IMPROVEMENTS IN TYRES FOR RAILWAY WHEELS, AND IN THE METHOD OF APPLYING THE SAID IMPROVEMENTS
Year: 1877

page_text: LETTERS PATENT to Frank Wirth, of the Firm of Wirth and Company,
Patent Agency, of Frankfort-on-the-Maine, in the Empire of Germany, for tho
Invention of "IMPROVEMENTS IN TYRES FOR RAILWAY WHEELS, AND IN
THE METHOD OF APPLYING THE SAID IMPROVEMENTS." A communication
from Wilhelm Schmidt, Engineer, residing at Heidelberg, in the Empire of
Germany, and François Gittens, Shipbroker, residing at Antwerp, in the
Kingdom of Belgium.
PROVISIONAL SPECIFICATION left by the said Frank Wirth at the Office
of the Commissioners of Patents on the 28th March 1877.
• FRANK WIRTH, of the Firm of Wirth and Company, Patent Agency, of Frankfort-
on-the-Maine, in the Empire of Germany, "IMPROVEMENTS IN TYRES FOR RAILWAY
WHEELS, AND IN THE METHOD OF APPLYING THE SAID IMPROVEMENTS.”
A com-
munication from Wilhelm Schmidt, Engineer, residing at Heidelberg, in tho
Empire of Germany, and François Gittens, Shipbroker, residing at Antwerp, in the
Kingdom of Belgium.
A long series of experiment and observation has led to the conviction that the
model or pattern of tyres for railway wheels hitherto used is defective, and that the
mode followed before bringing old tyres to their original conicalness, that is, before
refacing the tyre, is viscious and causes much prejudice.
Commissions of technical engineers have decided that the conicalness of the tyre
should not be less than 5%, whereas I propose that the original conicity should
in no case exceed 2°, nor be allowed to be worn to more than 5%.
The method hitherto followed before refacing or "turning off" old tyres has been
as follows, that is to say, when the tyres of passenger carriages have been partly
worn out, they are replaced by others, and then adapted to goods' trucks, where they
are allowed to run until they have become utterly unfit for service, that is, when the
conicalness has obtained from 20 to 25%. The prejudice caused by this system
will easily be understood by examining the accompanying Drawing, wherein we
mathematically show the augmentation of the wear on a scale of conicalness
extending from 1 to 21%.

page_text: °
Figure 1 shows the wear on a tyre reaching from 1 to 20% cone, and it is to be
observed that the deepest wearing point in the smaller degree of conicalness is
about one-third of the breadth of the tyre from the flange, whereas in the greater
degrees of conicaluess it comes much nearer to the flange, each portion of wear
increasing the conicalness by one-third.
The wearing surface of the tyre and rail is shewn in Figure 2. It is to be
observed that a newly turned wheel has a narrower wearing surface on the rounded
rail, and therefore wears deeper, but I propose that the tyres should be as much as
possible uniformly maintained at their original conicalness of 2%, and should not
be allowed to exceed 5°, excepting in the transition from the old to the new form,
when I should temporarily and exceptionally allow up to 8%, but not more; the sur-
face of the rail will soon acquire a wearing surface in conformity with the uniform cone
of the tyre, and as the wear will then stretch over a broader space it will also become
thinner. This feature has its importance, as it would otherwise appear from the
scale indicated by the table in the Drawing, that by this Invention a tyre would
have to be faced off five times instead of once; now, if so, the benefit of the said
Invention would be partly lost. This is, however, not the case, and the turning off
or facing will at the most be required twice instead of five times, and from the table
on the Drawing it will be seen that it is more profitable to turn off twice,
according to the said Invention, than to turn off only once, according to the method
now in vogue.
This Invention therefore is not only based on scientific laws, but it also rests on
practical observation, and constitutes an Invention in that sense that I not only
propose that the conicalness of the tyre of railway wheels should be reduced to 2º
but that my improved method essentially differs from the method bitherto followed, 2
and from the decisions of technical commissions, which decisions now virtually rule
the working of railway traffic.
The advantages resulting from the use of this Invention are as follows, namely,
considerable economy in the wear of tyres and rails, a smoother running of the
carriages, and economy in the force of traction.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Frank Wirth in the Great Seal Patent Office on the 27th
September 1877.
FRANK WIRTH, of the Firm of Wirth and Company, Patent Agency, of Frankfort-
on-the-Maine, in the Empire of Germany. "IMPROVEMENTS IN TYRES FOR RAILWAY :
WHEELS, AND IN THE METHOD OF APPLYING THE SAID IMPROVEMENTS." A com-
munication from Wilhelm Schmidt, Engineer, residing at Heidelberg, in the
Empire of Germany, and François Gittens, Shipbroker, residing at Antwerp, in the
Kingdom of Belgium.
This Invention relates to railway wheels, and consists in the improvements 4
herein-after specified.
The said Invention is illustrated in the accompanying Drawing, in which,―
Figure 1 is a section of a tyre.
Figure 2 is a diagram showing the bearing surfaco.
Figure 3 shows another section of a tyre.
Figure 4 illustrates the bearing of a wheel on a steel rail.
The improvement in the shape of the tyre results from the following facts, which
are to be taken into consideration :-
Breadth of the Road.-The space between the rails is generally on a straight
road, 1,435 meters, or 4 feet 8.2 inches English measurement.
Wheels. By the breadth of the road is understood the spacing of the wheels on
the axle, the tyres having on the inside a flange, which serves to prevent their
5

