IMPROVEMENTS IN AND CONNECTED WITH ELASTIC WHEEL TYRES
Year: 1871

page_text: LETTERS PATENT to William Firth, of Rose Villa, Viewforth, Edin-
burgh, for the Invention of "IMPROVEMENTS IN AND CONNECTED WITH
ELASTIC WHEEL TYRES."
Sealed the 11th August 1871, and dated the 11th May 1871.
PROVISIONAL SPECIFICATION left by the said William Firth at the
Office of the Commissioners of Patents, with his Petition, on the
11th May 1871.
I, WILLIAM FIRTH, of Rose Villa, Viewforth, Edinburgh, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN AND
CONNECTED WITH ELASTIC WHEEL TYRES," to be as follows:-
:-
These improvements relate to certain forms and arrangements of the
several pieces employed in making a compressible and elastic segmental
wheel tyre, for which Letters Patent dated the 20th October 1869,
No. 3059, were granted to me, and to the Specification of which Letters
Patent I now crave to refer, and particularly to the four special
constituents therein set forth as forming the elements of my Invention.

page_text: The first of my present improvements consists in forming the metallic
treading pieces like a T or, the horizontal arms of which are placed
'to coincide with the circumference or bearing surface of the wheel, and
may each of them extend circumferentially from an inch to several
inches from the perpendicular arm, which may in like manner extend
radially from one to several inches from the horizontal ones. The
perpendicular branches of such treading pieces will therefore coincide
or nearly so with the planes of the radii of the wheel, and these pieces
are made to extend across the wheel face either in one or by several
pieces.
The chief feature of improvement consists in forming the end of the
perpendicular branch of any such metallic treading piece with a loop or
eye or longitudinal hole in a direction parallel to the axis of the wheel,
through which opening I pass a suitable metallic bolt, or tube, or pin,
the ends of which project beyond the side surfaces of the tyre, and if
desired through openings or holes of any convenient form in the flanges
or sides of the wheel to which the treading pieces and with them the
bearing pieces or other parts of the segmental tyre are secured by nuts
.made to screw on to the ends of these bolts or tubes; or they may be
linked together inside of the flanges or otherwise secured or linked in
various ways to the wheel. The bearing pieces of india-rubber or other
elastic material which rest on the rigid inner tyre are formed with
grooves into which the treading pieces are placed, or the bearing pieces
are placed between them and are formed to lock with the metallic
treading pieces. The radial thickness of the bearing pieces is made an
inch or two greater than the radial length of the perpendicular or radial
arm of the T shaped treading piece in order to provide for the radial
motion of the latter; and these bearing pieces may be made on metal
mandrills, the ends of which may if desired also pass through the wheel
flanges. These treading pieces I sometimes form of a U shape (instead
of the form just described), and sometimes triangular; generally any
form will do which will permit of a bolt or pin passing through it for
the purposes already described.
Another improvement consists in the employment of side rings
through holes or openings in which the bolts, or tubes, or other linking
or binding pieces of these segmental wheel tyres are passed, and to
which they are secured by nuts or otherwise; these side rings are made
flat in the form of washers and broad enough to extend inwards towards

page_text: the centre of the wheel beyond the inner surface of the compressible
tyre. This inward projection thus forms a groove into which the wheel
formed for that purpose (with a smooth or waved face) without flanges
moves or runs. Instead of these side rings being made continuous I
sometimes prefer to substitute for the same a double series of links on
each side of the elastic tyre, each link perforated with two or more holes
through which the linking bolts or tubes or pins of the treading or
bearing pieces are made to pass, and to which they are secured by nuts
or in any other convenient way. These side links I similarly make, to
perform the functions of rigid flanges.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Firth in the Great Seal Patent Office on
the 11th November 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
FIRTH, of Rose Villa, Viewforth, Edinburgh, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eleventh day of May, in the year of
our Lord One thousand eight hundred and seventy-one, in the thirty-
fourth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said William Firth, Her special licence that
I, the said William Firth, my executors, administrators, and assigns, or
such others as I, the said William Firth, my executors, administrators,
and assigns, should at any time agree with, and no others, from time
to time and at all times thereafter during the term therein expressed,
should and lawfully might make, use, exercise, and vend, within the
United Kingdom of Great Britain and Ireland, the Channel Islands, and
Isle of Man, an Invention for "IMPROVEMENTS IN AND CONNECTED WITH
ELASTIC WHEEL TYRES," upon the condition (amongst others) that I, the
said William Firth, my executors or administrators, by an instrument
in writing under my, or their, or one of their hands and seals, should
particularly describe and ascertain the nature of the said Invention, and
in what manner the same was to be performed, and cause the same to
be filed in the Great Seal Patent Office within six calendar months
next and immediately after the date of the said Letters Patent.

