GB561341A - Improvements in or relating to tandem bicycles - Google Patents

Abstract

561,341. Convertible tandem bicycles. CROW, E. S. Sept. 25, 1942, No. 13512. [Class 136 (iii)] An attachment for enabling a normally dimensioned tandem bicycle to be pedal assisted by a juvenile rider seated on a normallypositioned saddle of the machine, comprises an auxiliary pedalling device with means for supporting it in the existing frame of the machine above the level but in the general region of the normal crank bracket pertaining to the saddle which the rider is to occupy, and auxiliary drive transmitting means operatively connecting the auxiliary pedalling device to part of the normal driving gear of the machine, the supporting means including means for securing the auxiliary pedalling device to the seat tube between the saddle and crank bracket and means for securing it to at least one other adjacent element of the tandem frame. As shown, the auxiliary pedalling device comprises a crank bracket 9 and pedal cranks 11, 11a cottered to the axle 10, crank 11a being integral with a spider screwed to the driving sprocket 44, and the bracket 9 being adjustably fixed to the seat tube 1 by a screw clip consisting of an arcuate seating member 14, Fig. 2, on the bracket shell 9a and a strap 15 with tightening screws 16. The device is further supported by an adjustable screw strut 18 mounted between .a frame clip 17 on the centre bar 2 and a lug 9b on the bracket shell 9a. A driving chain 19 connects the sprocket 44 with a driving sprocket 20 on the main crank axle 7, the sprocket 20 being the outer ring of a standard free wheel clutch secured on a threaded adaptor keyed to the axle. Tensioning of the chain 19 may be effected by adjustment of the bracket 9 and strut 18, but preferably is effected by a jockey sprocket 24 adjustably or yieldingly mounted on an arm 25, clipped to the seat tube 1. Instead of the screw clip 14, 15, 16, one or more adjustable or pivoted struts similar to the strut 18 may connect the crank bracket 9 to the frame tube 1 or a strut or an auxiliary frame structure may be interposed between the crank bracket 9 and the normal bottom bracket 3 and the jockey sprocket 24 mounted on the auxiliary frame. Although chain gearing is shown, any suitable form of gearing may be used for transmitting the drive from the crank bracket 9 to one of the normal crank axles of the machine, which latter is preferably stripped of its normal cranks and pedals and furnished with the auxiliary driven wheel.