page_text: leaving the rails. The flanges have between the rails a play of 15 to 2 centimetres,
and in the curves from 1 to 1.5 more. The diameters of the wheels attached to the
same axle must be equal.
Tyres. These have a half diameter of 50 contimetres, that of the journal being
4 contimetres, a breadth of 10 centimetres, and a medium conicity of 0-6 centimetres.
This varies from 1 to 1/2. in the breadth, according to the judgment of the
engineers.
The resistances in the attrition are as follows :—
Attrition of the Axle.-This is in sliding. Coefficient of friction 0-050 (when well
greased); the total weight is 10,000 kil., of which rests on the axle 0-8 = 8000 kil. ;
the friction = 8000 × 0.050 = 400 kil; the circuit of the axle is 25 cm., that of the
= 400
tyre 312 cm., consequently the friction of the axle at the circuit of the tyre
25
312
kil. = 32 kilogrammeter.
A
Resistance of Rolling.-Between the wheels and the rails, although so denomi-
nated, this is in reality a sliding friction (generally dry). Coefficient of the
resistance =
03. This results from the conical form of the tyres; the greatest
circumference 3.14 x 1000/ = 3140 mm.; the smallest = 3.14 x 988 m.m. =
3102 m.in.; the difference is 38 m.m. The smallest circumference of the conus
must accomplish its road in sliding, so as to follow the largost; but as the conical
plan of the tyre touches the rails only on ½, or % of its breadth, the road which
the wheel must slide on the rails diminishes in the same proportion, thus 1/3 to 1/
× 38 m.m., and in the same measure the resistance of the friction thereby occasioned
= 10.000 × 0.3 = = 60 kilogrammeter × 0.25 to 0.33 = 15 to 20 kilogram.
net. The plane sliding surface (see Fig. 2) is a sharp angle A, consequently the
resistance is to km. = 75 to 10. Sum of both resistances KM. Friction of
the axle 32 km. x friction at wheels and rails = 10 km. = 42 k.m. These
= 42 km.
results have been proved by the experiments of wood to be of the load
=
15
20
2
5000
50
It will therefore be seen that the resistance between the wheels and the rails is
75 to 10 KM., or nearly one quarter of the total resistance. This result is chiefly
due to the great conicity in the form of the tyres, which has been adopted to
prevent the wheels leaving the rails or curves, and to diminish the friction on the
sides of the flanges.
be
If the conical form of the tyre, which has hitherto reached from 1/12 to 1/20
reduced to from 1/25 to 1/50, and instead of 6 to 8 metres, as heretofore, there is
a cone of 2 mi.m., which is % or 1½ of the former, the road is diminished, and
consequently the friction; the resistance and the wear diminish in the same
proportion. In consequence, as the friction between the wheels and the rails
becomes by this improvement, 1 or 1% less than formerly, the wear and the
destruction of wheels and rails will only be /, or ¼ of what they are when the
strong cone is used. And as the total resistance of a waggon with a load as above
indicated diminishes in consequence of the same improvement by about 66 to
7.5 km., that is to say, about one-sixth, the force of traction which is necessary
will also be one-sixth less.
Therefore the application of these improvements in the shape of the tyres of railway
wheels affords a saving of from two-thirds to three-quarters of the annual expenditure
in the maintenance of rails and wheels, and of one-sixth in the face of traction. The
said improvement furthermore diminishes jumping and oscillation of the vehicles.
If the course of a train in motion on a straight road with wheels, as used hitherto,
is observed it will be seen that the motion follows a serpentine line of which the
twisting or oscillation corresponds with the breadth of the arc which the wheels
can describe in proportion to their cone and their play between the rails; the
alteration in the direction of the axle produces a jump in the axle guards, and at
the rails the tyres become heated and very often to the point of breaking the half
diameter of the bow which the carriage or waggon describes = 71 metres; the
smallest curve of a railway has a radius of 200 metres.

