I got the inspiration for this lift after seeing Alocke's ball machine Tartarus. As you can guess by the name, when the car gets up to the top it suddenly free falls. This is do to the special gearing mechanism. I modified a medium knex gear by taking off some of the teeth leaving only 17 left. When the teeth of the medium gear catch hold of the small gear (see picture 10) it turns the shaft which is connect to a wheel-like device which winds in the string (or chain) connect to the car thus pulling the car up. When the car gets up to the top there are no more teeth turning the blue gear thus making the car fall. Enjoy the video.
Step 5: The Wheel and Crankshaft
Step 7: The Gearing Mechanism
For this step you will have to modify two knex parts, a tan locking clip and a medium gear with teeth. You'll have to sand down the top part of a tan locking clip so that it doesn't rub against the black hinge half. (see picture 6 and 7) You'll also have to take off 17 teeth on a medium size gear so that only 17 teeth remain. (see picture 6 and 7)
Step 9: The Elevator
For this step you can either use string, fishing line, or mini chain links as seen in the last three pictures. Make sure you cut the string (or fishing line) just long enough so that the elevator touches the ground. Sorry, I forgot to count how many mini chain links to use.
Step 10: The Back Support
Step 11: The Sides Part 1
Step 12: The Sides Part 2
Step 13: All Done!
Congrats! You've finished the elevator free fall lift. Make sure you flip the switch to the left or it won't work.