THE MECHANISM OF BICYCLES. 
399 
is known technically as an “ harmonic motion.” 
Elliptic (Fig, 3). 
Since there is scarcely any form of machine in which a f cam 3 does 
not take its place in the mechanism, it is not to be wondered at that a 
“Cam Bicycle ” has been put before the public. (See diagram H.) 
The one exhibited shows two bevel cam discs keyed to the crank 
spindle; two links which hang from the frame terminate in rollers 
which fit into the cam grooves. To these rollers are also fastened 
connecting rods which are attached (by eccentric hoops) to the hub 
of the driving wheel and so the reciprocating motion of the rollers is 
converted into the circular movement of the wheel. It will be 
observed that here we have an equal pull 
on each side of the machine. The cam 
and rollers are enclosed in a dust proof 
box. Interchangable cam discs are pro¬ 
vided for the alteration of gear and the 
change can be effected in a few minutes. 
The ratio of the number of revolutions of 
the driving wheel to that of the cranks 
depends upon the number of curves in the 
cam plates. 
Mr. Pedersen has very kindly lent me 
one of his rather peculiar looking machines 
to show you. He tells me that the discom¬ 
forts of the ordinary bicycle saddle 
induced him to make various experi¬ 
ments which resulted in his adopting 
The 66 Eedersen,” a kind of hammock seat, com- 