page_text: With regard to the run or way of the curves, it is at least doubtful if the form
of the cone united to the centrifugal force due to a given rapidity does not con-
siderably increase instead of diminishing the liability of the wheels to leave the rails.
By lengthening the oscillation the force of the jumping is greatly diminished,
and the wear of the flanches nearly as much, and by the great reduction of the
friction the heating, the hardening, and the fracture of the tyres will probably be
entirely prevented, and the necessity for placing the tyres on the lathe will also be
reduced because the wear becomes so much less, while the object sought in giving
the conical form to the tyres will not be less effectually attained.
The facts above stated having been undeniable, attention was directed to the
mode hitherto used in turning the tyres when partly worn, and the experiments
made led to the establishment of a method which should be followed not only to
maintain the advantages of this Invention but also to increase these advantages in
a considerable measure.
The method which has hitherto been followed to determine the time of service
when the wheels of railway carriages must be turned anew is as follows, that is to
sayWhen the wheels of passenger carriages are partly worn and it becomes
necessary to renew them, these carriages are supplied with newly turned wheels,
and the old wheels are adapted to goods' waggons, where they remain in service
until they are so worn that they are utterly unfit for further use, that is, when they
have attained a conicity of 20 to 25%, which is left to the judgment of the engineer
in service.
According to the decision taken in the technical conference of the German,
French, and Belgian railway engineers, the conicity of the running surfaces should
at least be 5° whereas my system implies a conicity not exceeding 2°. How-
ever, no limit having hitherto been established to the degree of injury caused by
the wear till the moment when the new turning of the wheels is generally resorted
to, I annex hereto a table which shows the augmentation of the measure of friction
and wear corresponding with the conicity of wheel tyre from 1 to 21%, from
which table may be easily obtained the conviction that delay in turning causes
more prejudice than an original excess of cone, because the conicity constantly
increases during the time of the service.
Hitherto wheels have been allowed to run with a cone varying between 5
and 25%, which is shown in Figure 3; when the cone is the weaker, the deepest
point of wear is distant a third of the breadth of the tyre from the flange a, b,
100mm; where the cone is stronger, this point comes nearer and nearer to the flanch,
and the consequence is that each portion of wear increases the conicity.
=
The following principles have been taken as base for the said table :-In order
to establish the measure of attrition let it be supposed that 21 wheels are fixed on
an axle, of which wheels the cone varies from 1 to 21%. The smallest diameter
is the same for each wheel; the augmentation of the circumference of the greater
diameter has been calculated, the sum divided by 2, and the product admitted as
the measure of attrition, so called according to Colomb. The measure of wear was
established according to measurements formerly taken. The wear of a tyre with
a cone of 4% showed from 1-75 to 200m/ wear, thus as indicated in our table
4 × 5 = 90% cone. The cones hold is shown in our table. Column of the measure
of attrition.
°
°
ㅍ
The following are measures of attrition :-The aforesaid 2.00m/ wear, were
divided on the 122m/m measure of attrition, and to avoid too sinall parts of fractions
the wear per each measure of attrition was taken for 0.16m/. But as the running
part of a newly turned wheel, that is, on a straight surface, has on the round rails
but a very narrow working surface, the consequence is that the wearing is confined
to a narrow surface but is proportionally deep, however, when through a lengthened
time of service the working surface becomes broader, the wear is also distributed
over a broader surface and becomes consequently less deep. This fact has been
taken into consideration, as will be seen on the table, by diminishing the measure
of wear in proportion to the increase of the breadth of wear.

page_text: The actual cost or value has been determined by taking as a basis the price of
an ordinary tyre or frs. 210, the tyre having a thickness of 50m/ of which 35m/
are to be used.
210
95
The value of one m/m is therefore as follows:-1 metre = = 6 francs, conse-
quently 0.01m/ = 6 centimes, which amount has been carried into account for cach
"
0.01mm of wear.
Particular attention 'should be given to the column indicated in the table as
'measure of attrition," as this column which is mathematically precise indicates
clearly the remarkable increase of attrition, which results from increase in the
conicity. The value of the other columns varies according to the quality and price
of the material.
TABLE of the Increase of Attrition and Wear, and of the Value of the Wear
Established According to Progressive Conicity of the Tyre of Railway Wheels
from 1 to 0701 cone
st
2213
A glance at the preceding table shows better than any argument that a strong
conicity does but augment the defect which it is sought to remedy, thus the column
'measure of attrition" shows that a tyre with a conicity of 2% only gives a
measure of attrition of 6.28 / whereas a conicity of 21% gives 65.94 m/m that
is to say, ten times more attrition and wear for an equal use; so that a conicity of
2% is ten times more advantageous than a conicity of 21% which is not rarely
seen in use now. However, as this conicity can not be constantly maintained a
conicity is admitted, varying from 2 to 5%, that is giving 1 m/m of wear, so that
the space which a wheel actually runs, and which reaches to 21 % conicity, will be
subdivided into 5 equal parts. Supposing that the first part is allowed to run until
it reaches 5%, that is 1 / of wear, and that it is then turned off to its original
conicity of 2%, the five parts will then have cost francs 4.25 each, or together,
francs 21-25, whereas by the process now used the cost is as shown in our table,
francs 53.30, thus an economy of nearly 60%. But it would then seem that a