page_text: NOW KNOW YE, that I, the said William Firth, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement :-
These improvements relate to certain forms and arrangements of 5
the several parts or pieces and to certain contrivances to be employed
in conjunction or otherwise with the several pieces or constituents
employed in making a compressible elastic and articulated segmental
wheel tyre for the wheels of traction engines or carriages, for which
Letters Patent dated the Twentieth October 1869, No. 3059, and the 1
Twentieth of August 1870, No. 2296, were granted to me, and to the
Specifications of which Letters Patent I now crave to refer, and par-
ticularly to the first thereof, wherein the four elementary constituents
forming the elements of my said Invention are set forth.
In carrying out these my said Inventions I find that a very great 1
number of modifications or forms of the several pieces or constituent
elements thereof may be employed. These modifications depend largely
on the forms given to the treading pieces or metal shoes which come in
contact with the road, and whose functions are very important, for they
are required not only to protect the more tender india-rubber or other
elastic materials placed between them and the inner rigid tyre of the
wheel or its equivalent, but also to promote the adhesion of the wheels
to the irregular and varying surfaces of roads. They are also required
to be sufficiently strong and durable in order to avoid frequent delays
for repairs, and in common with the elastic bearing pieces susceptible
of being repaired and replaced in detail and in localities far removed
from workshops or manufactories where such repairs could ordinarily
be effected. These requirements can be best provided for by making the
elastic bearing pieces of such a size as will permit of their being placed
between two contiguous treading pieces and formed so as to lock with
or articulate with these pieces. For this end one very convenient form
for such treading pieces will be that of a T or r, the horizontal arms
of which coincide with the bearing surface of the wheel. Each of these
arms may extend from one to two inches circumferentially from the
perpendicular or radial arm which may extend radially two or three
inches.
The chief feature of improvement in this form consists in making a
swell at the upper end of the radial arm in order to lock it with the

page_text: contiguous bearing pieces and so prevent the treading piece from falling
out. I prefer to form treading pieces of malleable cast iron, and hence
a longitudinal hole or eye can be easily formed in this swell, and
through it I pass a suitable metallic bolt or pin, the ends of which
project beyond the side surfaces of the tyre, and, if desired, through
wide circular or triangular or other openings in the flanges or sides
of the wheel. These openings together with the bolts determine or
regulate the distance to which these treading pieces can extend from
the centre of the wheel, and hence can be used in binding the tyre to
the wheel, for the bearing pieces between the treading pieces will be
held by the horizontal arms of the latter pieces. But I prefer to make
the bearing pieces on metal mandrills which I pass through suitable
openings in the wheel sides, and make the treading pieces articulate
close enough with the bearing pieces, so that the treading pieces shall
be held to them by the swells on the radial arms and the bearing pieces
themselves by the mandrills to the wheel.
Several other forms of treading pieces articulating or alternating with
the bearing pieces may be employed, and various forms of these of the
same principle of construction as above described are adopted, together
with contrivances for linking, keying, or binding them together as
herein-after set forth with reference to the Drawings accompanying
these Presents.
Another improvement consists in employing inside treading pieces or
shoes between the bearing pieces and the rigid inner tyre of the wheel
in order to prevent the abrasion of the rubber of said tyre. One very
convenient form for such treading pieces is also a 5, the employment
of which in conjunction with the outside shoes and in an inverted
position relative thereto admits with suitable linking arrangements of
forming a tyre like a chain, and which may be applied outside of a
rigid wheel tyre in the same way as a continuous rubber band tyre.
The equivalents of these inner shoes are grooves in the rigid tyre across
its face, or ribs or bars fastened thereto to form grooves or cells.
Another improvement consists in employing side rings between the
sides of the elastic tyre and the sides or flanges of the wheel to which
to attach the inside and outside shoes in order to form a tyre of the
composite character already stated and which may be removed from the
wheel as a continuous band. The treading pieces most advantageous
to use with these rings are formed like hollow triangular prisms placed

