One of the 3/4-in. thick pieces is fastened solidly to one end of the foot board with the ends flush. The other piece is swiveled with the bolt at the opposite or front end of the foot board so that at least one-half of the piece projects beyond the end. The steering post is hinged to the projecting end. The skates are fastened to the 3/4-in. pieces for runners. The manner of propelling the racer is the same as for the pushmobile.—Contributed by W. E. Crane, Cleveland, O.
Homemade Ellipsograph
By Chelsea Curtis Fraser
An efficient ellipsograph is the only device that will make true ellipses of various sizes quickly, and such a machine is in demand on some classes of work in a drafting room. Its cost, however, is prohibitive where only few ellipses are to be drawn, but a person handy with tools can make an apparatus that will do the work as well as the most expensive instrument.
Practically Any Size or Proportion of Ellipse, from 1-1/2 to 16 In. Maximum Diameter, can be Drawn with an Instrument of This Size, and Larger Instruments will Work Equally Well (Fig. 1)
The completed ellipsograph, herein described, will appear as shown in Fig. 1. It consists of two main parts, the base and the arm. The former is a hardwood piece, A, Fig. 2, to the side center of which is attached another hardwood piece, B. This latter piece may be dovetailed into A, but an ordinary butt joint will suffice, as a one-piece base, C, also of hard wood, is glued to the bottom surfaces of the pieces A and B, thus securely holding them together. Before gluing, however, care must be taken to see that the piece B is exactly at right angles with the piece A. This can be done with a try-square. Dimensions are given in Fig. 2. The same letters are used throughout for the same parts.
(Fig. 2)
A 1/16-in. groove, H, is cut out at the juncture of A and B, to admit the flange of the minor-axis swivel head. Another groove, J, is made along the longitudinal center of the piece B, to receive the spine of the major-axis swivel head. Sheet brass plates, D and E, are cut from 1/16-in. stock and attached to the top of the piece A with screws. The plates F and G are of the same material and fastened in a like manner to the upper surface of the piece B. All plates project slightly where they touch the groove borders, as shown. This is to provide a bearing for the projections on the sliding parts against metal instead of wood. A piece of thin celluloid or brass plate, K, is inserted in the bottom side of the base C so that the point will be exactly in line with the center groove J, and extend outward 1/8 in. This point indicates the center of all ellipses to be drawn. In the bottom of the base C, at each end, drive an ordinary pin and cut it off so that a part of it will project beyond the surface of the wood. These extending ends are pointed with a file, and serve to keep the instrument from slipping when in use.