513] 
209 
513. 
ON A BICYCLIC CHUCK. 
[From the Philosophical Magazine, vol. xliii. (1872), pp. 365—367.] 
The apparatus, although I have called it a chuck, is constructed not for turning, 
but for drawing; viz. it rotates horizontally on a table (being moved, not from the 
inside by the axle of the lathe, but from the outside by a handle-frame), carrying a 
drawing-board which works under a fixed pencil supported by a bridge. Two points 
of the drawing-board describe circles; and the curve traced out on the drawing-board 
is consequently that described by a fixed point upon a moving plane two points of 
which describe circles; or, what is really the same thing, it is the curve described 
on a fixed plane by a point rigidly connected with two points each of which describes 
a circle. The apparatus is at once convertible into an oval chuck of nearly the ordinary 
construction; viz. it may be arranged so that the curve described on the drawing- 
board shall be an ellipse. 
Bottom plane is a rectangular board (1) (see figure) about 30 inches by 24 inches, 
having in the middle a sliding-piece (2) carrying a block (3). 
Second plane contains two circular segments (4) fixed to the bottom plane, serving 
as an axle for the moving piece (5) next referred to, and allowing the block (3) to 
move between them. And in the same plane we have a moving piece (5) in the form 
of a rectangle with a circle cut out thereof, rotating about the segments (4), and 
having upon it a groove in which works a sliding-piece (6) carrying a block (7); there 
is in this block a circular hole, D. The second plane includes also two sides (8) of 
a handle-frame, which two sides slide along two of the sides of the piece (5). 
Third plane consists of a rectangular piece (9) rotating about an axle fixed to 
the block (3), and having a sliding-piece (10) in which is a circular hole, G. The 
third plane includes also the before-mentioned block (7), having upon it the hole D; 
C. VIII. 27