page_text: in an inverted position relative to each other with lozenge shaped
bearing pieces between contiguous pairs. These treading and bearing.
pieces are held to the side rings or directly to the sides of the wheel by
mandrills as already referred to. These side rings can be made broad
enough to extend beyond the rigid inner tyre, when the flanges of the
wheel may be dispensed with, and the wheel, then a cylinder, left free
to move, run, or roll in the groove thus formed by the side rings and
the elastic tyre. But the most important use of these side rings is in
connection with a wheel wherein the rigid tyre is replaced by a series
of bolts, bars, or pins, or tubes extending from side to side near the
outer edges of the sides and to which they are held or united by nuts or
otherwise for which Letters Patent dated 20th August 1870, No. 2296,
were granted to me. Such rings (two or more in number) may be
united near their circumferences by bolts or bars or tubes passing
through holes in them and being made of such a size as permits of the
bars or bolts uniting them to rest on the inner surfaces of the bearing
pieces they are the equivalent of a rigid inner tyre or hoop not rigidly
attached to the wheel sides but free to move up and down between
them. By such rings or hoops the pressure from the comparative
small bearing part of the compressible tyre is transferred from the lower
to nearly the entire inner surface of the compressible tyre.
Side rings
or their equivalents used in this way I call transfer rings or transfer
hoops. They promote softness of tread to the wheels, ease and freedom
from shock to the machinery of the engine, permit of a flexible and less
compressible tyre being used with the advantages of a more compressible
one. Further they distribute pressure, and if desired may be used to
limit the amount of compression to which the bearing or other elastic
pieces shall be subjected.
Another improvement consists in the employment of an elastic

page_text: In order that those improvements which constitute my present
Invention and the mode of carrying them into practice may be properly
understood I have appended hereto five Sheets of illustrative Drawings,.
which I now proceed to describe. And in order that these Drawings
and the following description may be readily understood I call attention:
to the four constituent elements of my first Invention above referred
to and observe that the first of these elements, namely, the elastic
bearing pieces, are marked throughout the Drawings by the letter B.
In like manner the second of these or the metallic shoes or treading
pieces are marked by the letter S.
Similarly the third of these or the elastic junction pieces are marked
by the letter J or the letter C or the letters J, B.
Again the metal linking or binding pieces whether bolts, bars, tubes,
or such like are marked by the letters m, n, or v.
Further the rigid inner tyre of the wheel is marked by R and the
sides or flanges of the wheel by f.
Lastly when a number or a dash is used with a letter it simply
indicates another constituent or piece of the same character as that
indicated by the letter.
Also throughout these Drawings the elastic elements are indicated
as in section by broken lines, and the metal portions with which they
articulate are indicated as in section by continuous lines, and in the
side views one only of each of the pieces forming a tyre is shown as in
section. All the others being similar pieces are shown in outline.
Fig. 1 represents a side view of a portion of a wheel with the flange f
partially removed shewing the arrangement of parts with triangular
treading pieces S held by bolts m which pass through ☐ shaped studded
washers y (Fig. 2), whose studs journal in a larger hole in the wheel
sides than would be required for m. They touch loosely washers w
carried by the mandrill n passing through bearing pieces B.
Fig. 2 is a cross section, one half (the right) through m, and the other
half (the left) through n in Fig. 1. R is the rigid wheel tyre; it is
supposed (Fig. 2) free to move slightly eccentric to the wheel sides, but
it may be attached to them in the ordinary way. In the former case
it transfers pressure to the inner surface of the upper
which is communicated to the resistances m by the
half of the tyre,
pieces B and J,

