March 2004. In this project, I have finally succeeded in the realization of a LEGO continuously variable transmission (CVT) with a wide range of transmissions and torques. The creations consists of a CVT invented by Terry Lester and a power splitter, using two planetary gear transmissions, working together as an infinitely variable transmission (IVT). In order to get the maximum amount of torque, I have allowed my self to add one manual control to this creation: the amount of fringe load on the output of the CVT.
The first picture is used to give an overview of all the relevant parts. The motor left transmits full speed torque to the powersplitter, which is a pair of planetary wheel transmitters in the lower half of the construction, and the input of the CVT in the upper half of the construction. The output torque of the CVT is transmitted to the gears and wheel at the top right part of the construction. The CVT output torque is finally transmitted to the 40-tooth gears in the powersplitter. The output of the power splitter is the torque on the wheel at the lower right side of the construction.
This picture gives an impression of the rotation speeds when the output wheel when there is no load on the output of the power splitter and the CVT.
When the output of the power splitted is loaded by manually slowing down the wheel, the rotating speed of the CVT slows down while the weights in the CVT start rotating. A strong torque can be felt on the output wheel. The maximum torque that can be felt is comparible to a LEGO motor that is geared down by a factor of 16. This torque can only be felt when the output of the CVT is fully blocked.
The following pictures show how the load on the output of the CVT can be controlled by pulling a string. A worm gear construction keeps the tension of the string to a fixed magnitude.
This picture shows the details of the CVT. It appeared to be difficult to built smaller versions of this design.
The planetry gear transmissions in the power splitter are smaller versions of the planetary gear of Mike Fusions LEGO Technic and Mindstorm pages
February 2005. Finally, I decided to do some experiments with this CVT in a car.
The car appeared to behave well. The working range of the cvt-ivt can be easily controlled with the worm wheel string construction. If the car is blocked , the output torque becomes so big that the wheels will slip despite of the rubber tires!
October 2005. A Lego Hybrid CVT-IVT has been realized!
The page with all my transmission and CVT designs!