A Convertible Single or Tandem Bicycle.
Year: 1897

page_text: Date of Application, 11th June, 1897
Complete Specification Left, 10th Mar., 1898-Accepted, 11th June, 1898
A Convertible Single or Tandem Bicycle.
I, THOMAS DALRYMPLE WILSON, Major, late Royal Scots Fusiliers, of 71,
Philbeach Gardens, Earls Court, London, S.W., do hereby declare the nature of
this invention to be as follows:
My invention relates to a convertible bicycle and tandem bicycle, that is to say
a bicycle capable of being readily adapted to be ridden either by one or by two
persons as may be required.
The invention consists in making the steering head tube and fork detachable
from the main frame of the bicycle and in providing an additional frame to be
interposed between the main frame of the single bicycle and the steering head tube
for the purpose of increasing the length of the frame to the extent required for
two riders tandem. This intermediate or lengthening frame is suitably braced to
the main frame of the single bicycle and it carries a handle bar for the rear rider
and a saddle and pedal driving gear for the front rider, all that is necessary to
convert a single bicycle into a tandem being to detach the steering head tube from
the former, and attach it to the intermediate frame, to connect and
brace the intermediate frame to the frame of the single machine, and
to couple the pedal axis of the front rider lo the pedal axis of
the rear rider by the usual chain, an additional sprocket wheel being provided on
the last mentioned axis to receive it as usual in tandem machines. The connection
of the steering head tube with the frame of the single machine or with the inter-
mediate frame of the tandem may be made by clamps embracing the former and
provided with pairs of ears which receive between them, and are bolted to,
corresponding ears formed on the front of the frame.
To enable the machine to be converted to the open frame form for ladies' use
the top tube of the ordinary diamond frame may be pivoted to the head tube and
be detachable from the upper part of the down tube and be connected to a point
near the lower part thereof so as to still act as a brace between the head tube and
the down tube.

page_text: this invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:-
1
My invention relates to a convertible bicycle and tandem bicycle, that is to say
a bicycle capable of being readily adapted to be ridden either by one or by two
persons as may be required.
The invention will be described with reference to the accompanying drawings
forming part of this Specification wherein Figure 1 is an elevation shewing the
parts separately and Figure 2 shews the same parts united to form the frame of a
tandem. Figure 3 shews the same as converted into a single machine by the
removal of the intermediate frame. Figure 4 is a plan of one of the joints. The
same letters of reference denote like parts in all the figures.
The invention consists in making the steering head tube (A) in which the
front fork is pivoted detachable from the main frame (B) of the bicycle and in
providing an additional or intermediate frame such as that shewn at (C) to be
interposed between the main frame (B) of the single bicycle and the steering head
tube (A) as shewn in Figures 1 and 2 for the purpose of increasing the length of
the whole frame of the machine to the extent required for two riders tandem.
This intermediate or lengthening frame (C) is preferably made of the form shewn
and is suitably connected to the main frame (B) of the single bicycle and to the
steering head (A) so as to brace the whole structure and it carries a saddle and
pedal driving gear for the front rider as well as a handle bar for the rear rider.
All that is necessary to convert a single bicycle, such as shewn in Figure 3,
into a tandem, as shewn in Figure 2, is to detach the steering head tube (A) from
the frame (B) and attach it to the intermediate frame (C); to connect and brace
the intermediate frame (C) to the frame (B); and to couple-the pedal axis of the
front rider to the pedal axis of the rear rider by the usual chain, an additional
sprocket wheel being provided on the last mentioned axis to receive such chain,
as usual in tandem machines. The connection of the steering head tube (A)
with the frame (B) of the single machine or, as the case may be, with the inter-
mediate frame (C) of the tandem; and of the intermediate frame (C) with the
frame (13) is made by joints in the top and bottom members as shewn at (D), all
these joints being alike in construction. For this purpose the steering head
tube (A) is provided with short tubular members adapted to match with the top
and bottom members either of the frame (B) or the intermediate frame (C). The
preferred form of joint is shewn in plan in Figure 4 and consists of solid plugs or
end pieces (d, d) brazed into sockets or ferrules on the ends of the tubular members
to be united, the projecting ends (, ) of the plugs being longitudinally
"halved" together forming tenons or of approximately semi-cylindrical form, their
abutting faces being respectively provided with a transverse lug (d³) on the one
interlocking with a corresponding slot in the other and the two tenons being
clamped together by a transverse bolt (4) traversing both, the head of the bolt
being countersunk and a nut being screwed on the other end so as to ensure a
rigid and firm interlocking connection of the two parts. I do not, however, limit
myself to this particular form of joint, nor to the precise situations of the joints,
as these may be varied without departing from the invention.
The intermediate frame (C) comprises a down tube (c) and top and bottom
members (c¹, c²) similar in every respect to the corresponding members (b, b', b²)
of the frame (B) so that the joint tenons on the steering head tube (A) will be
adapted to be coupled to the one frame or the other, as the case may be. In
addition, it has a member (c) extending rearwardly from the bottom bracket (c)
and adapted to be connected by a joint similar to that above described, to the
bottom bracket (64) of the frame (B) so as to brace the frame of the tandem.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is:-
A convertible single or tandem bicycle consisting in the combination with a

page_text: steering head tube detachably connected to the bicycle frame, of an intermediate
frame provided with saddle and driving gear adapted to be interposed between the
steering head and main frame and to be coupled thereto substantially as and for
the purpose specified.
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.