page_text: which will thereby be slightly compressed, but much less so than
similar pieces on the under half of the tyre.
Fig. 3 represents a portion of a wheel wherein the tyre is arranged
for T shaped shoes S to be carried by two bolts m and m₁, both of which
pass and journal in a studded washer y which again journals in the
sides of the wheel. The mandrills n pass through washers w which
bear against the rubber bearing pieces B on the one side, and the
washers y on the other, and thus prevent abrasion of the rubber by
the rocking of y. The sponge rubber junction piece C and the upper
half of the bearing piece B as well as the shoes S may be in one or
more pieces across the wheel face. The mandrills n project beyond the
washers w, and touch loosely the edges of the washers y and regulate
the rocking thereof.
Fig. 4 represents a portion of the side of a wheel arranged for another
form of shoe S locking with bearing pieces B, which bear against
triangular shaped bolts Q instead of a rigid inner tyre. These bolts have
their ends turned to journal in the wheel sides f, to which they may be
secured by nuts (not shown in the Drawing). The bearing picces may
be made in one piece or in two pieces, one on each side of the solid
or hollow mandrill m, which passes by preference through a circular
studded washer y journalling in the wheel sides f, and furnished with
an oblong hole or slot for the mandrill to play or move in. The shoes S
may
each be in one or in more pieces across the wheel face, and the
sides bearing against the rubber are made concave to provide for the
side distortion or expansion of the rubber bearing pieces, as indicated
by dotted lines. Any mud getting between these shoes will pass inside
the wheel, whence it can easily be removed.
Figs. 5 and 6 represent respectively a cross section and side view of
a portion of a wheel furnished with another form of shoe S, which
carries inside a hollow or solid mandrill m passing through a rubber
socketting piece K and through a studded washer y journalling and
sliding through a slot in the wheel sides f. The rubber bearing pieces B
expand into the spaces C, which may be filled with sponge rubber.
The junction pieces J key, lock, and articulate with the shoes S. The
rigid tyre R. may be fixed to the sides for used as a transfer hoop
(Fig. 5).
Fig. 7 shews portion of a wheel with tyre formed with hollow
T shaped shoes S carrying a bolt n passing through washers 10₁, 10., &c.,

page_text: bearing against washers w carried on mandrills m passing through
rubber junction pieces J. These washers in virtue of the locking of
the pieces S and J also lock with each other and would keep the tyre
to the wheel without the oblong journal holes in the wheel sides of for
the washers w.
Fig. 8 shows another form of shoes S locking with bearing and
junction pieces B, J, carrying a large tube mandrill carried by
bolts m passing through and secured to the wheel sides ƒ (by nuts).
The mandrills v pass through washers wo, which bear loosely against
double studded oblong washers y carried by the sides f. The large
mandrills allow play or room for the mandrills m, which may be
rigidly attached to the wheel sides.
Fig. 9 represents portion of a wheel side having a tyre formed with
another form of shoe S bearing against curved bearing pieces B resting
on a curved or waved rigid tyre R, r, being curving pieces rivetted or
otherwise attached thereto. Between and locking with the treading
pieces S are the junction pieces J carrying hollow mandrills or tubes
covering solid mandrills m passing through slot holes in the wheel
sides f.
Fig. 10 represents portion of a wheel side with a tyre having
T shaped shoes S locking with bearing pieces B carrying a tube
mandrill v covering a solid bolt m passing through oblong holes in the
wheel sides f. The bearing pieces bear against lunar shaped bars Q
performing the function of a rigid wheel tyre. Their ends journal in the
wheel sides f, and thus they are free to rock with the bearing pieces.
The form of shoe here shown is available for frosty roads.
Fig. 11 represents the side of a tyre furnished with inside shoe S₁
protecting the rubber bearing pieces B from abrasion by the rigid tyre R.
These shoes carry bolts n₁, which are connected with the bolts n carrying
the outer shoes S by means of holes in the side rings x, which are also
furnished with gaps for the mandrills m passing through the bearing
pieces B to play or move in. Between the outer shoes S and the inner
shoes S, are sponge rubber junction pieces C. These several pieces may
be continuous across the face of the wheel, or in, say, three divisions, as
shown in cross sectional Drawing, Fig. 12, the middle division being a
section through m, and the side divisions through n. The rigid tyre R
may also be in three divisions, which may be used as transfer hoops
having their eccentricity determined and themselves supported by bolts b

