A BIKE THAT CAN REALLY SHIFT

Details are given off an automatic transmission, based on a variable-diameter chainwheel, for bicycles. The chain wheel shrinks as the rider puts more pressure on the pedals to accelerate or climb a hill and this lowers its ratio to match the greater torque requirements. When the rider relaxes pressure on the pedals, the chainwheel expands accordingly. The bicycle's chainwheel has six small sprockets spaced equally around the circumference. These sprockets slide in and out along radial slots so that the working diameter of the chainwheel varies from 250 mm to 125 mm; the effective number of teeth on the wheel reduces from 64 to 32, comparable with a conventional 10-speed derailleur gears. The radial movement of the sprockets is synchronised by an independent control disc set behind the wheel and linked to it by springs. The tips of the sprocket spindles fit in individual spiral slots in this disc, so if any one sprocket slides the others follow it by the same amount. The rider changes the ratio only when he drives the pedal crank on the right through a 60-degree sector just below the horizontal. At this point, increased or reduced tension on the chain alters the radial force on the top sprocket on the wheel, making it slide in or out. There are two non-rotary and four rotary sprockets. The rotary sprockets do not rotate freely but at a controlled rate which is determined by a small pinion wheel behind each of them. These pinions mesh with a rack alongside the slot. So they roll while Sliding. (TRRL)

  • Availability:
  • Corporate Authors:

    IPC Magazine Limited

    King's Reach Tower, Stamford Street
    London SE1 9LS,   England 
  • Publication Date: 1980-6-26

Media Info

  • Features: Photos;
  • Pagination: p. 398
  • Serial:
    • NEW SCIENTIST
    • Volume: 86
    • Issue Number: 1207
    • Publisher: REED BUSINESS INFORMATION LTD
    • ISSN: 0262-4079

Subject/Index Terms

Filing Info

  • Accession Number: 00329594
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD, TRIS
  • Created Date: May 21 1981 12:00AM