Year: 1886

page_text: I, THOMAS SPENCER JAMES, of 68, Commercial Road, Peckham, Surrey, Engineer
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 :—
The object of my Invention is to gain greater leverage and consequently greater
power by means of my improved compound crank, without increasing the radius
described by any ordinary crank; that is to say: an ordinary crank of 6 inches
throw describes a circle of 12 inches and the leverage of such crank is limited to
6 inches, but by my improved compound crank the circle still remaining at
12 inches the leverage gained shall be say, 8 inches or more, or less, as required.
For the purpose of my Invention, I place the centres of two cranks A and B
(see Figures 1, 2, 3, 4, of the annexed Drawings) a certain distance from each other,
the crank pin C of the one being common to both. The crank B is fast to the shaft
to be driven and the centre of this crank I call the working centre. Behind this
crank B is placed the crank A working upon a disc G, which forms the centre of the
crank A, and is fast or solid with the frame of machine; the distance between the
centres of the cranks A and B is determined according to the extra leverage or
power required. A slot D is formed in the crank B a crank pin C, being placed on
the crank A passing through and sliding in the slot D.
The action of my crank is as follows; Whilst describing a circle of a certain
radius I am enabled to lengthen or increase the leverage one half of the circle
described, shortening or decreasing the leverage on the other half, as described and
desired; by this means I obtain great power applicable to all, or nearly all classes
of machinery such as Gas, Steam and Marine Engines Bycycles, Trycycles, Cranes,
Lathes and other machinery of whatever kind where a crank is adaptable or can
be used.
I sometimes make the disc G moveable and not stationary, the disc G being
slotted for that purpose, as shewn in Fig. 5 and 6 dotted lines; by which I am
enabled to allow the rider of a Bycycle for example, by suitable means to alter the
centre's of the cranks at will and have the option of using my invention as a
power increasing crank as described; or as an ordinary crank, that is to say, a rider
going up hill will require and be glad of as much power as he can possibly get. My

page_text: invention gives it, when the circle described by the pedal or crank pin C is
excentric to the centre of the axle of the wheel driven, but by shifting the disc G,
I enable the rider to cause the pedal or crank pin to describe a circle concentric
with the axle of the wheel, making my crank for the time being an ordinary crank.
The centres of my crank can be placed in any position required; by placing them 5
in a vertical position, I can enable a rider to ride a much higher and larger bycycle
than he otherwise could. Two sets of my crank are sometimes joined together by
the pin C, forming a crank suitable for Marine or other Engines or Machinery
where such cranks are applicable or desired.
Having now particularly described and ascertained the nature of my said 1
Invention, and in what manner the same is to be performed, I declare that what
I claim is
The improved compound crank as described; and substantially as shewn in the
drawings.