A system for providing an automated axial force to a continuously variable transmission (CVT) in a wheelchair. An electronic transmission control receives one or more input signals generated by throttle position or other variables. The microprocessor generates an output signal that adjusts the axial force applied to a CVT thereby automatically adjusting the input to output ratio. The invention also provides a manually-controlled variator is designed for use on a wheelchair. The manual shifter hydraulically adjusts an axial force imparted on a variator in communication with a wheelchair wheel and a hand rim. Application of the axial force causes the hand rim input and wheelchair wheel output ratio to change, permitting a wheelchair operator to manually adjust the input to output ratio to more easily operate the wheelchair.
1. A wheelchair, comprising:
(a) at least two continuously variable transmissions (CVTs) arranged in series and mounted to each of the rear drive wheels, wherein the CVTs adjust the RPM ratio between the drive wheels and hand rims mounted on the drive wheels;
(b) at least one manual lever for adjusting the transmission ratio of the CVTs;
(c) at least one hydraulic system that provides communication between said manual lever and the CVTs.
2. The wheelchair according to claim 1 , wherein the hydraulic system further comprises:
(i) a first piston bounded by a first fluid reservoir and second fluid reservoir;
(ii) a hydraulically actuated second piston having a pushing fluid reservoir and a pulling fluid reservoir;
wherein application of downward force to the first piston via the manual lever causes fluid to exit from the second fluid reservoir and enter the pulling fluid reservoir, while simultaneously, fluid is pulled into the first fluid reservoir and out of the pushing fluid reservoir, causing the hydraulically actuated second piston to move in a first axial direction away from the CVT; and
wherein application of upward force to the piston via the manual lever causes fluid to exit from the first fluid reservoir and enter the pushing fluid reservoir, while simultaneously, fluid is pulled into the second fluid reservoir and out of the pulling fluid reservoir, causing the hydraulically actuated second piston to move in a second axial direction towards the CVT.