Power assist for bicycles

A package operable to provide power assist to a two-wheel bicycle having pedals and a frame and longitudinally spaced front and rear wheels with associated front and rear axes of rotation, the package being in combination with said bicycle comprising

• a) a carrier,
• b) a ground engaging drive wheel supported by the carrier, the drive wheel having lowermost extent, and an electric battery operated drive to rotate the drive wheel,
• c) the bicycle having a frame and a rear wheel with lowermost extent, and connecting arm structure associated with the carrier and projecting forwardly and providing pivoted connection to the bicycle frame to position and laterally guide the carrier for free up and down pivoted movement in close association with the bicycle rear wheel and generally parallel thereto at predetermined spacing, with the drive wheel lowermost extent spaced less than about six inches to the rear of a lateral axis through the lowermost extent of the bicycle rear wheel during non-banking travel of the bicycle, said pivoted connection located forwardly of an upright plane containing the bicycle rear wheel axis,
• d) the bicycle having a pedal cyclic path of travel, and the drive wheel and carrier having forwardmost portions located rearwardly of said cyclic path of travel of the bicycle pedal during pedaling of the bicycle so that neither the drive wheel nor the carrier will interfere with said pedal cyclic path of travel,
• e) and wherein the bicycle has a frame and said connecting arm structure includes upper and lower arms extending forward to a common pivotal connection to the bicycle frame forward of the carrier, the upper and lower arms connected to the carrier at spaced upper and lower locations, respectively, whereby the carrier is constrained for up-down pivotal movement while located directly adjacent the bicycle rear wheel.