page_text: wheel should be turned anew five times during a year, whereas once is now sufficient,
and this would nullify the advantages of the present Invention. This is however
not the case, for as soon as a uniform cone has been established and maintained a
surface will form itself on the rails that will fully accord with the regular shape of
the wheels, and then the surface of contact between wheels and rails will successively
double, treble, or more, and the thickness or depth of the wear will diminish in the
same proportion. The turning, which now takes place once a year, will at the most
be wanted twice, but with this notable difference, that only 1 m/m will have to bo
turned off cach time, whereas it is necessary now to turn off from 6 to 8 m/m, which
does evidently necessitate more time and more power than the double turning of
only 1 / each time.
m'
According to my Invention proceeding from the above named basis, not only is
the conicity of 2° maintained, as shall henceforth be established, but the tyres shall
as much as possible be maintained at this reduced inclination, and shall not be
allowed to wear to more than 5% cone, thus allowing but 1 metre of wear.
Exceptionally only, and to facilitate the transition from the old to the improved
method, a wear of 2 m/m that is 8 % cone, will be allowed. But then it must be
turned off.
°
The advantages of this Invention are the following, namely:-
1st. The rails and wheels will be obtained as they must be, and the carriages or
waggons will run without notable oscillation or jumping.
2nd. The wear throughout the service will be considerably diminished, because
the conicity reduced from 5 to 2% reduces the attrition from 40 to 50%, and
because the working surface of rails and wheels will develop itself on a breadth of
threefold or fourfold greater extent as soon as the wheels have been rendered
uniform. This result arises from the fact that the medium conicity which is now
used, and which is from 5+9=14% is replaced by a conicity of 2+15=35%
as above set forth. In consequence thereof the wear resulting from the attrition,
and which is already reduced to 60 %, will again be reduced 3/4 or 45°, so that
the real diminution of wear will be 40+45=85 %% on the wheels and on the
rails.
3rd. Economy in the force of traction. By the suppression of such great
conicity the continual oscillation of the weight of the vehicles, and the consequent
shocks and jumping will disappear. Hence an economy in the force of traction
of 50% as is demonstrated by the following calculation. The force of truction has
been established in the following manner, namely:-
The weight of a vehicle was estimated=10,000 kilograms, the speed 12 metres,
the middle conicity 15%, the clearance or play between the rails and the wheel
flanch 15 Cm. By each movement of the wheels from one side of the rails
to the other the whole weight on that side=5000 kilogrammes is lifted from
15x15 225 m/m, and the centre of gravity inclines to the opposite side. This
happens twice per second, and there will be consequently 2 x 5000 kilogrammes;
2.2 of lift=45-4 kilogrammes metres. From this must be deducted the neces-
sary force to effect the lift of the remaining portion, namely, about 2 kilogr. metres.
There remains 43 kilogr. metres, whereas the force necessary to overcome the total
attrition of the vehicle is but 42 kilogr. metres. This calculation is founded on the
mathematical laws which rule mechanics and the attrition. It therefore admits
neither of doubt or contrary proof, and is to be applied according to the same process
with proper proportions to locomotives.
To ensure a good result the following limits should be allowed and maintained :-
For the diameter of the wheels
Play of the axle guards and axle bands
-
-
0.5
2.0m/m
For the angle of the large axle of the vehicle with the axle 1.0
-
An advantageous method of carrying this Invention into effect either on railways
in existance or on new lines is to unite a double mould to measure the shape of the
turning, so as to have both to rest at the same time on both wheels. This method

page_text: allows an accurate adaptation of the mould, and gives at the same time the exact
space between the wheels. It is also to be observed that in the commencement the
wheels would have to be turned off slightly, more often than later, when the correct
running surface shall have been obtained.
Having thus fully described the said Invention and the manner of performing
the same, I wish it understood that I claim,-
First. The improvements in the construction or formation of the tyres of railway
wheels, as above set forth and for the purposes specified.
Second. The apparatus comprising the double mould for carrying the said
Invention into effect, as above set forth.
In witness whereof, I; the said Frank Wirth, have hereunto set my hand
and seal, this Twenty-fourth day of September, in the year of our Lord One
thousand eight hundred and seventy-seven.
F. WIRTH. (L.S.)