VECTr – Variably Expanding Chain Transmission

Crank-mounted bicycle transmissions have been hampered by a method of changing gears which induces friction and thus wear on the drive chain and which has the possibility of causing the chain to come off the gearing altogether. Moreover, there are only a very limited number of gear options available. Normally, circular chain rings of at most three discrete radii are used on bicycle cranks to achieve the effect of varying power transfer, but this method has the disadvantage of requiring the use of a derailleur, which rubs against the drive chain to change the chain’s position between each chain ring. Furthermore, the change of chain rings spans a gap in the number of teeth on each chain ring that makes the change abrupt. Perhaps worst of all, the use of a derailleur system can cause the chain to completely fly off of the chain rings, bringing the bicycle to a sudden and ignominious halt.

The key to the VECTr – Variably Expanding Chain Transmission is the arrangement of four gear segments, which slide inwardly or outwardly, to expand or contract, increasing or decreasing the effective gear radius where they each engage the chain. Each gear segment is locked into its radial position by a spring-biased locking toggle which protrudes from the face of the gear segment.

VECTr in fully expanded position – 45t equivalent

To increase the gear radius, the control plates are moved toward the rear of the bicycle, which engages the locking toggle on each gear segment. The toggle then releases the gear segment to slide outward from the center of the device as it is pushed by the contour of the control plate. When the toggle reaches the edge of the control plate, the gear segment is in the desired radial position, and the locking toggle again locks the gear segment into place.

VECTr in fully contracted position – 30t equivalent

A similar process decreases the gear radius. The control plates are moved toward the front of the bicycle, which also engages the locking toggle on each gear segment. The toggle then releases the gear segment to slide toward the center of the device as it is pushed by the contour of the control plate. When the toggle reaches the edge of the control plate, the gear segment is in the desired radial position, and the locking toggle again locks the gear segment into place.

On January 1, 2019, patent number 10,167,055 was issued for Variably Expanding Chain Transmission!