Improvements in Cycle Frames.
Year: 1896

page_text: Date of Application, 17th July, 1896-Accepted, 22nd Aug., 1896
COMPLETE SPECIFICATION.
Improvements in Cycle Frames.
We, WILLIAM ALFRED DAWSON and ALFRED FYSON, of 1, Victoria Street,
Westminster, London, S.W., Civil Engineers, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
This invention relates to improvements in the frames of bicycles, said improvements
being applicable either to the frames of velocipedes intended for a single rider, as
in the ordinary safety bicycle, or to machines designed to carry two riders as in the
multicycle or tandem, the object of our invention being to obviate the necessity of
the top horizontal bar as used in the "diamond frame bicycle as adapted for men's
use, and also the strengthening generally of cycles intended for the use of ladies.
Where our improved frame is employed, the same bicycle can be used without
alteration by either sex, a suitable space being left to accommodate the skirt of the
lady rider.
We claim for this invention that a frame constructed after this improved design is
at once stronger and stiffer than any "open-fronted" frame at present known or in
use, while it is also sufficiently strong to be used by men in place of that known
as the ordinary "diamond" frame.
The objects of this invention are successfully accomplished by the form of the
frame being designed on true mechanical principles, the members constituting the
frame meeting at points forming complete triangles, thus all cross strains or bending
actions on the parts are avoided, while the truss forming the principle part of this
invention does not depend for its strength on the resisting power of the tubes etc.,
in a transverse direction, nor on the rigidity of the joints as do the frames in
general use; but its strength and rigidity are due to its parts being under the
influence of direct strains only, as simple struts or simple ties.
In order that our invention may be more fully understood, we will now proceed to
describe same with reference to the accompanying drawings in which Fig. 1 is a
side elevation of a frame of a bicycle designed or intended for a single rider and
Fig. 2 a perspective view of same.
Like letters of reference indicate corresponding parts in both views.
The principal truss is along the lines, b, c, eh, ha, gb, and gc, (Fig. 1) and is
composed of the following parts viz., a c, bc, ch, hf, hg, gb, ja, gf, and cf, cg,
(Figs. 1 and 2).
As the parts a k, bk, ck, and the front fork l m, (Fig. 2) are substantially similar
to the usual form of construction it is unnecessary to describe them.
The principal truss as shown in Fig. 1 consists of the "king post" truss bch gbge,
of which the members bc, hg, gb, and 9 c, are double while the member ch, is
single.
The strains in this truss may be considered as being induced by three principal
forces viz. :
Firstly, the downward force due to the weight of the rider resting on the point k.
Secondly, the longitudinal force due to the varying resistances to the wheels
on the road, and
Thirdly, the sideways eccentric force due to the pressure of the feet upon the
pedals.
In the first case the weight of the rider at k is transmitted through the
action of the truss partly on to the back wheel at a and b, and partly on to the front
wheel through the front wheel fork at h, (Fig. 2) and direct strains of compression
Puce 8d 1

page_text: are set up in the members a c, bc, ch, cg, and cf, (Fig. 2), and direct strains of
tension are set up in the members a f, bg, gh, fh, and fg, (Fig. 2).
In the second case longitudinal forces produced by the reaction of the road
which tend to bring band (Fig. 1) together or to separate them, are resisted in
a direct manner by the members of the principal truss. Thus an obstacle checking
the forward movement of the front wheel, would tend to throw the point h nearer
the point, (Fig. 1), and this would produce direct strains of tension and compression
on the truss, similar to those already described as due to the action of the weight
of the rider, whilst an obstacle tending to retard the progress forward of the back
wheel, would produce strains of direct compression and tension in a contrary
manner.
In the third case the sideway forces due to the eccentric pressure of the feet upon
the pedals, resolve themselves into forces, one of which is downward and is resisted
by the whole truss, while the other which is scientifically termed a "couple" is
resisted by the action of the double and inclined members a c, bc, and af, bg,
and the connecting members cf; cg:
This means of producing lateral stiffness is an essential part of the design when
taken in conjunction with the inclined members fh, gh. The two last named
members may be made either to converge or diverge at h, or they may be arranged
parallel to each other.
In order to maintain the proper inclination of the front wheel fork / m, another
member, is introduced which so far as its junction with the front fork at j is
concerned, does not differ with that in general use in "open-fronted" bicycles, but
by joining with the joint c in the principal truss already described all forces acting
along the line; c, whether of tension or compression are direct, and do not cause
any cross or transverse strain inj c, itself, or on any member of the truss as is the
case with the "diamond" and "open-fronted "frames now in general use.
If more space for ladies skirts is required, the lower junction of the member; c;
can be made at any point in the line g, c, (Fig. 1), and in the case of a bicycle for a
light weight, je may be dispensed with and a new member such as indicated at jn,
(Fig. 1) can be introduced, its lower end being joined to any point of the front of
the principal truss.
As the strains in the principal truss above described are either direct compression
or direct tension, less material is required to resist then, than if the parts were under
the influence of cross strain. It is also easy to calculate those direct strains and
therefore the required 'sizes of the parts can be apportioned to them with the greatest
nicety.
It may be desirable to bring the points c org, in the principal truss (Fig. 1),
towards the line of the crank axle bearing at e. This can be done without affecting
the principle of the design'as indicated by the dotted lines.
Although our improvements have been described as applied to the frame of a
bicycle for a single rider it is obvious that the same principles are also applicable to
the frames for tandems intended for two riders, in which case the parts constituting
the frame shown in Figs. 1 and 2, may be duplicated, thus enabling the machine to
be used by either two-ladies or two gentlemen or as required, or the improved frame
as shown in the drawings may be retained to which is added the well understood and
necessary parts for forming the ordinary "diamond" front or back portion for the
gentleman, as required.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claimis:-
1. The improvements in cycle frames substantially as herein described and shown
and for the purposes specified.
2. In an " open-fronted" cycle frame, the formation and arrangement of the
principal truss comprising the members a c, bc, ch, hf, hg, gb, fa, jg, ef; and g
(Fig. 2) substantially as herein described and shown and for the purposes specified.

page_text: 3. The means for producing lateral stiffness and for resisting a part of the forces
due to the action of the feet upon the pedals, comprising the arrangement of the
double and inclined members a c, b c, and a fb y, and the connecting members cf, cg,
in combination or conjunction with the inclined members fh, h g, substantially as
herein described and shown in the accompanying drawings.
Dated this 100
July Logo.
F. G. CASSELL
(Of Cassell & Co.),
22, Glasshouse Street, Regent Street, London, W.,.
Agent for the Applicants.