Page:Popular Science Monthly Volume 89.djvu/941

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A Moto^pycle Bob

���VredericB. Hart

��Convert Your Motorcycle into an Inexpensive Power Bobsled

��IX designing this motor-bob it is assumed that the building will be done by motor- cycle owners having limited facilities, therefore everything is made in the simplest form, of materials casiK- obtained. Except the woodwork, nothing is required beyond some pieces of i-in. gas-pipe, a small piece of boiler-plate for the kingbolt support, some 3^-8-in. outside diameter brass tubing and steel wire for the ignition and throttle controls, and some ^ g-'m- rod and heavy strap-iron for the clutch-control and gear- shift. Many dimensions will have to be varied to conform with the motorcycle used for the power plant, so only general dimensions that are applicable to any ma- chine are given, and c\en these may be changed to meet the requirements of the builder.

Only a general outline is suggested for a two-passenger seat and a hood for the motorcycle. If such a hood is used it should be open in front or covered with a wire screen. Vents for windows in the sides of the hood would be advisable.

��Frame Constructiott The frame is constructed like the three- point suspension used on automobile en- gines, one point at each rear runner and the other at the kingbolt. The frame sides A, Figs. I and 2, are made of oak or other hard- wood, 4>< in. wide, iM in. thick, and if the details of the drawings are adhered to, the length should be 9 ft. 9 In. The rear cross-member B is 30 in. long, 8 in. wide and 2 in. thick. There is a second rear brace C directly under B at the extreme end of the frame; this is 30 in. long, 4 in. wide and 2 in. thick. From this point the frame is somewhat narrowed, principally for appearance sake, and the front cross- members, E and F, are 24 in. at the forward edge and slightly tapered to conform with the lines of the frame sides. The cross- member £ is 5 in. wide and 2 in. thick and the piece F is 2^4 in. wide and 2 in. thick. At the center of the piece £ is a block G 5 in. long and 2 in. thick, and with a width ecjual to that of the distance between the fork-ends on the motorcvcle. Further de-

���Plan view giving a general layout for the parts, frame and steering arrangement


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