page_text: secured to the sides or flanges f and fi of the wheel. Thus the mud
which passes between the divisions will pass away from the tyre. The
bolts n₁ and n may be linked together by washer with oblong holes
embracing both bolts. (The flanges fand fi are not shown in Fig. 11.)
If the bolts n, m, and mandrill m be furnished with nuts and secured to
the rigid side rings x, and if these rings extend inward beyond the
rigid tyre R, the wheel formed without flanges will be free to move
and will be retained between these rings. Fig. 13 represents portion of
the side of a wheel with T shaped shoes S locking with bearing pieces B
and junction pieces C, each in three divisions across the wheel face, as
shown in Fig. 14, a cross section through the axis of m, which is a solid
mandrill grasped and held by a split tube by which it is expanded to
fit loosely a hollow mandrill v₁ carried by B, B₁, B,, the several bearing
pieces on one such compound mandrill, the solid core of which passes
through the wheel sides.
Three different forms for the middle longitudinal section of the
treading pieces or shoes S are shewn by Fig. 15. Thus the webs or upright
arms or locking arms of all these shoes may have one or more ribs, or
they may be hollowed or pierced with one large or several small holes
around, into, or through which the bearing pieces are fitted or pressed,
and by which or equivalent contrivances the shoes are prevented from
moving crosswise or from side to side of the wheel.
Fig. 16 represents a side view of part of a wheel furnished with a tyre
constructed with a combination of V and U shaped treading pieces in
sets arranged so as to form a polygonal compressible tyre outside of the
rigid tyre R. A circular tyre in revolving is continually forming the
side of a polygon in the present arrangement. The sides of one polygon
are intermittently forming the sides of another polygon, thus the
shoes S and S. alternately occupy the middle and the extremity
of the side of such a polygon. This is accomplished by arranging
a set of Ushaped shoes S₁, S, S,, S., of reducing sizes one within
the other and alternating with junction pieces J₁, J, J., J., which
also perform the function of bearing pieces, whereby a succession
of compressions is obtained thus the compression of J₁ will be one
compression for itself and all in the nest or set with it, and so of the
others, hence the radial movement of S. will be equal to four com-
pressions from the junction piece in addition to that obtained from the
bearing junction pieces J, B, whose compression brings the bearing

page_text: piece B carried by S in contact with the tyre R. The greater part of B
may be wood, and if the rigid tyre be used as a transfer hoop the
piece B may be wholly of wood. If desired the piece B may carry a
metal mandrill passing through oblong holes or slots in the wheel
sides f. The alternate bolts m, m2, &c. each carry a nest of treading
and junction pieces, and the alternate bolts m₁, m,, &c. carry the larger
shoes S. It will be most convenient to alternate this arrangement if
the pieces are in three divisions as shewn in cross sectional Drawing
Fig. 17, taken through centre of m or m., wherein corresponding letters
indicate corresponding parts. The headed bolt m carries a nut at one
end, by which it is secured to the wheel sides f and also washers w
separating divisions. The binding bolts for the wheel sides, one of which
is shewn in Fig. 17, can be easily arranged to control the eccentric
motion of the transfer hoops R and so limit the outward pressure on
bolts m when on the upper half of the wheel.
Fig. 18 represents portion of the side of a wheel arranged for nests
or sets of trough treading pieces or shoes S, S₁, S,, having bearing
pieces B and junction pieces J and C between them on all sides. The
primary bearing piece B rests on the bottom of a trough, which rests
on the bottom of an inverted trough r. The sides of both these troughs
rest against and may be rivetted to the arms R, and the sides f of the
wheel. The rigid wheel tyre is thus transformed into a cellular one
and marked by the letter R. It may be formed cellular in other
ways. In each of these cells a nest or set of shoes S with their bearing
pieces B and junction pieces J or C are placed and held to the
bottom of the cell R, r, by a bolt m furnished with a nut N resting on.
a rubber buffer spring D, which keeps the swelled head of the bolt m
tight against the final bearing piece of the set B,, and hence all the
pieces of the set are held in the cell of the wheel. This arrangement-
forms a set of compressible projections, which may be called by the
technical term "spuds," or it forms a waved wheel face circumferentially
and a curved wheel face across, as shewn in Fig. 19, a cross section
through m, in Fig. 18. All the parts in Fig. 19 are only changed in form
when viewed in section to suit the parallel wheel sides finstead of the
inclined radial arms R₁ of the wheel. If the binding bolt m be made
with a large round tapering head it will itself form a shoe, and with
such a shoe the nest of pieces in the cell may be replaced by one rubber
bearing piece, whose sides resting against the bottom and sides of the.

