determine
ton of the form and character of structure
most suitable to the requirements OF aerlal
vehicles: and the invention, while especially
applicable thereto. has additional and I'M
portant applications to other structures
where properties of great strength and
rightly, combined with lightness, are re-
quired and where facility in transportation
and assembling the elements of the struc-
ture is desirable. The Investigations that
Prof. Bell has conducted with these struc-
lures have been where the tetrahedron
principal was applied to kites, the obserya-
tons being directed to the qualities of
strength and stability in all three dimen-
sions and to steadiness in flight as we'll as
to comparative lifting power.
Prof. Bells Explanation.
1.-THE recent developments in kite struc-
ture have been largely due to the investi-
cations of Laurence Hargrave," Prof. Bell
states in explaining his invention, 1.-The re-
suits of which are represented in the we'll
known cellular box kite. Although multi
cellular kites have been constructed upon
the Hargrave principle they have not been
found to possess any substantial advan-
tage over one composed of two cells only.
Hence the familiar form of -Hargrave kite
Is one composed of two rectangular cells.
These two cells are disposed with their cor
responding surfaces in the same planes
and are separated by considerable spaci
bridged over by connecting framework
of solid material, which Is an essential fea-
ture of the structure and adds weight to
the kite without contributing to the lift.
The rectangular cell Is structurally weak
and easily distorted. requiring internal
Sracing, which also adds to the dead load,
besides opposing additional head resistance
to the wind, increasing the drift of the kite.
Moreover, there is limitation to the lifting
power of kites of this description, since
the mere increase of the dimensions of the
kite In its several parts does not increase
porting surfaces, but just the reverse. This
is due to the fact that the weight increases
as the cube Of the dimensions, whereas the
surface exposed to the action of the air
only as the square. Hence in
two kites differing only in dimensions the
ito of weight to surface will be greater
for the larger kite than for th~ smaller.
The Tetrahedral Cell.
II have found that the desired qualities
mentioned above reside in a high degree in
a cell constructed in the form of a skele-
ton of a tetrahedron. and cells Of this form
constitute the units or elements from which
a great variety of structures contemplated
by this invention are or may be built up.
The tetrahedral skeleton or frame may be
composed of six bars or rods so connected
at their ends as to form the outlines of
four triangles. If. as is preferred, the form
is that of regular tetrahedron, the bars
will be of equal length, and the triangles
Will be eQuilateral. For some purposes a
tetrahedral frame in which two of the
sides are right-angled triangles is advan-
tageous, and for other purposes the bars
may be hollow or constitute closed tubes
capable of floating in water and may be
triangular in cross-section. This tetrahe-
oral cell or frame is found to possess, with
minimum weight of materials the qualities
of rightly and strength to a remarkable
degree and for this reason is adaptable to
great variety of structural uses. More
over, the finished structures compounded
of these elements partake of the Qualities
or the latter, and the facility with which
they may be assembled, connected and
dismembered, and the ease of transporta-
tion from place to place further contribute
to their utility. Considering particularly
the subject of aerial vehicles such as kites
the tetrahedral cell possesses rightly or
strength in three directions-that is to saw
virtically, laterally and longitudinally-so
that internal bracing is entirely sinner
huous and Is dispensed with When one
OF the bars is taken as a keel and the two
opposlte triangular surfaces rising there
from are covered with silk or other suit
apie material, the other two trianeles being
left uncovered. we have a structure which
&c cal a winged tetrahedral CELL Each of
the obllque surfaces of this winged cell Ia
.Le resultant land equivalent for the pur-
poses In view of its horizontal and varticaI
components, constituting a decided pain IN
ilgntness as we'll as in rigidity Obviously
IN pulldlng up compound structure nv
connecting together a number of these
winged cells the ratio of weight n n,;,n
surface remains practically uniforno us
pertinent shows that kite structures ne
great size, compounded of these winged
.etrdheoral cells, fly equally as we'll in tha
same breeze as kites composed Of j. raIa
tlVely small number of such elements
A Great Field of Usefulness
continuing his explanation DR.. ReII statas
.hat structures of many different kinds can
oe maze OF tetrahedral elements, so great
Is the neld of usefulness of this particular
Nv h.eil.ion that 1t Is impossible to state at
ms stage of its use just how MANY forms
1here are IN which 1T can be used The ole
menus or units have been applied to the
construction Of windbrakes, boats, small
IN taa' ana are declared to be most useful
IN the construction of temporary bridges.
seaHoidlng and the like, wherever the prime
are lightness and stabiIitv
cempined with great strength. In conclud-
- .tio oApiaiidtioH Dr. Bell states that 1t
s not essential that the compound structure
Or whole structure built of tetrahedraI
units shall give the form of tetrahedron.
and for some purposes such form is mad,
nlssible. The tetrahedral skeletons or
ceIis are units or elements susceptible of
;omplnatlon in many ways, but the tetrahe-
IL al form Of the compound structure has
oeen specially mentioned because excellent
'esults have been obtained Herewith in kite
NV
Prof. Bells patent is numbered no 626
and the application Is signed by w. M
Mitchell