page_text: cell are concave, and these concavities into which the rubber will
expand or distort when under pressure may be filled with sponge rubber.
Further the U shaped troughs in Fig. 16 or triangular troughs or other
modifications may be used indifferently for those shewn in Fig. 18 or
Fig. 16.
Fig. 20 represents portion of a wheel with tyre formed with triangular
shoes S carried on mandrills m, which rest on socketting pieces of
rubber K. When these shoes are under pressure the bolt m will be near
the centre of pressure on the several sides of S, for which reason it
projects considerably beyond m. The bearing pieces B bear against
tubes q which are carried by bolts or bars Q passing through holes in
the transfer rings x, which with said bars Q and tubes q perform the
function of a rigid inner tyre. These transfer rings are free to move
eccentric to the wheel sides to an extent that may be regulated by
carrying the bolts Q concentrically through a larger circular hole in the
sides of the wheel. This is shown on the left, where Q occupies the
eccentric position it will do when on the top part of the wheel.
It is to be observed that the eccentric motion of the transfer rings x
will lift all the bars or bolts Q parallel to each other, hence there will
be provision made for a certain amount of flattening of the tyre taking
place before or while compression is taking place. Further the rings x
may approach the bolts m to any required degree, hence the amount
of compression to which the bearing pieces B on the under side of the
wheel are to be subjected can be regulated, for when the rings touch
the bolts further pressure on B ceases. The wheel will however still be
resting on the cushion obtained by the transfer rings from the under side
of the upper half of the elastic tyre.
Fig. 21 is a cross section, the middle thereof being taken through the
centre of m, and the sides through the centre of Q. It will be observed
that four transfer rings are used, and that the tyre is formed by three
divisions which may be kept apart by washers carried by mandrill m
between them.
Fig. 22 represents a side view of portion of a wheel fitted with a
flexible and compressible tyre with triangular outside treading pieces or
shoes S carried by mandrills m which are carried by studded washers or
bushes y whose studs pass through oblong openings or elliptic holes in the
wheel sides f. These washers or bushes when the tyre is in its normal state
bear against the sides of these holes furthest from the centre of the wheel.

page_text: These triangular shoes S have gaps in the part passing over m in order to
the suspension of the inside shoes or troughs S₁, which may be formed by
suspending triangular iron straps 3 from the mandrills m, which straps
have sheet iron covers 2 rivetted on them and are thus formed into
triangular troughs with gaps in their bottoms alternating with the gaps
in S. Between the pairs of shoes suspended from one mandrill and
those on the contiguous mandrills are the bearing junction pieces B,
lozenge shaped, and inside of the inside shoes S₁ are wood or other
fillings F bearing against rubber bearing picces B, and finally against
the rigid transfer hoop R or x, free to move eccentric to the wheel sides.
The spaces C are filled with sponge rubbers C resting against metal
bars r rivetted or otherwise attached to the transfer hoop x serving to
keep the bearing pieces B in position.
Fig. 23 represents a cross section on the radial plane passing through
m, in which corresponding parts are marked by corresponding letters or
figures. The arrangement of parts in this form are similar to those
described with reference to Fig. 20 in the following respect, namely,
that provision is made for the wheel flattening, thus suiting it for soft
ground. This is obtained by suspending the tyres from the mandrills
and making these last free to move towards the centre of the wheel by
means of the oblong side holes in the sides. The transfer hoop x
(Fig. 22) is not essential for this end, as the pieces are there formed to
dispense with it. It will be preferable to use it as an additional support.
The mechanical equivalent of this arrangement would be obtained were
the tyre or hoop R or x rigidly attached to the sides, and its bearing are
at any particular instant susceptible of flattening to a chord of its
circle. The arrangement of parts herein set forth may be said to con-
stitute the suspension of the wheel by the tyre which results from the
use of the transfer hoop x.
Fig. 24 represents a full sized end view of the simple T formed
treading pieces or shoes, of which all the others are modifications, and
Fig. 25 represents a similar view showing the application of sponge
rubber C put in under pressure and reduced in cubical space, and thus
provided with a greater range of elasticity. Thus any gapping between
S and B will be prevented from letting in mud, as the expansion of C
will more than fill any probable opening.
Having now described the nature of my Invention, and in what
manner the same is to be performed, I desire it to be understood that I

page_text: do not confine myself to details and to the exact combinations shown,
for several features shown with more prominence in one Drawing may
be equally applied to others which set forth more prominently other
features of my said Invention; but what I believe to be new as con-
stituting my present Invention I declare to be as follows:-
1. The several forms of metal treading pieces or shoes herein set
forth, ranging in form from the simple T form shown in Fig. 24 to the
expanded modifications thereof, namely, the triangular or trough-shaped
forms described with reference to Figs. 16 to 23 inclusive, by which and
the linking arrangements an alternation, articulation, and locking of the
several parts of a compressible, elastic, and articulated composite wheel
tyre are secured for the purposes herein set forth.
2. I claim the superposition of these treading pieces so as to form a
polygonal or waved wheel or tyre surface, and to obtain a multiplied
compression described with reference to Figs. 16 to 19 inclusive.
3. I claim the use of inside or rigid inner tyre metal treading pieces
for protecting the inside of the elastic bearing pieces from abrasion, and
also the equivalent of these, namely, cells in the outside surface of the
rigid inner tyre, whether formed by bars or ribs or such like or other-
wise, and I also claim the forming of holes in said tyres for the passage
of mud from the compressible tyre to the inside of the rigid one.
4. I claim the use of that preparation of india-rubber called sponge
rubber placed in such positions as those marked C in the accompanying
Drawings for the purposes herein set forth.
5. I claim the use of side rings for the linking of the outside and
inside shoes or treading pieces described with reference to Figs. 11
and 12.
6. I claim the use of side rings in conjunction with bolts or pins
resting on the inside of the rubber bearing pieces whereby the pressure
can be transferred from the bearing part of the wheel (at any instant) to
the inner surface of the upper half of the elastic wheel tyre, and I also
claim the equivalent thereof, namely, a rigid inner tyre unattached to
the sides of the wheel described with reference to several Drawings, and
particularly with reference to Figs. 20 to 23.
7. I claim the use of oblong openings or slots of any convenient form
in conjunction with these transfer side rings or loose rigid inner tyres or
hoops for the purpose of obtaining a flattening of the compressible tyre

page_text: with slight compression, more particularly described with reference to
Figs. 22 and 23.
8. Lastly, I claim the use of the studded washers or bushes marked y
throughout these Drawings, whether free to rock or revolve or rigidly
attached to the sides of the wheel for the purposes set forth; the whole
of these constituents being parts of the Invention the nature whereof is
herein-before particularly set forth and described.
In witness whereof, I, the said William Firth, have hereunto set
my hand and seal, this Eighth day of November, in the year of
our Lord One thousand eight hundred and seventy-one.
Witness,
ALEX. LAWSON,
5, Rosebank Cottages,
Edinburgh.
TIIVII.